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)

The antibiotic rifampicin forms a very tight complex with DNA-dependent RNA polymerase of Escherichia coli. The rate constants of association and dissociation of this complex have been measured and found to be dependent on the purity of the enzyme. Thus a crude RNA polymerase (fraction-3 enzyme) has rate constants different from those of an enzyme further purified by DEAE-cellulose chromatography (fraction-4 enzyme). The complex produced by the antibiotic and the fraction-3 enzyme is about ten times more stable and is formed about ten times more slowly than the complex with fraction-4 enzyme. It has been shown that the RNA present in the crude enzyme and removed by chromatography on DEAE-cellulose is the cause of the change in the kinetics of the complex. tRNA of rat liver and crude rat liver RNA added to purified RNA polymerase have a similar effect. Mg2+, which has no intrinsic influence, augments the effect of the nucleic acids, whereas monovalent cations do not. Since nucleic acids increase the stability of the complex, but at the same time decrease the rat of its formation, the equilibrium constant, Keq, remains almost the same. The possible effects of nucleic acids on the rifampicin binding site are discussed.
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PMID:On the kinetics of the rifampicin-RNA-polymerase complex. Differences between crude and purified enzyme fractions. 78 Jan 10

RNA synthesis in yeast is rapidly inhibited by 8-hydroxyquinoline and the phenazine antibiotic lomofungin (5-formyl-1-methoxycarbonyl-4,6,8-trihydroxyphenazine). It is shown that lomofungin, like 8-hydroxyquinoline, is a chelating agent for bivalent cations. The mechanism of inhibition of RNA synthesis by lomofungin and 8-hydroxyquinoline was investigated in experiments with isolated Escherichia coli RNA polymerase. The results show that both inhibitors are capable of inhibiting polymerase activity solely by chelating the dissociable cations Mn2+ and Mg2+. Evidence is presented which shows that inhibition may occur in the absence of any direct contact between the RNA polymerase or DNA template and the inhibitor. The possibility that inhibition might also occur by chelation of the Zn2+, which is tightly bound to the polymerase, is discussed: it is concluded that lomofungin or 8-hydroxyquinoline is likely to inhibit the enzyme by removal of Mn2+ and Mg2+ before chelating the Zn2+. On the basis of inhibition by chelation of Mn2+ and Mg2+, explanations are proposed for why lomofungin and 8-hydroxyquinoline inhibit synthesis of ribosomal and polydisperse RNA more than that of 5S RNA and tRNA, and for why protein synthesis is not immediately inhibited in the intact yeast cell.
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PMID:The mechanism of inhibition of ribonucleic acid synthesis by 8-hydroxyquinoline and the antibiotic lomofungin. 81 Jan 37

A new form of DNA-dependent RNA polymerase termed enzyme III has been purified from sporulating cells of Bacillus subtilis. In addition to the subunits of core RNA polymerase (beta', beta, alpha, and omega), enzyme III contains sporulation-specific polypeptides of 85,000 (P85) and 27,000 (P27) daltons. P85 corresponds to an RNA polymerase-binding protein previously identified by precipitation of RNA polymerase from crude extracts of sporulating cells with antibody directed against core enzyme. Both P85 and P27 co-purified with RNA polymerase highly purified by gel filtration, DEAE-cellulose chromatography, phosphocellulose chromatography, and glycerol gradient centrifugation. Enzyme III bound more tightly to phosphocellulose and sedimented more rapidly during zone centrifugation than did RNA polymerase lacking the sporulation polypeptides. RNA polymerase containing P85 and P27 transcribed B. subtilis DNA about 4.5 times more actively than did core RNA polymerase, although both enzymes exhibited similar activities with poly(dA-dT) and phage phie DNA as templates. Enzyme III and core RNA polymerase also differed in their response to increasing concentrations of Mg2+ and KCl.
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PMID:RNA polymerase from sporulating Bacillus subtilis. Purification and properties of a modified form of the enzyme containing two sporulation polypeptides. 81 62

