G15SecL05Tpc3: Difference between revisions

Line 8:

<scene name='G15SecL05Tpc3/Ospb/1'>Osp-B</scene> is a primary outer-surface lipoprotein molecule found in the Lyme disease spirochete ''Borrelia burgdorferi'', a molecule essential for the survival of the bacterium. Since its primary function is to serve both as a site of antibody recognition and as the microvillar attachment to the ''Ixodes scapularis'' midgut, it is constitutively expressed (Becker, 2005). Osp-B is highly conserved among B. burgdorferi spirochetes, encoded on the linear plasmid “54” and is generally expressed by a common promoter with Osp-A (Neelakanta et al, 2007). Despite being documented about the structurally and functionally similar to Osp-A, the entirety of Osp-B’s functions and its independent roles in the life cycle of spirochetes ultimately remains unclear (Neelakanta et al, 2007). "JOINED" The formation of the OspB-CB2 and OspB-H6831 complexes were dependent upon a single lysine residue in Osp-B <scene name='G15SecL05Tpc3/Lys253/2'>Lys-253</scene>, for binding and thus leading to lysis of the outer membrane of the spirochete; the structural changes that result culminate into molecular instability and protease susceptibility that eventually lead to said lysis, though the exact physiological consequences of these changes are not yet fully sequenced nor understood (Connoly et al, 2005). These antibodies demonstrate enormous selective pressure; growth of ''Borrelia burgdorferi'' spirochetes in their presence generated escape mutants that lacked the critical Lys 253 amino acid on Osp-B for antibody binding, and were thus less infectious in experimental mouse models and ''in vitro'' experimental assays (Connoly et al, 2005). Variation in the synthesis of Osp-B and other outer surface proteins is the means by which ''B. burgdorferi'' evades the host immune system and adapts to various host ~~microenvironments~~, such as those in the common tick vector. ''B. burgdorferi'' selectively expresses specific Osps in distinct phases of its life cycle and in specific tissue locations: expression of Osp-B is immediately turned on when the spirochetes enter and reside within the tick vector. However, during transmission from the tick vector to a vertebrate host, ''B. burgdorferi'' down-regulates OspB expression and up-regulates the expression of proteins such as OspC, DbpA, and BBK32. This selective gene expression of Osp-B (and additionally OspA) suggests that this protein may function during early spirochete colonization and persistence within the tick vector (Neelakanta et al, 2007).

<scene name='G15SecL05Tpc3/Ospb/1'>Osp-B</scene> is a primary outer-surface lipoprotein molecule found in the Lyme disease spirochete ''Borrelia burgdorferi'', a molecule essential for the survival of the bacterium. Since its primary function is to serve both as a site of antibody recognition and as the microvillar attachment to the ''Ixodes scapularis'' midgut, it is constitutively expressed (Becker, 2005). Osp-B is highly conserved among B. burgdorferi spirochetes, encoded on the linear plasmid “54” and is generally expressed by a common promoter with Osp-A (Neelakanta et al, 2007). Despite being documented about the structurally and functionally similar to Osp-A, the entirety of Osp-B’s functions and its independent roles in the life cycle of spirochetes ultimately remains unclear (Neelakanta et al, 2007). "JOINED" The formation of the OspB-CB2 and OspB-H6831 complexes were dependent upon a single lysine residue in Osp-B <scene name='G15SecL05Tpc3/Lys253/2'>Lys-253</scene>, for binding and thus leading to lysis of the outer membrane of the spirochete; the structural changes that result culminate into molecular instability and protease susceptibility that eventually lead to said lysis, though the exact physiological consequences of these changes are not yet fully sequenced nor understood (Connoly et al, 2005). These antibodies demonstrate enormous selective pressure; growth of ''Borrelia burgdorferi'' spirochetes in their presence generated escape mutants that lacked the critical Lys 253 amino acid on Osp-B for antibody binding, and were thus less infectious in experimental mouse models and ''in vitro'' experimental assays (Connoly et al, 2005). Variation in the synthesis of Osp-B and other outer surface proteins is the means by which ''B. burgdorferi'' evades the host immune system and adapts to various host micro-environments, such as those in the common tick vector. ''B. burgdorferi'' selectively expresses specific Osps in distinct phases of its life cycle and in specific tissue locations: expression of Osp-B is immediately turned on when the spirochetes enter and reside within the tick vector. However, during transmission from the tick vector to a vertebrate host, ''B. burgdorferi'' down-regulates OspB expression and up-regulates the expression of proteins such as OspC, DbpA, and BBK32. This selective gene expression of Osp-B (and additionally OspA) suggests that this protein may function during early spirochete colonization and persistence within the tick vector (Neelakanta et al, 2007).

