title: A 3-aminobenzamide-resistant labeled protein in [32P]NAD+-labeled cells.
abstract: A series of proteins are covalently labeled when human lymphocytes are incubated with [32P]NAD+. The majority of this labeling is effectively inhibited when the lymphocytes are coincubated with 3-aminobenzamide, a potent inhibitor of poly(ADP-ribose) polymerase. However, labeling of a 72 000 molecular weight protein was resistant to the inhibitory effect of 3-aminobenzamide. Labeling of this protein from [32P]NAD+ was shown to be Mg2+-dependent. The 72 000 molecular weight protein could also be labeled on incubation with [alpha-32P]ATP, [gamma-32P]ATP and [32P]orthophosphate, but not from [3H]NAD+ or [14C]NAD+. In the present study, we show that the 72 000 molecular weight protein is not ADP-ribosylated but rather, phosphorylated on incubation with [32P]NAD+. This phosphorylation appears to occur via an Mg2+-dependent conversion of NAD+ to AMP with the eventual utilization of the alpha-phosphate for phosphorylation of the 72 000 molecular weight protein.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D001549:Benzamides / Q000037:antagonists & inhibitors*; D002463:Cell Membrane Permeability; D004492:Edetic Acid / Q000494:pharmacology; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism*; D008970:Molecular Weight; D009243:NAD / Q000378:metabolism*; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011506:Proteins / Q000378:metabolism*
chemical_list: D001549:Benzamides; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011506:Proteins; D009243:NAD; C025160:3-aminobenzamide; D000255:Adenosine Triphosphate; D004492:Edetic Acid