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)

Various analogues of linear gramicidin were tested for their biological activity in restoring the normal spore phenotype of gramicidin-negative mutants of Bacillus brevis and for their ability to increase cation conductivity of black lipid membranes and to inhibit bacterial RNA polymerase. Whereas many biologically active gramicidin analogues had no effect on membrane permeability, all biologically active peptides were able to inhibit ribonucleic acid (RNA) polymerase. These observations make it unlikely that membranes are the site of action of gramicidin during bacterial sporulation, but they are consistent with the notion that gramicidin functions to control RNA synthesis during the transition from vegetative growth to sporulation (Sarkar & Paulus, 1972). The relationship between peptide structure and the ability to restore normal sporulation and inhibit RNA polymerase showed that the eight amino-terminal residues have little influence on the function of gramicidin, whereas the highly nonpolar repeating sequence D-leucyl-L-tryptophan is essential for biological activity and may represent the site of interaction with RNA polymerase.
...
PMID:Comparison of the effect of linear gramicidin analogues on bacterial sporulation, membrane permeability, and ribonucleic acid polymerase. 9 82

We have isolated two regulatory mutants altered in the leader region of the Escherichia coli tryptophan (trp) operon. In one mutant, trpL29, the AUG translation start codon for the trip leader peptide is replaced by AUA. The other mutant, trpL75, has a G leads to A change at residue 75, immediately after the UGA translation stop codon for the trp leader peptide. In vivo, trpL29 and trpL75 increase the efficiency of transcription termination at the trp attenuator 3- to 5-fold. trpL29 and trpL75 also fail to respond fully to tryptophan starvation and other conditions that normally relieve transcription termination at the trp attenuator. The trpL29 mutation, which presumably reduces synthesis of the trp leader peptide, is cis dominant. The effect of starvation for a number of the amino acids in the trp leader peptide was determined. Only starvation for tryptophan and arginine, amino acids that occur at residues 10, 11, and 12 of the 14-residue trp leader peptide, elicits relief of transcription termination. Our findings suggest that translation of trp leader RNA is involved in regulation of transcription termination at the attenuator. A model is discussed in which the location of the ribosome synthesizing the leader peptide is communicated to the RNA polymerase transcribing the leader region.
...
PMID:Translational control of transcription termination at the attenuator of the Escherichia coli tryptophan operon. 36 6

In vivo, termination of transcription at the attenuator site of the tryptophan (trp) operon of E. coli is influenced by the protein termination factor rho. In vitro, termination does not depend on rho factor, and is very efficient in a purified system consisting only of RNA polymerase, the DNA template, nucleoside triphosphates, and buffer. The extent of termination in this system is unaffected over a wide range of salt and nucleoside triphosphate concentration. However, there is a 10-fold stimulation of trp leader mRNA synthesis if rho factor is present during the transcription reaction. This stimulation occurs only at low molar ratios of polymerase to template, and can be blocked by rifampicin. It is thus most likely due to the recycling of RNA polymerase molecules that have been released from the attenuator site by rho factor. In fact, transcription of the trp leader region in vitro results in the fomration of a stable termination complex which can be observed on sucrose gradients or by binding to nitrocellulose filters. These data indicate that a major function of rho at the trp attenuator is to release completed transcripts from a pre-formed termination complex, rather than to cause the cessation of elongation.
...
PMID:The attenuator of the tryptophan operon in E.coli: rho-mediated release of RNA polymerase from a transcription termination complex in vitro. 37 Jul 76

Ribonucleic acid (RNA) synthesis has been studied in vitro with a partially purified preparation of RNA polymerase from a mutant strain of Escherichia coli with a reduced rate of accumulation of tryptophan RNA (P.H. Pouwels and H.J. Scholten, J. Bacteriol. 139:393-397, 1979). The incorporation of radioactive label into RNA with polymerase from mutant bacteria is considerably lower than that with the enzyme from wild-type bacteria. These results are explained by the presence in mutant bacteria, but not in wild-type bacteria, of a factor which suppresses the accumulation of RNA. Mutant bacteria contain a factor which renders RNA synthesis with mutant and wild-type RNA polymerase resistant to various inhibitors of RNA synthesis, e.g. rifampin, streptolydigin, and heparin. We conclude that in mutant bacteria a factor is modified which suppresses the accumulation of some RNA species and lowers the sensitivity of RNA polymerase to some transcription inhibitors.
...
PMID:Escherichia coli mutant strain with altered expression of the tryptophan operon: ribonucleic acid synthesis in vitro. 37 68

