Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Rifampicin-resistant mutants of Salmonella typhimurium were isolated and tested for pleiotropic defects in the regulation of pyr gene expression. Seven per cent of all the Rifr mutants were inhibited in growth by addition of uracil (uracil-sensitive). The uracil-sensitive phenotype ( UraS ) was reversed by arginine or citrulline, but not by ornithine, and it was suppressed by mutations in either argR or pyrH , which causes increased expression of pyrA . It was shown that the basal levels of carbamoylphosphate synthase (the pyrA gene product) was reduced to approximately 60% in the mutants, and that addition of arginine and/or uracil to the growth medium caused hyperrepression of pyrA expression. The expression of other genes of the arginine and pyrimidine biosynthetic pathways was not affected significantly in the mutants. The mutations were located in the rpoB gene coding for the beta-subunit of RNA polymerase, suggesting a regulatory function of RNA polymerase in the control of pyrA expression.
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PMID:Salmonella typhimurium mutants with altered expression of the pyrA gene due to changes in RNA polymerase. 676 40

1. DNA-dependent RNA polymerases I and II were purified approx 3900- and 13,000-fold, respectively, from sonicated nuclear extract of cherry salmon (Oncorhynchus masou) liver by DEAE-Sephadex, heparin-Sepharose and DNA-cellulose column chromatography. 2. The purified RNA polymerases exhibited a requirement for four kinds of ribonucleoside 5'-triphosphates, an exogeneous template and divalent cation. 3. The activities of RNA polymerases I and II were inhibited by Actinomycin D (24 micrograms/ml) but not by Rifampicin (200 micrograms/ml). 4. RNA polymerase I preferred native DNA as template, while polymerase II preferred single-stranded DNA. 5. RNA polymerase II was inhibited by a low concentration of alpha-amanitin (0.02 micrograms/ml). RNA polymerase I was also inhibited by the relatively high concentration of alpha-amanitin (IC50 = 100 micrograms/ml and IC70 = 750 micrograms/ml). 6. RNA polymerases from cherry salmon exhibited a higher activity at low temperature than from rat liver.
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PMID:Partial purification and characterization of DNA-dependent RNA polymerases I and II from cherry salmon (Oncorhynchus masou). 686 71

Pure and absolutely DNA-dependent RNA polymerase has been isolated from the extremely halophilic archaebacterium, Halococcus morrhuae. It is composed of five heavy (142 000; 88 000; 73 000; 52 500; and 49 500 Da) and five small components (13 300; 11 200; 10 800; 10 500; 9 900 Da). The peptides of 49 500 Da and 52 500 Da probably represent one component in different modification states. Single-stranded DNA shows the highest template efficiency, although archaebacterial chromosomal DNAs are efficiently transcribed. Rifampicin, streptolydigin and alpha-amanitin do not inhibit transcription by this enzyme. Heparin permits elongation but not initiation of transcription. The activity of H. morrhuae RNA polymerase is strongly stimulated by glycerol and dimethylsulfoxide.
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PMID:DNA-dependent RNA polymerase from the extremely halophilic archaebacterium Halococcus morrhuae. 688 65

The purpose of this work was to study if the steatogenic effect on the liver of Rifampicin, which is an inhibitor of the RNA polymerases DNA dependent in bacteria, can be prevented by an anabolic steroid: 19 nortestosterone phenylproprionate (19-NTPP) which probably stimulates the RNA polymerase activity in eukariotic cells. 19-NTPP (25 mg/kg/24 h, i.p.) was administered to male and both intact and ovariectomized female rats for 8 days prior to the administration of Rifampicin (400 mg/kg/24 h for 8 days). In male rats, 19-NTPP does not prevent the Rifampicin-induced fatty liver. On the contrary, in female rats, 19-NTPP exerts a partial protective effect in intact as well as in ovariectomized animals. These results show that the protective effect of 19-NTPP against Rifampicin fatty liver is less complete and little specific, comparated to the protective effect obtained against another steatogenic compound in female rats: alpha-Amanitin, which is a potent inhibitor of RNA polymerase II in eukariotic cells. In conclusion, the inhibitor effect of Rifampicin on the hepatic apolipoprotein biosynthesis appears as less specific and more intricate than the comparable effect of alpha-Amanitin.
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PMID:Study of the protective effect of an anabolic steroid, 19-nortestosterone phenylpropionate (19-NTPP) on the fatty liver induced by high doses of rifampicin in the rat. 693 30

