TWO MODES OF BINDING OF MYOSIN HEADS TO ACTIN FILAMENTS

描述：申请人和他的同事早些时候表明， 肌球蛋白头（S1）可以附着在一个或两个肌动蛋白原体上， 肌动蛋白丝，取决于纤维是否饱和， 不饱和的S1。该项目的目标是测试一个 假设，这是由这一发现刺激，一个主要部分， 骨骼肌的动力冲程包括方向性变化 与肌球蛋白头部从结合状态的转变有关 从一个肌动蛋白转变为与两个肌动蛋白结合的状态。 在这 他们提出的应用程序来测试这一假设：（一）检查 S1与不饱和丝结合的动力学是否 与1 S1结合2肌动蛋白一致;（ii）鉴定氨基 参与S1和肌动蛋白之间第二次接触的酸性残基; (iii)在S1中诱导点突变，以证明 第二肌动蛋白结合位点;（iv）测试是否在僵硬中交叉桥 肌肉与两个肌动蛋白结合;（v）测试这两个结合状态是否 在ATP的水解过程中可以看到。 这个项目的重要性在于它提出了一个关键的 关于收缩性基本问题的假设，并提出 实验性地测试它。 两个绑定状态的概念， 将检查它们之间的过渡是否涉及部队生成 骨骼肌和平滑肌，但可能适用于更广泛的 电机驱动的过程。 测试这个想法肯定会 有助于理解发生在 acto-S1在收缩期间。 很可能， 骨骼肌和平滑肌收缩的分子机制将 导致更好的治疗患病肌肉的方法。

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.