Perron B, Lewit-Bentley A, Geny B, Russo-Marie F
Institut Cochin de Génétique Moléculaire, U332 INSERM, 22 rue Méchain, 75014 Paris, France.
J Biol Chem. 1997 Apr 25;272(17):11321-6. doi: 10.1074/jbc.272.17.11321.
Annexin III, a putative inositol (1,2)-phosphohydrolase, was co-crystallized with inositol 2-phosphate, the inhibitor of the reaction, and its structure was solved to 1.95 A resolution. No enzyme active site was observed in the structure. Assays for enzymatic activity were also negative. Search for annexin III-inositol phosphate interactions using the BIAcoreTM system revealed an affinity for inositol cyclic (1,2)-phosphate, suggesting annexin III may sequester the molecule in the cell. The BIAcoreTM system used with different phospholipids showed that annexin III displays specificity for phosphatidylethanolamine, but not for phosphatidylinositols. Interestingly, a molecule of ethanolamine was found bound to the protein in the crystal structure. Coupled with the fact that this is a particularly abundant phospholipid in granules specific to neutrophils, cells where annexin III is highly expressed, our finding could be pointing to a physiological role of annexin III.
膜联蛋白III是一种假定的肌醇（1,2）-磷酸水解酶，它与该反应的抑制剂肌醇2-磷酸共结晶，其结构解析至1.95埃分辨率。在该结构中未观察到酶活性位点。酶活性测定结果也为阴性。使用BIAcoreTM系统搜索膜联蛋白III与肌醇磷酸的相互作用，发现其对环肌醇（1,2）-磷酸具有亲和力，这表明膜联蛋白III可能在细胞中隔离该分子。与不同磷脂一起使用的BIAcoreTM系统表明，膜联蛋白III对磷脂酰乙醇胺具有特异性，而对磷脂酰肌醇没有特异性。有趣的是，在晶体结构中发现一个乙醇胺分子与该蛋白质结合。再加上这是中性粒细胞特有的颗粒中一种特别丰富的磷脂，而膜联蛋白III在这些细胞中高度表达，我们的发现可能指向膜联蛋白III的一种生理作用。