Open complexes of Escherichia coli RNA polymerase core enzyme with a poly[d(A-T)]-poly[d(A-T)]template have been characterized and compared with the previously characterized holoenzyme open complexes on the same template (Hansen, U. M., and McClure, W. R. (1979) J. Biol. Chem. 254, 5713-5717). The open complexes were monitored by the abortive initiation synthesis of the dinucleotide pApU, which is catalyzed by both enzymes. The major differences between the two complexes were: 1) the Michaelis constant for UTP was 60 times higher for core enzyme than for holoenzyme, 2) the intrinsic binding constant of core enzyme to the DNA was 3 orders of magnitude less than that of holoenzyme, and 3) cooperative binding of 2 core units was required for activity. Thus, the presence of the sigma subunit significantly altered the nature and extent of open complex formation. The rate of formation of the open complexes, however, was rapid for both enzymes. Rifampicin is shown to have a slight stimulatory effect on the extent of open complex formation of the core enzyme.
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PMID:Role of the sigma subunit of Escherichia coli RNA polymerase in initiation. I. Characterization of core enzyme open complexes. 700 Jul 58

The interaction of sigma subunit of E. coli RNA polymerase with DNA, either double or single-stranded, and with two inhibitors of RNA synthesis was investigated by using antibodies directed against the subunit. Free sigma subunit was shown to interact with poly(dA), poly(dT), poly(dAC).poly(dGT), T7 DNA and, to a lesser degree, with lambda DNA. When the sigma subunit forms part of the holo enzyme, sigma also interacts with poly(dG).poly(dC). Rifampicin and streptolydigin interact with sigma in the holo enzyme and with free and core bound sigma subunit, respectively. The results suggest that sigma recognizes mainly AC-GT-sequences in double-stranded DNA. The findings are correlated with the base composition in RNA polymerase binding regions of promoters and suggest at least a general interaction between sigma subunit and single-stranded DNA in open complexes.
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PMID:Sequence-specific interaction of sigma subunit of E. coli RNA polymerase with DNA. 700 37

Rifampin-resistant mutants of Escherichia coli were isolated which had altered patterns of resistance or sensitivity to the inhibitory compounds 5-methyltryptophan and 5-methylanthranilate. The levels of tryptophan (trp) operon polypeptides in different rifampin-resistant mutants were elevated or reduced, in a manner consistent with their sensitivity to the two analogs. Complementation tests established that the mutations were in rpoB, the structural gene for the beta subunit of ribonucleic acid polymerase. Introduction of these rpoB mutations into mutant strains which terminate transcription abnormally at the trp operon attenuator established that the rpoB mutations alter trp operon expression by increasing or decreasing transcription termination at the attenuator. The rpoB mutations affected transcription termination at the attenuator only in strains which were able to form what is thought to be a ribonucleic acid termination structure. These findings suggest that alteration of the beta subunit of ribonucleic acid polymerase directly or indirectly affects ribonucleic acid polymerase's recognition of the transcription termination signal at the trp operon attenuator.
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PMID:Rifampin resistance mutations that alter the efficiency of transcription termination at the tryptophan operon attenuator. 700 79

