Nikitina L V, Kopylova G V, Shchepkin D V, Katsnel'son L B
Biofizika. 2008 Nov-Dec;53(6):956-61.
A series of experiments in an in vitro motility assay with reconstructed thin filaments has been performed to determine the dependence of the velocity of thin filament movement on the concentration of calcium in solution (in the pCa range from 5 to 8) for rabbit cardiac isomyosins V1 and V3. The "pCa-velocity" curves had the sigmoid form. It was found for each isoform that sliding velocities of regulated thin filaments (at the saturating calcium concentration (pCa 5)) and actin filaments did not differ from each other. The Hill coefficient was 1.04 and 0.75 for isomyosins V1 and V3, respectively. The calcium sensitivity of V3 was found to be higher than that of V1. In the framework of the same method, the relationship between the velocity of thin filament sliding and the concentration of the actin-binding protein a-actinin (analog of the "force-velocity" relationship) has been estimated for each isoform V1 and V3 at the saturating calcium concentration. The results obtained suggest that the calcium regulation of the contractile activity of isomyosins V1 and V3 occurs by different mechanisms.
已进行了一系列使用重构细肌丝的体外运动分析实验，以确定兔心脏肌球蛋白V1和V3细肌丝运动速度对溶液中钙浓度（pCa范围为5至8）的依赖性。“pCa-速度”曲线呈S形。对于每种同工型，发现调节型细肌丝（在饱和钙浓度（pCa 5）下）和肌动蛋白丝的滑动速度彼此无差异。肌球蛋白V1和V3的希尔系数分别为1.04和0.75。发现V3的钙敏感性高于V1。在相同方法的框架内，已在饱和钙浓度下估计了每种同工型V1和V3的细肌丝滑动速度与肌动蛋白结合蛋白α-辅肌动蛋白浓度之间的关系（类似于“力-速度”关系）。所得结果表明，肌球蛋白V1和V3收缩活性的钙调节通过不同机制发生。
