Covalent modification of proteins by ADP-ribosylation

Abstract In addition to its well established role as a cofactor in redox reactions, NAD + serves also as a substrate for a ubiquitous group of enzymes called ADP-ribosyl transferases. These enzymes are found in both the nucleus and cytosol of eukaryotic cells, as components of pathogenic bacterial toxins, and as part of a mechanism for inactivating host cell protein biosynthetic machinery in bacteriophage-infected cells. In this article we provide a brief overview of all known ADP-ribosylation reactions.