Sandbox Reserved 779: Difference between revisions

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<Structure load='2Q2M' size='400' frame='true' align='right' caption='Native β-Lactoglobulin (β-LG)' scene='Insert optional scene name here' />
<Structure load='2Q2M' size='400' frame='true' align='right' caption='Native β-Lactoglobulin (β-LG)' scene='Insert optional scene name here' />


<scene name='56/564055/Native_beta-lactoglobulin/1'>TextToBeDisplayed</scene>
<scene name='56/564055/Native_beta-lactoglobulin/1'>Native_beta-lactoglobulin</scene>




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Lipocalins have been associated with many biological processes, among them immune response, pheromone transport, biological prostaglandin synthesis, retinoid binding, and cancer cell interactions.
Lipocalins have been associated with many biological processes, among them immune response, pheromone transport, biological prostaglandin synthesis, retinoid binding, and cancer cell interactions.


short description of protein fold: They share limited regions of sequence homology and a common tertiary structure architecture.[2][3][4][5][6] This is an eight stranded antiparallel beta-barrel with a repeated + 1 topology enclosing an internal ligand binding site.[5][4]
 
Therefore  To know more abouts and the related deseases you can follow the link that leads you to [http://swissvar.expasy.org/cgi-bin/swissvar/result?global_textfield=merlin the Portal to Swiss-Prot diseases and variants ]
 
organisms:These proteins are found in gram negative bacteria, vertebrate cells, and invertebrate cells, and in plants.  
organisms:These proteins are found in gram negative bacteria, vertebrate cells, and invertebrate cells, and in plants.  


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== Structure of β-LG ==
== Structure of β-LG ==
overall description of the structure of the protein:
a. oligomeric state
b. description of secondary structure
c. description of active residues of the protein and where they are on the protein
d. description of any ligands in the structure
e. methods used to solve the structure : X-ray crystallography, NMR, EM


At physiological conditions, bovine b-lactoglobulin forms a dimer, with each monomer consisting of 162 amino acid residues and characterized by a molecular mass of 18,350. Below pH 3, the dimer dissociates into monomers which preserve their native conformation. Genetically, b-lactoglobulin may exist as one of several variants, among which the variants A and B are the most abundant. The A and B variants of the protein differ from each other by amino acid residues at positions Asp64 (Gly64 in variant B) and Val118 (Ala118 in variant B). These differences in primary structure render the two variants slightly different with respect to isoelectric point, solubility, self-association properties, as well as pressure and temperature stability. However, the structural characteristics of the A and B variants of bovine b-lactoglobulin are virtually indistinguishable. In its native state, b-lactoglobulin is a predominantly b-sheet protein containing nine b-strands and three a-helices. The core of the protein is formed by a flattened b-barrel (a calyx) composed of eight antiparallel b-strands (A to H).<ref>PMID:11734004</ref>
At physiological conditions, bovine b-lactoglobulin forms a dimer, with each monomer consisting of 162 amino acid residues and characterized by a molecular mass of 18,350. Below pH 3, the dimer dissociates into monomers which preserve their native conformation. Genetically, b-lactoglobulin may exist as one of several variants, among which the variants A and B are the most abundant. The A and B variants of the protein differ from each other by amino acid residues at positions Asp64 (Gly64 in variant B) and Val118 (Ala118 in variant B). These differences in primary structure render the two variants slightly different with respect to isoelectric point, solubility, self-association properties, as well as pressure and temperature stability. However, the structural characteristics of the A and B variants of bovine b-lactoglobulin are virtually indistinguishable. In its native state, b-lactoglobulin is a predominantly b-sheet protein containing nine b-strands and three a-helices. The core of the protein is formed by a flattened b-barrel (a calyx) composed of eight antiparallel b-strands (A to H).<ref>PMID:11734004</ref>
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on the monomer–dimer equilibrium [30,32,42,43] and the reactivity of the thiol group of Cys121 deeply buried between the α-helix and H
on the monomer–dimer equilibrium [30,32,42,43] and the reactivity of the thiol group of Cys121 deeply buried between the α-helix and H
strand [44–48] revealed other important properties of βLG.<ref>PMID:19362581</ref>
strand [44–48] revealed other important properties of βLG.<ref>PMID:19362581</ref>
overall description of the structure of the protein:
a. oligomeric state
b. description of secondary structure
c. description of active residues of the protein and where they are on the protein
d. description of any ligands in the structure
e. methods used to solve the structure : X-ray crystallography, NMR, EM
===Molecular mechanism of the Tanford transition===
Equilibrium transition
Although βLG exists in a native state over a wide range of pH
values, it shows slight conformational changes during a change of pH
[54]. Among the pH-dependent conformational changes of βLG, the
Tanford transition is the most important because it is thought to be
related to the function of βLG. Tanford et al. [55] observed a change in optical rotatory dispersion at pH 7.0 representing a certain conformational change. Subsequently, they found that this conformational change is accompanied by a deprotonation of a carboxyl group with an anomalous pKa of 7.5 [20,55].
==Subunit structure==
Under physiological conditions beta-lactoglobulin exists as an equilibrium mixture of monomeric and dimeric forms.
Subcellular location: Secreted.
Tissue specificity: Synthesized in mammary gland and secreted in milk.
Post-translational modification : Alternate disulfide bonds occur in equal amounts in all variants examined.
Allergenic properties:Causes an allergic reaction in human. Is one of the causes of cow's milk allergy.
Miscellaneous The B variant sequence is shown.




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describe any uses or application that have been made of the protein  
describe any uses or application that have been made of the protein  
===Molecular mechanism of the Tanford transition===
Above pH 6.5, b-lactoglobulin undergoes the so-called Tanford transition which is triggered by protonation of Glu89 exhibiting an anomalously
high pKa value. The Tanford transition involves displacement of the loop EF (residues 85 to 90) that acts as a lid which closes the protein interior/binding site below pH 7.3 and opens it at higher pH. The Tanford transition may involve some other structural changes as well. For example, the transition is accompanied by a change in the microenvironment of Tyr428 and causes an alteration in the relative orientation of monomers in the dimer by as much as 5 degrees�. It should be noted that all transitions that take place between pH 2 and pH 9 do not cause any appreciable changes in the nativelike b-barrel conformation of b-lactoglobulin.
<ref>PMID:11734004</ref>
==Subunit structure==
Under physiological conditions beta-lactoglobulin exists as an equilibrium mixture of monomeric and dimeric forms.
Subcellular location: Secreted.
Tissue specificity: Synthesized in mammary gland and secreted in milk.
Post-translational modification : Alternate disulfide bonds occur in equal amounts in all variants examined.
Allergenic properties:Causes an allergic reaction in human. Is one of the causes of cow's milk allergy.
Miscellaneous The B variant sequence is shown.




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