The crystal structure of a calcium-bound form of bovine annexin VI has been determined with X-ray diffraction data to 2.9 A by molecular replacement. Six Ca2+ ions were found, five in AB loops, one in a DE loop. Two loops (II-AB, which binds calcium, and V-AB, which does not) have conformations that differ significantly from those in calcium-free, human recombinant annexin VI. There are only small differences between the calci- and the apo-annexin VI in the rest of the molecule. Calcium by itself does not promote a major conformational change.
Crystal structure of bovine annexin VI in a calcium-bound state.,Avila-Sakar AJ, Creutz CE, Kretsinger RH Biochim Biophys Acta. 1998 Sep 8;1387(1-2):103-16. PMID:9748523
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