The Cytoplasmic Region of Plasmodium falciparum SURFIN(4.2) Is Required for Transport from Maurer’s Clefts to the Red Blood Cell Surface

Background: Plasmodium, the causative agent of malaria, exports many proteins to the surface of the infected red blood cell (iRBC) in order to modify it toward a structure more suitable for parasite development and survival. One such exported protein, SURFIN(4.2), from the parasite of human malignant malaria, P. falciparum, was identified in the trypsin-cleaved protein fraction from the iRBC surface, and is thereby inferred to be exposed on the iRBC surface. SURFIN(4.2) also localize to Maurer’s clefts—parasite-derived membranous structures established in the RBC cytoplasm and tethered to the RBC membrane—and their role in trafficking suggests that they are a pathway for SURFIN(4.2) transport to the iRBC surface. It has not been determined the participation of protein domains and motifs within SURFIN(4.2) in transport from Maurer’s clefts to the iRBC surface; and herein we examined if the SURFIN(4.2) intracellular region containing tryptophan-rich (WR) domain is required for its exposure on the iRBC surface. Results: We generated two transgenic parasite lines which express modified SURFIN(4.2), with or without a part of the intracellular region. Both recombinant SURFIN(4.2) proteins were exported to Maurer’s clefts. However, only SURFIN(4.2) possessing the intracellular region was efficiently cleaved by surface treatment of iRBC with proteinase K. Conclusions: These results indicate that SURFIN(4.2) is exposed on the iRBC surface and that the intracellular region containing WR domain plays a role on the transport from Maurer’s clefts to the iRBC membrane.