Dynamical mechanism of stepping of the molecular motor myosin V along actin filament and simulation in an actual system

Abstract

On the base of the random motion of myosin, the structural asymmetry of the actin filament, and the interaction between the motor and the track, the present study proposes a physical mechanism for the processive stepping of the two-headed molecular motor myosin V along the actin filament. The detachment from actin filament and forward swing of the trailing head, which are caused by increased entropy and the release of the bending energy in the neck region, are the initial steps of the stepping process. The detached head then rotates and randomly moves around the still attached head. A step is completed after the detached head detects the next binding site. In the mechanism, the direction of myosin V movement was determined on the basis of the configuration of the actomyosin system. The role of ATP is the energy provider for the local random motion. The applicability of the dynamic mechanism was evaluated on a simulation system that preserved most of the characteristics of the actomyosin system.