The cargo-binding domain regulates structure and activity of myosin 5

Myosin V: special delivery There is growing interest in the mechanisms that cells use to deliver specific components to correct sites. Myosin motor proteins perform many of these transport roles. Now Liu et al. have determined the three-dimensional structure of an inhibited state of myosin V: the structure suggests a novel mechanism for solving the problem of returning a molecular motor from its destination to its starting position. When myosin V has no cargo it has a compact structure that binds to rapidly treadmilling actin filaments. In a separate paper, Thirumurugan et al. show that, in the absence of cargo, the cargo-binding domain of myosin V binds to a specific target on its own motor domain to inhibit its own movement along the actin track and weaken its binding to actin. These two papers reveal the elegant method used by cells to keep cargo transport under control.