Protein unfolding is an essential requirement for transport across the parasitophorous vacuolar membrane of Plasmodium falciparum.

Plasmodium falciparum traffics a large number of proteins to its host cell, the mature human erythrocyte. How exactly these proteins gain access to the red blood cell is poorly understood. Here we have investigated the effect of protein folding on the transport of model substrate proteins to the host cell. We find that proteins must pass into the erythrocyte cytoplasm in an unfolded state. Our data strongly support the presence of a protein-conducting channel in the parasitophorous vacuolar membrane, and additionally imply an important role for molecular chaperones in keeping parasite proteins in a 'translocation competent' state prior to membrane passage.