INTERACTION OF INVERTEBRATE MYOSINS WITH ACTIN

在滑动肌动蛋白体外运动试验中， 荧光标记的肌动蛋白丝在肌球蛋白是可视化使用 显微镜 为了直接观察肌球蛋白， 肌动蛋白的运动与其在肌球蛋白上的位置，天然粗丝必须 被利用 作为我们研究鲎天然粗丝的第一步，我们 从鲎横纹肌中分离肌球蛋白， 肌动蛋白丝在纯化肌球蛋白上的速度。 鲎肌是 由薄（肌钙蛋白和原肌球蛋白）和厚（肌球蛋白）调节 轻链磷酸化）丝调控系统， 钙依赖性 我们的研究结果表明， 系统占主导地位，并为肌动蛋白丝的最大运动发生 磷酸化鲎肌球蛋白和活化的肌钙蛋白， 需要原肌球蛋白系统。 原肌球蛋白来源 当与肌动蛋白结合时，似乎使滑动速度增加5-10倍。 另一方面，钙不会显著改变 缺乏肌钙蛋白和原肌球蛋白。

In the sliding actin in vitro motility assay, movement of fluorescently-labeled actin filaments over myosin is visualized using a microscope. In order to directly visualize myosin and, thus, correlate actin's movement with its position on myosin, native thick filaments must be used. As our first step to study Limulus native thick filaments, we isolated myosin from Limulus striated muscle and examined the sliding velocity of actin filaments over the purified myosin. Limulus muscle is regulated by both the thin (troponin and tropomyosin) and thick (myosin light chain phosphorylation) filament regulatory system which are calcium-dependent. Our results demonstrated that the "off' state of either system is dominant, and for maximal movement of actin filaments to occur both phosphorylated Limulus myosin and an activated troponin and tropomyosin system is required. Tropomyosin from different sources appeared to increase the sliding velocity 5-10 fold when bound to actin. Calcium, on the other hand, does not alter the velocity significantly in the absence of both troponin and tropomyosin.