Iino M, Takano-Ohmuro H, Kawana Y, Endo M
Department of Pharmacology, Faculty of Medicine, University of Tokyo, Japan.
Biochem Biophys Res Commun. 1992 Jun 15;185(2):713-8. doi: 10.1016/0006-291x(92)91684-i.
Calpain treatment of rabbit skinned muscle fibers resulted in proteolysis of junctional foot protein or Ca2+ release channel of the sarcoplasmic reticulum. Electrophoretic and immunoblot analyses indicate that calpain cleaves off approximately 130 kDa peptide from the N-terminus. After such treatment, Ca2+ capacity of the sarcoplasmic reticulum remained normal and both Ca2+ and adenine nucleotide dependence of Ca2+-induced Ca2+ release mechanism were retained. However, the Ca2+-activated Ca2+ release rate was increased by two fold after the proteolysis. The results suggest the presence of functional domains in the junctional foot protein, and the N-terminus domain controls the activity of the Ca2+ channel without changing Ca2+ and nucleotide sensitivities.
用钙蛋白酶处理兔去皮肤肌纤维会导致肌浆网连接足蛋白或钙释放通道的蛋白水解。电泳和免疫印迹分析表明，钙蛋白酶从N端切割掉约130 kDa的肽段。经过这种处理后，肌浆网的钙容量保持正常，并且钙诱导的钙释放机制对钙和腺嘌呤核苷酸的依赖性得以保留。然而，蛋白水解后钙激活的钙释放速率增加了两倍。结果表明连接足蛋白中存在功能域，并且N端结构域在不改变钙和核苷酸敏感性的情况下控制钙通道的活性。
