Unconventional myosins.

Myosins are molecular motors that upon interaction with actin filaments convert energy from ATP hydrolysis into mechanical force. Evidence has emerged for the existence of a large, widely expressed and evolutionarily ancient superfamily of myosin genes. In addition to the well-catheterized conventional, filament-forming, two-headed myosin-II of muscle and nonmuscle cells, at least ten additional classes of myosins have been identified. In vertebrates, at least seven of the eleven classes are expressed, and many myosins can be expressed in a single cell type. This review summarizes known structural and functional features of these novel unconventional myosins.