2iic
From Proteopedia
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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
Page seeded by OCA on Tue Jan 29 20:41:38 2008
