New class of microbial toxins ADP-ribosylates actin

Various microbial toxins ADP-ribosylate regulatory eukaryotic protein thereby affecting the cellular function of the target cell. Diphtheria toxin and Pseudomonas exotoxin A inhibit protein synthesis by ADP-ribosylation of elongation factor 2. Other bacterial toxins modify GTP-binding proteins (G-proteins) involved in transmembrane signal transduction. Cholera toxin and Escherichia coli heat-labile enterotoxin ADP-ribosylates G sub(s), which ultimately activates adenylate cyclase. Pertussis toxin ADP-ribosylates G sub(i) thereby abolishing hormone-induced inhibition of adenylate cyclase. Furthermore, a whole family of homologous G-proteins (transducin, G sub(o), G sub(n)) act as substrate of cholera and/or pertussis toxin. It has been shown recently that botulinum C2 toxin also belongs to the family of microbial toxins with ADP-ribosyltransferase activities.