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

结果如下：1.肌动蛋白-肌球蛋白在肌肉中滑动的单位距离的测量：Yamada，Sugi等人表明，当甘油化的骨骼肌纤维被笼状ATP的激光闪光光解激活时，其释放的ATP分子的数量等于纤维内肌球蛋白分子的总数，甘油化的骨骼肌纤维沿着其整个长度均匀地缩短沿着10 nm/半肌节。对闪光引起的纤维缩短的分析表明，抗缩短的内阻力与最大等长力几乎相同，这表明在等长条件下肌动蛋白-肌球蛋白滑动的单位距离约为10 nm。2.通过基因工程技术研究肌球蛋白运动域的功能：Sutoh和其他人成功地从黏菌Dictyosteomycin中制备了突变的肌球蛋白，并发现（1）肌球蛋白亚片段1（S-1）的一段仅由760个氨基酸残基组成的片段仍能与肌动蛋白丝产生滑动力，（2）亚片段2（S-2）区域缺少氨基酸残基的突变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。Kinosita和其他人开发了一种光学显微镜系统，通过该系统，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和单个ATP分子之间的机械化学反应非常有用。另一方面，安藤等人成功地将原子力显微镜与荧光显微镜结合起来，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.