Anthrax Toxin - Anthrax Toxin Is An A/B Toxin

Anthrax Toxin Is An A/B Toxin

Interestingly, each individual anthrax toxin protein is, in fact, nontoxic. Toxic symptoms are not observed when these proteins are injected individually into laboratory animals. However, the co-injection of PA and EF causes edema, and the co-injection of PA and LF is lethal. The former combination is called edema toxin, and the latter combination is called lethal toxin. Thus the manifestation of physiological symptoms requires PA, in either case.

The PA requirement observed in animal-model experiments demonstrates a common paradigm for bacterial toxins, called the A / B paradigm. The A component is enzymatically active, and the B component is the cell binding component. Anthrax toxin, in fact, is of the form A₂B, where the two enzymes, EF and LF, are the A components and PA is the B component. Thus PA acts as a Trojan Horse, which carries EF and LF through the plasma membrane into the cytosol, where they may then catalyze reactions that disrupt normal cellular physiology.