Effect of calcium-sensitizing mutations on calcium binding and exchange with troponin C in increasingly complex biochemical systems.
Effect of calcium-sensitizing mutations on calcium binding and exchange with troponin C in increasingly complex biochemical systems.
复制标题
在日益复杂的生化系统中，钙敏化突变对钙结合以及与肌钙蛋白 C 交换的影响。
DOI：
10.1021/bi901867s
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发表时间：
2010
期刊：
影响因子：
2.9
通讯作者：
Davis,JonathanP
中科院分区：
文献类型：
--
作者：
Tikunova,SvetlanaB;Liu,Bin;Swindle,Nicholas;Little,SeanC;Gomes,AldrinV;Swartz,DarlR;Davis,JonathanP
肌钙蛋白C（TnC）与其他细丝和粗丝蛋白之间的钙依赖性相互作用在调节心肌收缩中起关键作用。将TnC调控结构域中的5个疏水残基（Phe 20、Val 44、Met 45、Leu 48和Met 81）分别替换为极性Gln，以检测这些突变对（1）在日益复杂的生化系统中与TnC的钙结合和交换以及（2）肌动球蛋白ATP酶的钙敏感性的影响。疏水残基突变极大地影响钙结合和交换与TnC在日益复杂的生化系统，表明侧链内和分子间的相互作用，这些残基起着至关重要的作用，在确定如何TnC响应钙。然而，使孤立的TnC对钙敏感的突变并不一定增加肌钙蛋白（Tn）复合物或有或无肌球蛋白S1的重构细丝的钙敏感性。此外，钙敏感性重建细丝（在没有肌球蛋白S1）是一个更好的预测肌动球蛋白ATP酶活性的钙依赖性比TnC或Tn复合物。因此，在日益复杂的生化系统中，TnC的内在特性及其与其他收缩蛋白的相互作用在调节钙与TnC的结合中起着至关重要的作用。
The calcium-dependent interactions between troponin C (TnC) and other thin and thick filament proteins play a key role in the regulation of cardiac muscle contraction. Five hydrophobic residues (Phe20, Val44, Met45, Leu48, and Met81) in the regulatory domain of TnC were individually substituted with polar Gln, to examine the effect of these mutations that sensitized isolated TnC to calcium on (1) the calcium binding and exchange with TnC in increasingly complex biochemical systems and (2) the calcium sensitivity of actomyosin ATPase. The hydrophobic residue mutations drastically affected calcium binding and exchange with TnC in increasingly complex biochemical systems, indicating that side chain intra- and intermolecular interactions of these residues play a crucial role in determining how TnC responds to calcium. However, the mutations that sensitized isolated TnC to calcium did not necessarily increase the calcium sensitivity of the troponin (Tn) complex or reconstituted thin filaments with or without myosin S1. Furthermore, the calcium sensitivity of reconstituted thin filaments (in the absence of myosin S1) was a better predictor of the calcium dependence of actomyosin ATPase activity than that of TnC or the Tn complex. Thus, both the intrinsic properties of TnC and its interactions with the other contractile proteins play a crucial role in modulating the binding of calcium to TnC in increasingly complex biochemical systems.