title: Inhibition of bacteriophage-Q beta ribonucleic acid polymerase by guanosine triphosphate analogues.
abstract: Sixteen compounds related to GTP were evaluated as inhibitors of bacteriophage-Q beta poly(C)-dependent poly(G) polymerase. Non-phosphorylated compounds, including guanine, guanosine and deoxyguanosine, were inactive. Phosphorylated compounds gave significant inhibition at millimolar concentrations. For nucleotides the feature important for inhibition was the 5'-phosphate chain. Four triphosphates, XTP, ITP, 7-methyl-GTP and 2'-O-methyl-GTP, gave 50% inhibition of both the poly(C)- and poly(U2,C)-dependent reactions at concentrations from 0.1 to 5 mM. XTP was 10-fold more potent an inhibitor of the reaction with poly(U2,C) as template. None of these four compounds was able to substitute for GTP as substrate to a significant extent. The most active compound, 2'-O-methyl-GTP, was a competitive inhibitor (Ki = 0.4 mM) of GTP in the poly(C)-dependent reaction.
mesh_terms: D003090:Coliphages / Q000201:enzymology*; D012321:DNA-Directed RNA Polymerases / Q000037:antagonists & inhibitors*; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D007700:Kinetics; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D006160:Guanosine Triphosphate; D012321:DNA-Directed RNA Polymerases