Myosin V : tight grip and big steps

Moving a muscle and moving an organelle are two very different propositions. Myosin II in muscle, safely held in place in the highly structured sarcomere, can give an occasional shove between lengthy rests. But myosin V is diffusely distributed on organelles, and therefore must maintain a tight grip on an actin cable to prevent random diffusion of the organelle. On page 625, Moore et al. first provide evidence that a single myosin V molecule maintains that grip at least half of the time (compared with less than 5% of the time for myosin II), and then give a measure of the large power stroke that drives myosin V along the actin filament.The power stroke has been the subject of much contention in the myosin field. Toshio Yanagida (Osaka University, Osaka,...