title: The mechanism of ADP-ribosylation of elongation factor 2 catalyzed by fragment A from diphtheria toxin.
abstract: Measurements of the initial rate of ADP-ribosylation of elongation factor 2 (EF-2) catalyzed by Fragment A from diphtheria toxin support a sequential mechanism and suggest that the reaction proceeds through a central ternary complex involving Fragment A and the substrates, EF-2 and NAD. The Michaelis constants for EF-2 and NAD are 0.15 and 1.4 muM, respectively. As determined by equilibrium gel permeation, EF-2 does not bind Fragment A significantly, alone or in the presence of adenine, ADPribose, nicotinamide or NADH. Based on these and earlier results, we propose an ordered sequential mechanism for the reaction; the sequence of binding of substrates is NAD, followed by EF-2.
mesh_terms: D000225:Adenine / Q000494:pharmacology; D000247:Adenosine Diphosphate Sugars / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002846:Chromatography, Affinity; D002850:Chromatography, Gel; D004167:Diphtheria Toxin / Q000494:pharmacology*; D007700:Kinetics; D009243:NAD / Q000378:metabolism; D009536:Niacinamide / Q000494:pharmacology; D009702:Nucleoside Diphosphate Sugars / Q000378:metabolism*; D010445:Peptide Elongation Factors; D010446:Peptide Fragments / Q000494:pharmacology; D011817:Rabbits; D012156:Reticulocytes; D012266:Ribose / Q000378:metabolism*
chemical_list: D000247:Adenosine Diphosphate Sugars; D004167:Diphtheria Toxin; D009702:Nucleoside Diphosphate Sugars; D010445:Peptide Elongation Factors; D010446:Peptide Fragments; D009243:NAD; D009536:Niacinamide; D012266:Ribose; D000225:Adenine