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 guanosine tetraphosphate (ppGpp) and guanosine pentaphosphate (pppGpp), both produced by E. coli, were measured on the activities of several genes in a cell-free system. Gene activity is measured as gene-directed synthesis of biochemically competent protein or transfer RNA. Both ppGpp and pppGpp stimulated the activities of the ara, lac, and trp operons and inhibited the arg operon. Production of transfer-RNA(Tyr) was unaffected by moderate levels of either ppGpp or pppGpp and only slightly inhibited at higher levels of ppGpp. Since the cell-free reaction mixtures hydrolyze pppGpp to ppGpp, we performed similar studies with a hydrolysis-resistant analog of pppGpp, the beta-gamma methylenyl derivative (pcppGpp). In general, pcppGpp shows the same inhibitory potency as pppGpp for the arg operon, but lacks the stimulatory effects on the ara, lac, and trp operons. This result suggests that the stimulation of these gene activities is specific for ppGpp.Under similar conditions, pppGpp and ppGpp show a slight inhibitory effect on the messenger-directed synthesis of beta-galactosidase and no effect on the messenger-directed synthesis of MS2 viral-coat protein. These observations, together with the fact that in the same system these nucleotides affect coupled transcription and translation, lead us to surmise that the activities of pppGpp and ppGpp are exerted at the level of RNA polymerase activity.
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PMID:Effects of guanosine tetraphosphate, guanosine pentaphosphate, and beta-gamma methylenyl-guanosine pentaphosphate on gene expression of Escherichia coli in vitro. 435 31

Fusidic acid or chloramphenicol was used to inhibit peptide synthesis to 1% of normal in Escherichia coli B, strain AS19. After 10 min of inhibition, peptide synthesis could be quickly restored to 80% of the normal rate after washing the bacteria on a filter. However, even in the presence of adenosine 3'-5'-cyclic-monophosphoric acid to block catabolite repression, beta-galactosidase, the first enzyme of the lactose operon (lac), could only be induced to 10% of normal, and the last enzyme of the operon, galactoside acetyltransferase, even less. The first and last enzymes of the operon for tryptophan synthesis could be derepressed to about 30% of normal. The lac ribonucleic acid (RNA) induced during recovery showed a smaller than normal size distribution on sucrose gradients. The operator-proximal or -distal parts of this RNA were specifically labeled. Hybridization to phi80dlac deoxyribonucleic acid (DNA) suggested that although the distal parts of the lac RNA were barely detectable, initiation was occurring at normal rates in recovery. Either normal levels of distal messenger RNA (mRNA) are made but then rapidly degraded or the mRNA is not completed. The small amount that is made decayed abnormally slowly, probably as a result of slower transcription. Total mRNA decay was multiphasic with all components decaying slower than normal. We propose that there is a residual level of inhibition of peptide synthesis during recovery. The probability that a ribosome is blocked at any codon can be estimated from the data. The longer the message, the less likely its complete translation. We propose that the RNA polymerase can transcribe translatable mRNA for only a finite distance beyond the lead ribosome. Because ribosomes can load at the start of each message in a polycistronic mRNA, the probability that a distal message will be synthesized and translated is a function of the number of more proximal messages and the distances between their ribosome-loading sites.
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PMID:Residual polarity and transcription-translation coupling during recovery from chloramphenicol or fusidic acid. 435 50

After addition of l-arabinose to growing Escherichia coli, the l-ribulokinase (EC 2.7.1.16) and l-arabinose isomerase (EC 5.3.1.4) first appear at about 0.7 and 1.4 min, respectively. These times are consistent with the distances of the genes from the ribonucleic acid polymerase initiation site in the operon. The kinetics of appearance of these enzymes as well as those of beta-galactosidase (EC 3.2.1.23) in the same strain are consistent with a peptide elongation rate of no less than 14 amino acids per second. A measurement of the average peptide elongation rate made by measuring the kinetics of radioactive amino acid appearance in completed polypeptides yielded a rate of about 12 amino acids per s. Convenient assays of the arabinose isomerase and ribulokinase are also given.
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PMID:Induction kinetics of the L-arabinose operon of Escherichia coli. 457 56

