Transfer of ADP-ribose from NAD to choleragen: a subunit acts as catalyst and acceptor protein.
Choleragen selectively incorporates 3H from [3H]NAD labeled on the adenosine moiety and not 14C from [14C]NAD labeled on the nicotinamide moiety. This reaction does not require protein in addition to choleragen. Incorporation of isotope does not proceed at 4 degrees, requires dithiothreitol, is stable after extensive washing with cold trichloroacetic acid, and is decreased 80% by boiling in trichloroacetic acid. Studies with the A and B subunits of choleragen show that the A subunit catalyzes ADP-ribosylation and serves as an acceptor protein. The B subunit does not show catalytic or acceptor activity. We conclude that choleragen and its A subunit catalyze the hydrolysis of NAD and the enzymatic transfer of ADP-ribose to the A subunit.
D000247:Adenosine Diphosphate Sugars / Q000378:metabolism*; D002384:Catalysis; D002772:Cholera Toxin / Q000378:metabolism*; D004229:Dithiothreitol / Q000494:pharmacology; D009243:NAD / Q000378:metabolism*; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D012266:Ribose
D000247:Adenosine Diphosphate Sugars; D009702:Nucleoside Diphosphate Sugars; D010455:Peptides; D009243:NAD; D012266:Ribose; D002772:Cholera Toxin; D004229:Dithiothreitol