2iic
From Proteopedia
(New page: 200px<br /><applet load="2iic" size="350" color="white" frame="true" align="right" spinBox="true" caption="2iic, resolution 2.930Å" /> '''Calcium bound struc...) |
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==Overview== | ==Overview== | ||
| - | Alpha-11 giardin is a member of the multi-gene alpha-giardin family in the | + | Alpha-11 giardin is a member of the multi-gene alpha-giardin family in the intestinal protozoan, Giardia lamblia. This gene family shares an ancestry with the annexin super family, whose common characteristic is calcium-dependent binding to membranes that contain acidic phospholipids. Several alpha giardins are highly expressed during parasite-induced diarrhea in humans. Despite being a member of a large family of proteins, little is known about the function and cellular localization of alpha-11 giardin, although giardins are often associated with the cytoskeleton. It has been shown that Giardia exhibits high levels of alpha-11 giardin mRNA transcript throughout its life cycle; however, constitutive over-expression of this protein is lethal to the parasite. Determining the three-dimensional structure of an alpha-giardin is essential to identifying functional domains shared in the alpha-giardin family. Here we report the crystal structures of the apo and Ca(2+)-bound forms of alpha-11 giardin, the first alpha giardin to be characterized structurally. Crystals of apo and Ca(2+)-bound alpha-11 giardin diffracted to 1.1 A and 2.93 A, respectively. The crystal structure of selenium-substituted apo alpha-11 giardin reveals a planar array of four tandem repeats of predominantly alpha-helical domains, reminiscent of previously determined annexin structures, making this the highest-resolution structure of an annexin to date. The apo alpha-11 giardin structure also reveals a hydrophobic core formed between repeats I/IV and II/III, a region typically hydrophilic in other annexins. Surprisingly, the Ca(2+)-bound structure contains only a single calcium ion, located in the DE loop of repeat I and coordinated differently from the two types of calcium sites observed in previous annexin structures. The apo and Ca(2+)-bound alpha-11 giardin structures assume overall similar conformations; however, Ca(2+)-bound alpha-11 giardin crystallized in a lower-symmetry space group with four molecules in the asymmetric unit. Vesicle-binding studies suggest that alpha-11 giardin, unlike most other annexins, does not bind to vesicles composed of acidic phospholipids in a calcium-dependent manner. |
==About this Structure== | ==About this Structure== | ||
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==Reference== | ==Reference== | ||
| - | Apo and | + | Apo and calcium-bound crystal structures of Alpha-11 giardin, an unusual annexin from Giardia lamblia., Pathuri P, Nguyen ET, Svard SG, Luecke H, J Mol Biol. 2007 Apr 27;368(2):493-508. Epub 2007 Feb 20. PMID:[http://ispc.weizmann.ac.il//pmbin/getpm?pmid=17355882 17355882] |
[[Category: Giardia intestinalis]] | [[Category: Giardia intestinalis]] | ||
[[Category: Single protein]] | [[Category: Single protein]] | ||
[[Category: Luecke, H.]] | [[Category: Luecke, H.]] | ||
| - | [[Category: Nguyen, E | + | [[Category: Nguyen, E T.]] |
[[Category: Pathuri, P.]] | [[Category: Pathuri, P.]] | ||
[[Category: CA]] | [[Category: CA]] | ||
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[[Category: helix-turn-helix]] | [[Category: helix-turn-helix]] | ||
| - | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on | + | ''Page seeded by [http://oca.weizmann.ac.il/oca OCA ] on Thu Feb 21 17:53:03 2008'' |
Revision as of 15:53, 21 February 2008
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Calcium bound structure of alpha-11 giardin
Overview
Alpha-11 giardin is a member of the multi-gene alpha-giardin family in the intestinal protozoan, Giardia lamblia. This gene family shares an ancestry with the annexin super family, whose common characteristic is calcium-dependent binding to membranes that contain acidic phospholipids. Several alpha giardins are highly expressed during parasite-induced diarrhea in humans. Despite being a member of a large family of proteins, little is known about the function and cellular localization of alpha-11 giardin, although giardins are often associated with the cytoskeleton. It has been shown that Giardia exhibits high levels of alpha-11 giardin mRNA transcript throughout its life cycle; however, constitutive over-expression of this protein is lethal to the parasite. Determining the three-dimensional structure of an alpha-giardin is essential to identifying functional domains shared in the alpha-giardin family. Here we report the crystal structures of the apo and Ca(2+)-bound forms of alpha-11 giardin, the first alpha giardin to be characterized structurally. Crystals of apo and Ca(2+)-bound alpha-11 giardin diffracted to 1.1 A and 2.93 A, respectively. The crystal structure of selenium-substituted apo alpha-11 giardin reveals a planar array of four tandem repeats of predominantly alpha-helical domains, reminiscent of previously determined annexin structures, making this the highest-resolution structure of an annexin to date. The apo alpha-11 giardin structure also reveals a hydrophobic core formed between repeats I/IV and II/III, a region typically hydrophilic in other annexins. Surprisingly, the Ca(2+)-bound structure contains only a single calcium ion, located in the DE loop of repeat I and coordinated differently from the two types of calcium sites observed in previous annexin structures. The apo and Ca(2+)-bound alpha-11 giardin structures assume overall similar conformations; however, Ca(2+)-bound alpha-11 giardin crystallized in a lower-symmetry space group with four molecules in the asymmetric unit. Vesicle-binding studies suggest that alpha-11 giardin, unlike most other annexins, does not bind to vesicles composed of acidic phospholipids in a calcium-dependent manner.
About this Structure
2IIC is a Single protein structure of sequence from Giardia intestinalis with as ligand. Full crystallographic information is available from OCA.
Reference
Apo and calcium-bound crystal structures of Alpha-11 giardin, an unusual annexin from Giardia lamblia., Pathuri P, Nguyen ET, Svard SG, Luecke H, J Mol Biol. 2007 Apr 27;368(2):493-508. Epub 2007 Feb 20. PMID:17355882
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