Folding and regulation in myosins II and V

The enzymatic activity of many myosins is regulated by various means including calcium binding, phosphorylation or binding of receptor molecules. In this review we compare and contrast the regulation of smooth muscle myosin II and myosin Va with particular emphasis on the structural basis for the regulation. Both myosins adopt folded compact conformations in their off states, but the details of the conformations are markedly different. In the regulated smooth muscle myosin II, the key feature is an asymmetric interaction between the two heads of the molecule with contributions of specific tail-head interactions. In myosin V the key feature is an interaction between the heads and the globular tail domain.