Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:6.1.1.20 (phenylalanyl-tRNA synthetase)
 358 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The structural genes for threonyl-tRNA synthetase (ThrRS) and phenylalanyl-tRNA synthetase (PheRS) are closely linked on the Escherichia coli chromosome. To study whether these enzymes share a common regulatory element, we have investigated their synthesis in mutants which were selected for overproduction of either ThrRS or PheRS. It was found that mutants isolated previously for overproduction of ThrRS as strains resistant to the antibiotic borrelidin (strains Bor Res 3 and Bor Res 15) did not show an elevated level of PheRS. PheRS-overproducing strains were then isolated as revertants of strains with structurally altered enzymes. Strain S1 is a temperature-resistant derivative of a temperature-sensitive PheRS mutant, and strain G118 is a prototrophic derivative of a PheRS mutant which shows phenylalanine auxotrophy as a consequence of an altered K(m) of this enzyme for the amino acid. In both kinds of revertants, S1 and G118, the concentration of PheRS and ThrRS was increased by factors of about 2.5 and 1.8, respectively, whereas the level of other aminoacyl-tRNA synthetases was not affected by the mutations. Genetic studies showed that the simultaneous overproduction of PheRS and ThrRS in revertants G118 and S1 is based upon gene amplification, since this property was easily lost after growing the cells in the absence of the selective stimulus, and since this loss could be prevented by the presence of the recA allele. By similar criteria, the four- and eightfold overproduction of ThrRS in strains Bor Res 3 and Bor Res 15, respectively, was very stable genetically, indicating that it is caused by a mutational event other than gene amplification. From these results, we conclude that the concomitant increase of PheRS and ThrRS in strains G118 and S1 is an expression of gene duplication and not of a joint regulation of these two aminoacyl-tRNA synthetases. This conclusion is further supported by the result that, in mutant G118 as well as in its parental strain G1, growth in minimal medium lacking phenylalanine led to an additional twofold increase of their PheRS concentration. This increase was restricted to the PheRS, since the level of other aminoacyl-tRNA synthetases, including the ThrRS, stayed unchanged.
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PMID:Escherichia coli mutants overproducing phenylalanyl- and threonyl-tRNA synthetase. 36 26

A set of lambda transducing phages carrying varying lengths of the E. coli chromosome around the structural gene for initiation factor IF3 (infC) was derived from lambda p2 which is known to carry, besides infC, the structural genes for the alpha subunit of phenylalanyl-tRNA synthetase (pheS), the beta subunit of phenylalanyl-tRNA synthetase (pheT) and the structural gene for threonyl-tRNA synthetase (thrS). The E. coli coding content of these derived phages was analysed by genetic complementation of a set of mutants and by SDS-polyacrylamide gel analysis of the proteins synthesized in UV irradiated cells infected with these phages. The segregation pattern of the different genes among these derived phages indicates that the order of the genes is pheT - pheS - "P12" - (infC, thrS) where infC is probably between "P12" and thrS. "P12" is the structural gene of a 12,000 molecular weight unidentified protein.
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PMID:Genetic organization of the E. coli chromosome around the structural gene for initiation factor IF3 (infC). 37 55

The construction of three lambda bacteriophages containing parts of the structural gene for threonyl-tRNA synthetase, thrS, and those for the two subunits of phenylalanyl-tRNA synthetases, pheS and pheT, is described. These phages were used as hybridization probes to measure the in vivo levels of mRNA specific to these three genes. Plasmid pB1 carries the three genes thrS, pheS, and pheT, and strains carrying the plasmid show enhanced levels of mRNA corresponding to these genes. Although the steady-state levels of threonyl-tRNA synthetase and phenylalanyl-tRNA synthetase produced by the presence of the plasmid differed by a factor of 10, their pulse-labeled mRNA levels were about the same. Mutant derivatives of pB1 were also analyzed. Firstly, a cis-acting insertion located before the structural genes for phenylalanyl-tRNA synthetase caused a major decrease in both pheS and pheT mRNA. Secondly, mutations affecting either structural gene pheS or pheT caused a reduction in the mRNA levels for both pheS and pheT. This observation suggests that autoregulation plays a role in the expression of phenylalanyl-tRNA synthetase.
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PMID:Escherichia coli phenylalanyl-tRNA synthetase operon: transcription studies of wild-type and mutated operons on multicopy plasmids. 621 95

