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

---

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

To determine the stringent response, a repression of gene activity during amino acid starvation assumed to be mediated by the effector necleotide guanosine tetraphosphate (ppGpp), of metabolically regulated constitutive genes, we measured the transcription of ribosomal protein genes, the constitutive lac operon, and stable RNA genes in a variety of growth media and after amino acid starvation in a relA+/relA pair of Escherichia coli B/r strains. For rRNA and tRNA (stable RNA) it has previously been shown that the distinction between stringent control and growth rate control is unfounded, as the function describing the stable RNA gene activities at different concentrations of guanosine tetraphosphate is independent of growth conditions (exponential growth or amino acid starvation) and of the relA allele present. Here, the results indicated that the stringent responses of ribosomal protein genes and lac differ from their metabolic control during exponential growth in different media. This can be explained by polarity and RNA polymerase sink effects during amino acid starvation which are irrelevant for stable RNA genes but which are superimposed on mRNA gene activities.
...
PMID:Transcription of ribosomal component genes and lac in a relA+/relA pair of Escherichia coli strains. 609 Mar 95

The extent of productive RNA chain initiation in vitro by Escherichia coli RNA polymerase holoenzyme from the bacteriophage T7 A1 and A2 promoters on purified T7 DNA templates has been investigated at very low concentrations of the ribonucleoside triphosphate substrates. As the concentration of ribonucleoside triphosphates in the reaction is decreased from 10 to 1 micro M, the extent of productive RNA chain initiation at these promoter sites drops precipitously at about 3 micro M. At 1 micro M substrate concentration, productive chain initiation from the A1 promoter does not occur even after extended incubation although the dinucleoside tetraphosphate pppApU is produced at a significant rate under these conditions. The reason for the inability of RNA polymerase to carry out productive RNA chain initiation at 1 micro M substrate concentration is not yet understood. The phenomenon is not due to substrate consumption, enzyme inactivation, or a requirement for a nucleoside triphosphatase activity in the reaction. The possibility is raised that there are additional nucleoside triphosphate binding sites on E. coli RNA polymerase which play some role in the process of productive RNA chain initiation.
...
PMID:The effect of low substrate concentrations on the extent of productive RNA chain initiation from T7 promoters A1 and A2 by Escherichia coli RNA polymerase. 615 92

The rate of formation of dinucleoside tetraphosphate, pppApU, from ATP and UTP by RNA polymerase on the A1 promoter of the mutant D111 of bacteriophage T7 is distinctly and specifically reduced not only by the third template-directed nucleotide, CTP, but also by CMP. The inhibitory effect of CMP is not changed when the enzyme contains prebound rifampicin. The synthesis of pppApU is also strongly reduced after preincubation of the enzyme with RNA. This inhibitory effect of RNA is, however, distinctly diminished by rifampicin bound to the enzyme prior to the addition of RNA. On the other hand RNA can suppress the specific binding of the antibiotic to the RNA polymerase subassembly alpha 2 beta.
...
PMID:Competition of rifampicin with binding of substrate and RNA to RNA polymerase. 617 35

Parameters relating to RNA synthesis were measured after a temperature shift from 30 to 42 degrees C, in a relA+ and relA- isogenic pair of Escherichia coli strains containing a temperature-sensitive valyl tRNA synthetase. The following results were obtained: (i) the rRNA chain growth rate increased 2-fold in both strains; (ii) newly synthesized rRNA became unstable in both strains; (iii) the stable RNA gene activity (rRNA and tRNA, measured as stable RNA synthesis rate relative to the total instantaneous rate of RNA synthesis) decreased 1.7-fold in the relA+ strain and increased 1.9-fold in the relA mutant; and (iv) the RNA polymerase activity (measured by the percentage of total RNA polymerase enzyme active in transcription an any instant) decreased from 20 to 3.6% in the relA+ strain and remained unchanged (or increased at most to 22%) in the relA mutant. It is suggested that both rRNA gene activity and the RNA polymerase activity depend on the intracellular concentration of guanosine tetraphosphate, whereas the altered chain elongation rate and stability of rRNA are temperature or amino acid starvation effects, respectively, without involvement of relA function.
...
PMID:relA-dependent RNA polymerase activity in Escherichia coli. 617 1

For Escherichia coli B/r growing in glucose minimal medium, the following parameters of RNA synthesis remained invariant between 20 and 40 degrees C: RNA polymerase concentration (RNA polymerase/mass), rRNA and tRNA concentration (RNA/mass), RNA polymerase activity (fraction of total RNA polymerase actively engaged in RNA chain elongation), and stable RNA synthesis relative to total RNA synthesis. The following parameters increased 3.4-fold over the same temperature range: rRNA chain elongation rate, guanosine tetraphosphate (ppGpp) concentration, and culture growth rate. Above 40 degrees C, the changes became more complex, and the growth rate began to decrease. The observation that most RNA synthesis parameters are temperature invariant despite the increase of ppGpp suggests that the mechanism of RNA synthesis control by ppGpp, assumed to involve an interaction of RNA polymerase wtih ppGpp, is itself temperature dependent such that, with increasing temperature, higher concentrations of ppGpp are required to affect the RNA polymerase.
...
PMID:Temperature dependence of RNA synthesis parameters in Escherichia coli. 617 24

