Fig. 7

Brownian ratchet mechanism underpinned by position-dependent weak binding. a The accessibility and the dwell time depend on the binding position. The accessibility (blue) is plotted against the left axis, and the dwell time (magenta) is plotted against the right axis. The states whose positions are within peaks ± 1 SD in Fig. 6b were used to calculate the accessibility and dwell time. The dashed line indicates the inferred mean position of the detached state, which is the cyan plot in Fig. 6a. The dwell time is prolonged 250 times upon the transition from weak binding to strong binding. b Force generation of the actomyosin complex is done by the Brownian ratchet mechanism and the multiple-step lever-arm swing. A myosin head achieves strong biased binding from weak binding during free diffusion as a Brownian ratchet, followed by a multiple-step and reversible lever-arm swing.