Abstract

The Plasmodium translocon for exported proteins (PTEX) has been established as the machinery responsible for the translocation of all classes of exported proteins beyond the parasitophorous vacuolar membrane of the intraerythrocytic malaria parasite. Protein export, particularly in the asexual blood stage, is crucial for parasite survival as exported proteins are involved in remodelling the host cell, an essential process for nutrient uptake, waste removal and immune evasion. Here we have truncated the conserved C-terminus of one of the essential PTEX components, PTEX150, in Plasmodium falciparum in an attempt to create mutants of reduced functionality. Parasites tolerated C-terminal truncations of up to 125 amino acids with no reduction in growth, protein export or the establishment of new permeability pathways. Quantitative proteomic approaches however revealed a decrease in other PTEX subunits associating with PTEX150 in truncation mutants, suggesting a role for the C-terminus of PTEX150 in regulating PTEX stability. Our analyses also reveal three previously unreported PTEX-associated proteins, namely PV1, Pf113 and Hsp70-x (respective PlasmoDB numbers; PF3D7_1129100, PF3D7_1420700 and PF3D7_0831700), and demonstrate that core PTEX proteins exist in various distinct multimeric forms outside the major complex.

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B.E. is recipient of an Australian Post Graduate Awards and S. C. C. is recipient of a Monash Graduate Scholarship. We thank the Australian Red Cross Blood Bank for the provision of human blood, Jacobus Pharmaceuticals for providing WR99210 and Monash Micro Imaging. We are grateful to Brian Cooke and Alan Cowman for the SBP and KAHRP antibodies to Eugene Kapp for providing the non-redundant LudwigNR protein database, respectively, and to Hnin (Honey) Pwint Oo for technical support. The authors gratefully acknowledge funding from the Victorian Operational Infrastructure Support Program received by the Burnet Institute and for grants from the National Health and Medical Research Council of Australia (1068287, 1021560 and 637406).