PDBsum entry 2ii2

Metal binding protein

PDB id: 2ii2

Contents

Protein chain

304 a.a. *

Ligands

SO4 ×2

Waters ×625

* Residue conservation analysis

PDB id:

2ii2

Name:

Metal binding protein

Title:

Crystal structure of alpha-11 giardin

Structure:

Alpha-11 giardin. Chain: a. Engineered: yes

Source:

Giardia intestinalis. Organism_taxid: 5741. Expressed in: escherichia coli. Expression_system_taxid: 562.

Resolution:

1.10Å R-factor: 0.196 R-free: 0.225

Authors:

P.Pathuri,E.T.Nguyen,H.Luecke

Key ref:

P.Pathuri et al. (2007). Apo and Calcium-bound Crystal Structures of Alpha-11 Giardin, an Unusual Annexin from Giardia lamblia. J Mol Biol, 368, 493-508. PubMed id: 17355882 DOI: 10.1016/j.jmb.2007.02.016

Date:

27-Sep-06 Release date: 17-Apr-07

Protein chain

Q4VPP2  (Q4VPP2_GIAIN) -  Alpha-11 giardin from Giardia intestinalis

Seq: 307 a.a.

Struc: 304 a.a.

Enzyme reactions

• Enzyme class: E.C.?

DOI no: 10.1016/j.jmb.2007.02.016

J Mol Biol 368:493-508 (2007)

PubMed id: 17355882

Apo and Calcium-bound Crystal Structures of Alpha-11 Giardin, an Unusual Annexin from Giardia lamblia.

P.Pathuri, E.T.Nguyen, S.G.Svärd, H.Luecke.

ABSTRACT

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.

Selected figure(s)

Figure 7.
Figure 7. Overlay of alpha-11 giardin (blue) and annexin A4 (orange) crystal structures. (a) Side view of the structure and (b) top view from the convex side. The N termini (Nt) of alpha-11 giardin and annexin A4 are labeled in their respective colors. Superposition of the alpha-11 giardin and annexin A4 structures was performed in Coot^39 and the Figures were produced with the molecular graphics program Pymol [http://pymol.sourceforge.net/].

Figure 8.
Figure 8. Arrangement of the four monomers in the asymmetric unit of Ca^2+-bound alpha-11 giardin. Monomer A is shown in yellow, monomer B in purple, monomer C in green and monomer D in teal. Calcium ions bound to the DE loop of repeat I in each of the four monomers are illustrated as red spheres. The Figure was prepared with the molecular graphics program Pymol [http://pymol.sourceforge.net/].

The above figures are reprinted by permission from Elsevier: J Mol Biol (2007, 368, 493-508) copyright 2007.

Figures were selected by an automated process.