Myosin is a protein that binds to actin and has ATPase activity that is activated by actin. Myosin id may have a role in chemotaxis and aggregation; it could serve to stabilize and even retract cortical structures, such as pseudopods and lamellopods. Involved in the process of phagocytosis. Myosin I heavy chain is single-headed. Dimer of a heavy and a light chain. Inability to self-assemble into filaments. Highest concentration just beneath the plasma membrane in the anterior pseudopod at the leading edge of the cell. Found at leading edges of lamellipodia and at sites of cell-cell contact in stationary stage cells. Also present in filopodia. Largely disappears from lamellipodia and cell-cell contact regions in aggregation stage cells, suggesting the occurrence of a developmentally regulated relocalization to the cytoplasm. Myosin tail domain binds directly to anionic phospholipid membranes; myosins I could therefore move actin relative to membranes and vice versa. TH.2 and SH3 bind tightly to F-actin; this together with the nucleotide-sensitive site in the head, allows single molecules of myosin I to cross-link actin filaments. MyoB and myoD double mutant exhibits reduction in the speed of whole cell translocation. 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.