Mapping subdomains in the C-terminal region of troponin I involved in its binding to troponin C and to thin filament
Mapping subdomains in the C-terminal region of troponin I involved in its binding to troponin C and to thin filament
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DOI：
10.1074/jbc.274.26.18189
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发表时间：
1999-06-25
影响因子：
4.8
通讯作者：
Ramos, CHI
中科院分区：
文献类型：
--
作者：
Ramos, CHI
肌钙蛋白 I (TnI) 是肌钙蛋白的抑制性成分，肌钙蛋白是调节骨骼和心肌收缩的三元复合物。先前的研究表明，TnI 的 C 末端区域与“抑制区”（残基 98-116）连接时，具有该分子的主要调节功能（Farah, C. S.、Miyamoto, C. A.、Ramos, C. H. I.、Silva, A. C. R.、Quaggio, R. B.、Fujimori, K.、Smillie, L. B. 和 Reinach, F. C. (1994) 化学杂志 269, 5230-5240)。为了更详细地研究这些功能，构建了 TnI C 端区域的连续缺失突变体。这些实验表明，较长的 C 端缺失会导致对肌动球蛋白 ATP 酶活性的抑制较低，并削弱与肌钙蛋白 C (TnC) N 端结构域的相互作用，这与这两种蛋白质之间相互作用的反平行模型一致。结论是 TnI 的整个 C 末端区域对于其完整的调节活性是必需的。残基 137 和 144 之间的区域被证明与抑制区中的残基 108-115 具有同源性（Farah, C. S. 和 Reinach, F. C. (1995) FASEB J. 9, 755-767)，参与与 TnC 的结合。残基 98 和 129 之间的区域参与调节 TnC 对钙的亲和力。 C 端残基 166-182 参与 TnI 与细丝的结合。讨论了 TnI 功能的模型。
Troponin I (TnI) is the inhibitory component of troponin, the ternary complex that regulates skeletal and cardiac muscle contraction. Previous work showed that the C-terminal region of TnI, when linked to the "inhibitory region" (residues 98-116), possesses the major regulatory functions of the molecule (Farah, C. S., Miyamoto, C. A., Ramos, C. H. I., Silva, A. C. R., Quaggio, R. B., Fujimori, K., Smillie, L. B., and Reinach, F. C. (1994) J. Biol. Chem. 269, 5230-5240). To investigate these functions in more detail, serial deletion mutants of the C-terminal region of TnI were constructed. These experiments showed that longer C-terminal deletions result in lower inhibition of the actomyosin ATPase activity and weaken the interaction with the N-terminal domain of troponin C (TnC), consistent with the antiparallel model for the interaction between these two proteins. The conclusion is that the whole C-terminal region of TnI is necessary for its full regulatory activity. The region between residues 137 and 144, which was shown to have homology with residues 108-115 in the inhibitory region (Farah, C. S., and Reinach, F. C. (1995) FASEB J. 9, 755-767), is involved in the binding to TnC. The region between residues 98 and 129 is involved in modulating the affinity of TnC for calcium. The C-terminal residues 166-182 are involved in the binding of TnI to thin filament. A model for the function of TnI is discussed.