An intermediate along the recovery stroke of myosin VI revealed by X-ray crystallography and molecular dynamics

Significance Myosins are motor proteins involved in the transport of cellular cargoes and muscle contraction. Upon interaction with actin, the motor domain undergoes a conformational transition, called powerstroke, in which the lever arm is swung to generate force and directional motion. The recovery stroke reprimes the motor by coupling the reverse swing of the lever arm to ATP hydrolysis. Using X-ray crystallography and molecular simulations, we characterize a putative intermediate along the recovery stroke of myosin VI, which challenges existing models of myosin chemomechanical transduction. Intriguingly, the new structure suggests that the repriming of the lever arm would be uncoupled from ATPase activity until the very end of the recovery stroke and mostly driven by thermal fluctuations.