Class II myosin (Myosin II)

Class II myosin is a conventional myosin protein and the best-characterized member of the myosin superfamily[3][5]. It is composed of two heavy chains (with head, neck, and tail domains) and typically four light chains. The head domain binds both actin filaments and ATP, catalyzing its hydrolysis and converting chemical energy into directional mechanical force[1][2][7]. In muscles, myosin II forms thick filaments, enabling contraction by sliding past actin thin filaments in structures called sarcomeres[1][7]. Nonmuscle myosin II isoforms (NM2) are essential for cellular events including cytokinesis (cell division), migration, and cellular tension maintenance[2][3]. Regulation involves phosphorylation of the regulatory light chain and assembly of myosin filaments[2]. Mutations or dysregulation of class II myosins are implicated in diseases such as cardiomyopathies, cancers (by impacting cell division and migration), and certain muscle disorders[2][3][6]. Blebbistatin and related compounds can inhibit myosin II as research tools and potential drug leads, but therapeutic targeting risks include contractile dysfunction and off-target effects[2].

Other names

Conventional myosinmuscle myosinnonmuscle myosin IINM2Myh2Myh3MYH7 (paralog-specific)myosin heavy chain II

Inhibition of ATPase activity - Impairment of actin–myosin interaction - Disruption of filament assembly