Conformational changes induced in troponin I by interaction with troponin T and actin/tropomyosin.
Conformational changes induced in troponin I by interaction with troponin T and actin/tropomyosin.
复制标题
通过与肌钙蛋白 T 和肌动蛋白/原肌球蛋白相互作用诱导肌钙蛋白 I 的构象变化。
DOI：
10.1016/s0167-4889(99)00050-6
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Gergely,J
中科院分区：
文献类型：
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作者：
Tao,T;Gong,BJ;Grabarek,Z;Gergely,J
肌钙蛋白I（TnI）是横纹肌钙调节蛋白肌钙蛋白（Tn）的抑制组分。肌钙蛋白的另外两种成分是肌钙蛋白C（TnC）（钙结合成分）和肌钙蛋白T（TnT）（原肌球蛋白结合成分）。我们使用有限的胰凝乳蛋白酶消化来探测游离状态下TnI、二元TnC·TnI复合物、三元TnC·TnI·TnT（Tn）复合物以及重建的Tn·原肌球蛋白·F-肌动蛋白丝中的局部构象。单独或在TnC + TnI复合物中的TnI消化最初通过在所谓的抑制区中的Phe 100和Asp 101之间的肽键的切割产生两个主要片段。在三元Tn复合物裂解发生在Leu 140和Lys 141之间的一个新的网站。在不存在Ca 2+的情况下，随后在Leu 122和Met 116处消化1-140片段。在重构的细丝中，产生了与三元复合物的情况相同的片段，但是在不存在Ca 2+的情况下消化的速率比在存在Ca 2+的情况下慢。这些结果首先表明，无论是游离的TnI还是与TnC复合的TnI，在抑制区都有一个暴露的柔性位点。其次，TnT影响TnI在抑制区和包含140-141键的区域中的构象。第三，TnI的140-141区域可能在Ca ~（2+）缺失时与重构细丝中的肌动蛋白相互作用。这些发现被讨论的TnI在细纤维调节机制中的作用，并根据我们以前的结果[Y.罗，J. - L. Wu，J. German，T. Tao，Biochemistry 36（1997）13449-13454]对TnI的全局构象的研究。
Troponin I (TnI) is the inhibitory component of the striated muscle Ca2+regulatory protein troponin (Tn). The other two components of Tn are troponin C (TnC), the Ca2+-binding component, and troponin T (TnT), the tropomyosin-binding component. We have used limited chymotryptic digestion to probe the local conformation of TnI in the free state, the binary TnC⋅TnI complex, the ternary TnC⋅TnI⋅TnT (Tn) complex, and in the reconstituted Tn⋅tropomyosin⋅F-actin filament. The digestion of TnI alone or in the TnC⋅TnI complex produced initially two major fragments via a cleavage of the peptide bond between Phe100 and Asp101 in the so-called inhibitory region. In the ternary Tn complex cleavage occurred at a new site between Leu140 and Lys141. In the absence of Ca2+this was followed by digestion of the 1–140 fragment at Leu122 and Met116. In the reconstituted thin filament the same fragments as in the case of the ternary complex were produced, but the rate of digestion was slower in the absence than in the presence of Ca2+. These results indicate firstly that in both free TnI and TnI complexed with TnC there is an exposed and flexible site in the inhibitory region. Secondly, TnT affects the conformation of TnI in the inhibitory region and also in the region that contains the 140–141 bond. Thirdly, the 140–141 region of TnI is likely to interact with actin in the reconstituted thin filament when Ca2+is absent. These findings are discussed in terms of the role of TnI in the mechanism of thin filament regulation, and in light of our previous results [Y. Luo, J.-L. Wu, J. Gergely, T. Tao, Biochemistry 36 (1997) 13449–13454] on the global conformation of TnI.