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Zhang, Chong

Molecular Physiology and Biophysics

2009

MS

Myosin V is a double-headed molecular motor that moves processively along actin filaments. Its processivity requires coordination between its two heads to keep their ATPase cycles out of phase, preventing both heads from detaching actin simultaneously. However, the kinetic scheme that two-headed myosin V takes during its processive run has long been debated. To address this issue, we studied the processivity (velocity and run length) of myosin V at multiple substrate conditions under zero load. We found that increasing [ATP] decreased the run length of myosin V, and a high phosphate concentration in the solution decreased both velocity and run length, as well as marlcedly increased the ratio of backsteps. Theses results are well explained by a lunetic model (Baker et al., 2004) in which myosin V proceeds through a branched kinetic pathway.