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1x2w
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(New page: 200px<br /><applet load="1x2w" size="450" color="white" frame="true" align="right" spinBox="true" caption="1x2w, resolution 2.29Å" /> '''Crystal Structure of...)
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Revision as of 03:41, 21 November 2007
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Crystal Structure of Apo-Habu IX-bp at pH 4.6
Overview
Coagulation factor IX-binding protein, isolated from Trimeresurus, flavoviridis (IX-bp), is a C-type lectin-like protein. It is an, anticoagulant consisting of homologous subunits, A and B. Each subunit has, a Ca(2+)-binding site with a unique affinity (K(d) values of 14muM and, 130muM at pH 7.5). These binding characteristics are pH-dependent and, under acidic conditions, the Ca(2+) binding of the low-affinity site was, reduced considerably. In order to identify which site has high affinity, and to investigate the pH-dependent Ca(2+) release mechanism, we have, determined the crystal structures of IX-bp at pH 6.5 and pH 4.6 (apo, form), and compared the Ca(2+)-binding sites with each other and with, those of the solved structures under alkaline conditions; pH 7.8 and pH, 8.0 (complexed form). At pH 6.5, Glu43 in the Ca(2+)-binding site of, subunit A displayed two conformations. One (minor) is that in the alkaline, state, and the other (major) is that at pH 4.6. However, the corresponding, Gln43 residue of subunit B is in only a single conformation, which is, almost identical with that in the alkaline state. At pH 4.6, Glu43 of, subunit A adopts a conformation similar to that of the major conformer, observed at pH 6.5, while Gln43 of subunit B assumes a new conformation, and both Ca(2+) positions are occupied by water molecules. These results, showed that Glu43 of subunit A is much more sensitive to protonation than, Gln43 of subunit B, and the conformational change of Glu43 occurs around, pH6.5, which may correspond to the step of Ca(2+) release.
About this Structure
1X2W is a Protein complex structure of sequences from Trimeresurus flavoviridis with CL, RB and SO4 as ligands. Full crystallographic information is available from OCA.
Reference
pH-Dependent structural changes at Ca(2+)-binding sites of coagulation factor IX-binding protein., Suzuki N, Fujimoto Z, Morita T, Fukamizu A, Mizuno H, J Mol Biol. 2005 Oct 14;353(1):80-7. PMID:16165155
Page seeded by OCA on Wed Nov 21 05:48:56 2007
