3BRX
Crystal Structure of calcium-bound cotton annexin Gh1
Summary for 3BRX
| Entry DOI | 10.2210/pdb3brx/pdb |
| Related | 1N00 |
| Descriptor | Annexin, PHOSPHATE ION, CALCIUM ION, ... (4 entities in total) |
| Functional Keywords | calcium binding, membrane binding, annexin, membrane protein |
| Biological source | Gossypium hirsutum (upland cotton) |
| Total number of polymer chains | 1 |
| Total formula weight | 36750.03 |
| Authors | Hu, N.-J.,Hofmann, A. (deposition date: 2007-12-21, release date: 2008-05-06, Last modification date: 2024-03-13) |
| Primary citation | Hu, N.-J.,Yusof, A.M.,Winter, A.,Osman, A.,Reeve, A.K.,Hofmann, A. The crystal structure of calcium-bound annexin Gh1 from Gossypium hirsutum and its implications for membrane binding mechanisms of plant annexins. J.Biol.Chem., 283:18314-18322, 2008 Cited by PubMed Abstract: Plant annexins show distinct differences in comparison with their animal orthologues. In particular, the endonexin sequence, which is responsible for coordination of calcium ions in type II binding sites, is only partially conserved in plant annexins. The crystal structure of calcium-bound cotton annexin Gh1 was solved at 2.5 A resolution and shows three metal ions coordinated in the first and fourth repeat in types II and III binding sites. Although the protein has no detectable affinity for calcium in solution, in the presence of phospholipid vesicles, we determined a stoichiometry of four calcium ions per protein molecule using isothermal titration calorimetry. Further analysis of the crystal structure showed that binding of a fourth calcium ion is structurally possible in the DE loop of the first repeat. Data from this study are in agreement with the canonical membrane binding of annexins, which is facilitated by the convex surface associating with the phospholipid bilayer by a calcium bridging mechanism. In annexin Gh1, this membrane-binding state is characterized by four calcium bridges in the I/IV module of the protein and by direct interactions of several surface-exposed basic and hydrophobic residues with the phospholipid membrane. Analysis of the protein fold stability revealed that the presence of calcium lowers the thermal stability of plant annexins. Furthermore, an additional unfolding step was detected at lower temperatures, which can be explained by the anchoring of the N-terminal domain to the C-terminal core by two conserved hydrogen bonds. PubMed: 18441010DOI: 10.1074/jbc.M801051200 PDB entries with the same primary citation |
| Experimental method | X-RAY DIFFRACTION (2.5 Å) |
Structure validation
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