Fig. 4.

Schematic view demonstrating how the motion of myosin is associated with ATP hydrolysis. The solid curve, E₁, represents the energy landscape found in our study (see Fig. 2), while the dotted curves, and E₂, represent putative energy landscapes for the strong actin-binding (nucleotide-free) and the detached (ATP-bound) states, respectively. For convenience, different colors are used for the high-energy (magenta) and low-energy (blue) regions. Arrows constitute a possible sequence of myosin motion coupled with ATP hydrolysis: (a) unidirectional, stepwise Brownian motion as found in our study (see Fig. 1) in the presumed ADP·Pi-bound state, (b) transition into the strong binding state upon products (ADP and Pi) release, (c) dissociation from the actin filament upon new ATP binding, (d) essentially isotropic Brownian motion in the ATP-bound state, (e) reentry to E₁ upon ATP hydrolysis (i.e., in the ADP·Pi-bound state).