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)

Deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase (EC 2.7.7.6) from Acinetobacter calcoaceticus was purified to apparent homogeneity and its properties were compared with those of the Escherichia coli B enzyme. The molecular weights of the two native active enzymes as well as their alpha and beta subunits appeared to be similar. No subunit corresponding to that of sigma from E. coli was found, and furthermore no separation between the beta subunits could be detected by gel electrophoresis. A number of different DNAs were transcribed by the enzyme from A. calcoaceticus. Maximal RNA synthesis occurred at pH 8.7, 10 mM Mg2+, or 0.3 mM Mn2+ and at a total ionic strength of 0.1. Higher ionic strengths led to increasing inhibition of transcription and at mu = 0.4 complete inhibition was observed. The mechanism of inhibition of salt was not related to the initiation event as observed with T4 core RNA polymerase (R.Kleppe, 1975). In an attempt to understand the mechanism of inhibition by salt, the effect of ionic strength on the sedimentation properties of the enzyme was investigated. At low ionic strength, enzyme species with sedimentation coefficients, s20,w, of 5.8S, 12.4S, and 19.3S were present. In buffers with higher ionic strengths the relative amounts of the 12.4S species decreased. It is suggested, therefore, that the inhibition of activity at higher salt concentrations is caused by a decrease in concentration of the active enzyme species.
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PMID:Preparations and properties of ribonucleic acid polymerase from Acinetobacter calcoaceticus. 0 80

The endogenous RNApolymerase activity of isolated cell nuclei and chloroplasts from young pea plants (Pisum sativum) has been studied. The presence of all four nucleoside triphosphates and Mg2+ ions is necessary for the reaction. The missing of one of these nucleotides from the reaction mixture, especially ATP, sharply decreases the transcription. Chloroplasts synthesize RNA per DNA unit more intensively, than nuclei. In spring such predominance is especially pronounced. Maximal synthesis of RNA is observed at pH 8.3 both in nuclei and chloroplasts. Maximal transcription was observed at 25 degrees in chloroplasts and at 30--35 degrees in nuclei. Actinomycin D inhibited the process of transcription both in nuclei and some stimulation in chloroplasts were observed, when rifamicin B was added. It is suggested that there are differences in nuclear and chloroplast forms of RNA polymerase.
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PMID:[Comparative study of endogenous RNA-polymerase activity of the cell nuclei and chloroplasts of pea leaves]. 0 71

Acidification of a T7 DNA sample was found to be partly irreversible as ultraviolet difference spectra measured at various sub-melting temperatures were different from those observed for a 'normal' DNA sample. This implies some subtle conformational change which is not reversed by return to neutral pH. In the same conditions, only poly(purine)-poly(pyrimidine) polymers behaved in a different manner, during premelting, according to whether they were previously acidified or not. The properties of acidified and reneutralized T7 DNA were also investigated for Escherichia coli RNA polymerase binding and transcription. An inhibition of RNA synthesis and chain initiation was observed. The results suggest that the binding of the enzyme is affected. RNA synthesized is specific but there is a decrease in the number and in the stability of the RNA-polymerase-DNA complexes.
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PMID:Influence of DNA acidification on DNA premelting and template properties. 0 56

The properties of poly(G) polymerase and poly(A) polymerase activities in the DNA-dependent RNA polymerase [nucleosidetriphosphate: RNA nucleotidyltransferase EC 2.7.7.6] I fraction from cauliflower (Brassica oleracea var. botrytis) were comparatively investigated. The pH optimum, the effect of ionic strength, the effect of substrate concentration on the rate of synthesis, the effect of divalent metal ion concentration, and the time course of synthesis at different temperatures were all different for the three polymerase activities. The enzyme fraction preferentially utilized denatured DNA. Synthetic poly(C) and poly(U) were more effectively utillized for the synthesis of polyguanylate and polyadenylate, respectively. Further, it was found that poly(G) and poly(A) formed in vitro by the enzyme fraction had chain length of 25-28 and 84-89 nucleotides, respectively, and that poly (adenylate-gluanylate) chain was hardly formed when ATP and GTP were added together as substrates in the same reaction medium.
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PMID:Comparative studies on polyguanylate polymerase and polyadenylate polymerase activities in the DNA-dependent RNA polymerase I fraction from cauliflower. 0 54

