Myosin-2 (Myosin II / NM2)

Myosin-2 is a large molecular motor protein composed of two heavy chains (approximately 2000 amino acids each) that forms the major structural component of muscle thick filaments and drives force generation in both muscle and nonmuscle cells[1][7]. The protein converts energy from ATP hydrolysis into mechanical force through cyclic interactions with actin filaments, with its structure consisting of N-terminal head domains (the motor unit) connected to long α-helical coiled-coil tail domains that mediate protein assembly[1][3]. Myosin-2 exists in multiple isoforms—including cardiac, skeletal, smooth muscle, and nonmuscle variants—each with specialized regulatory mechanisms suited to their tissue type[2]. The protein is regulated through phosphorylation of its regulatory light chains and through interactions with accessory proteins such as myosin-binding protein C, which modulates cardiac contractility[1][5]. Mutations in myosin-2, particularly in the coiled-coil S2 region, are associated with familial hypertrophic cardiomyopathy, a leading cause of sudden cardiac death[1]. The structural flexibility of the S2 subfragment is critical for both force generation and regulation, making it an important region for understanding both normal muscle physiology and disease pathogenesis[1][3].

Other names

Myosin IIClass-2 myosinNonmuscle myosin-2 (NM2)Smooth muscle myosin-2Cardiac myosin-2Skeletal myosin-2

ATP hydrolysis-dependent cyclic interaction with actin filaments to produce force\nConformational changes in the motor domain driven by ATPase activity\nRegulation through phosphorylation of regulatory light chains (RLC) in the autoinhibited 10S state\nRegulation through myosin-binding protein C interactions in cardiac muscle