Not involved in actin polymerisation, instead functions to stimulate nucleotide exchange on monomeric actin and influence turnover of the small amount of cytosolic actin microfilaments. Essential for erythrocytic schizogony. Interacts with monomeric actin, does not bind to actin polymers. Expressed throughout the life cycle, in oocyst sporozoites that invade the mosquito salivary glands, salivary gland sporozoites infectious to the mammalian liver, and schizonts/merozoites that invade erythrocytes. Belongs to the actin-binding proteins ADF family.