Anthrax toxins

Though its lethal effects were ascribed to an exotoxin almost half a centur y ago, the pathogenesis of anthrax has yet to be satisfactorily explained. Subsequent work has led to the molecular identification and enzymatic chara cterization of three proteins that constitute two anthrax toxins. Protectiv e antigen binds an as yet unknown cell receptor and mediates the entry of t he other two components to the cytoplasm via the endosomal pathway. Edema f actor, so named for its ability to induce edema, is a Ca2+ /calmodulin-depe ndent adenylate cyclase. Lethal factor, the dominant virulence factor assoc iated with the toxin, proteolytically inactivates mitogen-activated protein kinase kinases, key players in signal transduction. We describe the fascin ating work that has led to these discoveries End discuss their relevance to our understanding of the pathogenesis of anthrax.