Escherichia coli RNA polymerase loses 55-65% of its catalytic activity on reaction with Nbf-Cl (4-choro-7-nitrobenzofurazan). This partial inactivation was shown to be the result of specific impairment of RNA-chain elongation, since initiation of RNA chains was not altered after treatment with Nbf-Cl. The site of reaction was shown to be a unique thiol on the beta-subunit. This thiol is not accessible to reaction with 5,5'-dithiobis-(2-nitrobenzoic acid). No protection of the enzyme against reaction with Nbf-Cl could be obtained with the inhibitor rifamycin nor with calf thymus DNA, GTP or 1,10-phenanthroline, indicating that the unique thiol is probably not within the active site. The specific impairment of RNA-chain elongation thus appears to be the result of a local conformational change which leaves chain initiation unimpaired. Changes observed in the tryptophan fluorescence spectrum of the enzyme or reaction with Nbf-Cl are consistent with formation of a Meisenheimer complex of the reagent with a nucleophilic group on the enzyme near the reactive thiol. It is proposed that formation of such a complex and a subsequent conformational change renders this thiol unusually susceptible to reaction with Nbf-Cl.
...
PMID:Impairment of the catalytic activity of Escherichia coli ribonucleic acid polymerase by a unique reaction of 4-chloro-7-nitrobenzofurazan. 39 51

The effects of fasting, and subsequent force-feeding of L-tryptophan on the activity of hepatic nuclear DNA-dependent RNA polymerases were studied in adult (5-6 weeks old), and old (5-6 months) male Wistar rats. Liver nuclei, nucleoli, and nucleoplasmic fraction were isolated from rats following a single tube-feeding of tryptophan or water, and were assayed in vitro for the activity of different RNA polymerases. Whereas in adult rats 24 h of fasting caused a significant reduction in the activity of RNA polymerase I and II, in old rats the activity of only polymerase II was decreased after 24 h of fasting. In fasted adult rats administration of tryptophan promptly restored the activities of both polymerases to the respective normal fed levels, while in old rats none of the polymerases were affected by tryptophan. In fasted adult rats the pattern of response for both forms of polymerases to a single tube-feeding of tryptophan, over a period of 5 h, was found to be biphasic. When ribonuclease activity of nuclei was suppressed by performing incubations at low temperatures (17-30 degrees C) the difference between the two groups for polymerase I was greatly reduced, and for polymerase II the difference was fully abolished. Pre-treatment of fasted adult rats with cycloheximide (1.5 mg/kg) was found to abolish the 30 min tryptophan-mediated stimulation of both polymerase I and II activities. In cycloheximide pretreated rats the activity of polymerase II, but not polymerase I returned to its original level 5 h after tryptophan force-feeding.
...
PMID:Effects of fasting and tryptophan force-feeding on the activity of hepatic nuclear RNA polymerases in rats. 52 54

