Proteopedia - User contributions [en]

Cowpea Chlorotic Mottle Virus

2012-08-06T07:10:34Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2012-08-06T07:10:14Z

Inna Blyakhman: /* 3D structures of cowpea chlorotic mottle virus */

<Structure load='1CWP' size='500' frame='true' align='right' caption='Cowpea chlorotic mottle virus coast protein complex with RNA [[1cwp]]' scene=/>

===Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis===

<scene name='Cowpea_Chlorotic_Mottle_Virus/Full_capsid/2'>Assembled Capsid</scene>

'''Introduction'''

The cowpea chlorotic mottle virus is a plant virus that infects the cowpea plant. It is a naked (non-enveloped), icosahedral virus. Its capsomeres are stabilized by cationic metal binding (a motif similar to calmodulin in eukaryotic cells)<ref name=Speir>PMID:7743132</ref> and by the interactions of the negatively charged nucleic acid with the basic amino- terminus arms. CCMV contains a positive-sense RNA genome. Therefore, its encapsidated nucleic acids can be directly translated by host machinery to make the protein components for progeny virions. Its replication strategy requires the formation of a negative-sense template that can be used to synthesize new positive-sense RNA.

An intriguing feature of virus is its ability to undergo a major structural change without destroying the tertiary structure of its subunits under certain environmental conditions. Specifically, when conditions are acidic (pH 5) the capsid is in a stable, assembled form. However, when the pH is raised ~6.5-7 or placed into solution of low ionic strength, the capsid undergoes a concerted structural change called swelling. <ref name=Speir>PMID:7743132</ref>
During this process, 60 pores (2 nanometers in diameter) open along the threefold axis of the capsid, and the size of the virion swells to an increased volume of 10%. Although the capsid expands, the RNA to protein ratio remains constant. The formation of these pores makes it possible for molecules to exit and enter the capsid, allowing this structure to function as a nano-reactor.
Furthermore, if the pH is increased to 7.5, the particles will completely dissociate into dimer subunits.

'''Significance and Applications of CCMV Structural Transitions '''

In the field of virology, CCMV is relevant to mammalian research due to the similarity in structural transitions that human polio virus undergoes (picornaviridae family)<ref name=Speir>PMID:7743132</ref>
(another naked icosahedral virus).

More influentially, the properties of the capsid allow the virus to be exploited in nanotechnology. Capsid proteins can be obtained through two main strategies.
First, virus can be directly extracted from plant leaves in high yields (1 kg of infected plant tissue can yield 1–2 g of virus<ref name=Liepold>PMID:Liepold16280622</ref>). By raising the pH to 7.5 and dissociating the capsid into dimers, the protein can be isolated from the RNA. The purified proteins can then self-assemble into functional virus-like particles when restored to more acidic conditions.

A more modern strategy involves the use of recombinant DNA technology. In this approach, the capsid-encoding genes of the virus can be transfected into a yeast expression vector.<ref name=Liepold>PMID:Liepold16280622</ref>) As the yeast replicate, they amplify the number of protein producing units, and the secreted protein products can be readily collected from the media. The major benefit to this method, aside from high yield production, is that the genome can be modified prior to insertion into the vector. This can be used to generate capsid subunits with differing chemical properties. Such a procedure was performed by Dr. J. J. L. M. Cornelissen in the Netherlands. He attempted to solve the problem that many reactants of interest, particularly enzymes, are sensitive to the and the acidic requirements for capsid stability by looking for other stabilization strategies. He found that nickel atoms could stabilize the capsid at pH 7.5. This was a promising alternative to the large polyelectrolytes that were being used to stabilize capsids because they do not fill the capsid volume.

Histidine residues were able to readily coordinate with nickel, and this property was used to purify the modified proteins from the media of their expression vectors. This purification was performed with a column of nickel atoms immobilized to a resin enriched with a metal chelating agent (NTA). Once the proteins were isolated, a experimental, pH-sensitive, protein (EGFP) was coupled with the capsomeres.<ref name=Liepold>PMID:Liepold16280622</ref>)

The metal ion induced stabilization was likely due to a different mechanism than older polyelectrolyte methods since the metal ions are substantially smaller than polyelectrolytes, and they are positively charged.<ref name=Liepold>PMID:Liepold16280622</ref>)

The field of nanovirology using these cage structures has branched into both biomedical sciences and physical virology. In particular, CCMV capsids have been investigated as a drug delivery vessels, and scaffolds for highly ordered crystal growth. Scaffold synthesis in other viral systems has enabled the production of quantum dots used as fluorescent dyes in biotechnology.

<scene name='Cowpea_Chlorotic_Mottle_Virus/Isolated_rna/1'>Isolated RNA</scene>

'''General Capsid Structure'''

The viral capsid of CCMV is a complex of proteins stabilized by metal coordination between capsomeres and RNA binding on its internal surface.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Protein_and_rna/1'>Protein Core with Stabilizing RNA Interactions</scene>
The viral genome encodes three capsid proteins that are chemically identical. These subunits, arbitrarily called A, B, and C, dimerize with each other and assemble into into hexamers and pentamers that comprise the viral capsomeres.<ref name=Speir>PMID:7743132</ref> The complete capsid structure takes the form of a truncated icosahedron. It is described as a T=3 capsid, where the T value describes the number of structural units per equilateral face of the icosahedron.[http://www.nlv.ch/Virologytutorials/Structure.htm]

'''Capsomere Structure'''

The hexameric capsomeres are formed by the B and C subunits. The N-terminus arms (residues 27 through 49) of the subunits intertwine to form a parallel beta barrel.<ref name=Speir>PMID:7743132</ref> The N-terminus is therefore key to the hexamer composition.<ref name=Speir>PMID:7743132</ref>
<scene name='Cowpea_Chlorotic_Mottle_Virus/Residues_27-49/1'>N-terminus arms</scene>
The atoms of residues 27-49 are colored blue for clarity.

Residues 29-33 line the channel created at the center of the hexamers and stabilize the subunits with the interactions of their side chains and adjacent residues. For example, the "side chain oxygens of Gln29 residues hydrogen bond with the main chain nitrogens of adjacent Gln29 residues, making a circular ring of interactions" and the "valine residues stack upon one another inside the the beta-tube forming a circle of hydrophobic bonds."<ref name=Speir>PMID:7743132</ref> The hydrophobic valine side chain atoms are protected from the interior of the virus by the side chain atoms of the glutamine residue, and they are surrounded by the hydrogen bonding environment of the beta barrels.<ref name=Speir>PMID:7743132</ref>

In the <scene name='Cowpea_Chlorotic_Mottle_Virus/Interior_of_beta_barrel/1'>interior of beta barrel</scene> we can see these residues filling the channel formed at the center of the capsomere: glutamine 29 (in red), valine 31 (in orange), and valine 33 (in green).

Pentamer capsomeres, on the other hand, are formed exclusively from the contribution of A subunit chains.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Pentamer/1'>Pentamer capsomeres</scene> also have amino-terminus arms that extend into the interior of the capsid, however, unlike the hexameric barrel structures, the amino terminus is unordered.The positively charged Lys 42 residue is colored in blue as a marker for the arms of the N-terminus. Residues before Lys42 do not have detectable electron density for the techniques used to render the structure.

Interestingly, although the subunits are chemically identical, hexamer formation predominates in the capsid. In 1962 Caspar and Klug predicted a classical model for a perfect icosahedral structure- one that would have "a sheet of hexamers interspersed with 12 pentamers arranged to form a closed shell with icosahedral symmetry." In this geometrical shape, the number of pentamers is constrained to 12, a structure with greater than 60 subunits, however, must be accounted for by an increased number of hexamers. For viruses, a perfect 60-faced icosahedron would severely limit genome packaging.[http://www.nlv.ch/Virologytutorials/Structure.htm]

Prior to the characterization of CCMV's structure, no RNA viruses (in plants and insects) were found to rigorously observe this model. Their prediction necessitated that the pentamer and hexamer subunits would from a single chemical structure (realized in CCMV due to its identical A,B, and C gene products). However, the "molecular switch" that determines whether a pentamer or a hexamer would form, was left undefined.
It appears that after dimerization, hexamers are responsible for initiating capsid self-assembly. The authors propose that the hexamers form nucleation sites for particle formation, and "that there are probably no pentamers in in solution. It is likely that they only form during the assembly process." <ref name=Speir>PMID:7743132</ref> The basis for the additional hexamer stability comes from the relative number of stabilizing interactions within each capsomere.<ref name=Speir>PMID:7743132</ref> The hexamers have an interlaced beta barrel structure at their amino terminus, whereas pentamers form an unordered amino terminus cluster.

