A hand-over-hand diffusing model for myosin-VI molecular motors

Single molecules of dimeric myosin-VI have been demonstrated to be able to move processively towards the pointed end of actin filament with a mean step size of ∼ 36 nm. Here we present a hand-over-hand diffusing mechanism for this unidirectional movement. Based on this mechanism, its dynamical behaviors such as the step-size distribution, dwell-time distributions and mean dwell time at various ATP and ADP concentrations and under various loads are studied in detail. The calculated results show good agreement with previous experimental results. The processive movement of mutant myosin-V with its neck domains truncated to only one IQ motif can also be explained by using this hand-over-hand diffusing model.