Processivity of molecular motors under vectorial loads

Abstract

Molecular motors are cellular machines that drive the spatial organisation of the cells by transporting cargoes along intracellular filaments. Although the mechanical properties of single molecular motors are relatively well characterised, it remains elusive how the three-dimensional geometry of a load imposed on a motor affects its processivity, i.e., the average distance that a motor moves per interaction with a filament. Here, we theoretically explore this question for a single kinesin molecular motor by analysing the load-dependence of the stepping and detachment processes. We find that the processivity of kinesin increases with lowering the load angle between kinesin and microtubule filament, due to the deceleration of the detachment rate. When the load angle is large, the processivity is predicted to enhance with accelerating the stepping rate, through an optimal distribution of the load over the kinetic transition rates underlying a mechanical step of the motor. These results provide new insights into understanding of the design of potential synthetic biomolecular machines that can travel long distances with high velocities.