Two forms of RNA polymerase [EC 2.7.7.6], RPase L1 and RPase L2, isolated from a highly synchronized vegetative culture of Bacillus subtilis Marburg strain are described. RPase L1 is the major component (identical and the vegetative RNA polymerase already reported) and RPase L2 is a minor, new component corresponding to 3--5% of the total activity. The enzymes differed in their requirements for divalent ions, though the differences depended on the template DNA employed. PRase L1 is able to transcribe phage M2 DNA in the presence of Mg2+ ions and both B. subtilis DNA and phage M2 DNA in the presence of Mn2+ ions. On the other hand, RPase L2 activity can be detected only in the presence of 3 mM Mn2+ ions with all the templates. It is of interest that the transcription of phage M2 DNA by both enzymes stringently requires KC1. It may be due to this ion dependence that RPase L2 has not been detected previously. RPase L2 consists of 1beta', 1beta gamma, 1sigma, and 2alpha subunits. The molecular weight of the beta gamma subunit (about 110,000) is close to the value reported for the beta subunit of RNA polymerase prepared from sporulating cells. However, RPase L2 as a whole molecule is different from the RNA polymerase of sporulating cells or spores in the following two respects: RPase L2 contains sigma subunit as a component essential for selective transcription, and it is resistant to 1 mug of rifampicin per ml. Elimination of the sigma subunit from RPase L2 greatly stimulates RNA synthesis by the enzyme. Conversely, the addition of sigma subunit to the core-enzyme is inhibitory.
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PMID:RNA polymerase in vegetative cells of Bacillus subtilis. I. Purification and properties of RNA polymerase L1 and L2. 82 46

Two polypeptides named FI and FII were isolated from vegetative cells of Bacillus subtilis Marburg. The molecular weights of FI and FII were 15,000 and 30,000 daltons, respectively. They were able to stimulate the transcription of phage M2 DNA in the presence of Mg2+ ions by RPase L1 and RPase L2 [RNA polymerase; EC 2.7.7.6]. Although both core- and holo-RPase L2 hardly exhibited transcription activity under these conditions, the factors could stimulate both activities up to the level of RPase L1 activity. The stimulation was much less marked when B. subtilis DNA was used as a template. These stimulatory functions were found to lie not in the chain elongation but in the initiation step of transcription, following the preinitiation step. To obtain stimulation by the factors, preincubation with RNA polymerase was necessary. FI stimulated RPase L1 or RPase L2 only when preincubated in the stimultaneous presence of FII, forming a complex, RPase L1(or L2)-FI-FII. On the other hand, FII alone could stimulate transcription, forming a complex. RPase L1 (or L2)-FII. In these complexes, the ratio of FI, FII, and RPase L1(or L2) was 1 : 1: 1. Although the core-RPase L2 activity was inhibited by sigma subunits, it was not inhibited by was rather stimulated when the enzyme was present as a complex with FI and FII. Thus the complex, consisting of RPase L2 and the factors, resembled RPase L1 with respect to molecular weight, template specificity, the effect of sigma subunit, and sensitivity to rifampicin.
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PMID:RNA polymerase in vegetative cells of Bacillus subtilis. II. New polypeptide factors, FI and FII, stimulating in vitro RNA synthesis directed by phage M2 DNA. 82 47

The influenza virion transcriptase is capable of synthesizing in vitro complementary RNA (cRNA) that is similar in several characteristics to the cRNA synthesized in the infected cell, which is the viral mRNA. Most of the in vitro cRNA is large (approximately 2.5 X 10(5) to 10(6) daltons), similar in size to in vivo cRNA. The in vitro transcripts initiate in adenosine (A) or guanosine (G) at the 5' end, as also appears to be the case with in vivo cRNA (R.M. Krug et al., 1976). The in vitro transcripts contain covalently linked polyadenylate [poly(A)] sequences, which are longer and more heterogeneous than the poly(A) sequences found on in vivo cRNA. The synthesis in vitro of cRNA with these characteristics requires both the proper divalent cation, Mg2+, and a specific dinulceside monophosphage (DNMP), ApG or GpG. These DNMPs stimulate cRNA synthesis about 100-fold in the presence of Mg2+ and act as primers to initiate RNA chains, as demonstrated by the fact that the 5'-phosphorylated derivatives of these DNMP's, 32pApG or 32pGpG, are incroporated at the 5' end of the product RNA. The RNA synthesized in vitro differs from in vivo cRNA in that neither capping nor methylation of the in vitro transcripts has been detected. The virion does contain a methylase activity, as shown by its ability to methylate exogenous methyl-deficient Escherichia coli tRNA.
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PMID:Influenza virion transcriptase: synthesis in vitro of large, polyadenylic acid-containing complementary RNA. 83 24