==Osp-B and H6831==

Line 18:

----

H6831 is a specific IgG class antigen binding fragment that has a series of significant residues that bind to the epitope on Osp-B and lyse it without the aid of a complement, resulting in a unique molecular interaction that causes a physical change in the shape of Osp-B upon binding. In order to better analyze the changes, crystallized structures of Osp-B and the Osp-B H6831 complex were taken and comparatively analyzed: X-ray diffraction showed that the structure of OspB-CT contains twelve anti parallel beta strands and a single alpha helix (Becker et al, 2005). Strands 1-4 form the Osp-B’s central sheet: this is a free standing sheet that is located at the N-terminus of the protein. The remaining strands 5-12 form two additional sheets that together with the alpha helix form a barrel-like domain. Analysis of the bound complex revealed that the central beta sheet is either destroyed or removed by proteolysis upon binding (Becker et al, 2005). Ultimately the structural changes to Osp-B appear to result only indirectly from the addition of Fab (Becker et al, 2005).

Almost the entirety of this binding process is centered around distinct residues that were discovered due to comparative analysis of Osp-A and Osp-B’s crystal structures. A charged triad is formed in both structures whose united physical form presents itself as a favorable binding site. In Osp-B, this triad consists of amino-acid residues Arg-162, Glu-184, and <scene name='G15SecL05Tpc3/Arg214/3'>Arg214</scene>. These residues form a prominent cleft with density void space in between each other. This space is well suited for an all trans-structures to bind into, and such a structure was located on the crystallized Osp-B-H6831 bound complex. This complex is a combination of Osp-B-CT residues 202-296 and the Fabs’ heavy and light chains. A notable feature of the OspB-CT-H6831 interaction is the prevalence of aromatic residues contributed by the Fab: these aromatic residues are the points at which Lys-253 on Osp-B guides itself to bind with Glu-50. Specifically, Lys 253 wedges itself between residues Try-33 and Tyr-101 of the H6831 heavy chain to be able reach the Glu-50 so the ion-pair binding between the two residues can occur (Becker et al, 2005). This interaction, along with an amine hydrogen bond and ion pair with a glutamate from the Fab heavy chain, a second hydrogen bond with a main chain carbonyl from loop "1" of Osp-B-CT, and a water mediated hydrogen bond to a histidine from the Fab heavy chain constitute the three main series of interactions in the OspB-H6831 bound complex. Lys-253 is the absolute key component of the formation of this bound complex; if Lys-253 were to be substituted with another amino acid or be missing entirely via external influential mutation, the binding could not occur (Connolly et al, 2005).

Almost the entirety of this binding process is centered around distinct residues that were discovered due to comparative analysis of Osp-A and Osp-B’s crystal structures. A charged triad is formed in both structures whose united physical form presents itself as a favorable binding site. In Osp-B, this triad consists of amino-acid residues Arg-162, Glu-184, and <scene name='G15SecL05Tpc3/Arg214/3'>Arg214</scene> (with <scene name='G15SecL05Tpc3/Thr276/1'>Thr-276</scene> additionally aiding the binding process though not part of the triad). These residues form a prominent cleft with density void space in between each other. This space is well suited for an all trans-structures to bind into, and such a structure was located on the crystallized Osp-B-H6831 bound complex. This complex is a combination of Osp-B-CT residues 202-296 and the Fabs’ heavy and light chains. A notable feature of the OspB-CT-H6831 interaction is the prevalence of aromatic residues contributed by the Fab: these aromatic residues are the points at which Lys-253 on Osp-B guides itself to bind with Glu-50. Specifically, Lys 253 wedges itself between residues Try-33 and Tyr-101 of the H6831 heavy chain to be able reach the Glu-50 so the ion-pair binding between the two residues can occur (Becker et al, 2005). This interaction, along with an amine hydrogen bond and ion pair with a glutamate from the Fab heavy chain, a second hydrogen bond with a main chain carbonyl from loop "1" of Osp-B-CT, and a water mediated hydrogen bond to a histidine from the Fab heavy chain constitute the three main series of interactions in the OspB-H6831 bound complex. Lys-253 is the absolute key component of the formation of this bound complex; if Lys-253 were to be substituted with another amino acid or be missing entirely via external influential mutation, the binding could not occur (Connolly et al, 2005).

