Myosin is a protein that binds to actin and has ATPase activity that is activated by actin. Myosin-2 heavy chain is two-headed. It self-assembles into filaments. Hexamer of 2 heavy chain subunits (MHC), 2 alkali light chain subunits (MLC) and 2 regulatory light chain subunits (MLC-2). Associates with elmoA. Highest concentration in the posterior cell cortex. Limited proteolysis of myosin heavy chain produces 1 light meromyosin (LMM) and 1 heavy meromyosin (HMM). HMM can be further cleaved into 2 globular subfragments (S1) and 1 rod-shaped subfragment (S2). The rodlike tail sequence is highly repetitive, showing cycles of a 28-residue repeat pattern composed of 4 heptapeptides, characteristic for alpha-helical coiled coils. Phosphorylation inhibits thick filament formation and reduces the actin-activated ATPase activity. Dictyostelium myosin-2 has no K(2)EDTA ATPase activity, perhaps correlated with the absence of a Cys at the SH-1 position (688). Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Myosin family.