Extensive studies on the dynamic aspects of myofilament sliding in muscle as a micromachine.

所得结果总结如下：1。肌动蛋白-肌球蛋白在肌肉中滑动的单位距离测量：Yamada， Sugi等人表明，当激光闪光光解笼状ATP，释放出与纤维内肌球蛋白分子总数相等的ATP分子时，甘油化的骨骼肌纤维沿其整个长度均匀缩短10 nm/半个肌瘤。对纤维瞬间变短的分析表明，纤维内部抗变短的阻力与最大等距力基本一致，表明在等距条件下，肌动蛋白-肌球蛋白滑动的单位距离约为10 nm。用基因工程技术研究肌球蛋白运动结构域的功能Sutoh等人成功地从黏菌Dictyostelium中制备了肌球蛋白突变体，发现(1)仅由760个氨基酸残基组成的肌球蛋白亚片段1 （S-1）片段仍然可以与肌动蛋白丝产生滑动力，(2)亚片段2 （S-2）区域缺乏氨基酸残基的突变体肌球蛋白可以以比对照肌球蛋白更慢的速度滑动肌动蛋白丝，这表明S-2参与肌肉收缩。操纵单分子技术的发展：Kinosita和其他人开发了一种光学显微镜系统，由于背景荧光减少，可以清楚地观察到单个荧光团。该系统对于研究单个肌球蛋白与单个ATP分子之间的机械化学反应非常有用。另一方面，Ando等人成功地将原子力显微镜与荧光显微镜相结合，也为研究肌动球蛋白- atp系统的单分子动力学提供了系统。

The results obtained are summarized as follows.1.Measurement of the unitary distance of actin-myosin sliding in muscle : Yamada, Sugi and others showed that a glycerinated skeletal muscle fiber shortens uniformly along its entire length by 10 nm/half sarcomere, when it is activated by laser flash photolysis of caged ATP releasing ATP molecules whose number was equal to the total number of myosin molecules within the fiber. Analysis of the flash-induced fiber shortening indicated that the internal resistance against shortening was nearly the same as the maximum isometric force, suggesting that the unitary distance of actin-myosin sliding is about 10 nm in the isometric condition.2.Function of myosin motor domains as studied by techniques of genetic engineering : Sutoh and others succeeded in preparing mutant myosins from a slime mold, Dictyostelium, and found (1) a segment of myosin subfragment 1 (S-1) consisting only of 760 amino acid residues could still generate sliding force with actin filaments, and (2) mutant myosins, in which amino acid residues are lacking in the subfragment 2 (S-2) region, could slide actin filaments past them with velocities slower than those for control myosin, suggesting the involvement of S-2 in muscle contraction.3.Development of techniques manipulating single molecules : Kinosita and others developed a light microscope system, with which single fluorosphores could be clearly observed as a result of reduced background fluorescence. This system is extremely useful for studying the mechanochemical reaction between single myosin and single ATP molecules. Ando and others, on the other hand, succeeded in combining an atomic force microscope with a fluorescent microscope, also providing the system for studying the single molecule dynamics of actomyosin-ATP system.