Mellgren R L, Lane R D, Mericle M T
Department of Pharmacology, Medical College of Ohio, Toledo 43699-0008.
Biochim Biophys Acta. 1989 Nov 9;999(1):71-7. doi: 10.1016/0167-4838(89)90032-0.
Animal cells contain a non-lysosomal proteolytic system which degrades various protein substrates in the presence of calcium ion. The calcium-dependent proteinases (calpains) co-exist in cells with a specific protein inhibitor called calpastatin. Distribution of this inhibitor to different subcellular sites could be important in overall regulation of the calpains. Previously, myocardial calpastatin was shown to be present in preparations of sarcoplasmic reticulum and sarcolemma. In the present work, we show that purified bovine myocardial calpastatin binds to the acidic phospholipids, phosphatidylinositol and phosphatidylserine, but not to the neutral phospholipids, phosphatidylcholine and phosphatidylethanolamine. Large forms of calpastatin from canine myocardium and rabbit liver also were bound to phosphatidylinositol. Smaller forms of calpastatin present in the preparations did not bind to acidic phospholipids. Bovine large calpastatin was subjected to CNBr digestion, and a phospholipid-binding fragment representing approximately one-sixth of the intact protein mass was purified. Amino acid sequence analysis indicated that the phospholipid-binding fragment was derived from the amino terminus of the large calpastatin.
动物细胞含有一种非溶酶体蛋白水解系统，该系统在钙离子存在的情况下可降解各种蛋白质底物。钙依赖性蛋白酶（钙蛋白酶）与一种名为钙蛋白酶抑制蛋白的特异性蛋白质抑制剂共存于细胞中。这种抑制剂在不同亚细胞位点的分布可能对钙蛋白酶的整体调节很重要。此前已表明，心肌钙蛋白酶抑制蛋白存在于肌浆网和肌膜制剂中。在本研究中，我们发现纯化的牛心肌钙蛋白酶抑制蛋白可与酸性磷脂磷脂酰肌醇和磷脂酰丝氨酸结合，但不与中性磷脂磷脂酰胆碱和磷脂酰乙醇胺结合。犬心肌和兔肝脏中的大型钙蛋白酶抑制蛋白也与磷脂酰肌醇结合。制剂中较小形式的钙蛋白酶抑制蛋白不与酸性磷脂结合。对牛大型钙蛋白酶抑制蛋白进行了溴化氰消化，并纯化了一个代表完整蛋白质质量约六分之一的磷脂结合片段。氨基酸序列分析表明，该磷脂结合片段来自大型钙蛋白酶抑制蛋白的氨基末端。