'''Conclusion'''

Cowpea Chlorotic Mottle Virus is used in many actively researched fields. It provides a readily manipulatable construct for nanoreactors and synthesis scaffolds without a significant biosafety risk for experimenters.

Cowpea Chlorotic Mottle Virus

2011-12-01T19:31:40Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

<Structure load='1CWP' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />

===Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis===

<scene name='Cowpea_Chlorotic_Mottle_Virus/Full_capsid/2'>Assembled Capsid</scene>

'''Introduction'''

The cowpea chlorotic mottle virus is a plant virus that infects the cowpea plant. It is a naked (non-enveloped), icosahedral virus. Its capsomeres are stabilized by cationic metal binding (a motif similar to calmodulin in eukaryotic cells)<ref name=Speir>PMID:7743132</ref> and by the interactions of the negatively charged nucleic acid with the basic amino- terminus arms. CCMV contains a positive-sense RNA genome. Therefore, its encapsidated nucleic acids can be directly translated by host machinery to make the protein components for progeny virions. Its replication strategy requires the formation of a negative-sense template that can be used to synthesize new positive-sense RNA.

An intriguing feature of virus is its ability to undergo a major structural change without destroying the tertiary structure of its subunits under certain environmental conditions. Specifically, when conditions are acidic (pH 5) the capsid is in a stable, assembled form. However, when the pH is raised ~6.5-7 or placed into solution of low ionic strength, the capsid undergoes a concerted structural change called swelling. <ref name=Speir>PMID:7743132</ref>
During this process, 60 pores (2 nanometers in diameter) open along the threefold axis of the capsid, and the size of the virion swells to an increased volume of 10%. Although the capsid expands, the RNA to protein ratio remains constant. The formation of these pores makes it possible for molecules to exit and enter the capsid, allowing this structure to function as a nano-reactor.
Furthermore, if the pH is increased to 7.5, the particles will completely dissociate into dimer subunits.

'''Significance and Applications of CCMV Structural Transitions '''

In the field of virology, CCMV is relevant to mammalian research due to the similarity in structural transitions that human polio virus undergoes (picornaviridae family)<ref name=Speir>PMID:7743132</ref>
(another naked icosahedral virus).

More influentially, the properties of the capsid allow the virus to be exploited in nanotechnology. Capsid proteins can be obtained through two main strategies.
First, virus can be directly extracted from plant leaves in high yields (1 kg of infected plant tissue can yield 1–2 g of virus<ref name=Liepold>PMID:Liepold16280622</ref>). By raising the pH to 7.5 and dissociating the capsid into dimers, the protein can be isolated from the RNA. The purified proteins can then self-assemble into functional virus-like particles when restored to more acidic conditions.

A more modern strategy involves the use of recombinant DNA technology. In this approach, the capsid-encoding genes of the virus can be transfected into a yeast expression vector.<ref name=Liepold>PMID:Liepold16280622</ref>) As the yeast replicate, they amplify the number of protein producing units, and the secreted protein products can be readily collected from the media. The major benefit to this method, aside from high yield production, is that the genome can be modified prior to insertion into the vector. This can be used to generate capsid subunits with differing chemical properties. Such a procedure was performed by Dr. J. J. L. M. Cornelissen in the Netherlands. He attempted to solve the problem that many reactants of interest, particularly enzymes, are sensitive to the and the acidic requirements for capsid stability by looking for other stabilization strategies. He found that nickel atoms could stabilize the capsid at pH 7.5. This was a promising alternative to the large polyelectrolytes that were being used to stabilize capsids because they do not fill the capsid volume.

Histidine residues were able to readily coordinate with nickel, and this property was used to purify the modified proteins from the media of their expression vectors. This purification was performed with a column of nickel atoms immobilized to a resin enriched with a metal chelating agent (NTA). Once the proteins were isolated, a experimental, pH-sensitive, protein (EGFP) was coupled with the capsomeres.<ref name=Liepold>PMID:Liepold16280622</ref>)

The metal ion induced stabilization was likely due to a different mechanism than older polyelectrolyte methods since the metal ions are substantially smaller than polyelectrolytes, and they are positively charged.<ref name=Liepold>PMID:Liepold16280622</ref>)

The field of nanovirology using these cage structures has branched into both biomedical sciences and physical virology. In particular, CCMV capsids have been investigated as a drug delivery vessels, and scaffolds for highly ordered crystal growth. Scaffold synthesis in other viral systems has enabled the production of quantum dots used as fluorescent dyes in biotechnology.

<scene name='Cowpea_Chlorotic_Mottle_Virus/Isolated_rna/1'>Isolated RNA</scene>

'''General Capsid Structure'''

The viral capsid of CCMV is a complex of proteins stabilized by metal coordination between capsomeres and RNA binding on its internal surface.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Protein_and_rna/1'>Protein Core with Stabilizing RNA Interactions</scene>
The viral genome encodes three capsid proteins that are chemically identical. These subunits, arbitrarily called A, B, and C, dimerize with each other and assemble into into hexamers and pentamers that comprise the viral capsomeres.<ref name=Speir>PMID:7743132</ref> The complete capsid structure takes the form of a truncated icosahedron. It is described as a T=3 capsid, where the T value describes the number of structural units per equilateral face of the icosahedron.[http://www.nlv.ch/Virologytutorials/Structure.htm]

'''Capsomere Structure'''

The hexameric capsomeres are formed by the B and C subunits. The N-terminus arms (residues 27 through 49) of the subunits intertwine to form a parallel beta barrel.<ref name=Speir>PMID:7743132</ref> The N-terminus is therefore key to the hexamer composition.<ref name=Speir>PMID:7743132</ref>
<scene name='Cowpea_Chlorotic_Mottle_Virus/Residues_27-49/1'>N-terminus arms</scene>
The atoms of residues 27-49 are colored blue for clarity.

Residues 29-33 line the channel created at the center of the hexamers and stabilize the subunits with the interactions of their side chains and adjacent residues. For example, the "side chain oxygens of Gln29 residues hydrogen bond with the main chain nitrogens of adjacent Gln29 residues, making a circular ring of interactions" and the "valine residues stack upon one another inside the the beta-tube forming a circle of hydrophobic bonds."<ref name=Speir>PMID:7743132</ref> The hydrophobic valine side chain atoms are protected from the interior of the virus by the side chain atoms of the glutamine residue, and they are surrounded by the hydrogen bonding environment of the beta barrels.<ref name=Speir>PMID:7743132</ref>

In the <scene name='Cowpea_Chlorotic_Mottle_Virus/Interior_of_beta_barrel/1'>interior of beta barrel</scene> we can see these residues filling the channel formed at the center of the capsomere: glutamine 29 (in red), valine 31 (in orange), and valine 33 (in green).

Pentamer capsomeres, on the other hand, are formed exclusively from the contribution of A subunit chains.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Pentamer/1'>Pentamer capsomeres</scene> also have amino-terminus arms that extend into the interior of the capsid, however, unlike the hexameric barrel structures, the amino terminus is unordered.The positively charged Lys 42 residue is colored in blue as a marker for the arms of the N-terminus. Residues before Lys42 do not have detectable electron density for the techniques used to render the structure.

Interestingly, although the subunits are chemically identical, hexamer formation predominates in the capsid. In 1962 Caspar and Klug predicted a classical model for a perfect icosahedral structure- one that would have "a sheet of hexamers interspersed with 12 pentamers arranged to form a closed shell with icosahedral symmetry." In this geometrical shape, the number of pentamers is constrained to 12, a structure with greater than 60 subunits, however, must be accounted for by an increased number of hexamers. For viruses, a perfect 60-faced icosahedron would severely limit genome packaging.[http://www.nlv.ch/Virologytutorials/Structure.htm]

Prior to the characterization of CCMV's structure, no RNA viruses (in plants and insects) were found to rigorously observe this model. Their prediction necessitated that the pentamer and hexamer subunits would from a single chemical structure (realized in CCMV due to its identical A,B, and C gene products). However, the "molecular switch" that determines whether a pentamer or a hexamer would form, was left undefined.
It appears that after dimerization, hexamers are responsible for initiating capsid self-assembly. The authors propose that the hexamers form nucleation sites for particle formation, and "that there are probably no pentamers in in solution. It is likely that they only form during the assembly process." <ref name=Speir>PMID:7743132</ref> The basis for the additional hexamer stability comes from the relative number of stabilizing interactions within each capsomere.<ref name=Speir>PMID:7743132</ref> The hexamers have an interlaced beta barrel structure at their amino terminus, whereas pentamers form an unordered amino terminus cluster.