During the course of kinetic studies on the synthesis of RNA polymerase subunits in Escherichia coli K12, strain Km7 (CP372), certain anomalies were found that seemed to be associated with the system of reversible inhibition of RNA and protein synthesis by rifampicin. To find a possible explanation for these anomalies, effects of rifampicin on RNA chain elongation and on residual synthesis of polymerase subunits were investigated with several strains including Km7. Examination of mRNA synthesis for the tryptophan operon suggested that RNA chain growth as well as RNA chain initiation is inhibited at high drug concentration (500 mug/ml), wheras RNA chain initiation is inhibited specifically at low concentration (20 mug/ml). Analysis of effect of rifampicin concentration on total RNA synthesis gave results that are also consistent with this conclusion. These results emphasize the need for selecting a proper drug concentration whenever rifampicin or other related antibiotic is used as a specific inhibitor of transcription initiation. When rifampicin was added to a culture of these strains absolute rates of synthesis of all subunits of RNA polymerase increased for several minutes and then decreased. The extent of this transient stimulation varied depending on the strain, drug concentration and other conditions, but was most striking for the beta and sigma subunits with strain Km7 at high drug concentration (500 mug/ml). With a rifampicin-sensitive wild-type strain tested, the maximum stimulation was found at about 50 mug/ml of the drug, with a particularly marked effect for sigma subunit. Streptolydigin, on the other hand, inhibited the synthesis of core subunits much faster than the bulk of protein, but inhibited synthesis of sigma subunit only after a lag. Hence a specific effect of rifampicin but not the inactivation of beta subunit per se appears to be involved in transient stimulation of polymerase synthesis observed. Implications of these findings on the control of RNA polymerase synthesis are discussed.
...
PMID:Effects of rifampicin on synthesis and functional activity of DNA-dependent RNA polymerase in Escherichia coli. 78 14

The volume of nucleolar material per nucleus and the activity of RNA polymerase I (RNA nucleotidyltransferase I) become doubled in the liver cells of rats that are fed for several days a diet that lacks essential amino acids. Omission of methionine from a fully supplemented diet is equivalent to leaving out all the amino acids, and the responses to a deficiency of tryptophan are about 40% as great. Deprivation of one of the remaining essential amino acids gives either small responses or none at all. Supplementation of the methionine-free diet with cystine blocks the nucleolar enlargement and the enhancement of the polymerase activity that would otherwise take place, but the dispensable amino acid does not affect the responses to a deprivation of one of the other essential amino acids. After deprivation of all the essential amino acids or only methionine, hepatocytes make DNA when the rat is fed a meal with protein. A preparatory diet lacking in tryptophan is much less effective; a deficiency in any of the other indispensable compounds tested fails to prepare the liver for DNA synthesis. The results give hope that elucidation of the means by which methionine deprivation affects the nucleolus will also provide information on the regulation of nuclear DNA replication in liver. One attractive possibility is that the amino acid deficiency acts by producing some imbalance in protein metabolism.
...
PMID:Amino acids and control of nucleolar size, the activity of RNA polymerase I, and DNA synthesis in liver. 106 12

The nucleotide sequence of the region preceding the transcription initiation site of the tryptophan operon of Escherichia coli was determined. Essentially all of the trp operator precedes the transcribed portion of the operon. The deduced sequence contains the recognition site of endonuclease Hpa I. This site is protected from Hpa I cleavage by RNA polymerase and by trp repressor. Regions of 2-fold symmetry are present in the DNA sequence.
...
PMID:Nucleotide sequence of region preceding trp mRNA initiation site and its role in promoter and operator function. 108 25

The DNA dependent synthesis of proteins was studied with a system composed of DNA, washed ribosomes, centrifuged (150,000 X g) bacterial extract from Escherichia coli and purified initiation factors IF-1 and IF-2. Synthesis of active enzymes encoded by the tryptophan (trp)-operon of E. coli was found to depend strongly on the addition of IF-3, with the same IF-3 dependency for all 5 gene-products of this operon, irrespective of the presence of the promotor proximal gene trpE. Synthesis of T7 RNA polymerase with T7 DNA as a template, however, was completely independent of the addition of IF-3. The same difference in IF-3 requirement was found when we compared the overall protein synthesis directed by these templates. This difference could be related to the effect of IF-3 on the formation of initiation complexes with the in vitro prepared mRNA: initiation complexes are readily formed with T7 mRNA also in the absence of IF-3, whereas the formation of these complexes with phi80trp mRNA almost completely depends on the presence of this factor.
...
PMID:The role of IF-3 in the translation of T7- and phi80trp messenger RNA. 110 44


1 2 3 4 5 6 7 8 9 10 Next >>

---