PNAS Plus Significance Statements

Myosin II from the soil amoeba Acanthamoeba castellanii is a member of the largest of the 35 classes of the superfamily of molecular motors that, together with actin filaments, convert the energy of hydrolysis of ATP into force or motion that drives numerous cellular and intracellular processes. In this paper (pp. E23–E32) we show that the actin-activated ATPase of Acanthamoeba myosin II is regulated by phosphorylation of a specific serine in a region of the myosin motor domain that is known to be at the myosin–actin interface. No other myosin has been shown to be regulated in this way.