'''Conclusion'''

Cowpea Chlorotic Mottle Virus is used in many actively researched fields. It provides a readily manipulatable construct for nanoreactors and synthesis scaffolds without a significant biosafety risk for experimenters.

<ref name=Speir>PMID:7743132</ref>
{{Reflist}}

Cowpea Chlorotic Mottle Virus

2011-12-01T11:46:27Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

<Structure load='1CWP' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />

===Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis===
<scene name='Cowpea_Chlorotic_Mottle_Virus/Full_capsid/2'>Assembled Capsid</scene>

'''Introduction'''

The cowpea chlorotic mottle virus is a plant virus that infects the cowpea plant. It is a naked (non-enveloped), icosahedral virus, and it contains a positive-sense RNA genome. Therefore, its encapsidated nucleic acids can be directly translated by host machinery to make the protein components for progeny virions. Its replication strategy requires the formation of a negative-sense template that can be used to synthesize new positive-sense RNA.

An intriguing feature of virus is its ability to undergo a major structural change without destroying the tertiary structure of its subunits under certain environmental conditions. Specifically, when conditions are acidic (pH 5) the capsid is in a stable, assembled form. However, when the pH is raised ~6.5-7 or placed into solution of low ionic strength, the capsid undergoes a concerted structural change called swelling. <ref name=Speir>PMID:7743132</ref>
During this process, 60 pores (2 nanometers in diameter) open along the threefold axis of the capsid, and the size of the virion swells to an increased volume of 10%. Although the capsid expands, the RNA to protein ratio remains constant. The formation of these pores makes it possible for molecules to exit and enter the capsid, allowing this structure to function as a nano-reactor.
Furthermore, if the pH is increased to 7.5, the particles will completely dissociate into dimer subunits.

'''Significance and Applications of CCMV Structural Transitions '''

In the field of virology, CCMV is relevant to mammalian research due to the similarity of structural transitions in human polio virus, of the picornaviridae family<ref name=Speir>PMID:7743132</ref>
(another naked icosahedral virus).

More influentially, the properties of the capsid allow the virus to be exploited in nanotechnology. Capsid proteins can be obtained through two main strategies.
First, virus can be directly extracted from plant leaves in high yields (1 kg of infected plant tissue can yield 1–2 g of virus<ref name=Liepold>PMID:Liepold16280622</ref>). By raising the pH to 7.5 and dissociating the capsid into dimers, the protein can be isolated from the RNA. The purified proteins can then self-assemble into functional virus-like particles when restored to more acidic conditions.

A more modern strategy involves the use of recombinant DNA technology. In this approach, the capsid-encoding genes of the virus can be transfected into a yeast expression vector.<ref name=Liepold>PMID:Liepold16280622</ref>) As the yeast replicate, they amplify the number of protein producing units, and the secreted protein products can be readily collected from the media. The major benefit to this method, aside from high yield production, is that the genome can be modified prior to insertion into the vector. This can be used to produce capsid subunits with differing chemical properties. Such a procedure was performed by Dr. J. J. L. M. Cornelissen in the Netherlands. He attempted to solve the problem of pH sensitivity in reactants, particularly enzymes, and the acidic conditions required for capsid stability. It was found that nickel atoms could stabilize the capsid at pH 7.5. This was a promising alternative to the large polyelectrolytes that were used to stabilize the capsid because they often filled the capsid and limited reagent concentration.

Histidine residues were able to readily coordinate with nickel, and this property was used to purify the modified proteins from the media of their expression vectors. This purification was performed with a column of nickel atoms immobilized to a resin enriched with a metal chelating agent (NTA). Once the proteins were isolated, a experimental, pH-sensitive, protein (EGFP) was coupled with the capsomeres.<ref name=Liepold>PMID:Liepold16280622</ref>)

The metal ion induced stabilization was likely due to a different mechanism than older polyelectrolyte methods since the metal ions are substantially smaller than polyelectrolytes, and they are positively charged.<ref name=Liepold>PMID:Liepold16280622</ref>)

The field of nanovirology using these cage structures has branched into both biomedical sciences and physical virology. In particular, CCMV capsids have been investigated as a drug delivery vessels, and scaffolds for highly ordered crystal growth. Scaffold synthesis in other viral systems has enabled the production of quantum dots used as fluorescent dyes in biotechnology.

<scene name='Cowpea_Chlorotic_Mottle_Virus/Isolated_rna/1'>Isolated RNA</scene>

'''General Capsid Structure'''

The viral capsid of CCMV is a complex of proteins stabilized by metal coordination between capsomeres and RNA binding on its internal surface.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Protein_and_rna/1'>Protein Core with Stabilizing RNA Interactions</scene>
The viral genome encodes three capsid proteins that are chemically identical. These subunits, arbitrarily called A, B, and C, dimerize with each other and assemble into into hexamers and pentamers that comprise the viral capsomeres.<ref name=Speir>PMID:7743132</ref> The complete capsid structure takes the form of a truncated icosahedron. It is described as a T=3 capsid, where the T value describes the number of structural units per equilateral face of the icosahedron.[http://www.nlv.ch/Virologytutorials/Structure.htm]

'''Capsomere Structure'''

The hexameric capsomeres are formed by the B and C subunits. The N-terminus arms (residues 27 through 49) of the subunits intertwine to form a parallel beta barrel.<ref name=Speir>PMID:7743132</ref> The N-terminus is therefore key to the hexamer composition.<ref name=Speir>PMID:7743132</ref>
<scene name='Cowpea_Chlorotic_Mottle_Virus/Residues_27-49/1'>N-terminus arms</scene>
The atoms of residues 27-49 are colored blue for clarity.

Residues 29-33 line the channel created at the center of the hexamers and stabilize the subunits with the interactions of their side chains and adjacent residues. For example, the "side chain oxygens of Gln29 residues hydrogen bond with the main chain nitrogens of adjacent Gln29 residues, making a circular ring of interactions" and the "valine residues stack upon one another inside the the beta-tube forming a circle of hydrophobic bonds."<ref name=Speir>PMID:7743132</ref> The hydrophobic valine side chain atoms are protected from the interior of the virus by the side chain atoms of the glutamine residue, and they are surrounded by the hydrogen bonding environment of the beta barrels.<ref name=Speir>PMID:7743132</ref>

In the <scene name='Cowpea_Chlorotic_Mottle_Virus/Interior_of_beta_barrel/1'>interior of beta barrel</scene> we can see these residues filling the channel formed at the center of the capsomere: glutamine 29 (in red), valine 31 (in orange), and valine 33 (in green).

Pentamer capsomeres, on the other hand, are formed exclusively from the contribution of A subunit chains.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Pentamer/1'>Pentamer capsomeres</scene> also have amino-terminus arms that extend into the interior of the capsid, however, unlike the hexameric barrel structures, the amino terminus is unordered.The positively charged Lys 42 residue is colored in blue as a marker for the arms of the N-terminus. Residues before Lys42 do not have detectable electron density for the techniques used to render the structure.

Interestingly, although the subunits are chemically identical, hexamer formation predominates in the capsid. In 1962 Caspar and Klug predicted a classical model for a perfect icosahedral structure- one that would have "a sheet of hexamers interspersed with 12 pentamers arranged to form a closed shell with icosahedral symmetry." In this geometrical shape, the number of pentamers is constrained to 12, a structure with greater than 60 subunits, however, must be accounted for by an increased number of hexamers. For viruses, a perfect 60-faced icosahedron would severely limit genome packaging.[http://www.nlv.ch/Virologytutorials/Structure.htm]

Prior to the characterization of CCMV's structure, no RNA viruses (in plants and insects) were found to rigorously observe this model. Their prediction necessitated that the pentamer and hexamer subunits would from a single chemical structure (realized in CCMV due to its identical A,B, and C gene products). However, the "molecular switch" that determines whether a pentamer or a hexamer would form, was left undefined.
It appears that after dimerization, hexamers are responsible for initiating capsid self-assembly. The authors propose that the hexamers form nucleation sites for particle formation, and "that there are probably no pentamers in in solution. It is likely that they only form during the assembly process." <ref name=Speir>PMID:7743132</ref> The basis for the additional hexamer stability comes from the relative number of stabilizing interactions within each capsomere.<ref name=Speir>PMID:7743132</ref> The hexamers have an interlaced beta barrel structure at their amino terminus, whereas pentamers form an unordered amino terminus cluster.