The activity of the proline catabolic enzyme pyrroline-5-carboxylate dehydrogenase (EC 1.5.1.12) was induced up to three-hundred-fold by the addition of three hundred proline to the growth medium of the Gram-positive bacterium Streptomyces coelicolor A3(2). Rifampicin, an inhibitor of RNA polymerase activity, abolished induction, implying that regulation was at the level of activation of gene transcription. The enzyme was purified and SDS-PAGE of the highly purified enzyme preparation revealed a single subunit with M(r) 68,000. A single band of protein, which also stained for enzyme activity, was observed after native gel electrophoresis. The M(r) of the enzyme was estimated to be approximately 265,000 by native gel electrophoresis and approximately 305,000 by gel filtration, which indicated that the enzyme had a tetrameric quaternary structure. The apparent Km for pyrroline-5-carboxylate was 109 +/- 7.3 microM, whilst that for NAD+ was 43.3 +/- 2.5 microM. Product inhibition by NADH (apparent Ki 0.6mM) was observed. The observed Vmax was 22.0 +/- 1 mol min-1 (mg protein)-1. Neither 1 nor 5 mM proline had any effect on enzyme activity, whilst glutamate was a very weak inhibitor.
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PMID:Interaction between primary and secondary metabolism in Streptomyces coelicolor A3(2): role of pyrroline-5-carboxylate dehydrogenase. 755 Oct 40

Rifampicin and streptolydigin are antibiotics which inhibit prokaryotic RNA polymerase at the initiation and elongation steps, respectively. In Escherichia coli, resistance to each antibiotic results from alterations in the beta subunit of the core enzyme. However, in Bacillus subtilis, reconstitution studies found rifampicin resistance (RifR) associated with the beta subunit and streptolydigin resistance (StlR) with beta'. To understand the basis of bacterial StlR, we isolated the B. subtilis rpoC gene, which encodes a 1,199-residue product that is 53% identical to E. coli beta'. Two spontaneous StlR mutants carried the same D796G substitution in rpoC, and this substitution alone was sufficient to confer StlR in vivo. D796 falls within Region F, which is conserved among the largest subunits of prokaryotic and eukaryotic RNA polymerases. Among eukaryotes, alterations in Region F promote resistance to alpha-amanitin, a toxin which inhibits transcription elongation; among prokaryotes, alterations in Region F cause aberrant termination. To determine whether alterations in the beta subunit of B. subtilis could also confer StlR, we made three StlR substitutions (A499V, G500R, and E502V) in the rif region of rpoB. Together these results suggest that beta and beta' interact to form an Stl binding site, and that this site is important for transcription elongation.
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PMID:Streptolydigin resistance can be conferred by alterations to either the beta or beta' subunits of Bacillus subtilis RNA polymerase. 759 85

The Shigella sonnei plasmid pKYM replicates by a rolling-circle mechanism in Escherichia coli. A 571 nucleotides HincII restriction fragment of the pKYM DNA harbors two potential hairpin loops (I and II). We cloned the fragment into a -ori defective M13 vector phage, M13 delta lac183. The chimera phage, MDKY5, showed a larger plaque size, and increased phage yield and rate of progeny replicative form DNA (RF) synthesis. Rifampicin reduced rate of conversion of the single- to double-stranded RF DNA. In addition, we introduced nucleotide deletions within the cloned pKYM DNA, by Bal31 nuclease digestion. Each of the deletion mutants thus constructed was lacking in a sequence containing the hairpin loops and formed smaller plaques. The in vivo analyses revealed that a 136 nucleotides sequence containing the two hairpins I and II is the pKYM minus origin for complementary strand synthesis (single strand origin, referred to as SSO) and harbors a recognition site(s) by host E. coli RNA polymerase, for primer RNA synthesis. Moreover, we found a 24 nt sequence, upstream of the SSO domain having 83% homology to the recombination site A (RSA) which functions in plasmid sitespecific recombination and/or transfer.
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PMID:Determination of the single strand origin of Shigella sonnei plasmid pKYM. 784 Nov 95


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