Fig. 1.

Schematic diagram of attachment-detachment cycle between the cross-bridge (M) extending from the thick filament and actin (A) in the thin filament. M in the form of M·ADP·Pi attaches to actin to exert a power stroke, associated with release of Pi and ADP (from A to B). After the end of the power stroke, M remains attached to A, taking its postpower stroke configuration (B). Upon binding with ATP, M detaches from A to exert a recovery stroke, associated with reaction M·ATP → M·ADP·Pi (from C to D). M·ADP·Pi again attaches to A to again exert a power stroke (from D to A). M is assumed to attach rigidly to A, while its power and recovery strokes are assumed to result from swinging of the lever arm around the hinge.