'''Conclusion'''

Cowpea Chlorotic Mottle Virus is used in many actively researched fields. It provides a readily manipulatable construct for nanoreactors and synthesis scaffolds without a significant biosafety risk for experimenters.

<ref name=Speir>PMID:7743132</ref>
{{Reflist}}

Cowpea Chlorotic Mottle Virus

2011-12-01T11:37:02Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

<Structure load='1CWP' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />

===Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis===
<scene name='Cowpea_Chlorotic_Mottle_Virus/Full_capsid/2'>Assembled Capsid</scene>

'''Introduction'''

The cowpea chlorotic mottle virus is a plant virus that infects the cowpea plant. It is a naked (non-enveloped), icosahedral virus, and it contains a positive-sense RNA genome. Therefore, its encapsidated nucleic acids can be directly translated by host machinery to make the protein components for progeny virions. Its replication strategy requires the formation of a negative-sense template that can be used to synthesize new positive-sense RNA.

An intriguing feature of virus is its ability to undergo a major structural change without destroying the tertiary structure of its subunits under certain environmental conditions. Specifically, when conditions are acidic (pH 5) the capsid is in a stable, assembled form. However, when the pH is raised ~6.5-7 or placed into solution of low ionic strength, the capsid undergoes a concerted structural change called swelling. <ref name=Speir>PMID:7743132</ref>
During this process, 60 pores (2 nanometers in diameter) open along the threefold axis of the capsid, and the size of the virion swells to an increased volume of 10%. Although the capsid expands, the RNA to protein ratio remains constant. The formation of these pores makes it possible for molecules to exit and enter the capsid, allowing this structure to function as a nano-reactor.
Furthermore, if the pH is increased to 7.5, the particles will completely dissociate into dimer subunits.

'''Significance and Applications of CCMV Structural Transitions '''

In the field of virology, CCMV is relevant to mammalian research due to the similarity of structural transitions in human polio virus, of the picornaviridae family<ref name=Speir>PMID:7743132</ref>
(another naked icosahedral virus).

More influentially, the properties of the capsid allow the virus to be exploited in nanotechnology. Capsid proteins can be obtained through two main strategies.
First, virus can be directly extracted from plant leaves in high yields (1 kg of infected plant tissue can yield 1–2 g of virus<ref name=Liepold>PMID:Liepold16280622</ref>). By raising the pH to 7.5 and dissociating the capsid into dimers, the protein can be isolated from the RNA. The purified proteins can then self-assemble into functional virus-like particles when restored to more acidic conditions.

A more modern strategy involves the use of recombinant DNA technology. In this approach, the capsid-encoding genes of the virus can be transfected into a yeast expression vector.<ref name=Liepold>PMID:Liepold16280622</ref>) As the yeast replicate, they amplify the number of protein producing units, and the secreted protein products can be readily collected from the media. The major benefit to this method, aside from high yield production, is that the genome can be modified prior to insertion into the vector. This can be used to produce capsid subunits with differing chemical properties. Such a procedure was performed by Dr. J. J. L. M. Cornelissen in the Netherlands. He attempted to solve the problem of pH sensitivity in reactants, particularly enzymes, and the acidic conditions required for capsid stability. It was found that nickel atoms could stabilize the capsid at pH 7.5. This was a promising alternative to the large polyelectrolytes that were used to stabilize the capsid because they often filled the capsid and limited reagent concentration.

Histidine residues were able to readily coordinate with nickel, and this property was used to purify the modified proteins from the media of their expression vectors. This purification was performed with a column of nickel atoms immobilized to a resin enriched with a metal chelating agent (NTA). Once the proteins were isolated, a experimental, pH-sensitive, protein (EGFP) was coupled with the capsomeres.<ref name=Liepold>PMID:Liepold16280622</ref>)

The metal ion induced stabilization was likely due to a different mechanism than older polyelectrolyte methods since the metal ions are substantially smaller than polyelectrolytes, and they are positively charged.<ref name=Liepold>PMID:Liepold16280622</ref>)

The field of nanovirology using these cage structures has branched into both biomedical sciences and physical virology. In particular, CCMV capsids have been investigated as a drug delivery vessels, and scaffolds for highly ordered crystal growth. Scaffold synthesis in other viral systems has enabled the production of quantum dots used as fluorescent dyes in biotechnology.

<scene name='Cowpea_Chlorotic_Mottle_Virus/Isolated_rna/1'>Isolated RNA</scene>

'''General Capsid Structure'''

The viral capsid of CCMV is a complex of proteins stabilized by metal coordination between capsomeres and RNA binding on its internal surface.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Protein_and_rna/1'>Protein Core with Stabilizing RNA Interactions</scene>
The viral genome encodes three capsid proteins that are chemically identical. These subunits, arbitrarily called A, B, and C, dimerize with each other and assemble into into hexamers and pentamers that comprise the viral capsomeres.<ref name=Speir>PMID:7743132</ref> The complete capsid structure takes the form of a truncated icosahedron. It is described as a T=3 capsid, where the T value describes the number of structural units per equilateral face of the icosahedron.[http://www.nlv.ch/Virologytutorials/Structure.htm]

'''Capsomere Structure'''

The hexameric capsomeres are formed by the B and C subunits. The N-terminus arms (residues 27 through 49) of the subunits intertwine to form a parallel beta barrel.<ref name=Speir>PMID:7743132</ref> The N-terminus is therefore key to the hexamer composition.<ref name=Speir>PMID:7743132</ref>
<scene name='Cowpea_Chlorotic_Mottle_Virus/Residues_27-49/1'>N-terminus arms</scene>
The atoms of residues 27-49 are colored blue for clarity.

Residues 29-33 line the channel created at the center of the hexamers and stabilize the subunits with the interactions of their side chains and adjacent residues. For example, the "side chain oxygens of Gln29 residues hydrogen bond with the main chain nitrogens of adjacent Gln29 residues, making a circular ring of interactions" and the "valine residues stack upon one another inside the the beta-tube forming a circle of hydrophobic bonds."<ref name=Speir>PMID:7743132</ref> The hydrophobic valine side chain atoms are protected from the interior of the virus by the side chain atoms of the glutamine residue, and they are surrounded by the hydrogen bonding environment of the beta barrels.<ref name=Speir>PMID:7743132</ref>

In the <scene name='Cowpea_Chlorotic_Mottle_Virus/Interior_of_beta_barrel/1'>interior of beta barrel</scene> we can see these residues filling the channel formed at the center of the capsomere: glutamine 29 (in red), valine 31 (in orange), and valine 33 (in green).

Pentamer capsomeres, on the other hand, are formed exclusively from the contribution of A subunit chains.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Pentamer/1'>Pentamer capsomeres</scene> also have amino-terminus arms that extend into the interior of the capsid, however, unlike the hexameric barrel structures, the amino terminus is unordered.The positively charged Lys 42 residue is colored in blue as a marker for the arms of the N-terminus. Residues before Lys42 do not have detectable electron density for the techniques used to render the structure.

Interestingly, although the subunits are chemically identical, hexamer formation predominates in the capsid. In 1962 Caspar and Klug predicted a classical model for a perfect icosahedral structure- one that would have "a sheet of hexamers interspersed with 12 pentamers arranged to form a closed shell with icosahedral symmetry." In this geometrical shape, the number of pentamers is constrained to 12, a structure with greater than 60 faces must be accounted for by an increased number of hexamers. For viruses, a perfect 60-faced icosahedron would severely limit genome packaging.[http://www.nlv.ch/Virologytutorials/Structure.htm]

Prior to the characterization of CCMV's structure, no RNA viruses (in plants and insects) were found to rigorously observe this model. Their prediction necessitated that the pentamer and hexamer subunits would from a single chemical structure (realized in CCMV due to its identical A,B, and C gene products). However, the "molecular switch" that determines whether a pentamer or a hexamer would form, was left undefined.
It appears that after dimerization, hexamers are responsible for initiating capsid self-assembly. The authors propose that the hexamers form nucleation sites for particle formation, and "that there are probably no pentamers in in solution. It is likely that they only form during the assembly process." <ref name=Speir>PMID:7743132</ref> The basis for the additional hexamer stability comes from the relative number of stabilizing interactions within each capsomere.<ref name=Speir>PMID:7743132</ref> The hexamers have an interlaced beta barrel structure at their amino terminus, whereas pentamers form an unordered amino terminus cluster.

