title: 3'-Deoxy-NAD+ as a substrate for poly(ADP-ribose)polymerase and the reaction mechanism of poly(ADP-ribose) elongation.
abstract: Adenyl-32P-Labeled 3'-deoxy-NAD+ was utilized as a substrate by pure DNA-dependent poly(ADP-ribose)polymerase (EC 2.4.2.30) from calf thymus in the automodification reaction with an apparent Km of 20 microM and a Vmax of 80 nmol/min/mg of protein. Analysis by lithium lauryl sulfate-polyacrylamide gel electrophoresis revealed a single 32P-labeled protein of 116-kDa which comigrated with automodified enzyme. Addition of increasing amounts of histone H1 up to a concentration of 15 micrograms/ml stimulated the synthesis of protein-bound polymers of 3'-deoxy-ADP-ribose. However, the average polymer size was equal to 2 in the presence and 4 in the absence of histone H1, respectively. The synthesis of protein-bound oligomers of 3'-deoxy-ADP-ribose was inhibited by the polymerase inhibitors benzamide, nicotinamide, thymidine, and NaCl. A pulse labeling of polymer synthesis with 40 microM [32P]3'-deoxy-NAD+ either in the presence or absence of 15 micrograms/ml of histone H1, followed by a chase with 1 mM [3H]NAD+, was used to determine the mechanism of poly(ADP-ribose) elongation. Following enzyme digestion of these polymers with phosphodiesterase, it was found that 52 and 24% of the total 32P radiolabel was associated with the 3'-deoxy-AMP termini of the polymers synthesized in the pulse reactions, in the presence or absence of histone H1, respectively. In contrast, less than 10% of the total radioactivity was associated with 3'-deoxy-AMP in the product of the chase reactions. These results are consistent with the conclusion that the initially attached residue of 3'-deoxy-ADP-ribose to either the polymerase or histone H1, is elongated by the "protein-distal" addition of ADP-ribose residues to the AMP terminus of the growing polymer chain.
mesh_terms: D000818:Animals; D002417:Cattle; D006657:Histones / Q000494:pharmacology; D007700:Kinetics; D008962:Models, Theoretical; D008970:Molecular Weight; D009243:NAD / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D009702:Nucleoside Diphosphate Sugars / Q000096:biosynthesis*; D011064:Poly Adenosine Diphosphate Ribose / Q000096:biosynthesis*; D011065:Poly(ADP-ribose) Polymerases / Q000302:isolation & purification / Q000378:metabolism*; D013379:Substrate Specificity; D013950:Thymus Gland / Q000201:enzymology
chemical_list: D006657:Histones; D009702:Nucleoside Diphosphate Sugars; D009243:NAD; D011064:Poly Adenosine Diphosphate Ribose; C057676:3'-deoxynicotinamide adenine dinucleotide; D011065:Poly(ADP-ribose) Polymerases