Structural and Mechanistic Determinants of Myosin VI Processivity and Anchoring

Abstract

Myosin VI is a molecular motor that can function both as a transporter and anchor in cells. Its role is regulated through load, being capable of taking multiple consecutive 36 nm steps along an actin filament under zero load and switching to an anchor by stalling when placed under piconewton levels of load. The parameters necessary for such processivity and anchoring are not fully understood. We use high-speed gold nanoparticle tracking to study single molecules of myosin VI with millisecond resolution in the absence of load. Optical tweezers are used to observe the behavior of the molecules when perturbed by load. In order to probe the contribution of the myosin VI tail domain to processivity and anchoring, we have created and characterized a number of mutant tail domain constructs. Our results reveal the resiliency of myosin VI as a transporter and suggest that it has evolved its unusual tail domain for purposes other than efficient cargo transport in the absence of applied load. We present preliminary data investigating the role of the myosin VI tail domain in important cellular processes such as transport against load and load-induced anchoring.