Movie S8.

Two-step powerstroke of myosin V. Animation (accompanying Fig. 4B) illustrating the two-step powerstroke mechanism of myosin V. The transitions are animated by direct morphing between the three structures Prepowerstroke, ADP state, and Rigor. Starting with the Prepowerstroke conformation, myosin first rearranges to allow phosphate release without much change in its lever arm (29). Then, the first step of the powerstroke consists of a large swing of ∼58° of the lever arm toward the ADP state. The actin-binding cleft [between the U50 (blue) and L50 (white) subdomains] is closing for this transition, leading to the only state of the actomyosin cycle, which exhibits high affinity for both actin and the nucleotide. The second step of the powerstroke occurs upon ADP release and ends in the Rigor state after an additional lever arm swing of 9.5°.