Translocation of Bacillus anthracis lethal and oedema factors across endosome membranes

The two exotoxins of Bacillus anthracis, the causative agent of anthrax, are the oedema toxin (PA–EF) and the lethal toxin (PA–LF). They exert their catalytic activities within the cytosol. The internalization process requires receptor‐mediated endocytosis and passage through acidic vesicles. We investigated the translocation of EF and LF enzymatic moieties across the target cell membrane. By selective permeabilization of the plasma membrane with Clostridium perfringens delta‐toxin, we observed free full‐size lethal factor (LF) within the cytosol, resulting from specific translocation from early endosomes. In contrast, oedema factor (EF) remained associated with the membranes of vesicles.