G. Lan, and S. Sun. Biophys. J.88 (2):
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.