A DNA membrane fraction extracted from pneumococci can be separated into two subfractions with respect to macromolecular composition and DNA synthesis by centrifugation in a 30-60% w/v neutral sucrose gradient. Each fraction can be rebanded in a sucrose gradient or centrifuged to equilibrium in a CsCl density gradient without altering the ability of the fractions to synthesize DNA. The fast sedimenting (heavy) fraction contains 45% of the DNA, and the bulk of the phospholipid, protein, and RNA. The light fraction contains 50% of the DNA, and lower, but significant amounts of phospholipid, RNA, and protein. Both fractions contain a DNA replication complex consisting of a number of enzymes involved in synthesizing DNA or DNA precursors, as well as RNA polymerase activity. However, the specific activity of DNA polymerase in the light fraction is much greater than that in the heavy fraction. In addition, the following results suggest that the former is concerned primarily with replication of the genome while the latter has characteristics of a repair function for the genome. (1) newly synthesized DNA can be detected within 30 s in the light fraction but not until 4 min in the heavy fraction. (2) an RNA-DNA single-stranded hybrid can be demonstrated during initial stages of DNA synthesis in the light, but not heavy fraction. (3) extensive semiconservative DNA replication occurs in the light fraction, whereas little such replication is detected in the heavy fraction. (4) DNA polymerase activity in the light fraction has several of the characteristics of a polymerase identified by others as being concerned with normal DNA replication, such as inhibition by N-ethylmaleimide, and relatively high rates of chain elongation (4.9 x 10(4) nucleotides/min). In contrast, DNA polymerase activity in the heavy fraction has characteristic properties associated with DNA polymerase I, a possible repair enzyme. These include higher activity for a d(A-T)n template than that detected in the light fraction, no effect of N-ethylmaleimide, and relatively low rates of chain elongation (9 x 10(3) nucleotides/min).
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PMID:Two membrane sites for DNA synthesis in Pneumococcus. 1 91

Nucleoside triphosphate phosphohydrolase [EC 3.6.1.15] activity was found to be included in silkworm cytoplasmic polyhedrosis (CP) virus, which synthesizes mRNA carrying the 5'-terminal modification. This enzyme releases orthophosphate from the gamma-position in a nucleoside triphosphate, leaving nucleoside diphosphate. The rate of hydrolysis of ATP is faster than that of any other ribonucleoside triphosphate. Deoxy ATP is hydrolyzed rather faster than ATP. However, polynucleotides carrying triphosphate at the 5'-terminus, that is, 4S RNA which was synthesized by E. coli RNA polymerase [EC 2.7.7.6] using calf thymus DNA as a template, and the phage Q beta RNA (30S), are not effective substrates for this enzyme. Although the CP virion loses the viral genome and one kind of protein component on proteolytic treatment with pronase, the partially degraded virion still retains phosphohydrolase activity. The phosphohydrolase must therefore be associated firmly with the virion. This enzyme does not require the presence of nucleic acid for its function. Phosphohydrolysis of ATP by this enzyme activity represents a first step in the synthesis of the 5'-terminal modified mRNA of CP virus.
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PMID:Nucleoside triphosphate phosphohydrolase associated with cytoplasmic polyhedrosis virus. 1 44

