Anthrax toxin is composed of three distinct proteins known as the lethal factor (LF), edema factor (EF), and the protective antigen (PA). The PA binds to the cell surface via its carboxy-terminal domain. Subsequent cleavage of its N-terminal domain allows PA to form heptamers that bind LF and EF forming a complex. This complex enters the cell via endocytosis and the LF and EF translocate into the cytosol.

LF, a 90 kDa protease, is considereed to be critical for the pathogenesis of anthrax. It cleaves MAP kinase kinase (MAPKK) family of enzymes near their amino terminal, which removes the docking sequence for the downstream MAP kinases. This results in inhibtion of one or more signal transduction pathways. Hence, LF has become a potential target for therapeutic agents that would block its catalytic activity.