----

G15SecL05Tpc3: Difference between revisions

Navigation menu

Page actions

Page actions

Personal tools

Navigation

Search

Tools

@@ Line 8: / Line 8: @@
 <Structure load='1rjl' size='300' frame='true' align='right' caption='Osp-B Structure, Bound' scene='Insert optional scene name here' />
-<scene name='G15SecL05Tpc3/Ospb/1'>Osp-B</scene> is a primary outer-surface lipoprotein molecule found in the Lyme disease spirochete ''Borrelia burgdorferi'', a molecule essential for the survival of the bacterium. Since its primary function is to serve both as a site of antibody recognition and as the microvillar attachment to the ''Ixodes scapularis'' midgut, it is constitutively expressed (Becker, 2005). Osp-B is highly conserved among B. burgdorferi  spirochetes, encoded on the linear plasmid “54” and is generally expressed by a common promoter with Osp-A (Neelakanta et al, 2007). Despite being documented about the structurally and functionally similar to Osp-A, the entirety of Osp-B’s functions and its independent roles in the life cycle of spirochetes ultimately remains unclear (Neelakanta et al, 2007).  "JOINED" The formation of the OspB-CB2 and OspB-H6831 complexes were dependent upon a single lysine residue in Osp-B <scene name='G15SecL05Tpc3/Lys253/2'>Lys-253</scene>, for binding and thus leading to lysis of the outer membrane of the spirochete; the structural changes that result culminate into molecular instability and protease susceptibility that eventually lead to said lysis, though the exact physiological consequences of these changes are not yet fully sequenced nor understood (Connoly et al, 2005). These antibodies demonstrate enormous selective pressure; growth of ''Borrelia burgdorferi'' spirochetes in their presence generated escape mutants that lacked the critical Lys 253 amino acid on Osp-B for antibody binding, and were thus less infectious in experimental mouse models and ''in vitro'' experimental assays (Connoly et al, 2005). Variation in the synthesis of Osp-B and other outer surface proteins is the means by which ''B. burgdorferi'' evades the host immune system and adapts to various host microenvironments, such as those in the common tick vector. ''B. burgdorferi'' selectively expresses specific Osps in distinct phases of its life cycle and in specific tissue locations: expression of Osp-B is immediately turned on when the spirochetes enter and reside within the tick vector. However, during transmission from the tick vector to a vertebrate host, ''B. burgdorferi'' down-regulates OspB expression and up-regulates the expression of proteins such as OspC, DbpA, and BBK32. This selective gene expression of Osp-B (and additionally OspA) suggests that this protein may function during early spirochete colonization and persistence within the tick vector (Neelakanta et al, 2007).
+<scene name='G15SecL05Tpc3/Ospb/1'>Osp-B</scene> is a primary outer-surface lipoprotein molecule found in the Lyme disease spirochete ''Borrelia burgdorferi'', a molecule essential for the survival of the bacterium. Since its primary function is to serve both as a site of antibody recognition and as the microvillar attachment to the ''Ixodes scapularis'' midgut, it is constitutively expressed (Becker, 2005). Osp-B is highly conserved among B. burgdorferi  spirochetes, encoded on the linear plasmid “54” and is generally expressed by a common promoter with Osp-A (Neelakanta et al, 2007). Despite being documented about the structurally and functionally similar to Osp-A, the entirety of Osp-B’s functions and its independent roles in the life cycle of spirochetes ultimately remains unclear (Neelakanta et al, 2007).  "JOINED" The formation of the OspB-CB2 and OspB-H6831 complexes were dependent upon a single lysine residue in Osp-B <scene name='G15SecL05Tpc3/Lys253/2'>Lys-253</scene>, for binding and thus leading to lysis of the outer membrane of the spirochete; the structural changes that result culminate into molecular instability and protease susceptibility that eventually lead to said lysis, though the exact physiological consequences of these changes are not yet fully sequenced nor understood (Connoly et al, 2005). These antibodies demonstrate enormous selective pressure; growth of ''Borrelia burgdorferi'' spirochetes in their presence generated escape mutants that lacked the critical Lys 253 amino acid on Osp-B for antibody binding, and were thus less infectious in experimental mouse models and ''in vitro'' experimental assays (Connoly et al, 2005). Variation in the synthesis of Osp-B and other outer surface proteins is the means by which ''B. burgdorferi'' evades the host immune system and adapts to various host micro-environments, such as those in the common tick vector. ''B. burgdorferi'' selectively expresses specific Osps in distinct phases of its life cycle and in specific tissue locations: expression of Osp-B is immediately turned on when the spirochetes enter and reside within the tick vector. However, during transmission from the tick vector to a vertebrate host, ''B. burgdorferi'' down-regulates OspB expression and up-regulates the expression of proteins such as OspC, DbpA, and BBK32. This selective gene expression of Osp-B (and additionally OspA) suggests that this protein may function during early spirochete colonization and persistence within the tick vector (Neelakanta et al, 2007).
