Matsukubo M P, Singal P K, Dhalla N S
Basic Res Cardiol. 1981 Jan-Feb;76(1):16-28. doi: 10.1007/BF01908160.
Colloidal iron staining, calcium binding and enzyme activities were studied in the isolated rat heart sarcolemma. Colloidal iron staining of the sarcolemma revealed a high density of negatively charged sites associated with the cell surface. This membrane fraction was found to have calcium binding activity at both low (0.1 mM) and high (1.25 mM) concentrations of calcium. Pretreatment of the sarcolemma with either trypsin, phospholipase C or neuraminidase, was associated with a reduction in colloidal iron staining as well as decreased calcium-binding activity at high concentrations of calcium. Calcium binding at low concentrations was decreased by both trypsin and neuraminidase. Mg2+ ATPase, Ca2+ ATPase, and Na+-K+ ATPase activities were altered by neuraminidase and trypsin treatments, whereas phospholipase C treatment altered Na+-K+ ATPase only. It is concluded that both surface negative charge and calcium-binding sites associated with the isolated rat heart sarcolemma are contributed by a mosaic of biomolecules including proteins, phospholipids and glycoproteins, and alterations in the surface charge may influence the activities of membrane-bound enzymes.
对分离出的大鼠心肌肌膜进行了胶体铁染色、钙结合和酶活性研究。肌膜的胶体铁染色显示与细胞表面相关的高密度负电荷位点。发现该膜部分在低钙浓度（0.1 mM）和高钙浓度（1.25 mM）下均具有钙结合活性。用胰蛋白酶、磷脂酶C或神经氨酸酶对肌膜进行预处理，会导致胶体铁染色减少以及高钙浓度下钙结合活性降低。胰蛋白酶和神经氨酸酶均可降低低浓度下的钙结合。神经氨酸酶和胰蛋白酶处理会改变Mg2+ ATP酶、Ca2+ ATP酶和Na+-K+ ATP酶的活性，而磷脂酶C处理仅改变Na+-K+ ATP酶的活性。得出的结论是，与分离出的大鼠心肌肌膜相关的表面负电荷和钙结合位点均由包括蛋白质、磷脂和糖蛋白在内的生物分子镶嵌体贡献，并且表面电荷的改变可能会影响膜结合酶的活性。
