Anthrax Toxin Protective Antigen

Anthrax toxins are composed of three distinct proteins: the protective antigen (PA, 83 kDa before enzymatic cleavage and 63 kDa after cleavage), the lethal factor (LF, 90 kDa) and the edema factor (EF, 89 kDa). The lethal toxin, which plays a predominant role in the pathogenicity, is made up of PA and LF; and the edema toxin, which has a lesser role in the physiology of the disease, is made up of PA and EF. These proteins are secreted by the bacterium as non-toxic monomers, and assemble at the surface of the target cells to form toxic complexes.