Endogenous relatives of ADP-ribosylating bacterial toxins in mice and men: potential regulators of immune cell...

ADP-ribosylation of proteins, like phosphorylation, is a post-translational modification that can modulate protein function. Bacterial mono (ADP-ribosyl)transferases have been well studied, since potent and clinically important pathogenic exoenzymes such as diphtheria, cholera and pertussis toxins belong to this group. Some of these enzymes interfere with signal transduction mechanisms of host cells, and have become widely used as research tools in cell biology because of their high potency and selectivity. Recently, relatives of these toxins have been cloned from vertebrates. Seven members of a novel multigene family have been identified to date. Surprisingly, all are predicted to be extracellular proteins. Preferred tissues of expression are skeletal and cardiac muscle, testis and hematopoietic cells. ADP-ribosylation of target proteins on the cell surface of T cells and leukocytes have been found to modulate the transmission of extracellular signals to the cell interior.