THE VACUOLAR ATPASE PROTON PUMP IS REQUIRED FOR THE CYTOTOXICITY OF BACILLUS-ANTHRACIS LETHAL TOXIN

The nature of the cytopathic effect exerted by the lethal factor toxin (LF) of Bacillus anthracis on sensitive cells is unknown. The toxin r equires the passage through acidic vesicles in order to exert its effe ct within the cytosol. Here, we show that bafilomycins and concanamyci n A, selective inhibitors of the vacuolar ATPase proton pump, are the most powerful known inhibitors of LF macrophage toxicity. These inhibi tors are fully active long after LF addition to macrophages, suggestin g that LF enters the cytosol after having reached a late endosomal com partment.