 ==Osp-B and H6831==
@@ Line 18: / Line 18: @@
 ----
 H6831 is a specific IgG class antigen binding fragment that has a series of significant residues that bind to the epitope on Osp-B and lyse it without the aid of a complement, resulting in a unique molecular interaction that causes a physical change in the shape of Osp-B upon binding. In order to better analyze the changes, crystallized structures of Osp-B and the Osp-B H6831 complex were taken and comparatively analyzed: X-ray diffraction showed that the structure of OspB-CT contains twelve anti parallel beta strands and a single alpha helix (Becker et al, 2005). Strands 1-4 form the Osp-B’s central sheet: this is a free standing sheet that is located at the N-terminus of the protein. The remaining strands 5-12 form two additional sheets that together with the alpha helix form a barrel-like domain. Analysis of the bound complex revealed that the central beta sheet is either destroyed or removed by proteolysis upon binding (Becker et al, 2005). Ultimately the structural changes to Osp-B appear to result only indirectly from the addition of Fab (Becker et al, 2005).
-Almost the entirety of this binding process is centered around distinct residues that were discovered due to comparative analysis of Osp-A and Osp-B’s crystal structures. A charged triad is formed in both structures whose united physical form presents itself as a favorable binding site. In Osp-B, this triad consists of amino-acid residues Arg-162, Glu-184, and <scene name='G15SecL05Tpc3/Arg214/3'>Arg214</scene>. These residues form a prominent cleft with density void space in between each other. This space is well suited for an all trans-structures to bind into, and such a structure was located on the crystallized Osp-B-H6831 bound complex.  This complex is a combination of Osp-B-CT residues 202-296 and the Fabs’ heavy and light chains. A notable feature of the OspB-CT-H6831 interaction is the prevalence of aromatic residues contributed by the Fab: these aromatic residues are the points at which Lys-253 on Osp-B guides itself to bind with Glu-50. Specifically, Lys 253 wedges itself between residues Try-33 and Tyr-101 of the H6831 heavy chain to be able reach the Glu-50 so the ion-pair binding between the two residues can occur (Becker et al, 2005). This interaction, along with an amine hydrogen bond and ion pair with a glutamate from the Fab heavy chain, a second hydrogen bond with a main chain carbonyl from loop "1" of Osp-B-CT, and a water mediated hydrogen bond to a histidine from the Fab heavy chain constitute the three main series of interactions in the OspB-H6831 bound complex. Lys-253 is the absolute key component of the formation of this bound complex; if Lys-253 were to be substituted with another amino acid or be missing entirely via external influential mutation, the binding could not occur (Connolly et al, 2005).
+Almost the entirety of this binding process is centered around distinct residues that were discovered due to comparative analysis of Osp-A and Osp-B’s crystal structures. A charged triad is formed in both structures whose united physical form presents itself as a favorable binding site. In Osp-B, this triad consists of amino-acid residues Arg-162, Glu-184, and <scene name='G15SecL05Tpc3/Arg214/3'>Arg214</scene> (with <scene name='G15SecL05Tpc3/Thr276/1'>Thr-276</scene> additionally aiding the binding process though not part of the triad). These residues form a prominent cleft with density void space in between each other. This space is well suited for an all trans-structures to bind into, and such a structure was located on the crystallized Osp-B-H6831 bound complex.  This complex is a combination of Osp-B-CT residues 202-296 and the Fabs’ heavy and light chains. A notable feature of the OspB-CT-H6831 interaction is the prevalence of aromatic residues contributed by the Fab: these aromatic residues are the points at which Lys-253 on Osp-B guides itself to bind with Glu-50. Specifically, Lys 253 wedges itself between residues Try-33 and Tyr-101 of the H6831 heavy chain to be able reach the Glu-50 so the ion-pair binding between the two residues can occur (Becker et al, 2005). This interaction, along with an amine hydrogen bond and ion pair with a glutamate from the Fab heavy chain, a second hydrogen bond with a main chain carbonyl from loop "1" of Osp-B-CT, and a water mediated hydrogen bond to a histidine from the Fab heavy chain constitute the three main series of interactions in the OspB-H6831 bound complex. Lys-253 is the absolute key component of the formation of this bound complex; if Lys-253 were to be substituted with another amino acid or be missing entirely via external influential mutation, the binding could not occur (Connolly et al, 2005).
 ----