MAEBL Plasmodium falciparum protein peptides bind specifically to erythrocytes and inhibit in vitro merozoite invasion

MAEBL is an erythrocyte binding protein located in the rhoptries and on the surface of mature merozoites, being expressed at the beginning of schizogony. The structure of MAEBL originally isolated from rodent malaria parasites suggested a molecule likely to be involved in invasion. We thus became interested in identifying possible MAEBL functional regions. Synthetic peptides spanning the MAEBL sequence were tested in erythrocyte binding assays to identify such possible MAEBL functional regions. Nine high activity binding peptides (HABPs) were identified: two were found in the M1 domain, one was found between the M1 and M2 regions, five in the erythrocyte binding domain (M2), and one in the protein's repeat region. The results showed that peptide binding was saturable; some HABPs inhibited in vitro merozoite invasion and specifically bound to a 33kDa protein on red blood cell membrane. HABPs' possible function in merozoite invasion of erythrocytes is also discussed.