'''Conclusion'''

Cowpea Chlorotic Mottle Virus is used in many actively researched fields. It provides a readily manipulatable construct for nanoreactors and synthesis scaffolds without a significant biosafety risk for experimenters.

<ref name=Speir>PMID:7743132</ref>
{{Reflist}}

Cowpea Chlorotic Mottle Virus

2011-12-01T10:50:35Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

<Structure load='1CWP' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />

===Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis===
<scene name='Cowpea_Chlorotic_Mottle_Virus/Full_capsid/2'>Assembled Capsid</scene>

'''Introduction'''

The cowpea chlorotic mottle virus is a plant virus that infects the cowpea plant. It is a naked (non-enveloped), icosahedral virus, and it contains a positive-sense RNA genome. Therefore, its encapsidated nucleic acids can be directly translated by host machinery to make the protein components for progeny virions. Its replication strategy requires the formation of a negative-sense template that can be used to synthesize new positive-sense RNA.

An intriguing feature of virus is its ability to undergo a major structural change without destroying the tertiary structure of its subunits under certain environmental conditions. Specifically, when conditions are acidic (pH 5) the capsid is in a stable, assembled form. However, when the pH is raised ~6.5-7 or placed into solution of low ionic strength, the capsid undergoes a concerted structural change called swelling. <ref name=Speir>PMID:7743132</ref>
During this process, 60 pores (2 nanometers in diameter) open along the threefold axis of the capsid, and the size of the virion swells to an increased volume of 10%. Although the capsid expands, the RNA to protein ratio remains constant. The formation of these pores makes it possible for molecules to exit and enter the capsid, allowing this structure to function as a nano-reactor.
Furthermore, if the pH is increased to 7.5, the particles will completely dissociate into dimer subunits.

'''Significance and Applications of CCMV Structural Transitions '''

In the field of virology, CCMV is relevant to mammalian research due to the similarity of structural transitions in human polio virus, of the picornaviridae family<ref name=Speir>PMID:7743132</ref>
(another naked icosahedral virus).

More influentially, the properties of the capsid allow the virus to be exploited in nanotechnology. Capsid proteins can be obtained through two main strategies.
First, virus can be directly extracted from plant leaves in high yields (1 kg of infected plant tissue can yield 1–2 g of virus<ref name=Liepold>PMID:Liepold16280622</ref>). By raising the pH to 7.5 and dissociating the capsid into dimers, the protein can be isolated from the RNA. The purified proteins can then self-assemble into functional virus-like particles when restored to more acidic conditions.

A more modern strategy involves the use of recombinant DNA technology. In this approach, the capsid-encoding genes of the virus can be transfected into a yeast expression vector.<ref name=Liepold>PMID:Liepold16280622</ref>) As the yeast replicate, they amplify the number of protein producing units, and the secreted protein products can be readily collected from the media. The major benefit to this method, aside from high yield production, is that the genome can be modified prior to insertion into the vector. This can be used to produce capsid subunits with differing chemical properties. Such a procedure was performed by Dr. J. J. L. M. Cornelissen in the Netherlands. He attempted to solve the problem of pH sensitivity in reactants, particularly enzymes, and the acidic conditions required for capsid stability. It was found that nickel atoms could stabilize the capsid at pH 7.5. This was a promising alternative to the large polyelectrolytes that were used to stabilize the capsid because they often filled the capsid and limited reagent concentration.

Histidine residues were able to readily coordinate with nickel, and this property was used to purify the modified proteins from the media of their expression vectors. This purification was performed with a column of nickel atoms immobilized to a resin enriched with a metal chelating agent (NTA). Once the proteins were isolated, a experimental, pH-sensitive, protein (EGFP) was coupled with the capsomeres.<ref name=Liepold>PMID:Liepold16280622</ref>)

The metal ion induced stabilization was likely due to a different mechanism than older polyelectrolyte methods since the metal ions are substantially smaller than polyelectrolytes, and they are positively charged.<ref name=Liepold>PMID:Liepold16280622</ref>)

The field of nanovirology using these cage structures has branched into both biomedical sciences and physical virology. In particular, CCMV capsids have been investigated as a drug delivery vessels, and scaffolds for highly ordered crystal growth. Scaffold synthesis in other viral systems has enabled the production of quantum dots used as fluorescent dyes in biotechnology.

<scene name='Cowpea_Chlorotic_Mottle_Virus/Isolated_rna/1'>Isolated RNA</scene>

'''General Capsid Structure'''

The viral capsid of CCMV is a complex of proteins stabilized by metal coordination between capsomeres and RNA binding on its internal surface.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Protein_and_rna/1'>Protein Core with Stabilizing RNA Interactions</scene>
The viral genome encodes three capsid proteins that are chemically identical. These subunits, arbitrarily called A, B, and C, dimerize with each other and assemble into into hexamers and pentamers that comprise the viral capsomeres.<ref name=Speir>PMID:7743132</ref> The complete capsid structure takes the form of a truncated icosahedron (20 faces). It is described as a T=3 capsid, where the T value describes the number of structural units per equilateral face of the icosahedron.[http://www.nlv.ch/Virologytutorials/Structure.htm]

'''Capsomere Structure'''

The hexameric capsomeres are formed by the B and C subunits. The N-terminus arms (residues 27 through 49) of the subunits intertwine to form a parallel beta barrel.<ref name=Speir>PMID:7743132</ref> The N-terminus is therefore key to the hexamer composition.<ref name=Speir>PMID:7743132</ref>
<scene name='Cowpea_Chlorotic_Mottle_Virus/Residues_27-49/1'>N-terminus arms</scene>
The atoms of residues 27-49 are colored blue for clarity.

Residues 29-33 line the channel created at the center of the hexamers and stabilize the subunits with the interactions of their side chains and adjacent residues. For example, the "side chain oxygens of Gln29 residues hydrogen bond with the main chain nitrogens of adjacent Gln29 residues, making a circular ring of interactions" and the "valine residues stack upon one another inside the the beta-tube forming a circle of hydrophobic bonds."<ref name=Speir>PMID:7743132</ref> The hydrophobic valine side chain atoms are protected from the interior of the virus by the side chain atoms of the glutamine residue, and they are surrounded by the hydrogen bonding environment of the beta barrels.<ref name=Speir>PMID:7743132</ref>

In the <scene name='Cowpea_Chlorotic_Mottle_Virus/Interior_of_beta_barrel/1'>interior of beta barrel</scene> we can see these residues filling the channel formed at the center of the capsomere: glutamine 29 (in red), valine 31 (in orange), and valine 33 (in green).

Pentamer capsomeres, on the other hand, are formed exclusively from the contribution of A subunit chains.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Pentamer/1'>Pentamer capsomeres</scene> also have amino-terminus arms that extend into the interior of the capsid, however, unlike the hexameric barrel structures, the amino terminus is unordered.The positively charged Lys 42 residue is colored in blue as a marker for the arms of the N-terminus. Residues before Lys42 do not have detectable electron density for the techniques used to render the structure.

Interestingly, although the subunits are chemically identical, hexamer formation predominates in the capsid. In 1962 Caspar and Klug predicted a classical model for a perfect icosahedral structure- one that would have "a sheet of hexamers interspersed with 12 pentamers arranged to form a closed shell with icosahedral symmetry." In this geometrical shape, the number of pentamers is constrained to 12, a structure with greater than 60 faces must be accounted for by an increased number of hexamers. For viruses, a perfect 60-faced icosahedron would severely limit genome packaging.[http://www.nlv.ch/Virologytutorials/Structure.htm]

Prior to the characterization of CCMV's structure, no RNA viruses (in plants and insects) were found to rigorously observe this model. Their prediction necessitated that the pentamer and hexamer subunits would from a single chemical structure (realized in CCMV due to its identical A,B, and C gene products). However, the "molecular switch" that determines whether a pentamer or a hexamer would form, was left undefined.
It appears that after dimerization, hexamers are responsible for initiating capsid self-assembly. The authors propose that the hexamers form nucleation sites for particle formation, and "that there are probably no pentamers in in solution. It is likely that they only form during the assembly process." <ref name=Speir>PMID:7743132</ref> The basis for the additional hexamer stability comes from the relative number of stabilizing interactions within each capsomere.<ref name=Speir>PMID:7743132</ref> The hexamers have an interlaced beta barrel structure at their amino terminus, whereas pentamers form an unordered amino terminus cluster.

