B. anthracis Toxin

Bacillus anthracis, a Gram-positive bacterium, is the causative agent of anthrax. This organism is capsulogen and toxinogenic. It secretes two toxins which are composed of three proteins: the protective antigen (PA), the lethal factor (LF) and the edema factor (EF). The lethal toxin (PA+LF) provokes a subit death in animals, and the edema toxin (PA+EF) induces edema. The edema and the lethal factors are internalized into the eukaryotic target cells via the protective antigen. EF and LF exert a calmoduline dependent adenylate cyclase and a metalloprotease activity respectively. These three protein components work together to impart their physiological effects. Assembled complexes containing the toxin components are endocytosed. In the endosome, the enzymatic components of the toxin translocate into the cytoplasm of a target cell. Once in the cytosol, the enzymatic components of the toxin disrupt various immune cell functions, namely cellular signaling and cell migration. The toxin may even induce cell lysis, as is observed in macrophage cells. Anthrax toxin allows the bacteria to evade the immune system, proliferate, and ultimately kill the host animal.