PERTUSSIS TOXIN-CATALYZED ADP-RIBOSYLATION OF GTP-BINDING PROTEINS WITH DIGOXIGENIN-CONJUGATED NAD - IDENTIFICATION OF THE PROTEINS IN PLASMA-MEMBRANES AND NUCLEI

ADP-ribose moiety containing digoxigenin was transferred by pertussis toxin (IAP) to the ct subunit of Gi (G,cr) from digoxigenin-conjugated NAD (DIG-NAD) in a By subunit-dependent manner. ADP-ribosylation of c ia with DIG-NAD plus IAP was inhibited by native NAD. These results in dicate that nonradiolabeled DIG-NAD also serves as the substrate for I AP-catalyzed ADP-ribosylation of G proteins. Using DIG-NAD and fluores cein isothiocyanate-labeled anti-digoxigenin antibody, IAP-sensitive G protein(s) was found to be exist in nuclei as well as plasma membrane s of rat liver and HeLa cells. Thus, DIG-NAD is useful to identify per tussis toxin-substrate G proteins.