phi 227, a temperate phage from a group H streptococcus (Streptococcus sanguis), was propagated vegetatively in group H strain Wicky 4-EryR, and its characteristics were determined. A procedure dependent on multiplicity of infection, incubation time, and treatment of crude lysates with diatomaceous earth was found to optimize phage yield, resulting in titers of 1 X 10(10) to 2 X 10(10) PFU/ml. Without prior treatment with diatomaceous earth, subsequent purification procedures (methanol, ammonium sulfate, polyethylene glycol) gave recoveries of less than 1% of crude lysate titers. Adsorption of phi227 to host cells was relatively unaffected by the medium, but calcium (not substituted by magnesium) was required for formation of infectious centers. The phage receptor was present on purified cell walls, resisted trypsin and heat, and was removed ty hydrochloric acid, trichloracetic acid, and hot formamide: however, formamide-extracted material failed to inactivate phage, and the nature of the receptor is unknown. Single-step growth experiments showed a latent period of 39 min and a burst size of 100 PFU/infectious center; results were unaffected by omission of supplemental Ca2+, by supplementation with Mg2, addition of glucose, or changes of pH between 6.35 and 8.0; but increased temperature (40 to 43 degrees C) shortened the latent period and decreased the burst size. The latent period was prolonged in genetically competent host cells and in chemically defined medium; and in the latter, the burst size was smaller. Phage replication was sensitive to those metabolic inhibitors which inhibited the host streptococcus: these included rifampin, fluorodeoxyuridine, hydroxyurea, dihydrostreptomycin, and 6-P-hydroxyphenylazouracil. The data suggest that phi227 does not code for a rifampin-resistant RNA polymerase. However, in a rifampin-resistant host strain, phage replication and lysogen formation were both decreased suggesting that altered host core polymerase had less affinity for (some) promotors on the phi227 template. In transfection, a Ca2+-dependent stabilization step that was inhibited by Mg2+ was demonstrated; transformation was not affected by either Ca2+ or Mg2+, and the site and nature of the stabilization are unknown. More than one molecule of DNA was required for plaque formation. Biophysical characterization showed a type B phage of buoyant density (CsCl) 1.50, containing five proteins and 54.8% DNA. The duplex linear DNA had a molecular weight (calculated from contour length) of 23.2 X 10(6) and a guanine plus cytosine content (calculated from melting point) of 42.3 mol%. Similar characterizations of streptococcal phages, including biophysical data, have not been previously available.
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PMID:Characterization of group H streptococcal temperate bacteriophage phi 227. 1 33

Oligoribocytidylates of chain length 4 to 12 were found to interact with native T7 DNA at neutral and slightly acid pH. The results suggest that binding occurred at deoxycytosine clusters which may be displaced by the oligomers at neutral pH, while a local triple-stranded structure would be formed at acid pH. Transcription of DNA-(Cp)n complexes by Escherichia coli RNA polymerase showed a decrease in level without affecting the specificity of the transcription, suggesting that oligocytidylate binding did not occur on the promoters.
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PMID:Interaction of oligoribocytidylates with T7 DNA in neutral and acid media. 2 84

Two antiviral pyrimidine derivatives, known to partially inhibit RNA dependent RNA polymerase of Mengo virus in a cell-free system, were found to bind with biopolymers. The antiviral compounds, at concentration of 100 and 50 muM and lower, showed complete inhibition of the virus-induced cytopathic effect and plaque reduction. Both compounds showed fluorescence emission with a maximum at about 500 nm under the influence of UV light of the wavelength of 366 nm. The fluorescence intensity increased upon addition of aqueous solutions of DNA, RNA and human serum albumin. This indicates that both compounds are capable of binding with nucleic acids and proteins. Based on the binding experiments alone it cannot be decided whether interference with nucleic acid template activity, enzyme function, or both are responsible for the virostatic action. Irradiation with violet light considerably enhances the virostatic activity, a fact that may be caused by photodynamic processes.
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PMID:Antiviral pyrimidine derivatives: binding with biopolymers and photosensitization. 2 7

Under non optimal conditions- either with limiting substrate concentrations (1) or at low pH (2)- RNA polymerase of Escherichia coli synthesizes very short RNA chains. By sequencing one RNA species synthesized at pH 5.8 upon T7 DNA we were able to demonstrate that under these conditions transcription is initiated at a normal promoter site (here A1) but however is terminated soon afterwards at specific artificial sites not used in vivo.
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PMID:Short RNA chains synthesized at low pH are initiated at promoter sites. 2 44


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