Figure 9. Mechanism of the myosin step.
(A) ATP binding to the trailing head (yellow) and its detachment releases strain stored in the molecule. (B) The bound head (black with a gold nanoparticle attached) performs its power stroke which is accompanied by the AB transition (inset). The labeled head becomes a new trailing head (C) which detaches after ATP binding. (D) It moves forward in a partially twisting motion and occupies an off axis position (transient state). From this position, the head binds the desired binding site while ATP hydrolyses. (E) The step completes as the head binds actin and is repeated by the other head in the same direction dictated by the initial torsional strain. (F) Schematic representation of both heads' movement (lateral projection).