Actin is a highly conserved protein that polymerizes to produce filaments that form cross-linked networks in the cytoplasm. Polymerizes into shorter and less stable actin filaments compared to ACT2/actin-2; this is thought to facilitate gliding motility and host cell invasion. Has ATPase activity. ATP hydrolysis leads to the formation of a stable intermediate ADP-inorganic phosphate (Pi) actin, which is followed by the release of Pi. ATP hydrolysis affects filament stability; ADP-bound actin depolymerizes much faster than ATP- or ADP-Pi-bound actin. Plays an essential role during the asexual blood stage. At the segmented schizont stage, required for apicoplast migration and segregation into individual daughter merozoites. Also, required for the separation of daughter merozoites in the final stages of cytokinesis. Essential for merozoite invasion of, but not adhesion to or reorientation towards, host erythrocytes 