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 effects of Ca2+ on the RNA polymerase activity of the nuclei isolated from normal and denervated gastrocnemius muscles of the rabbit were studied. It was shown that 18 hrs after denervation the RNA synthesis in vitro, Ca2+ content and the Ca, Mg-ATPase activity of the nuclei are decreased. After addition of exogenous Ca2+ the incorporation of labelled UTP into the nuclei is stimulated in the denervated muscle and is inhibited in the control. Electrostimulation of the denervated muscle at the peripheral part of the sciatic nerve for 3 hrs increases both the RNA synthesis in the nuclei and the Ca2+ content, as well as the Ca, Mg-ATPase activity. Exogenous Ca2+ has an inhibitory effect on the nuclei of the stimulated muscle. The correlation established is indicative of participation of Ca2+ in the transmission of excitation in skeletal muscle sarcolemma to the processes occurring in nuclear structures.
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PMID:[Role of calcium in realization of nervous control during RNA synthesis in skeletal muscles]. 9 40

The DNA polymerase of early embryos of Drosophila melanogaster has been purified to near-homogeneity. The purified enzyme gave a single, catalytically active protein band after polyacrylamide gel electrophoresis, under nondenaturing conditions. Four polypeptides with molecular weights 43,000, 46,000, 58,000, and 148,000 were resolved when this band was electrophoresed under denaturing conditions. At high ionic strengths, the DNA polymerase had a sedimentation coefficient of 8.7 S, a Stokes radius of 78 A and frictional ratio of 1.81, parameters that yield a molecular weight of 280,000. The purified DNA polymerase possessed no detectable endo- or exodeoxyribonuclease, ATPase, or RNA polymerase activity. Using an "activated" DNA template-primer, the enzyme had a pH optimum of 8.5. It was stimulated by (NH4)2SO4, KCl, and to a lesser extent, NaCl. A divalent metal cation was absolutely required; MgCl2 stimulating activity 7-fold more than MnCl2. It was inhibited by low concentrations of N-ethylmaleimide and Aphidicolon. Thus the DNA polymerase of D. melanogaster resembles most closely the alpha-DNA polymerases that have been purified from mammalian cells.
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PMID:A high molecular weight DNA polymerase from Drosophila melanogaster embryos. Purification, structure, and partial characterization. 11 15

An adenosinetriphosphatase (ATPase) [EC 3.6.1.3] copurified with the DNA-dependent RNA polymerase [EC 2.7.7.6] from Escherichia coli was isolated to apparent homogeneity and some of its functional as well as structural properties were examined. Although the novel ATPase exhibited metal requirements similar to those of Mg2+, Ca2+-ATPase, its response to NaN3 and antisera appeared completely different from that of the Mg2+, Ca2+-ATPase. The purified ATPase was found to be a large protein with a molecular weight of 9.3X10(5) daltons, composed of identical subunits of 7X10(4) daltons. When viewed under an electron microscope, the ATPase appeared to be very similar to material previously misidentified as the RNA polymerase. The physiological role of the novel ATPase, however, remains unclear.
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PMID:A novel adenosine triphosphatase isolated from RNA polymerase preparations of Escherichia coli. II. Enzymatic properties and molecular structure. 13 30

The effect of RNA secondary structure on rho-independent and rho-dependent termination of transcription of T3 DNA by Escherichia coli RNA polymerase has been studied by incorporating, into nascent transcripts, base analogs that lead to altered base-pairing properties. A guanine --> hypoxanthine substitution, with attendant weakening of secondary structure, abolished the rho-independent termination at 20% of the genome; in contrast, replacement of cytosine with 5-bromocytosine, which forms stronger pairs with guanine, enhanced termination at this site. rho-Independent termination was not altered by replacing uracil with 5-bromouracil. There are two major rho-dependent termination sites on the T3 DNA-at 8 and 15%. The termination activity of rho in this system also depended on RNA secondary structure. The incorporation of 5-bromouracil instead of uracil into RNA did not alter the site specificity of rho action but rho was rendered inactive when cytosine was replaced by 5-bromocytosine. In contrast, replacement of GTP with ITP in the reaction increased rho-dependent inhibition of RNA synthesis, caused production of heterogeneous-sized transcripts, and stimulated rho-mediated ATP hydrolysis. The rho-associated ATPase activity, in the presence of isolated T3 RNA, was also stimulated by inosine substitution. Furthermore, the temperature-sensitive rho isolated from rho 15 mutant of E. coli, which does not terminate transcription in the presence of the common rNTPs, was active when GTP was replaced with ITP. These results suggest that strongly paired G.C-rich regions in RNA stem-loop structures or RNA.DNA hybrids are essential for rho-independent termination, whereas rho-dependent termination requires weakly paired cytosine residues for its action.
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PMID:Termination of transcription by Escherichia coli RNA polymerase: influence of secondary structure of RNA transcripts on rho-independent and rho-dependent termination. 15 60

A rat liver nuclear envelope fraction isolated essentially by the technique of Monneron et al. (J. Cell Biol. 55, 104-125 (1972) is characterized by high levels of glucose-6-phosphatase and 5'-nucleotidase. A broadly specific nucleoside triphosphatase activity is present. Cytochromes b5 and P-450 as well as NADPH- and NADH-cytochrome c reductase activities are present but at lower levels than found in microsomes. Cytochrome c oxidase activity is low. RNA polymerase activity is absent from the nuclear envelope fraction. Cytochemistry shows that glucose-6-phosphatase activity is strong and restricted to the nuclear envelope of nuclei. 5'-Nucleotidase shows weak reaction deposit in whole nuclei but in contrast gives clear reaction deposit in isolated nuclear envelopes. Cytochemical reaction deposit due to nucleoside triphosphatase activity is not restricted to the nuclear envelope but is found to a larger extent within the nucleus.
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PMID:An enzymic analysis of a nuclear envelope fraction. 18 34

