Several hundred malaria parasite proteins are exported beyond an encasing vacuole and into the cytosol of the host erythrocyte, a process that is key to the virulence and viability of the causative Plasmodium species. The trafficking machinery responsible for this export is unknown. Here, we identify a Plasmodium Translocon of EXported proteins (PTEX), which is located in the vacuole membrane. The PTEX complex is ATP-powered and comprises HSP101, which is a ClpA/B-like AAA+ ATPase of a type commonly associated with protein translocons, a novel protein termed PTEX150 and a known parasite protein EXP2. EXP2 is the potential channel as it is the membrane-associated component of the core PTEX complex. Two other proteins, a novel protein PTEX88 and a thioredoxin known as TRX2, were also identified as PTEX components. As a common portal for numerous crucial processes, this novel translocon offers an exciting new avenue for therapeutic intervention.

Plasmodium falciparum causes the virulent form of malaria and disease manifestations are linked to growth inside infected erythrocytes. In order to survive and evade host responses the parasite remodels the erythrocyte by exporting several hundred effector proteins beyond the surrounding parasitophorous vacuole membrane. A feature of exported proteins is a pentameric motif (RxLxE/Q/D) that is a substrate for an unknown protease. Here, we show the protein responsible for cleavage of this motif is Plasmepsin V, an aspartic acid protease located in the endoplasmic reticulum. Plasmepsin V cleavage reveals the export signal (xE/Q/D) at the N-terminus of cargo proteins. Expression of an identical mature protein with xQ at the N-terminus generated by signal peptidase was not exported demonstrating Plasmepsin V activity is essential and linked with other key export events. Identification of the protease responsible for export into erythrocytes provides a novel target for therapeutic intervention against this devastating disease.

Highlights d Specific compounds against P. falciparum Plasmepsin IX and X were identified d PMIX and PMX are modulators of parasite proteins for egress, invasion, and development d Anti-PMIX and anti-PMX compounds inhibit liver, blood, and mosquito stages of Plasmodium d One compound, WM382, can clear mouse models of P. berghei and P. falciparum parasites

A small molecule inhibitor of the malarial protease Plasmepsin V impairs protein export and cellular remodeling, reducing parasite survival in human erythrocytes.