Kramers-type elastic ratchet model for ATP gating during kinesin's mechanochemical cycle

ATP binding, acting as a gate, plays an important role in kinesin stepping. To understand the physical mechanism of the ATP gate, we propose a Kramers-type elastic ratchet model in which the free head undergoes a biased diffusive search. By first passage time analysis, we investigate the dependence of the mean dwell time on the load force for forward steps of kinesin and find that the forward dwell time varies exponentially with the backward load force which is consistent with the data of Carter and Cross, Nature 435 (2005) 308. Our work suggests that the gating mechanism triggered by ATP binding involves both Kramers-type elastic ratchet mechanism and power stroke movement.