'''Conclusion'''

Cowpea Chlorotic Mottle Virus is used in many actively researched fields. It provides a readily manipulatable construct for nanoreactors and synthesis scaffolds without a significant biosafety risk for experimenters.

<ref name=Speir>PMID:7743132</ref>
{{Reflist}}

Cowpea Chlorotic Mottle Virus

2011-12-01T10:10:31Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

<Structure load='1CWP' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />

===Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis===
<scene name='Cowpea_Chlorotic_Mottle_Virus/Full_capsid/2'>Assembled Capsid</scene>

'''Introduction'''

The cowpea chlorotic mottle virus is a plant virus that infects the cowpea plant. It is a naked (non-enveloped), icosahedral virus, and it contains a positive-sense RNA genome. Therefore, its encapsidated nucleic acids can be directly translated by host machinery to make the protein components for progeny virions. Its replication strategy requires the formation of a negative-sense template that can be used to synthesize new positive-sense RNA.

An intriguing feature of virus is its ability to undergo a major structural change without destroying the tertiary structure of its subunits under certain environmental conditions. Specifically, when conditions are acidic (pH 5) the capsid is in a stable, assembled form. However, when the pH is raised ~6.5-7 or placed into solution of low ionic strength, the capsid undergoes a concerted structural change called swelling. <ref name=Speir>PMID:7743132</ref>
During this process, 60 pores (2 nanometers in diameter) open along the threefold axis of the capsid, and the size of the virion swells to an increased volume of 10%. Although the capsid expands, the RNA to protein ratio remains constant. The formation of these pores makes it possible for molecules to exit and enter the capsid, allowing this structure to function as a nano-reactor.
Furthermore, if the pH is increased to 7.5, the particles will completely dissociate into dimer subunits.

'''Significance and Applications of CCMV Structural Transitions '''

In the field of virology, CCMV is relevant to mammalian research due to the similarity of structural transitions in human polio virus, of the picornaviridae family<ref name=Speir>PMID:7743132</ref>
(another naked icosahedral virus).

More influentially, the properties of the capsid allow the virus to be exploited in nanotechnology. Capsid proteins can be obtained through two main strategies.
First, virus can be directly extracted from plant leaves in high yields (1 kg of infected plant tissue can yield 1–2 g of virus<ref name=Liepold>PMID:Liepold16280622</ref>). By raising the pH to 7.5 and dissociating the capsid into dimers, the protein can be isolated from the RNA. The purified proteins can then self-assemble into functional virus-like particles when restored to more acidic conditions.

A more modern strategy involves the use of recombinant DNA technology. In this approach, the capsid-encoding genes of the virus can be transfected into a yeast expression vector.<ref name=Liepold>PMID:Liepold16280622</ref>) As the yeast replicate, they amplify the number of protein producing units, and the secreted protein products can be readily collected from the media. The major benefit to this method, aside from high yield production, is that the genome can be modified prior to insertion into the vector. This can be used to produce capsid subunits with differing chemical properties. Such a procedure was performed by Dr. J. J. L. M. Cornelissen in the Netherlands. He attempted to solve the problem of pH sensitivity in reactants, particularly enzymes, and the acidic conditions required for capsid stability. It was found that nickel atoms could stabilize the capsid at pH 7.5. This was a promising alternative to the large polyelectrolytes that were used to stabilize the capsid because they often filled the capsid and limited reagent concentration.

Histidine residues were able to readily coordinate with nickel, and this property was used to purify the modified proteins from the media of their expression vectors. This purification was performed with a column of nickel atoms immobilized to a resin enriched with a metal chelating agent (NTA). Once the proteins were isolated, a experimental, pH-sensitive, protein (EGFP) was coupled with the capsomeres.

The metal ion induced stabilization was likely due to a different mechanism than older polyelectrolyte methods since the metal ions are substantially smaller than polyelectrolytes, and they are positively charged.

The field of nanovirology using these cage structures has branched into both biomedical sciences and physical virology.

<scene name='Cowpea_Chlorotic_Mottle_Virus/Isolated_rna/1'>Isolated RNA</scene>

'''General Capsid Structure'''

The viral capsid of CCMV is a complex of proteins stabilized by metal coordination between capsomeres and RNA binding on its internal surface.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Protein_and_rna/1'>Protein Core with Stabilizing RNA Interactions</scene>
The viral genome encodes three capsid proteins that are chemically identical. These subunits, arbitrarily called A, B, and C, dimerize with each other and assemble into into hexamers and pentamers that comprise the viral capsomeres.<ref name=Speir>PMID:7743132</ref> The complete capsid structure takes the form of a truncated icosahedron (20 faces). It is described as a T=3 capsid, where the T value describes the number of structural units per equilateral face of the icosahedron.[http://www.nlv.ch/Virologytutorials/Structure.htm]

'''Capsomere Structure'''

The hexameric capsomeres are formed by the B and C subunits. The N-terminus arms (residues 27 through 49) of the subunits intertwine to form a parallel beta barrel.<ref name=Speir>PMID:7743132</ref> The N-terminus is therefore key to the hexamer composition.<ref name=Speir>PMID:7743132</ref>
<scene name='Cowpea_Chlorotic_Mottle_Virus/Residues_27-49/1'>N-terminus arms</scene>
The atoms of residues 27-49 are colored blue for clarity.

Residues 29-33 line the channel created at the center of the hexamers and stabilize the subunits with the interactions of their side chains and adjacent residues. For example, the "side chain oxygens of Gln29 residues hydrogen bond with the main chain nitrogens of adjacent Gln29 residues, making a circular ring of interactions" and the "valine residues stack upon one another inside the the beta-tube forming a circle of hydrophobic bonds."<ref name=Speir>PMID:7743132</ref> The hydrophobic valine side chain atoms are protected from the interior of the virus by the side chain atoms of the glutamine residue, and they are surrounded by the hydrogen bonding environment of the beta barrels.<ref name=Speir>PMID:7743132</ref>

In the <scene name='Cowpea_Chlorotic_Mottle_Virus/Interior_of_beta_barrel/1'>interior of beta barrel</scene> we can see these residues filling the channel formed at the center of the capsomere: glutamine 29 (in red), valine 31 (in orange), and valine 33 (in green).

Pentamer capsomeres, on the other hand, are formed exclusively from the contribution of A subunit chains.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Pentamer/1'>Pentamer capsomeres</scene> also have amino-terminus arms that extend into the interior of the capsid, however, unlike the hexameric barrel structures, the amino terminus is unordered.The positively charged Lys 42 residue is colored in blue as a marker for the arms of the N-terminus. Residues before Lys42 do not have detectable electron density for the techniques used to render the structure.

Interestingly, although the subunits are chemically identical, hexamer formation predominates in the capsid. In 1962 Caspar and Klug predicted a classical model for a perfect icosahedral structure- one that would have "a sheet of hexamers interspersed with 12 pentamers arranged to form a closed shell with icosahedral symmetry." In this geometrical shape, the number of pentamers is constrained to 12, a structure with greater than 60 faces must be accounted for by an increased number of hexamers. For viruses, a perfect 60-faced icosahedron would severely limit genome packaging.[http://www.nlv.ch/Virologytutorials/Structure.htm]

Prior to the characterization of CCMV's structure, no RNA viruses (in plants and insects) were found to rigorously observe this model. Their prediction necessitated that the pentamer and hexamer subunits would from a single chemical structure (realized in CCMV due to its identical A,B, and C gene products). However, the "molecular switch" that determines whether a pentamer or a hexamer would form, was left undefined.
It appears that after dimer formation, hexamers predominate in solution. The authors propose that the hexamers then form nucleation sites for particle formation. The basis for the additional hexamer stability comes from the relative number of interactions between molecules.

<ref name=Speir>PMID:7743132</ref>
{{Reflist}}

Cowpea Chlorotic Mottle Virus

2011-12-01T06:58:34Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

<Structure load='1CWP' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />

===Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis===
<scene name='Cowpea_Chlorotic_Mottle_Virus/Full_capsid/2'>Assembled Capsid</scene>

'''Introduction'''

The cowpea chlorotic mottle virus is a plant virus that infects the cowpea plant. It is a naked (non-enveloped), icosahedral virus, and it contains a positive-sense RNA genome. Therefore, its encapsidated nucleic acids can be directly translated by host machinery to make the protein components for progeny virions. Its replication strategy requires the formation of a negative-sense template that can be used to synthesize new positive-sense RNA.

