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Dynamics of Myosin-V Processivity

Ganhui Lan ^* and Sean X. Sun ^* 

^* Department of Mechanical Engineering, and Whitaker Institute of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland

Correspondence: Address reprint requests to Sean Sun, Tel.: 410-516-4003; E-mail: ssun{at}jhu.edu.

Myosin-V is an actin-associated processive molecular motor. Single molecule experiments revealed that myosin-V walks in a stepwise fashion with occasional backward steps. By combining the mechanical structure of the motor with the ATP hydrolysis kinetics, we construct a dynamical model that accounts for the stepwise processivity. The molecular properties of the protein chains connecting the myosin heads are important. A simple elastic model demonstrates that the stress transmitted from the leading head to the trailing head leads to net forward motion. The step-sizes are non-uniform. We also predict there are several substeps. The translational speed and step-size distributions are computed for several different conditions. The computed force-versus-velocity curve shows that under an external load, myosin-V slows down. However, the sizes of the steps remain the same.

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