I have sequenced the first 63 bases of mRNA transcribed in vitro from the UV5 promoter mutant of the E. coli lactose operon. Sonic fragments of DNA, 1000 base pairs long and purified to contain only the lac operator-promoter region, were used as template. The UV5 promoter mutation allows transcription of the lac operon in the absence of catabolite activator protein and cAMP; lac repressor controls the synthesis of this RNA. I find that during synthesis, RNA polymerase pauses at particular sites along the DNA, naturally generating several discrete sizes of RNA that provide overlaps useful for sequencing. The UV5 lac mRNA initiates within the lac operator and copies the operator sequence. The AUG initiator codon for beta-galactosidase occurs at position 39 of the message. The sequence is: pppA-A-U-U-G-U-G-A-G-C-G-G-A-U-A-A-C-A-A-U-U-U- C-A-C-A-C-A-G-G-A-A-A-C-A-G-C-U-A-U-G-A-C-C-A-U- G-A-U-U-A-C-G-G-A-U-U-C-A-C-U-G-G.
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PMID:The nucleotide sequence of the lactose messenger ribonucleic acid transcribed from the UV5 promoter mutant of Escherichia coli. 458 56

Phage T7 discontinues host gene expression by translational and transcriptional control mechanisms. Translational control is exerted by the T7 translational-repressor. This protein inhibits the synthesis of beta-galactosidase (EC 3.2.1.23) in vivo and in vitro and the synthesis of the T3 enzyme S-adenosylmethioninehydrolase (EC 3.3.1.-). The translational-repressor does not interfere with T7-specific enzyme synthesis. The T7 translational-repressor purifies with the initiation factors. The repressor interacts with the initiation of translation of host enzymes. The translational-repressor gene is close to the promotor for RNA polymerase of Escherichia coli.
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PMID:Translational control induced by bacteriophage T7. 459 93

1. Experiments with rifampicin and stringent strains of Escherichia coli (pro(-)purB(-)rel(+)) indicate that purine deficiency does not decrease and may considerably increase the potential for RNA synthesis by RNA polymerase molecules that are bound to DNA and have already commenced transcription. 2. DNA-RNA hybridization experiments indicate that purine starvation increases the distribution of bound RNA polymerase molecules between the cistrons for mRNA and those for stable RNA. 3. Synthesis of beta-galactosidase mRNA is more dependent on the ability to synthesize guanine nucleotides than on the ability to synthesize adenine nucleotides. 4. Amino acid starvation tends to decrease the potential for RNA synthesis by RNA polymerase molecules bound to DNA. 5. Since this effect differs from that due to purine starvation, amino acid control of RNA synthesis does not appear to operate solely by causing a deficiency of purine nucleotides. 6. The results are discussed in terms of the ability to initiate RNA chains and to extend them under different circumstances.
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PMID:Synthesis of ribonucleic acid in purine-deficient Escherichia coli and a comparison with the effects of amino acid starvation. 492 43

S1 nuclease was used to generate a series of deletions which extend into the CAP-cAMP binding site from upstream of the Escherichia coli lactose operon promoter (lacP). Deletion and insertion mutations were also created which changed the spacing region between the CAP-cAMP binding site and the lacP -35 region. The promoter activities of these mutations were compared by measuring the levels of beta-galactosidase gene expression in vivo. The results show that sequence information prior to 74 base pairs (-74) upstream from the transcription start site (designated as +1) is not necessary for the full activation of the lac promoter by the CAP-cAMP complex. However, the deletion which extends to the -71 position retains only one third of the promoter activity in the presence of the CAP-cAMP complex. Removal of one symmetrical element from the two fold symmetry in the CAP-cAMP binding site abolished the CAP-cAMP stimulation of the lac promoter. Spacer mutations which increase by one base pair or decrease by two base pairs the length of the spacing region between the CAP-cAMP binding site and the lacP -35 region drastically reduced the CAP-cAMP stimulation of the lac promoter. This suggests that the distance between the lac promoter transcription start site and CAP-cAMP binding site is crucial for the function of the lac promoter, despite the fact that this distance varies in other E. coli promoters positively regulated by CAP-cAMP. A deletion which extends to the -59 position results in a two fold enhanced expression of lac in the absence of CAP-cAMP. This is consistent with the existance of a competitive RNA polymerase binding site in this region which would normally act to inhibit RNA polymerase binding.
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PMID:Deletion analysis of the CAP-cAMP binding site of the Escherichia coli lactose promoter. 608 87

