Myosin Myosin Myosins () are a superfamily of motor proteins best known for their roles in muscle contraction and in a wide range of other motility processes in eukaryotes. They are ATP-dependent and responsible for actin-based motility. The term was originally used to describe a group of similar ATPases found in the cells of both striated muscle tissue and smooth muscle tissue. Following the discovery by Pollard and Korn (1973) of enzymes with myosin-like function in "Acanthamoeba castellanii", a global range of divergent myosin genes have been discovered throughout the realm of eukaryotes. Although myosin was originally thought to be restricted
Myosin head actin together with the products of ATP hydrolysis, performs a power stroke associated with release of hydrolysis products, and detaches from actin upon binding with new ATP. The detached myosin head then hydrolyses ATP, and performs a recovery stroke to restore its initial position. The strokes have been suggested to result from rotation of the lever arm domain around the converter domain, while the catalytic domain remains rigid. Myosin head Muscle contraction is caused by the sliding action of thick filaments over thin filaments of the myofibril. Myosin is a major component of thick filaments and most myosin molecules are