Figure 2.

The actin-activated myosin chemomechanical cycle. Step 1: ATP binding to the strongly-bound myosin head dissociates it from the actin. Step 2: ATP hydrolysis is associated with locking the weakly-bound head into a prestroke configuration. Step 3 (a and b): Rebinding of the head to actin in a strongly-bound state is associated with Pi release from the active site. Step 4: After strong binding of the myosin to the actin, the myosin undergoes an ∼10-nm power stroke. The head is now in a strongly-bound force-producing state and cannot bind ATP until the ADP is released from the active site. Step 5: ADP is released, allowing rapid ATP binding, and the cycle continues. Modified from Lymn and Taylor (95,96). To see this figure in color, go online.