Yu B P, Masoro E J, Morley T F
J Biol Chem. 1976 Apr 10;251(7):2037-43.
The nature of the protein components and their location in the sarcoplasmic reticulum membrane were studied using sarcoplasmic reticulum vesicles isolated from rat skeletal muscle and purified by a density gradient centrifugation system. On the basis of analysis by means of sodium dodecyl sulfate gel electrophoresis, the protein components appear to be similar if not identical with those reported by others for rabbit sarcoplasmic reticulum, and the relative amount of each component is also similar to that found with rabbit sarcoplasmic reticulum. Evidence is presented that radioiodine-labeled diazotized diiodosulfanilic acid is a nonpermeant labeling agent of the protein components of sarcoplasmic reticulum vesicles; this agent minimally disturbs the functional activities of these membranes. By means of this labeling agent and perturbing agents, it is concluded that the protein components with molecular weights greater than 120,000 and the (Ca2+ + Mg2+)-adenosine triphosphatase partially or totally reside on or at the external surface of the sarcoplasmic reticulum vesicles. In the case of the adenosine triphosphatase, highly controlled trypsin treatment cleaves the molecule into two products, a 65,000 molecular weight fragment and a 56,000 molecular weight fragment. The evidence indicates that the 65,000 molecular weight component of the (Ca2+ + Mg2+)-adenosine triphosphatase is located in a more exposed fashion on the external surface of the vesicles than the 56,000 molecular weight compoenet and that some adenosine triphosphatase molecules have a more exposed position on the external surface of the vesicle than others. The protein components designated by MacLennan (MacLennan, D. H. (1975) Can. J. Biochem. 53, 251-261) as "calsequestrin" and "high affinity Ca2+ binding protein" are shown not to be on the external surface of the rat sarcoplasmic reticulum vesicle but rather to reside either within the core of the membrane or on the inside surface of the vesicle. The results of this study are in agreement with the model for the organization of the protein components of the sarcoplasmic reticulum membrene recently proposed by MacLennan (MacLennan, D. H. (1975) Can. J. Biochem. 53, 251-261).
利用从大鼠骨骼肌中分离并通过密度梯度离心系统纯化的肌浆网小泡，研究了蛋白质成分的性质及其在肌浆网膜中的位置。基于十二烷基硫酸钠凝胶电泳分析，这些蛋白质成分即便与其他文献报道的兔肌浆网中的蛋白质成分不完全相同，也似乎很相似，而且每种成分的相对含量也与兔肌浆网中的情况相似。有证据表明，放射性碘标记的重氮化二碘代磺胺酸是肌浆网小泡蛋白质成分的一种非渗透性标记剂；该试剂对这些膜的功能活性干扰极小。借助这种标记剂和干扰剂可以得出结论，分子量大于120,000的蛋白质成分以及（Ca2 + + Mg2 +）-腺苷三磷酸酶部分或全部位于肌浆网小泡的外表面或外表面处。就腺苷三磷酸酶而言，经过高度控制的胰蛋白酶处理会将该分子裂解为两种产物，一种分子量为65,000的片段和一种分子量为56,000的片段。证据表明，（Ca2 + + Mg2 +）-腺苷三磷酸酶的分子量为65,000的成分比分子量为56,000的成分以更暴露的方式位于小泡的外表面，并且一些腺苷三磷酸酶分子在小泡外表面的位置比其他分子更暴露。麦克伦南（MacLennan, D. H. (1975) Can. J. Biochem. 53, 251 - 261）命名为“肌集钙蛋白”和“高亲和力Ca2 +结合蛋白”的蛋白质成分并非位于大鼠肌浆网小泡的外表面，而是位于膜的核心内或小泡的内表面。本研究结果与麦克伦南（MacLennan, D. H. (1975) Can. J. Biochem. 53, 251 - 261）最近提出的肌浆网膜蛋白质成分组织模型一致。
