Further studies of the self-induced translation model of myosin head motion along the actin filament.

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.