RNA biosynthesis catalyzed with DNA-dependent RNA polymerase was demonstrated in the reconstructed system containing isolated lymphocyte nuclei, Mg2+ or Mn2+ salts, ammonium sulphate, in the presence of four nucleosidetriphosphates. Both the Mg2+ and Mn2+-dependent forms of this enzyme were revealed in the nuclei of normal lymphocytes and those of patients suffering from melanoma, carcinoma of the lung and sarcoma. The activities of both forms of RNA-polymerase were greater in the nuclei of the lymphocytes from sick individuals than in the normal analogues. DNA-dependent RNA-polymerase sensitivity to dexamethasone and PHA of the nuclei of lymphocytes obtained from patients with carcinoma of the lung, melanoma, and sarcoma was decreased in comparison with the normal.
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PMID:[Sensitivity of the lymphocyte RNA-synthesizing system of patients with different malignant neoplasms to phytohemagglutinin and dexamethasone]. 85 72

Lomofungin is a potent inhibitor of RNA synthesis in yeast. Studies on the mode of action of the inhibitor were carried out using yeast RNA polymerases A and B and bacterial RNA polymerase. In vitro inhibition of RNA synthesis is independent of the nature and concentration of the template used and of the nucleoside triphosphate concentration. The extent of inhibition is strongly dependent upon the nature and concentration of divalent cations used to simulate transcription. The three RNA polymerases were inhibited to the same extent in the presence of Mn2+ ions whereas little inhibition was observed with Mg2+ ions. Spectrophotometric studies reveal the formation of different complexes between lomofungin and divalent cations (Mn2+, Mg2+, or Zn2+) with the respective stoichiometries of 0.5, 1, and 2 divalent cations per molecule of lomofungin. The complexes formed depend upon the nature of the divalent cation involved. No direct interaction between lomofungin and DNA could be observed in the presence of divalent cations but evidence is presented that lomofungin interacts with yeast RNA polymerase A. Inhibition of RNA synthesis occurs at the level of both chain initiation and elongation.
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PMID:On the mode of action of lomofungin, an inhibitor of RNA synthesis in yeast. 110 54

The RNA polymerase activities from the nuclei of the spleen of uninfected and Rauscher murine leukemia virus-infected NIH Swiss mice were resolved by DEAE-cellulose column chromatography, and their properties were compared. The RNA polymerase activities from infected and uninfected spleens were the same with respect to column elution profiles, optimum requirements for various salts, ratios of activities with Mn2+ and Mg2+, sedimentation values, and response to most templates. With the exception of minor differences in activities with certain DNA templates, the significance of which is not clear, no qualitative differences in the enzymes from these two sources were found, but an increase in the specific activity of the alpha-amanitin sensitive enzyme, RNA polymerase II, was found in the leukemic spleen. These preliminary results suggest that there may be no novel RNA polymerase induced by Rauscher murine luekemia virus-infection, and they are in keeping with the interpretation that the viral DNA genome is transcribed by a host RNA polymerase.
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PMID:Deoxyribonucleic acid-dependent ribonucleic acid polymerases from spleen of uninfected and Rauscher murine leukemia virus-infected NIH Swiss mice.? 112 31

A nuclear poly(A) polymerase has been isolated from oviducts of immature quails. It could be purified 4300-fold. The enzyme depends specifically on ATP as substrate and requires Mg2+. The most effective primer for the enzyme is a polynucleotide, isolated from oviduct tissue. A poly(A) sequence to a maximum of 60 AMP residues is covalently linked per primer molecule. The poly(A)-rich product of the enzymatic reaction can be annealed to oligo(dT)-cellulose. The purest fraction does not contain any detectable poly(A)-degrading enzyme activity. Only very low activities of RNA polymerase are present. The poly(A polymerase activity in the assay with ATP is reduced by the ATP analogue, beta, lambda-ATP-methylene-diphosphonate. Both K-m and V are lowered. The ATP analogue is incorporated to a smaller extent into the poly(A) sequence, synthesized by the enzyme. Several other analogues of adenine, adenine nucleosides and adenine nucleotides are without effect on the enzymatic reaction. By these properties poly(A) polymerase can be distinguished from RNA polymerases form I and form II, isolated from the same tissue. Actinomycin D and alpha-amanitin failed to inhibit poly(A) polymerase activity. The activity of poly(A) polymerase has been determined during primary stimulation with the estrogen analogue diethylstilbestrol (daily injection for 5 days), after withdrawal of the hormone for 17 days and after secondary stimulation with the hormone analogue. The enzyme activity does not change during primary stimulation, withdrawal of the hormone or secondary stimulation. However the activity of a poly(A) degrading enzyme, localized in the nucleus, is reduced in oviducts from hormone-treated quails.
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PMID:Poly(A) polymerase in quail oviduct. Changes during estrogen induction. 116 81


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