S1 is an NAD-dependent ADP-ribosyltransferase, which plays a crucial role in the pathogenesis of B.pertussis causing disruption of normal host cellular regulation. It catalyzes the ADP-ribosylation of a cysteine in the alpha subunit of host heterotrimeric G proteins. In the absence of G proteins it also catalyzes the cleavage of NAD+ into ADP-ribose and nicotinamide. It irreversibly uncouples the G-alpha GTP-binding proteins from their membrane receptors.
[1] Cloning and sequencing of the pertussis toxin genes: operon structure and gene duplication.Nicosia A., Perugini M., Franzini C., Casagli M.C., Borri M.G., Antoni G., Almoni M., Neri P., Ratti G., Rappuoli R.Proc. Natl. Acad. Sci. U.S.A. 83:4631-4635(1
