Poster Presentation First Malaria World Congress 2018

Identification of the molecular arrangement of EXP2, an essential component of the PTEX protein export machine within the malarial parasitopherous vacuole membrane reveals a pore-forming domain. (#482)

Paul R Sanders 1 , Sarah C Charnaud 1 , Benjamin K Dickerman 1 , Paul A Ramsland 1 , Brendan S Crabb 1 , Paul R Gilson 1
  1. Burnet Institute, Melbourne, VIC, Australia

Malaria parasites invade and renovate red blood cells to gain nutrients and avoid the immune system. Protein export is a crucial aspect for virulence and survival and is mediated by the PTEX translocon comprising of five core components of which EXP2 is considered to constitute the putative pore. This protein lacks a transmembrane domain despite its membrane association. Here we investigate the structure and function of EXP2. We find that EXP2 knockdown is lethal to the parasite, resulting in arrest by 24-40 hours post erythrocyte invasion. Using proteomic approaches, we identify that cysteines C113 and C140 appear to form a disulfide bond, while C201 is predominantly in a reduced form. This may be a key to its various multimeric states previously observed. We demonstrate that EXP2 possesses a protease resistant membrane-associated core of approximately 20 kDa from the N-terminus and show that its C-terminus projects into the PV space, while no part of it appears to reside within the infected erythrocyte cytosol. This resulted in the identification of an N-terminal region of EXP2 that, when synthesised as a peptide, results in hemolysis of erythrocytes and, in a PEG-based osmotic protection assay, we demonstrate the hemolytic pore is of comparable size to pores formed by the honey bee venom melittin. Taken together this work adds further insight into the role, function and cellular arrangement of EXP2 as the pore-forming component for protein translocation.