Model for Concerted Power Stroke Generation in Single Myosin V and F1-ATPase Imaging Trajectories

Abstract

The idea of a concerted mechanism of molecular group transfer and large conformational change in power stroke generation serves as the basis for an elasto-chemical theory of the rate constants that dictate the stepping kinetics in single F1-ATPase motors. The theory was employed to calculate the rate and equilibrium constant dependence on the rotor angle in experiments with magnetic tweezers. Using independent biochemical and single-molecule imaging data, the model was used to correctly predict the rates of binding and release of fluorescently labeled ATP without any adjustable parameters. This initial success of the model prompted its further development to other systems and experiments. In particular, the idea of group transfer elastically coupled to conformational change monitored by the probe is applied and extended to (1) calculate power stroke rate constants in two different force-spectroscopy experiments on single and double-headed myosin V; to (2) extract rate constants for hydrolysis and synthesis from controlled rotation data on F1-ATPase; and to (3) account for “dynamical effects” due to the internal and probe-related friction in the single-molecule imaging experiments. An important aspect of the analysis is the statistical modeling of biasing effects of finite time resolution in the photon-counting trajectories and the finite response time of the imaging probes.