TWO MODES OF BINDING OF MYOSIN HEADS TO ACTIN FILAMENTS

描述：申请人和他的同事早些时候证明了 肌球蛋白头部(S1)可以附着在一个或两个肌动蛋白原基上 肌动蛋白细丝，取决于细丝是饱和的还是 未饱和的S1‘S。该项目的目标是测试一个 这一发现刺激了一种假说，那就是 骨骼肌的有力划水包括方向的改变 与肌球蛋白头部从其结合状态转变有关 一个肌动蛋白与两个肌动蛋白结合的状态。在这 他们提出了通过以下方式检验这一假设的应用：(I)检验 S1与不饱和纤维的结合动力学是否为 与1个S1结合2个肌动蛋白一致；(Ii)鉴定氨基酸 参与S1与肌动蛋白二次接触的酸残基； (Iii)在S1中诱导点突变，以证明 第二个肌动蛋白结合部位；(Iv)检测跨桥是否僵硬 肌肉与两种肌动蛋白结合；(V)测试这两种结合状态 在三磷酸腺苷的水解过程中可以看到。 这个项目的意义在于它呈现了一个关键的 关于收缩的一个基本问题的假说，并提出 从实验上对其进行测试。两个结合态的想法，以及 它们之间的过渡是否涉及部队生成将被检查 在骨骼肌和平滑肌中，但可能适用于更广泛的 电机驱动过程的类别。测试这一想法肯定会 有助于理解发生在地球上的 Acto-S1在收缩过程中。很可能是对 骨骼肌和平滑肌收缩的分子机制 在治疗患病肌肉方面带来更好的方式。

DESCRIPTION: The applicant and his colleagues showed earlier that a myosin head (S1) can attach either to one or to two actin protomers in an actin filament, depending of whether filament is saturated or unsaturated with S1's. The objective of the project is to test a hypothesis, which was stimulated by this finding, that a major part of a power stroke of skeletal muscle consists of orientational change associated with transition of myosin head from a state in which it binds one actin to a state in which it binds to two actins. In this application they propose to the test this hypothesis by: (i) checking whether the kinetics of binding of S1 to unsaturated filament is consistent with 1 S1 binding to 2 actins; (ii) identifying the amino acid residues involved in making the second contact between S1 and actin; (iii) inducing point mutations in S1 to demonstrate the importance of the second actin binding site; (iv) testing whether cross-bridges in rigor muscle bind to two actins; (v) testing whether the two binding states can be seen during hydrolysis of ATP. The significance of this project is that it presents a critical hypothesis about a fundamental problem in contractility and proposes to test it experimentally. The idea of two binding states and that the transition between them is involved in force generation will be checked in skeletal and smooth muscle, but applies perhaps to the broader category of motor-driven processes. Testing this idea certainly will contribute to the understanding of the molecular changes occurring in acto-S1 during contraction. It is likely that the elucidation of the molecular mechanism of contraction of skeletal and smooth muscle will lead to better modalities in treating diseased muscle.