Essential for merozoite invasion of host cells by controlling rhoptry secretion (PubMed:31492901, PubMed:32179747). Binds to phosphatidic acid (PA) and phosphatidylinositol 4,5-bisphosphate (PIP2) lipids and thus, likely contributes to the assembly of the machinery that docks or primes the rhoptry to the parasite cell membrane prior to the fusion with the host cell membrane (PubMed:31492901). Localizes to the neck (apical part) of rhoptries in merozoites (PubMed:31492901). In the mature merozoite, localizes to the cytosolic face of the rhoptry bulb membrane (PubMed:32179747). During parasite asexual blood stages, expressed at the late schizont stage and in free merozoites (at protein level). The C2 domain is a non-calcium binding domain (By similarity). Cooperates with the PH domain in the binding to phosphatidic acid (PA) and phosphatidylinositol 4,5-bisphosphate (PIP2) (By similarity). The PH domain cooperates with the C2 domain in the binding to phosphatidic acid (PA) and phosphatidylinositol 4,5-bisphosphate (PIP2). Conditional knockout at the ring stage has no effect on parasite development during the first cycle and merozoites egress normally from host erythrocytes. However, these merozoites are unable to reinvade new erythrocytes (PubMed:31492901, PubMed:32179747). Impaired rhoptry secretion during merozoite invasion of host erythrocytes (PubMed:31492901, PubMed:32179747). Increases the spatial segregation between rhoptry neck protein RON4 and bulb protein RAP1, and impairs RAP1 processing (PubMed:32179747). No effect on rhoptry morphology (PubMed:31492901, PubMed:32179747). Microneme secretion is not affected (PubMed:31492901).