The structural genes for translational initiation factor IF3, threonyl-tRNA synthetase (TRS), the two subunits of phenylalanyl-tRNA synthetase (PRS), and a 12 000 mol. wt. protein of unidentified function are carried by the lambda p2 transducing phage. The localization of these genes on a restriction map of the Escherichia coli DNA insert was achieved by deletion mapping. In addition a set of plasmids carrying fragments of the original phage was constructed and helped to confirm these assignments. One plasmid, containing a 3.3 kb PstI fragment inserted into pBR322, does not code for any of the synthetase genes but causes strains carrying it to overproduce IF3.
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PMID:Physical localisation and cloning of the structural gene for E. coli initiation factor IF3 from a group of genes concerned with translation. 625 53

Plasmid pB1 carries the genes for threonyl-tRNA synthetase, phenylalanyl-tRNA synthetase, and translation initiation factor IF3. Strains carrying this plasmid overproduce phenylalanyl-tRNA synthetase about 100-fold. Spontaneous mutant plasmids were obtained which no longer caused the overproduction of the enzyme. Three classes of mutations were found. (i) Deletion mutations were found, some of which had the interesting property of fusing different genes together, e.g., putting phenylalanyl-tRNA synthetase under the control of the threonyl-tRNA synthetase promoter. (ii) Insertion mutations were found; one insertion in particular was studied. This insertion is located in front of the structural gene for phenylalanyl-tRNA synthetase and is shown to interrupt a cis-acting regulatory region. (iii) Mutations that showed no major change in DNA structure were found. One of these mutations is apparently purely structural, as it produces a small subunit of phenylalanyl-tRNA synthetase with a reduced molecular weight. This protein is less stable than the wild-type enzyme. These mutations represent useful tools to investigate how the phenylalanyl-tRNA synthetase operon is regulated.
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PMID:Escherichia coli phenylalanyl-tRNA synthetase operon: characterization of mutations isolated on multicopy plasmids. 629 Apr 44

Escherichia coli threonyl-tRNA synthetase (EC 6.1.1.3) expression has been examined in an acellular protein-synthesizing system programmed with a plasmid DNA carrying thrS, infC, pheS, and pheT, the gene for threonyl-tRNA synthetase, initiation factor 3, and the two protomers of phenylalanyl-tRNA synthetase (EC 6.1.1.20), respectively. The initial rate of synthesis of L-[35S]methionine-labeled threonyl-tRNA synthetase is markedly reduced by the addition of homogeneous RNase-free threonyl-tRNA synthetase to the assay, not by that of phenylanyl- or tyrosyl-tRNA synthetase (EC 6.1.1.1). The inhibition is 50% in the presence of 0.25 microM threonyl-tRNA synthetase and reaches 90% with 2 microM enzyme. Synthesis of mRNA in the acellular DNA-dependent protein-synthesizing system has been measured by molecular hybridization to gene-specific lambda DNA probes corresponding to thrS, pheS, and pheT. The addition to the assay of 2 microM threonyl-tRNA synthetase does not affect the extent of mRNA hybridizing to the thrS-specific DNA probe. This result is interpreted as reflecting an effect of the synthetase on its expression at the translational level. Analysis of the DNA sequence of the thrS gene predicts several potential secondary structures capable of forming in the thrS mRNA. One of these potential structures is a cloverleaf. The possible role of such structures in controlling expression of thrS is discussed.
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PMID:Autogenous repression of Escherichia coli threonyl-tRNA synthetase expression in vitro. 632 25