Parameters of RNA synthesis were measured after a temperature upshift in a pair of Escherichia coli B/r strains that are isogenic except for having relA and relA+ loci, to examine the cause for a reported anomaly in the correlation between guanosine tetraphosphate (ppGpp) and stable RNA (rRNA, tRNA) synthesis under such conditions. Two main results were: (i) the specific stable RNA gene activity (stable RNA per total RNA synthesis) correlated in the conventionally expected fashion with the level of ppGpp but was obscured by a nonspecific increase in the RNA chain elongation rate due to the higher temperature; (ii) the temperature upshift caused a transient reduction in the RNA polymerase activity (transcribing per total enzyme) that accounts for the previously observed oscillating RNA synthesis rate after a temperature shift.
...
PMID:Control of RNA synthesis in Escherichia coli after a shift to higher temperature. 617 25

An isogenic pair of relA+ and relA strains of Escherichia coli B/r with a mutation in the RNA polymerase subunit gene rpoB (Rifr) was isolated in which the relationship between guanosine tetraphosphate (ppGpp) concentration and stable RNA (rRNA, tRNA) gene activity was altered. The RNA polymerase in the rpoB strains was found to be about 20-fold more sensitive to ppGpp with respect to its stable RNA promoter activity than was the wild-type enzyme. The existence of such mutants is consistent with the idea that ppGpp interacts with the RNA polymerase enzyme and thereby alters its promoter selectivity, i.e., reduces its affinity for the stable RNA promoters. Under most conditions, the rpoB mutants had a reduced rate of growth and about a 10-fold-reduced intracellular concentration of ppGpp compared with the rpoB wild-type strains. The reduction of the level of ppGpp in the rpoB mutants during exponential growth was presumably a reflection of an indirect effect of the rpoB mutation on the control of relA-independent ppGpp metabolism.
...
PMID:rpoB mutation in Escherichia coli alters control of ribosome synthesis by guanosine tetraphosphate. 618 47

We have previously reported the isolation of Escherichia coli rpoB mutants in which the control of ribosome synthesis by the nucleotide effector guanosine tetraphosphate (ppGpp) is altered, owing to a 20-fold increased sensitivity of the mutant RNA polymerases to ppGpp. In these mutants, the level of ppGpp during exponential growth is decreased about 10-fold, relative to that of rpoB+ wild-type strains, such that a near normal partitioning of RNA polymerase occurs with respect to stable RNA (rRNA and tRNA) gene activity. Here, the physiological effects of two different rpoB alleles in a relA+ and relA background were analyzed in greater detail by comparison with their isogenic rpoB+ wild-type parents. For a given growth medium, the rpoB mutations were found to affect four parameters which resulted in a reduction of growth rate. The results reinforce a previous conclusion that a key element in control of the bacterial growth rate is a mutual relationship between control of ribosome synthesis by ppGpp and control of relA-independent ppGpp metabolism by the concentration and function of ribosomes.
...
PMID:Physiological characterization of Escherichia coli rpoB mutants with abnormal control of ribosome synthesis. 619 95

The rates of productive and abortive initiation of transcription in vitro at the lac UV5 promoter have been determined and compared to values determined for phage lambda and T7 promoters. The rate constants for productive initiation of lac transcript are consistently lower over a range of low to moderate concentration of initiating nucleoside triphosphate (ATP). Abortive initiation of lac dinucleoside tetraphosphate is also slower at low to moderate concentrations of ATP. These data demonstrate the existence of significant differences in initiation rate among promoters. We suggest that these differences may be a consequence of the initial mRNA sequences and extents of RNA polymerase cycling during initiation of promoter-specific transcription.
...
PMID:Productive and abortive initiation of transcription in vitro at the lac UV5 promoter. 645 Jun 14

In order to investigate the relationship between the stability of the ternary complex RNA polymerase-T7 D111 DNA-RNA product and the length of the bound RNA product, we have developed a protocol for the production of stable ternary complexes of known length and composition. The assembly of the ternary complex is achieved by utilizing a dinucleotide tetraphosphate (pppApU) as a selective primer, which is augmented by one or more appropriate nucleotides. The labeled products were characterized by autoradiography of gel electrophoresis patterns, which were then quantified. The criterion for stability is the protection from perturbations (a salt-jump or a rifampicin challenge), which effectively inhibit initiation. The formation of a bound ribotetranucleotide ternary complex confers stability and terminates abortive product synthesis.
...
PMID:RNA polymerase: correlation between transcript length, abortive product synthesis, and formation of a stable ternary complex. 709 17


<< Previous 1 2 3 4 5 6 7 Next >>

---