Mitsui T, Ohshima H
Department Physics, School of Science and Technology, Meiji University, Kawasaki, Japan.
Adv Exp Med Biol. 1993;332:377-82; discussion 382-3. doi: 10.1007/978-1-4615-2872-2_36.
We have extended and refined the model of myosin head motion along the actin filament which we proposed in 1988 (J. Muscle Res. Cell Motility 9, 248-260), and obtained the following results. (1) We assumed that the height of the induced potential depends upon tension with a maximum around the isometric tension, and got a force-velocity relation similar to the observation by Oiwa et al. (1990) that the velocity of the myosin-coated beads along the actin cables decreases with increasing centrifugal force applied in the direction of bead movement and then the velocity tends to increase when the force increases in the same direction beyond a certain value. (2) We introduced a correction factor in the relation between the measured tension and the microscopic tension produced by myosin head, and got a feature in force-velocity relation similar to the observation by Edman (1988) that the velocity drops sharply as the tension approaches to about 80% of the isometric tension. (3) We assumed that binding of an ATP-activated myosin head to an actin filament causes a local structural change extended roughly 20nm long along the filament, which provides a potential well spread over about 16nm for the myosin head, with three shallow potential wells in it. We studied kinetics of the myosin head in the potential well of about 16nm in order to explain the early tension recovery after the sudden change of muscle length observed by Ford, Huxley and Simmons (1977), with results in good agreement with their experimental data.
我们扩展并完善了1988年提出的肌球蛋白头部沿肌动蛋白丝运动的模型（《肌肉研究与细胞运动》9，248 - 260），并得到了以下结果。（1）我们假设感应电势的高度取决于张力，在等长张力附近达到最大值，从而得到了一种类似于大岩等人（1990年）观察结果的力 - 速度关系，即肌球蛋白包被的珠子沿肌动蛋白丝的速度随着沿珠子运动方向施加的离心力增加而降低，然后当力在同一方向上超过一定值继续增加时，速度趋于增加。（2）我们在测量的张力与肌球蛋白头部产生的微观张力之间的关系中引入了一个校正因子，得到了一种类似于埃德曼（1988年）观察结果的力 - 速度关系特征，即当张力接近等长张力的约80%时，速度急剧下降。（3）我们假设ATP激活的肌球蛋白头部与肌动蛋白丝的结合会导致沿细丝大约20nm长的局部结构变化，这为肌球蛋白头部提供了一个大约16nm宽的势阱，其中有三个浅势阱。我们研究了肌球蛋白头部在大约16nm势阱中的动力学，以解释福特、赫胥黎和西蒙斯（1977年）观察到的肌肉长度突然变化后的早期张力恢复情况，结果与他们的实验数据吻合良好。
