Cooke R
CRC Crit Rev Biochem. 1986;21(1):53-118. doi: 10.3109/10409238609113609.
Knowledge of the mechanism of contraction has been obtained from studies of the interaction of actin and myosin in solution, from an elucidation of the structure of muscle fibers, and from measurements of the mechanics and energetics of fiber contraction. Many of the states and the transition rates between them have been established for the hydrolysis of ATP by actin and myosin subfragments in solution. A major goal is to now understand how the kinetics of this interaction are altered when it occurs in the organized array of the myofibril. Early work on the structure of muscle suggested that changes in the orientation of myosin cross-bridges were responsible for the generation of force. More recently, fluorescent and paramagnetic probes attached to the cross-bridges have suggested that at least some domains of the cross-bridges do not change orientation during force generation. A number of properties of active cross-bridges have been defined by measurements of steady state contractions of fibers and by the transients which follow step changes in fiber length or tension. Taken together these studies have provided firm evidence that force is generated by a cyclic interaction in which a myosin cross-bridge attaches to actin, exerts force through a "powerstroke" of 12 nm, and is then released by the binding of ATP. The mechanism of this interaction at the molecular level remains unknown.
通过对溶液中肌动蛋白和肌球蛋白相互作用的研究、对肌肉纤维结构的阐明以及对纤维收缩的力学和能量学测量，人们已经获得了关于收缩机制的知识。溶液中肌动蛋白和肌球蛋白亚片段水解ATP的许多状态及其之间的转变速率已经确定。目前的一个主要目标是了解这种相互作用的动力学在肌原纤维的有序排列中发生时是如何改变的。早期关于肌肉结构的研究表明，肌球蛋白横桥方向的变化是产生力的原因。最近，附着在横桥上的荧光和顺磁探针表明，在产生力的过程中，至少横桥的一些结构域不会改变方向。通过对纤维稳态收缩以及纤维长度或张力阶跃变化后的瞬态进行测量，已经定义了活性横桥的一些特性。综合这些研究提供了确凿的证据，即力是由一种循环相互作用产生的，在这种相互作用中，肌球蛋白横桥附着在肌动蛋白上，通过12纳米的“动力冲程”施加力，然后通过ATP的结合而释放。这种相互作用在分子水平上的机制仍然未知。
