Calcium binding to the regulatory domain of skeletal muscle troponin C induces a highly constrained open conformation.
Calcium binding to the regulatory domain of skeletal muscle troponin C induces a highly constrained open conformation.
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钙与骨骼肌肌钙蛋白 C 调节域的结合诱导高度受限的开放构象。
DOI：
10.1006/jmbi.1998.1933
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Cheung,HC
中科院分区：
文献类型：
--
作者：
She,M;Xing,J;Dong,WJ;Umeda,PK;Cheung,HC
我们使用荧光共振能量转移研究了骨骼肌全长肌钙蛋白C突变体的载脂蛋白和钙负载状态的调控n端结构域的构象。所研究的每个突变体都含有一个色氨酸残基（位置22或90）和一个半胱氨酸残基（位置52或101）。每个突变体中的固有荧光团作为能量供体，将半胱氨酸偶联到受体探针5-（碘乙酰氨基乙基）氨基萘-1-磺酸上。在载子状态下，两个位点间距离（残基22和52之间，残基90和52之间）的分布很宽，表明相当大的结构动力学。这些分布转移到更长的距离，并在钙负载状态下显着锐化。向更远的距离移动8到11 Å表明钙诱导了n端结构域构象的开放。肌钙蛋白C结构从封闭构象到开放构象的转变伴随着载脂蛋白结构中主导的结构波动的大幅减少，其分布宽度的大幅减少证明了这一点。这种高度受限的开放构象是促进肌钙蛋白C和肌钙蛋白I之间有效相互作用以触发骨骼肌收缩的结构基础的一部分。
We have used fluorescence resonance energy transfer to investigate the conformation of the apo and calcium-loaded states of the regulatory N-terminal domain of full-length troponin C mutants from skeletal muscle. The mutants studied each contained a single tryptophan residue (position 22 or 90) and a single cysteine residue (position 52 or 101). The intrinsic fluorophore in each mutant served as an energy donor and the cysteine was conjugated to the acceptor probe 5-(iodoacetamidoethyl)amino-naphthalene-1-sulfonic acid. The distributions of two intersite distances (between residues 22 and 52, and residues 90 and 52) were broad in the apo state, indicative of considerable structural dynamics. These distributions were shifted to longer distances and considerably sharpened in the calcium-loaded state. The shifts to longer distances by 8 to 11 Å indicate a calcium-induced opening of the N-terminal domain conformation. The transition of the troponin C structure from a closed conformation to an open conformation is accompanied by a substantial reduction of structural fluctuations that dominate in the apo structure as evidenced from the large decrease of the widths of the distributions. This highly constrained open conformation is required as part of the structural basis to facilitate productive interaction between troponin C and troponin I to trigger contraction in skeletal muscle.