Proteins responsible for a punctate fluorescence pattern in Plasmodium falciparum merozoites

Mouse monoclonal antibodies (McAbs) have been used to characterize the proteins of the asexual erythrocytic cycle of Plasmodium falciparum. Three different McAbs react with antigens of the schizont and extracellular merozoite to give a punctate fluorescence pattern. In many cases, such areas of fluorescence were composed of two adjacent, fluorescent bodies; these were distinct from the nuclei. In contrast, McAbs which bound to the ring-stage parasite were not localized, but were diffusely distributed within or around the ring-stage parasite. These McAbs immunoprecipitated five prominent, 35S-methionine-labeled schizont proteins (p) of Mr 82K, 70K, 67K, 39K, and 37K. Only p82, p39, and p37 were immunoprecipitated from schizont-labeled ring-stage parasites; thus, it appears that p70 and p67 are modified, degraded, or secreted some time between intracellular merozoite maturation and erythrocyte invasion.