An intriguing feature of virus is its ability to undergo a major structural change without destroying the tertiary structure of its subunits under certain environmental conditions. Specifically, when conditions are acidic (pH 5) the capsid is in a stable, assembled form. However, when the pH is raised ~6.5-7 or placed into solution of low ionic strength, the capsid undergoes a concerted structural change called swelling. <ref name=Speir>PMID:7743132</ref>
During this process, 60 pores (2 nanometers in diameter) open along the threefold axis of the capsid, and the size of the virion swells to an increased volume of 10%. Although the capsid expands, the RNA to protein ratio remains constant. The formation of these pores makes it possible for molecules to exit and enter the capsid, allowing this structure to function as a nano-reactor.
Furthermore, if the pH is increased to 7.5, the particles will completely dissociate into dimer subunits.

'''Significance of Structural Transitions '''

CCMV is relevant to mammalian virology due to the similarity of structural transitions in human polio virus, of the picornaviridae family<ref name=Speir>PMID:7743132</ref>
(another naked icosahedral virus).

Of greater significance, the properties of the capsid allow the virus to be exploited in nanotechnology. Capsid proteins can be obtained through two main strategies.
First, virus can be directly extracted from plant leaves in high yields (1 kg of infected plant tissue can yield 1–2 g of virus<ref name=Liepold>PMID:Liepold16280622</ref>). By raising the pH to 7.5 and dissociating the capsid into dimers, the protein can be isolated from the RNA. The purified proteins can then self-assemble into functional virus-like particles when restored to more acidic conditions.

A more modern strategy involves the use of recombinant DNA technology. In this approach, the capsid-encoding genes of the virus can be transfected into a yeast expression vector.<ref name=Liepold>PMID:Liepold16280622</ref>) As the yeast replicate, they amplify the number of protein producing units, and the secreted protein products can be readily collected from the media. The major benefit to this method, aside from high yield production, is that the genome can be modified prior to insertion into the vector. This can allow the capsid subunits to take on differing chemical properties. This is best exemplified by the research of Prof. J. J. L. M. Cornelissen in the Netherlands. His group added a His-tag to N-termini of the capsomeres, allowing them to

<scene name='Cowpea_Chlorotic_Mottle_Virus/Isolated_rna/1'>Isolated RNA</scene>

'''General Capsid Structure'''

The viral capsid of CCMV is a complex of proteins stabilized by metal coordination between capsomeres and RNA binding on its internal surface.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Protein_and_rna/1'>Protein Core with Stabilizing RNA Interactions</scene>
The viral genome encodes three capsid proteins that are chemically identical. These subunits, arbitrarily called A, B, and C, dimerize with each other and assemble into into hexamers and pentamers that comprise the viral capsomeres.<ref name=Speir>PMID:7743132</ref> The complete capsid structure takes the form of a truncated icosahedron (20 faces). It is described as a T=3 capsid, where the T value describes the number of structural units per equilateral face of the icosahedron.[http://www.nlv.ch/Virologytutorials/Structure.htm]

'''Capsomere Structure'''

The hexameric capsomeres are formed by the B and C subunits. The N-terminus arms (residues 27 through 49) of the subunits intertwine to form a parallel beta barrel.<ref name=Speir>PMID:7743132</ref> The N-terminus is therefore key to the hexamer composition.<ref name=Speir>PMID:7743132</ref>
<scene name='Cowpea_Chlorotic_Mottle_Virus/Residues_27-49/1'>N-terminus arms</scene>
The atoms of residues 27-49 are colored blue for clarity.

Residues 29-33 line the channel created at the center of the hexamers and stabilize the subunits with the interactions of their side chains and adjacent residues. For example, the "side chain oxygens of Gln29 residues hydrogen bond with the main chain nitrogens of adjacent Gln29 residues, making a circular ring of interactions" and the "valine residues stack upon one another inside the the beta-tube forming a circle of hydrophobic bonds."<ref name=Speir>PMID:7743132</ref> The hydrophobic valine side chain atoms are protected from the interior of the virus by the side chain atoms of the glutamine residue, and they are surrounded by the hydrogen bonding environment of the beta barrels.<ref name=Speir>PMID:7743132</ref>

In the <scene name='Cowpea_Chlorotic_Mottle_Virus/Interior_of_beta_barrel/1'>interior of beta barrel</scene> we can see these residues filling the channel formed at the center of the capsomere: glutamine 29 (in red), valine 31 (in orange), and valine 33 (in green).

Pentamer capsomeres, on the other hand, are formed exclusively from the contribution of A subunit chains.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Pentamer/1'>Pentamer capsomeres</scene> also have amino-terminus arms that extend into the interior of the capsid, however, unlike the hexameric barrel structures, the amino terminus is unordered.The positively charged Lys 42 residue is colored in blue as a marker for the arms of the N-terminus. Residues before Lys42 do not have detectable electron density for the techniques used to render the structure.

Interestingly, although the subunits are chemically identical, hexamer formation predominates in the capsid. In 1962 Caspar and Klug predicted a classical model for a perfect icosahedral structure- one that would have "a sheet of hexamers interspersed with 12 pentamers arranged to form a closed shell with icosahedral symmetry." In this geometrical shape, the number of pentamers is constrained to 12, a structure with greater than 60 faces must be accounted for by an increased number of hexamers. For viruses, a perfect 60-faced icosahedron would severely limit genome packaging.[http://www.nlv.ch/Virologytutorials/Structure.htm]

Prior to the characterization of CCMV's structure, no RNA viruses (in plants and insects) were found to rigorously observe this model. Their prediction necessitated that the pentamer and hexamer subunits would from a single chemical structure (realized in CCMV due to its identical A,B, and C gene products). However, the "molecular switch" that determines whether a pentamer or a hexamer would form, was left undefined.
It appears that after dimer formation, hexamers predominate in solution. The authors propose that the hexamers then form nucleation sites for particle formation. The basis for the additional hexamer stability comes from the relative number of interactions between molecules.

<ref name=Speir>PMID:7743132</ref>
{{Reflist}}

Cowpea Chlorotic Mottle Virus

2011-12-01T06:48:39Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

<Structure load='1CWP' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />

===Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis===
<scene name='Cowpea_Chlorotic_Mottle_Virus/Full_capsid/2'>Assembled Capsid</scene>

'''Introduction'''

The cowpea chlorotic mottle virus is a plant virus that infects the cowpea plant. It is a naked (non-enveloped), icosahedral virus, and it contains a positive-sense RNA genome. Therefore, its encapsidated nucleic acids can be directly translated by host machinery to make the protein components for progeny virions. Its replication strategy requires the formation of a negative-sense template that can be used to synthesize new positive-sense RNA.

An intriguing feature of virus is its ability to undergo a major structural change without destroying the tertiary structure of its subunits under certain environmental conditions. Specifically, when conditions are acidic (pH 5) the capsid is in a stable, assembled form. However, when the pH is raised ~6.5-7 or placed into solution of low ionic strength, the capsid undergoes a concerted structural change called swelling. <ref name=Speir>PMID:7743132</ref>
During this process, 60 pores (2 nanometers in diameter) open along the threefold axis of the capsid, and the size of the virion swells to an increased volume of 10%. Although the capsid expands, the RNA to protein ratio remains constant. The formation of these pores makes it possible for molecules to exit and enter the capsid, allowing this structure to function as a nano-reactor.
Furthermore, if the pH is increased to 7.5, the particles will completely dissociate into dimer subunits.

'''Significance of Structural Transitions '''

CCMV is relevant to mammalian virology due to the similarity of structural transitions in human polio virus, of the picornaviridae family<ref name=Speir>PMID:7743132</ref>
(another naked icosahedral virus).

Of greater significance, the properties of the capsid allow the virus to be exploited in nanotechnology. Capsid proteins can be obtained through two main strategies.
First, virus can be directly extracted from plant leaves in high yields (1 kg of infected plant tissue can yield 1–2 g of virus<ref name=Liepold>PMID:Liepold16280622</ref>). By raising the pH to 7.5 and dissociating the capsid into dimers, the protein can be isolated from the RNA. The purified proteins can then self-assemble into functional virus-like particles under more acidic conditions.

