Nature. 1984;308(5962):864-6. doi: 10.1038/308864a0.
Phosphorylation of the regulatory light chains of vertebrate smooth muscle or cytoplasmic myosins alters the structure of myosin monomers, favours myosin filament formation and stimulates the actin-activated Mg2+-ATPase of myosin. Similarly, in Dictyostelium and Acanthamoeba phosphorylation of the myosin heavy chains exhibits both polymerization and actin-activated Mg2+ATPase. Unfortunately, the relationships between phosphorylation, myosin assembly and activation of ATP hydrolysis are not fully understood in any of these systems, as there has been no way of varying the extent of polymerization of intact myosin without changing solution conditions or the level of myosin phosphorylation, parameters that may have independent effects on ATPase activity. Taking an entirely new approach, we have used monoclonal antibodies against the tail of Acanthamoeba myosin-II that cause filament disassembly to show that myosin polymerization itself stimulates actomyosin ATPase activity. With a fixed level of myosin-II phosphorylation and constant solution conditions, depolymerization of myosin-II filaments by antibodies causes a concomitant loss of actin-activated ATPase activity.
脊椎动物平滑肌或细胞质肌球蛋白的调节轻链的磷酸化改变肌球蛋白单体的结构，有利于肌球蛋白丝的形成，并刺激肌球蛋白的肌动球蛋白激活的 Mg2+-ATP 酶。同样，在盘基网柄菌和粘菌中，肌球蛋白重链的磷酸化表现出聚合和肌动球蛋白激活的 Mg2+ATP 酶。不幸的是，在这些系统中的任何一个系统中，磷酸化、肌球蛋白组装和 ATP 水解的激活之间的关系都没有完全理解，因为没有办法在不改变溶液条件或肌球蛋白磷酸化程度的情况下改变完整肌球蛋白的聚合程度，这些参数可能对 ATP 酶活性有独立的影响。我们采用了一种全新的方法，使用针对粘菌肌球蛋白-II 尾部的单克隆抗体导致纤维丝解聚，结果表明肌球蛋白聚合本身就可以刺激肌球蛋白肌动球蛋白 ATP 酶的活性。在固定的肌球蛋白-II 磷酸化水平和恒定的溶液条件下，抗体引起的肌球蛋白-II 纤维丝的解聚导致肌动球蛋白激活的 ATP 酶活性的相应丧失。
