title: Characterization of the nucleoside triphosphate phosphohydrolase (ATPase) activity of RNA synthesi termination factor p. I. Enzymatic properties and effects of inhibitors.
abstract: The purification of p protein to homogeneity from Escherichia coli has shown that its RNA-dependent ATPase activity is physically inseparable from its termination activity. The biochemical properties of pATPase have been studied using poly(C) as the activating RNA. This reaction is stimulated by Mg2+ ions and Mn2+ ions and is prevented by excess EDTA; it is not stimulated by Ca2+ ions. The reaction is not affected by a Zn2+ ion chelator and is inhibited by 1 mM Zn2+. With Mg2+ present, the activity is essentially constant from pH 7 to pH 9.7. pATPase is sensitive to p-hydroxymercuribenzoate and to N-ethylmaleimide. All four ribonucleoside triphosphates are hydrolyzed by p action. ATP has the lowest Km (0.009 mM), while CTP has the highest Vmax. In a mixture containing all four nucleoside triphosphates at a concentration of 0.4 mM, p shows no strong preference for any one of the substrates. The response of p ATPase to a variety of inhibitors of other ATPases and GTPases and of transcription has been studied. Of the compounds tested, aurintricarboxylic acid, an inhibitor of protein-nucleic acid interactions, was found to be a potent inhibitor of p ATPase, while rifampicin and heparin had no effect. pATPase showed partial sensitivity to thiostrepton, fusidic acid, Dio 9, and sodium azide.
mesh_terms: D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D001312:Aurintricarboxylic Acid / Q000494:pharmacology; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000502:physiology*; D002413:Cations, Divalent; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors; D004492:Edetic Acid / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004926:Escherichia coli / Q000201:enzymology*; D005672:Fusidic Acid / Q000494:pharmacology; D006493:Heparin / Q000494:pharmacology; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D010618:Phenanthrolines / Q000494:pharmacology; D012329:RNA, Bacterial / Q000096:biosynthesis*; D012293:Rifampin / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: D001426:Bacterial Proteins; D002413:Cations, Divalent; D010618:Phenanthrolines; D012329:RNA, Bacterial; D001312:Aurintricarboxylic Acid; D004533:Egtazic Acid; D005672:Fusidic Acid; D006493:Heparin; D004492:Edetic Acid; D012321:DNA-Directed RNA Polymerases; D000251:Adenosine Triphosphatases; D008274:Magnesium; D012293:Rifampin