The majority of myosins are motor proteins that use the hydrolysis of ATP to drive movement along actin filaments. Myosins can be divided into two groups: conventional myosins (myosin II) are involved in generating the mechanical force for muscle contraction; unconventional myosins (all other classes) are involved in processes such as cell motility, cytokinesis and trafficking. A few members of the myosin superfamily lack ATPase activity and do not function as motor proteins. (Adapted from FBrf0134714, FBrf0213876 and FBrf0223842.)