Mono-ADP-ribosylation, a post-translational modification of proteins in which the ADP-ribose
moiety of NAD is transferred to an acceptor amino acid, occurs in viruses, bacteria, and
eukaryotic cells (1). The reaction is distinct from that catalyzed by poly (ADP-ribose)
polymerase, a nuclear protein involved in DNA repair, cell differentiation, and the
maintenance of chromatin structure (2). Among mono-ADP-ribosyltransferases, the bacterial
toxins, cholera toxin, pertussis toxin, diphtheria toxin, and Pseudomonas aeruginosa …