Journal Article

Direct observation of the myosin-Va power stroke and its reversal

Sellers, James R, Veigel, Claudia

2010

Overview

Motor proteins such as myosin use the energy from ATP to drive a conformational change that generates mechanical force, or power stroke. Using a single-molecule, optical-trap setup, the reverse movement could be observed for myosin-V heads bound to actin when external load is applied, which has implications for myosin's mechanochemical cycle. Complex forms of cellular motility, including cell division, organelle trafficking or signal amplification in the auditory system, require strong coordination of the myosin motors involved. The most basic mechanism of coordination is via direct mechanical interactions of individual motor heads leading to modification of their mechanochemical cycles. Here we used an optical trap–based assay to investigate the reversibility of the force-generating conformational change (power stroke) of single myosin-Va motor heads. By applying load to the head shortly after binding to actin, we found that, at a certain load, the power stroke could be reversed, and the head fluctuated between an actin-bound pre– and a post–power stroke conformation. This load-dependent mechanical instability might be critical to coordinate the heads of processive, dimeric myosin-Va. Nonlinear response to load leading to coordination or oscillations amongst motors might be relevant for many cellular functions.

• Publisher: Nature Publishing Group US,Nature Publishing Group
• Subject: 631/337/2265 / 631/57/2272/2273 / 631/80/128/1675 / Actin / Actins - chemistry / Actins - metabolism / Animals / Binding sites / Biochemistry / Biological Microscopy / Biomechanical Phenomena / Biomechanics / Biomedical and Life Sciences / Biophysics / Cellular biology / Life Sciences / Membrane Biology / Mice / Molecular biology / Muscle contraction / Myosin / Myosin Type V - chemistry / Myosin Type V - metabolism / Physiological aspects / Protein Binding / Protein Structure