Abstract

The disease-causing blood stage of the Plasmodium falciparum malaria parasite lifecycle is reliant on initial invasion of the human red blood cell (RBC). Invasion of the host RBC by malaria merozoites is a rapid process that requires co-ordinated interactions between a large number of proteins, many of which have no known function. We have characterised a protein (Peripherally Associated Rhoptry bulb Protein or PfPARP1) as wrapping around the cytosolic face of the club shaped rhoptry bulb membrane, a key organelle that excretes merozoite vaccine candidates during invasion. PfPARP1 lies in close juxtaposition with the rhoptry lumen marker PfRAP1. Attempts to knock-out PfPARP1 were unsuccessful, but glucosamine inducible PfPARP1 knock-down led to a significant growth defect that was caused by direct loss of merozoite invasion. Knock-down of PfPARP1 was associated with changes in rhoptry antigen structure, suggesting that PfPARP1 may have a direct role in rhoptry function that is essential to invasion.