RNA polymerase I was isolated from parsley cells grown in suspension culture and from soybean hypocotyls. Kinetic studies of the enzyme revealed that RNA polymerase I is an allosteric regulated enzyme. The enzyme activity was influenced by nucleoside triphosphates (NTP) and divalent cations. NTP exceeding a 1:1 ratio of these two components acted as allosteric inhibitors, contrary to free divalent cations, which had promotive effects on the RNA polymerase I. Furthermore, isolated nuclei from parsley exhibited a powerful nucleoside triphosphatase (NTPase) activity. Contrary to RNA polymerase I, this enzyme was stimulated by NTP exceeding the 1:1 ratio of NTP and divalent cations. Free divalent cations had an inhibitory effect. Assuming that a causal connection of these two processes does exist, a possible role of this NTPase would be the control of NTP pools in relation to divalent cations and thus regulating RNA synthesis.
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PMID:RNA polymerase I from higher plants. Evidence for allosteric regulation and interaction with a nuclear phosphatase activity controlled NTP pool. 23 67

We have resolved, by native gel electrophoresis, two intermediates in the transcription of a vaccinia virus early gene by the virus-encoded RNA polymerase. Polymerase holoenzyme containing the vaccinia virus early transcription factor (VETF) forms a complex of VETF bound to the promoter as the first step in a pathway leading to establishment of a committed ternary elongation complex. Formation of the VETF-DNA complex is stimulated by magnesium but is uninfluenced by nucleoside triphosphates. A stable binary complex of RNA polymerase bound to DNA is not detected. Assembly of a gel-stable polymerase-DNA complex depends on conditions permissive for RNA synthesis. Nucleotide omission experiments suggest that at least a tetrameric RNA must be made before a ternary complex is stabilized. RNA analysis indicates that complexes containing nascent transcripts 20 nucleotides long are stable and active. Ternary complex formation requires hydrolyzable ATP. This is consistent with an essential role for the ATPase activity of VETF at a step subsequent to DNA binding, as proposed by Broyles (S. S. Broyles, J. Biol. Chem. 266:15545-15548, 1991). The ternary complex, once formed, is resistant to dissociation by competitor DNA, as well as by salt, Sarkosyl, and heparin. The effects of these inhibitory agents on transcription complex formation suggest that they target different steps in the assembly pathway.
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PMID:Ternary complex formation by vaccinia virus RNA polymerase at an early viral promoter: analysis by native gel electrophoresis. 137 99

We previously purified RNA polymerase II transcription factor delta from rat liver and found that it has an associated DNA-dependent ATPase (dATPase) activity. In this report, we show that delta is also closely associated with a protein kinase activity that catalyzes phosphorylation of the largest subunit of RNA polymerase II. Kinase activity copurifies with transcription and DNA-dependent ATPase (dATPase) activities when delta is analyzed by anion- and cation-exchange HPLC as well as by sucrose gradient sedimentation, arguing that delta possesses all three activities. Phosphorylation of the largest subunits of both rat and yeast RNA polymerase II is stimulated by DNA, whereas phosphorylation of a synthetic peptide containing multiple copies of the carboxyl-terminal heptapeptide repeat is not. Although both ATP and GTP appear to function as phosphate donors, GTP is utilized less than 10% as well as ATP. These findings suggest that delta may exert its action in transcription at least in part through a mechanism involving phosphorylation of the largest subunit of RNA polymerase II.
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PMID:A carboxyl-terminal-domain kinase associated with RNA polymerase II transcription factor delta from rat liver. 138 28

Initiation of transcription by RNA polymerase II requires a TFIID factor, which can recognize the TATA element common to many promoters. Two distinct multisubunit TFIID factors can be resolved from extracts of mammalian cells, and both of them contain the well-characterized TATA-binding protein (TBP) and are capable of supporting RNA polymerase II transcription in an in vitro reaction system. The smaller complex, B-TFIID, was purified and its subunit composition was determined. B-TFIID consists of two subunits: the TBP and a TBP-associated factor (TAF) of 170 kDa. This TAF is specific for B-TFIID and appears not to be present in the D-TFIID complex. Furthermore, it was found that the highly purified B-TFIID fractions have (d)ATPase activity.
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PMID:Composition of transcription factor B-TFIID. 138 11

The high affinity branched-chain amino acid transport system (LIV-I) in Pseudomonas aeruginosa is composed of five components: BraC, a periplasmic binding protein for branched-chain amino acids; BraD and BraE, integral membrane proteins; BraF and BraG, putative nucleotide-binding proteins. By using a T7 RNA polymerase/promoter system we overproduced the BraD, BraE, BraF, and BraG proteins in Escherichia coli. The proteins were found to form a complex in the E. coli membrane and solubilized from the membrane with octyl glucoside. The LIV-I transport system was reconstituted into proteoliposomes from solubilized proteins by a detergent dilution procedure. In this reconstituted system, leucine transport was completely dependent on the presence of all five Bra components and on ATP loaded internally to the proteoliposomes. Alanine and threonine in addition to branched-chain amino acids were transported by the proteoliposomes, reflecting the substrate specificity of the BraC protein. GTP replaced ATP well as an energy source, and CTP and UTP also replaced ATP partially. Consumption of loaded ATP and concomitant production of orthophosphate were observed only when BraC and leucine, a substrate for LIV-I, were added together to the proteoliposomes, indicating that the LIV-I transport system has an ATPase activity coupled to translocation of branched-chain amino acids across the membrane.
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PMID:Solubilization and reconstitution of the Pseudomonas aeruginosa high affinity branched-chain amino acid transport system. 140 Apr 43


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