Localization and stage specific phosphorylation of Plasmodium falciparum phosphoproteins during the intraerythrocytic cycle.

Fifty-nine Plasmodium falciparum specific phosphoproteins with molecular weights between 15,000 and 192,000 were analyzed by SDS-PAGE and two-dimensional gel electrophoresis. 40 phosphoproteins were identified by [gamma-32P]ATP labeling of cell lysates, 19 by [32P]orthophosphate labeling of parasitic cultures in vivo. Changes in the phosphorylation pattern during the infectious erythrocytic cycle were determined for all proteins. In parallel, cell fractionation studies were done to follow up possible changes in the cellular distribution of these proteins. Several phosphoproteins are associated with the membrane fraction of infected erythrocytes. One pair of proteins of approx. 88 kDa and a pI of about 5.0 was further characterized. Both proteins are located in the parasitic fractions as well as in the membrane of infected erythrocytes during the entire cycle. Phosphorylation of these proteins, however, is restricted to the trophozoite and schizont stages. Peptide mapping studies demonstrated that both proteins are identical with the exception of minor modifications which are probably not the result of differences in phosphorylation.