Myosins of fast and slow skeletal muscles differ by the isoform composition of the heavy and light chains. We compared functional characteristics of myosin from the fast (m. psoas) and slow (m. soleus) muscles of rabbits. The parameters of single actin—myosin interaction were measured in an optical trap, and the characteristics of the Ca2+ regulation of actin—myosin interaction were studied using an in vitro motility assay. The duration of interaction of myosin from the fast muscle with actin was shorter and the filament sliding velocity over this myosin was higher than the corresponding parameters for myosin from the slow muscle. The dependence pCa—velocity for myosin from the fast muscle was less sensitive to Ca2+ than that of slow muscle myosin. Thus, functional properties of myosin determine not only mechanical and kinetic characteristics of muscle contraction, but also the peculiarities of its Ca2+ regulation.

中文翻译：

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快慢骨骼肌肌球蛋白功能特性比较

快速和慢速骨骼肌的肌球蛋白因重链和轻链的异构体组成不同而不同。我们比较了兔子快肌（腰大肌）和慢肌（比目鱼肌）的肌球蛋白功能特征。在光阱中测量单个肌动蛋白-肌球蛋白相互作用的参数，并使用体外运动试验研究肌动蛋白-肌球蛋白相互作用的 Ca2+ 调节特性。来自快肌的肌球蛋白与肌动蛋白相互作用的持续时间较短，并且该肌球蛋白上的细丝滑动速度高于来自慢肌的肌球蛋白的相应参数。与慢肌肌球蛋白相比，快肌肌球蛋白的依赖性 pCa 速度对 Ca2+ 的敏感性较低。因此，