Yanagida T, Arata T, Oosawa F
Nature. 1985;316(6026):366-9. doi: 10.1038/316366a0.
Muscle contraction results from a sliding movement of actin filaments induced by myosin crossbridges on hydrolysis of ATP, and many non-muscle cells are thought to move using a similar mechanism. The molecular mechanism of muscle contraction, however, is not completely understood. One of the major problems is the mechanochemical coupling at high velocity under near-zero load. Here, we report measurements of the sliding distance of an actin filament induced by a myosin crossbridge during one ATP hydrolysis cycle in an unloaded condition. We used single sarcomeres from which the Z-lines, structures which anchor the thin filaments in the sarcomere, had been completely removed by calcium-activated neutral protease (CANP) and trypsin, and measured both the sliding velocity of single actin filaments along myosin filaments and the ATPase activity during sliding. Our results show that the average sliding distance of the actin filament is less than or equal to 600 A during one ATP cycle, much longer than the length of power stroke of myosin crossbridges deduced from mechanical studies of muscle, which is of the order of 80 A (for example, ref. 15).
肌肉收缩源于肌动蛋白丝的滑动运动，这种运动由肌球蛋白横桥在ATP水解时引发，许多非肌肉细胞被认为也利用类似机制进行移动。然而，肌肉收缩的分子机制尚未完全明晰。其中一个主要问题是在接近零负载的高速状态下的机械化学偶联。在此，我们报告了在无负载条件下，一个ATP水解循环中肌球蛋白横桥诱导肌动蛋白丝的滑动距离的测量结果。我们使用了单个肌节，其中将肌节中锚定细肌丝的结构——Z线，通过钙激活中性蛋白酶（CANP）和胰蛋白酶完全去除，并且测量了单个肌动蛋白丝沿肌球蛋白丝的滑动速度以及滑动过程中的ATP酶活性。我们的结果表明，在一个ATP循环中，肌动蛋白丝的平均滑动距离小于或等于600埃，这比从肌肉力学研究推断出的肌球蛋白横桥的动力冲程长度长得多，后者约为80埃（例如，参考文献15）。
