THE LOWER-MOLECULAR-WEIGHT PROTEIN COMPLEX (RI) OF THE PLASMODIUM-FALCIPARUM RHOPTRIES LACKS THE GLYCOLYTIC ENZYME ALDOLASE

The gene for the Plasmodium falciparum glycolytic enzyme aldolase (PfA) has been cloned [6]. Since polyclonal antibodies raised to an affinity-purified preparation of an approximately 41-kDa parasite rhoptry protein were used to isolate this clone, and its nucleotide sequence was verified using amino acid sequence information generated from the purified 41-kDa protein, the authors concluded that this rhoptry protein was PfA. In the present report, monoclonal antibodies which immunoprecipitate those rhoptry protein complexes containing 39-kDa (p39) and 37-kDa proteins (p37) were used along with PfA-specific polyclonal antibodies to further examine this conclusion. The electrophoretic mobilities of PfA and the rhoptry proteins in the presence of sodium dodecyl sulfate differed from each other in both reducing and nonreducing conditions after immunoprecipitation with these antibodies. Lysates of P. falciparum-infected erythrocytes contained abundant aldolase activity which was removed by anti-PfA antibodies. However, no aldolase activity was associated with affinity-purified rhoptry proteins. Controlled proteolysis with the endoproteinase V8 protease generated different digestion patterns for PfA, p39, and p37. While both PfA and the rhoptry proteins were components of multimeric protein complexes, as demonstrated by sucrose gradient centrifugation, their cellular localization patterns were quite different. These results demonstrate that PfA and the rhoptry-associated proteins p39 and p37 are different entities. © 1990.