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首页> 外文期刊>Journal of Molecular Biology >A kinetic mechanism for the fast movement of Chara myosin.
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A kinetic mechanism for the fast movement of Chara myosin.

机译：Chara肌球蛋白快速运动的动力学机制。

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Endoplasmic streaming of characean cells of Nitella or Chara is known to be in the range 30-100 microm/second. The Chara myosin extracted from the cells and fixed onto a glass surface was found to move muscle actin filaments at a velocity of 60 microm/second. This is ten times faster than that of skeletal muscle myosin (myosin II). In this study, the displacement caused by single Chara myosin molecules was measured using optical trapping nanometry. The step size of Chara myosin was approximately 19nm. This step size is longer than that of skeletal muscle myosin but shorter than that of myosin V. The dwell time of the steps was relatively long, and this most likely resulted from two rate-limiting steps, the dissociation of ADP and the binding of ATP. The rate of ADP release from Chara myosin after the completion of the force-generation step was similar to that of myosin V, but was considerably slower than that of skeletal muscle myosin. The 19nm step size and the dwell time obtained could not explain the fast movement. The fast movement could be explained by the load-dependent release of ADP. As the load imposed on the myosin decreased, the rate of ADP release increased. We propose that the interaction of Chara myosin with an actin filament resulted in a negative load being imposed on other myosin molecules interacting with the same actin filament. This resulted in an accelerated release of ADP and the fast sliding movement.
机译：Nitella或Chara的characean细胞的内质流在30-100微米/秒的范围内。发现从细胞中提取并固定在玻璃表面上的Chara肌球蛋白以60微米/秒的速度移动肌动蛋白丝。这比骨骼肌肌球蛋白（myosin II）快十倍。在这项研究中，使用光阱纳米技术测量了由单个Chara肌球蛋白分子引起的位移。 Chara肌球蛋白的步长约为19nm。该步长大于骨骼肌肌球蛋白的步长，但比肌球蛋白V的步长短。步的停留时间相对较长，这很可能是由两个限速步所致，即ADP的解离和ATP的结合。力生成步骤完成后，Chara肌球蛋白的ADP释放速率与肌球蛋白V相似，但比骨骼肌肌球蛋白慢得多。 19nm步长和所获得的停留时间无法解释快速移动。快速移动可以通过ADP的负载相关释放来解释。随着施加到肌球蛋白上的负荷减少，ADP释放速率增加。我们提出Chara肌球蛋白与肌动蛋白丝的相互作用导致负负载施加在与同一肌动蛋白丝相互作用的其他肌球蛋白分子上。这导致ADP的加速释放和快速滑动。

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