The Escherichia coli dapB gene encodes dihydrodipicolinate reductase. This enzyme is part of the diaminopimelate-lysine pathway, and its synthesis is repressed by lysine. The dapB gene was cloned into pBR322 from a transducing lambda bacteriophage, its complete nucleotide sequence established, and the transcriptional start localized. The DNA sequence predicts that the dapB gene codes for a 273-amino acid polypeptide, Mr 28,798. No attenuation-type sequence can be found between the mRNA start and the coding sequence. The dapB promoter signals appear to be weak as compared to RNA polymerase consensus sequences. Nevertheless an efficient in vivo synthesis of beta-galactosidase was obtained when the lac operon was inserted in vitro in the dapB gene, downstream of the dapB regulatory signals. Further studies were performed on an in-frame gene fusion constructed in vitro between the dapB and the lacZ genes. They indicated that repression by lysine is exerted on a DNA region restricted to a 153-base pair fragment with only 102 nontranscribed nucleotides. Finally, dapB gene expression showed a gene dosage effect which suggests that it is not controlled by an element present in limiting amounts in the cell.
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PMID:Nucleotide sequence and expression of the Escherichia coli dapB gene. 609 78

The bactericidal activity of Tinopal AN [1,1-bis(3,N-5-dimethyl-benzoxazol-2-yl)-methine p-toluene sulphonate] was shown to be due to a mechanism entirely independent of its inhibitory effects upon NADH dehydrogenase which were reported previously. Whereas the compound had no significant effect upon DNA synthesis in Escherichia coli D22, RNA and protein synthesis were immediately and markedly inhibited. In confirmation, Tinopal AN caused an immediate cessation in inducible beta-galactosidase synthesis in the same organism. An in vitro assay of the transcription of calf-thymus DNA by purified E. coli RNA polymerase showed that this process was inhibited by Tinopal AN.
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PMID:The antibacterial action of Tinopal AN. 620

Mutations in the pts genes (which code for the enzyme I and HPr protein - the general components of the phosphoenolypyruvate-dependent phosphotransferase system) lead to decreases in enzyme-inducible synthesis at the level of transcription. The intracellular content of cyclic AMP in the ptsIH mutant was severely diminished, while the ptsH bacteria contain the same amounts of this nucleotide as the wild-type cells. Nevertheless expression of the lac operon was diminished in the ptsH as well as in the ptsIH mutant. The exogenous cyclic AMP did not prevent repression of beta-galactosidase synthesis in a delta cya ptsI mutant in a wide range of concentrations in the growth medium (from 0.05 mM to 5 mM). The combination of ptsI or ptsH mutations with rpoC1 (synthesis of thermosensitive beta' subunit of RNA polymerase) leads to greater disturbance of beta-galactosidase production at the nonpermissive temperature than demonstrated in the pts+ rpoC1 strain. The stimulatory effect of exogenous cyclic AMP was more pronounced in pts rpoC1 than in pts+ rpoC1 bacteria. The data presented confirm the hypothesis that pts mutations alter the function of CRP in initiation of transcription.
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PMID:Effect of ptsI and ptsH mutations on initiation of transcription of the Escherichia coli lactose operon. 630 97


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