Sugiura S, Yamashita H, Serizawa T, Iizuka M, Shimmen T, Sugimoto T
Second Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Japan.
Pflugers Arch. 1992 May;421(1):32-6. doi: 10.1007/BF00374730.
The active sliding of cardiac myosin on actin cables was studied using an in vitro movement assay. Cardiac myosin prepared from either adult rabbit or rat hearts was mixed with small latex beads to coat them. Actin cables were obtained from the internodal cells of green algae, Characeae. When the myosin-coated beads suspended in physiological buffer were introduced into the internodal cells, the myosin started to interact with the actin causing the beads to move. The sliding movement of the beads was observed under microscopy and the sliding velocity measured. The observed movement was smooth and the velocity was constant over a long distance. The movement was physiological in nature: a) it was ATP-dependent, but above a certain level of ATP, the velocity was constant; b) the velocity was maximum at pH 7.0, and decreased in both acidic and alkaline conditions. The average sliding velocity of cardiac myosin obtained from rabbit ventricles (0.31 +/- 0.11 micron/s) was slower than that from rat ventricles (1.04 +/- 0.26 micron/s) reflecting the lower ATPase activity of rabbit cardiac myosin. This assay system is considered to be a useful tool linking biochemistry and physiology at the molecular level.
利用体外运动分析方法研究了心肌肌球蛋白在肌动蛋白丝上的主动滑动。将从成年兔或大鼠心脏制备的心肌肌球蛋白与小乳胶珠混合以包裹它们。肌动蛋白丝取自绿藻轮藻科的节间细胞。当悬浮在生理缓冲液中的肌球蛋白包被珠被引入节间细胞时，肌球蛋白开始与肌动蛋白相互作用，导致珠子移动。在显微镜下观察珠子的滑动运动并测量滑动速度。观察到的运动是平滑的，并且速度在长距离内保持恒定。该运动本质上是生理性的：a）它依赖于ATP，但在一定水平的ATP以上，速度是恒定的；b）速度在pH 7.0时最大，在酸性和碱性条件下均降低。从兔心室获得的心肌肌球蛋白的平均滑动速度（0.31±0.11微米/秒）比从大鼠心室获得的速度（1.04±0.26微米/秒）慢，这反映了兔心肌肌球蛋白较低的ATP酶活性。该分析系统被认为是在分子水平上连接生物化学和生理学的有用工具。
