3CHK

Calcium bound structure of alpha-14 giardin

Summary for 3CHK

• Entry DOI: 10.2210/pdb3chk/pdb
• Related: 3CHJ 3CHL
• Descriptor: Alpha-14 giardin, CALCIUM ION (3 entities in total)
• Functional Keywords: calcium-binding, annexin, metal binding protein
• Biological source: Giardia lamblia
• Total number of polymer chains: 1
• Total formula weight: 38837.57

Authors

Pathuri, P.,Luecke, H. (deposition date: 2008-03-10, release date: 2009-01-06, Last modification date: 2024-02-21)

Primary citation

Pathuri, P.,Nguyen, E.T.,Ozorowski, G.,Svard, S.G.,Luecke, H.
Apo and calcium-bound crystal structures of cytoskeletal protein alpha-14 giardin (annexin E1) from the intestinal protozoan parasite Giardia lamblia
J.Mol.Biol., 385:1098-1112, 2009

PubMed Abstract: Alpha-14 giardin (annexin E1), a member of the alpha giardin family of annexins, has been shown to localize to the flagella of the intestinal protozoan parasite Giardia lamblia. Alpha giardins show a common ancestry with the annexins, a family of proteins most of which bind to phospholipids and cellular membranes in a Ca(2+)-dependent manner and are implicated in numerous membrane-related processes including cytoskeletal rearrangements and membrane organization. It has been proposed that alpha-14 giardin may play a significant role during the cytoskeletal rearrangement during differentiation of Giardia. To gain a better understanding of alpha-14 giardin's mode of action and its biological role, we have determined the three-dimensional structure of alpha-14 giardin and its phospholipid-binding properties. Here, we report the apo crystal structure of alpha-14 giardin determined in two different crystal forms as well as the Ca(2+)-bound crystal structure of alpha-14 giardin, refined to 1.9, 1.6 and 1.65 A, respectively. Although the overall fold of alpha-14 giardin is similar to that of alpha-11 giardin, multiwavelength anomalous dispersion phasing was required to solve the alpha-14 giardin structure, indicating significant structural differences between these two members of the alpha giardin family. Unlike most annexin structures, which typically possess N-terminal domains, alpha-14 giardin is composed of only a core domain, followed by a C-terminal extension that may serve as a ligand for binding to cytoskeletal protein partners in Giardia. In the Ca(2+)-bound structure we detected five bound calcium ions, one of which is a novel, highly coordinated calcium-binding site not previously observed in annexin structures. This novel high-affinity calcium-binding site is composed of seven protein donor groups, a feature rarely observed in crystal structures. In addition, phospholipid-binding assays suggest that alpha-14 giardin exhibits calcium-dependent binding to phospholipids that coordinate cytoskeletal disassembly/assembly during differentiation of the parasite.

PubMed: 19046974
DOI: 10.1016/j.jmb.2008.11.012

Experimental method

X-RAY DIFFRACTION (1.65 Å)