Plasmodium chabaudi-infected erythrocytes: Differential expression of trophozoite proteins in host cell plasma membranes.

Neoproteins were compared in host cell plasma membranes isolated as ghosts from erythrocytes infected with early and late trophozoites of Plasmodium chabaudi. Ghosts isolated from early trophozoites-infected erythrocytes (= et-ghosts) contain seven neoproteins with apparent molecular masses of about 154, 145, 90, 72, 67, 52 and 33 kDa, respectively. Two additional neoproteins with masses of about 42 and 38 kDa are detected in ghosts isolated from late trophozoites-infected erythrocytes (= lt-ghosts). All neoproteins, except the 154, 145 and 38 kDa-proteins, can be metabolically labeled with both [(14)C]isoleucine and [(35)S]methionine. The 90 kDa-protein is predominantly labeled in et-ghosts, while the 42 kDa-protein is exclusively labeled in lt-ghosts. Both proteins, however, contain only minor radioactivity in the corresponding parasites. Moreover, the pI of the 90 kDa-neoprotein shifts from about 4.5 in et-ghosts to about 5.6 in lt-ghosts as detected by 2 D-gel electrophoresis and western blotting using a 90 kDa-protein specific monoclonal antibody. The data indicate a posttranslational modification of the 90 kDa-neoprotein and a sequential expression of the 90 kDa- and 42 kDa-neoproteins in host cell plasma membranes during intraerythrocytic maturation of trophozoites.