The alpha and beta subunits of phenylalanyl-tRNA synthetase are encoded by the pheS and pheT genes, respectively. These genes are clustered closely together with the genes for threonyl-tRNA synthetase (thrS) and translation initiation factor IF3 (infC); the gene order is thrS infC pheS pheT. We have used two methods to study the transcription pattern within this cluster. The first was the in vitro transcription of DNA restriction fragments with purified RNA polymerase, followed by fractionation of the RNA products by polyacrylamide gel electrophoresis. The second method was the mapping of promoters by means of the "abortive initiation" reaction of McClure and co-workers. This procedure consists of the incubation of RNA polymerase with DNA restriction fragments plus one nucleoside monophosphate and one [alpha-32P]nucleoside triphosphate; the polymerase synthesizes dinucleotide products of known sequence at promoter sites in the DNA. We found that transcription initiated at an internal site within infC (designated P1), and at two promoter sites between infC and pheS (designated P2 and P3). Transcription terminated at two sites about 200 nucleotides apart, located just before pheS. The initiation and termination signals were arranged so as to yield a nested set of overlapping transcripts. At the P1 promoter, transcription initiated with G-C, at P2 with A-C and sometimes A-G, and at P3 with G-U. Promoter activity was also found in a 3000-base interval that includes the start of the thrS gene; eight or nine transcripts (not mapped in detail) were observed, which started with at least four different dinucleotides. All major initiation sites in the gene cluster represented purine starts, although some pyrimidine initiation was observed in trace amounts. No promoter activity was found between pheS and pheT with either of the two techniques; this observation supports the conclusion that these genes are co-transcribed. No evidence was found for any promoter between the termination sites and the beginning of the pheS gene. It is suggested that one of the terminators is an attenuation site controlling the extension of transcription into pheS and pheT. Attenuation may explain the observed regulation of phenylalanyl-tRNA synthetase by the amino acid supply.
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PMID:Transcription of a gene cluster coding for two aminoacyl-tRNA synthetases and an initiation factor in Escherichia coli. 636 38

A 22-kilobase fragment of the Escherichia coli chromosome which contains the genes for translation initiation factor 3, phenylalanyl-tRNA synthetase, and threonyl-tRNA synthetase was cloned into plasmid pACYC184. The hybrid plasmid (designated pID1) complements a temperature-sensitive pheS lesion in E. coli NP37. pID1-transformed NP37 overproduce initiation factor 3 and phenylalanyl-tRNA synthetase. Gene expression from pID1 was studied in vitro in a coupled transcription-translation system and in minicells. The results suggest that the genes for initiation factor 3 and phenylalanyl- and threonyl-tRNA synthetase are regulated by different mechanisms.
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PMID:Molecular cloning and regulation of expression of the genes for initiation factor 3 and two aminoacyl-tRNA synthetases. 674 10

The expression of the structural genes for the protein synthesis initiation factor 3 (IF-3), threonyl-tRNA synthetase and phenylalanyl-tRNA synthetase carried by the transducing phage lambda p2 was studied in a DNA-dependent transcription-translation system in vitro and the results were compared to the regulatory pattern in vivo. In vitro, the DNA of the phage lambda p2 gives rise to the formation of the two forms of IF-3 (IF-31 and IF-3S) which are known to be present in vivo. The kinetics of synthesis indicate an interconversion of IF-31 into IF-3S. Addition of excess purified IF-31 does not significantly repress IF-3 synthesis but does stimulate the rate of conversion of IF-31 into IF-3S. This apparent lack of autoregulation in vitro is in accordance with gene-dosage-dependent synthesis in vivo. The fact that strains with more than one copy of the IF-3 structural gene contain a higher relative amount of IF-3S than do haploid ones suggests that the proteolytic conversion of IF-31 into IF-3S may occur predominantly in the free (non-ribosome-bound) state. In vivo, the amount of IF-3 varies with the growth rate much like elongation factor Tu or aminoacyl-tRNA synthetases. As with the aminoacyl-tRNA synthetases, IF-3 synthesis is not significantly subject to a stringent control system. This coordinated regulatory response in vivo, however, is not paralleled by the susceptibility of synthesis in vitro to guanosine 3'-diphosphate 5'-diphosphate (ppGpp), since IF-3 formation is inhibited by ppGpp whereas that of threonyl-tRNA synthetase and phenylalanyl-tRNA synthetase is stimulated.
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PMID:Regulation of formation of threonyl-tRNA synthetase, phenylalanyl-tRNA synthetase and protein synthesis initiation factor 3 from Escherichia coli in vivo and in vitro. 704 43

The coding properties have been analyzed of in vitro constructed lambda recombinant phages carrying E. coli DNA fragments from around the structural gene for translation initiation factor IF3 (infC). This study shows that infC is expressed independently of the promoter of the threonyl-tRNA synthetase (thrS), which is the genes immediately preceding infC. It also shows that the two genes following infC, namely pheS and pheT, which form the phenylalanyl-tRNA synthetase operon, are not expressed from infC's promoter. Thus the four characterized genes of that region that were previously thought to be transcribed in the same direction are now shown to be expressed in vivo as three separate transcription units.
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PMID:Transcription units around the gene for E. coli translation initiation factor IF3 (infC). 705 Jun 31


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