Myosin is a protein that binds to actin and has ATPase activity that is activated by actin. Involved in the process of phagocytosis and appears to support streaming behavior. Myosin I heavy chain is single-headed. Dimer of a heavy and a light chain. Inability to self-assemble into filaments. Found in the leading edge of translocating cells. Exhibits significant reduction in initial rate of phagocytosis. MyoB and myoC double mutant exhibits profound defects in growth, endocytosis and rearrangement of F-actin. myoB, myoC and myoD triple mutant exhibits reduction in the speed of whole cell translocation. Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Myosin family.