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Figure 6 | Malaria Journal

Figure 6

From: A comparative study of the localization and membrane topology of members of the RIFIN, STEVOR and PfMC-2TM protein families in Plasmodium falciparum-infected erythrocytes

Figure 6

Model of the localization and membrane topology of RIFIN, STEVOR and PfMC-2TM proteins. a Localization of RIFIN, STEVOR and PfMC-2TM proteins during parasite development in the erythrocyte. In trophozoite-infected erythrocytes, RIFIN (blue), STEVOR (green) and PfMC-2TM (yellow) proteins were transported to the Maurer’s clefts (MC) and most of them onwards to the erythrocyte membrane (EM). In schizonts, all small VSAs were observed at the apical tip of merozoites. Particular STEVOR variants were found at the rhoptries and others were detected at the merozoites membrane. b Proposed transmembrane topology for RIFIN, STEVOR and PfMC-2TM proteins at the EM. RIFIN and STEVOR proteins are diminished upon surface trypsinization using antisera specific for the semi-conserved N-terminal region of the proteins. Hence, a one transmembrane topology is most likely for RIFIN and a subpopulation of STEVOR proteins, which extend their semi-conserved region into the extracellular space. On the contrary, the semi-conserved as well as the C-terminal domain of PfMC-2TM proteins inserted into the erythrocyte membrane were protected from protease cleavage. Consequently, PfMC-2TM proteins seem to be inserted by two transmembrane domains and expose just a few amino acids at the surface of IE. AC apical complex, CT C-terminal domain, EM erythrocyte membrane, FV Food vacuole, HR hydrophobic region, MC Maurer’s clefts, N nucleus, PM plasma membrane, PVM parasitophorous vacuole membrane, SC semi-conserved region, TM transmembrane domain, VR variable region.

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