Identification and characterisation of proteins associated with the rhoptry organelles of Plasmodium falciparum merozoites

We describe antigens of Plasmodium falciparum recognised by murine monoclonal antibodies which by immunofluorescence react with the rhoptry organelles of the extracellular merozoite stage. Immunoblotting shows that the antibodies recognise two major parasite antigens of M_r 82 and 65 kilodaltons (kDa). Immunoprecipitations from detergent extracts of [³⁵S]-methioninelabelled parasites show that the 82-kDa and 65-kDa antigens are parasite proteins. Pulse-chase experiments on synchronous parasite cultures show that the 82-kDa protein is synthesised during early schizogony and is later processed into the 65-kDa antigen in segmenting schizonts. In Nonidet P-40, these antigens are non-covalently associated with two other proteins of 40 kDa and 42 kDa. The 40/42-kDa doublet is synthesised in parallel with the 82 kDa antigen and persists, apparently unchanged, till the end of the cell cycle.Abbreviations HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - EDTA ethylenediaminetetraacetic acid - EGTA ethyleneglycolbis-(aminoethylether) tetraacetic acid - PMSF phenylmethylsulphonylfluoride - TLCK tosyl-L-lysine chloromethyl ketone - SDS-PAGE sodium dodecyl sulphate polyacrylamide gel electrophoresis - M_r relative molecular mass