title: NAD-dependent ADP-ribosylation of arginine and proteins by Escherichia coli heat-labile enterotoxin.
abstract: Escherichia coli heat-labile enterotoxin (labile toxin, LT) catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide and the ADP-ribosylation of arginine (Moss, J., and Richardson, S.H. (1978) J. Clin. Invest. 62, 281-285). Analysis of the product of the ADP-ribosylation of arginine by nuclear magnetic resonance spectroscopy indicated that the reaction was stereospecific and resulted in the formation of alpha-ADP-ribosyl-L-arginine. This reaction product rapidly anomerized to yield a mixture of the alpha and beta forms. In the presence of [adenine-U-14C]NAD, E. coli enterotoxin catalyzed the transfer of the radiolabel to proteins; the ADP-ribosylation of proteins was inhibited by arginine methyl ester, an alternative substrate. Digestion of the 14C-protein with snake venom phosphodiesterase released predominantly 5'-AMP. No product was obtained with a mobility similar to that of 2'-(5''-phosphoribosyl)-5'-AMP. This result is consistent with the covalent attachment by the enterotoxin of ADP-ribose rather than poly(ADP-ribose) to protein. Thus, LT is catalytically equivalent to choleragen, an enterotoxin of Vibrio cholerae, and activates adenylate cyclase through a similar stereospecific ADP-ribosylation reaction.
mesh_terms: D000247:Adenosine Diphosphate Sugars / Q000378:metabolism*; D001120:Arginine; D004355:Drug Stability; D004768:Enterotoxins / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism*; D006358:Hot Temperature; D009682:Magnetic Resonance Spectroscopy; D009243:NAD; D009244:NAD+ Nucleosidase / Q000378:metabolism; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D009713:Nucleotidyltransferases / Q000378:metabolism*; D011506:Proteins; D012266:Ribose
chemical_list: D000247:Adenosine Diphosphate Sugars; D004768:Enterotoxins; D009702:Nucleoside Diphosphate Sugars; D011506:Proteins; D009243:NAD; D012266:Ribose; D001120:Arginine; D009713:Nucleotidyltransferases; D009244:NAD+ Nucleosidase