A more modern approach involves the use of recombinant DNA technology. In this approach, the capsid-encoding genes of the virus can be transfected into a yeast expression vector.<ref name=Liepold>PMID:Liepold16280622</ref>) As the yeast replicate, they amplify the number of protein producing units, and the secreted protein products can be readily collected from the media. The major benefit to this strategy, aside from high yield production, is that the genome can be modified prior to insertion into the vector. This can allow the capsid subunits to take on differing chemical properties. This is best exemplified by the research of

<scene name='Cowpea_Chlorotic_Mottle_Virus/Isolated_rna/1'>Isolated RNA</scene>

'''General Capsid Structure'''

The viral capsid of CCMV is a complex of proteins stabilized by metal coordination between capsomeres and RNA binding on its internal surface.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Protein_and_rna/1'>Protein Core with Stabilizing RNA Interactions</scene>
The viral genome encodes three capsid proteins that are chemically identical. These subunits, arbitrarily called A, B, and C, dimerize with each other and assemble into into hexamers and pentamers that comprise the viral capsomeres.<ref name=Speir>PMID:7743132</ref> The complete capsid structure takes the form of a truncated icosahedron (20 faces). It is described as a T=3 capsid, where the T value describes the number of structural units per equilateral face of the icosahedron.[http://www.nlv.ch/Virologytutorials/Structure.htm]

'''Capsomere Structure'''

The hexameric capsomeres are formed by the B and C subunits. The N-terminus arms (residues 27 through 49) of the subunits intertwine to form a parallel beta barrel.<ref name=Speir>PMID:7743132</ref> The N-terminus is therefore key to the hexamer composition.<ref name=Speir>PMID:7743132</ref>
<scene name='Cowpea_Chlorotic_Mottle_Virus/Residues_27-49/1'>N-terminus arms</scene>
The atoms of residues 27-49 are colored blue for clarity.

Residues 29-33 line the channel created at the center of the hexamers and stabilize the subunits with the interactions of their side chains and adjacent residues. For example, the "side chain oxygens of Gln29 residues hydrogen bond with the main chain nitrogens of adjacent Gln29 residues, making a circular ring of interactions" and the "valine residues stack upon one another inside the the beta-tube forming a circle of hydrophobic bonds."<ref name=Speir>PMID:7743132</ref> The hydrophobic valine side chain atoms are protected from the interior of the virus by the side chain atoms of the glutamine residue, and they are surrounded by the hydrogen bonding environment of the beta barrels.<ref name=Speir>PMID:7743132</ref>

In the <scene name='Cowpea_Chlorotic_Mottle_Virus/Interior_of_beta_barrel/1'>interior of beta barrel</scene> we can see these residues filling the channel formed at the center of the capsomere: glutamine 29 (in red), valine 31 (in orange), and valine 33 (in green).

Pentamer capsomeres, on the other hand, are formed exclusively from the contribution of A subunit chains.
<scene name='Cowpea_Chlorotic_Mottle_Virus/Pentamer/1'>Pentamer capsomeres</scene> also have amino-terminus arms that extend into the interior of the capsid, however, unlike the hexameric barrel structures, the amino terminus is unordered.The positively charged Lys 42 residue is colored in blue as a marker for the arms of the N-terminus. Residues before Lys42 do not have detectable electron density for the techniques used to render the structure.

Interestingly, although the subunits are chemically identical, hexamer formation predominates in the capsid. In 1962 Caspar and Klug predicted a classical model for a perfect icosahedral structure- one that would have "a sheet of hexamers interspersed with 12 pentamers arranged to form a closed shell with icosahedral symmetry." In this geometrical shape, the number of pentamers is constrained to 12, a structure with greater than 60 faces must be accounted for by an increased number of hexamers. For viruses, a perfect 60-faced icosahedron would severely limit genome packaging.[http://www.nlv.ch/Virologytutorials/Structure.htm]

Prior to the characterization of CCMV's structure, no RNA viruses (in plants and insects) were found to rigorously observe this model. Their prediction necessitated that the pentamer and hexamer subunits would from a single chemical structure (realized in CCMV due to its identical A,B, and C gene products). However, the "molecular switch" that determines whether a pentamer or a hexamer would form, was left undefined.
It appears that after dimer formation, hexamers predominate in solution. The authors propose that the hexamers then form nucleation sites for particle formation. The basis for the additional hexamer stability comes from the relative number of interactions between molecules.

<ref name=Speir>PMID:7743132</ref>
{{Reflist}}

Cowpea Chlorotic Mottle Virus

2011-12-01T05:58:31Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-12-01T05:40:56Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T06:22:58Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T06:01:30Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T05:52:32Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:58:47Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:58:09Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:57:30Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:56:44Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:55:43Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:54:22Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:53:28Z

Inna Blyakhman:

Cowpea Chlorotic Mottle Virus

2011-11-30T04:26:09Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:19:20Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:18:03Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:16:21Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:15:36Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:14:47Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:10:58Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-30T04:09:57Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-29T23:47:32Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-29T22:49:41Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-29T21:54:43Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-29T06:46:27Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-29T06:23:26Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-29T06:02:00Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-29T04:38:18Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-29T03:19:54Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-28T23:02:30Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-28T22:56:43Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-26T01:42:53Z

Inna Blyakhman: /* Self-Assembling Cowpea Chlorotic Mottle Virus Capsid: Nanoreactor and Scaffold for Molecular Synthesis */

Cowpea Chlorotic Mottle Virus

2011-11-26T01:34:53Z

Inna Blyakhman:

Cowpea Chlorotic Mottle Virus

2011-11-26T01:23:35Z

Inna Blyakhman:

<Structure load='1CWP' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />

===STRUCTURES OF THE NATIVE AND SWOLLEN FORMS OF COWPEA CHLOROTIC MOTTLE VIRUS DETERMINED BY X-RAY CRYSTALLOGRAPHY AND CRYO-ELECTRON MICROSCOPY===

Cowpea Chlorotic Mottle Virus

2011-11-26T01:20:53Z

Inna Blyakhman: /* STRUCTURES OF THE NATIVE AND SWOLLEN FORMS OF COWPEA CHLOROTIC MOTTLE VIRUS DETERMINED BY X-RAY CRYSTALLOGRAPHY AND CRYO-ELECTRON MICROSCOPY */

<Structure load='1CWP' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />

{{STRUCTURE_1cwp| PDB=1cwp | SCENE= }}

===STRUCTURES OF THE NATIVE AND SWOLLEN FORMS OF COWPEA CHLOROTIC MOTTLE VIRUS DETERMINED BY X-RAY CRYSTALLOGRAPHY AND CRYO-ELECTRON MICROSCOPY===

Cowpea Chlorotic Mottle Virus

2011-11-26T01:19:41Z

Inna Blyakhman:

Cowpea Chlorotic Mottle Virus

2011-11-26T01:18:34Z

Inna Blyakhman:

Cowpea Chlorotic Mottle Virus

2011-11-16T05:58:34Z

Inna Blyakhman:

Cowpea Chlorotic Mottle Virus

2011-11-16T05:48:52Z

Inna Blyakhman:

<Structure load='1cwp' size='500' frame='true' align='right' caption='Insert caption here' scene='Insert optional scene name here' />[[Image:1cwp.png|left|200px]]

{{STRUCTURE_1cwp| PDB=1cwp | SCENE= }}

===STRUCTURES OF THE NATIVE AND SWOLLEN FORMS OF COWPEA CHLOROTIC MOTTLE VIRUS DETERMINED BY X-RAY CRYSTALLOGRAPHY AND CRYO-ELECTRON MICROSCOPY===

Cowpea Chlorotic Mottle Virus

2011-11-16T05:46:11Z

Inna Blyakhman:

[[Image:1cwp.png|left|200px]]

{{STRUCTURE_1cwp| PDB=1cwp | SCENE= }}

===STRUCTURES OF THE NATIVE AND SWOLLEN FORMS OF COWPEA CHLOROTIC MOTTLE VIRUS DETERMINED BY X-RAY CRYSTALLOGRAPHY AND CRYO-ELECTRON MICROSCOPY===

Cowpea Chlorotic Mottle Virus

2011-11-16T05:45:11Z

Inna Blyakhman:

[[Image:1cwp.png|left|200px]]

Cowpea Chlorotic Mottle Virus

2011-11-16T05:44:19Z

Inna Blyakhman: New page: