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)

To investigate the identity determinants of E. coli threonine tRNA, various transcripts were prepared by in vitro transcription system with T7 RNA polymerase. Substitutions of the anticodon second letter G35 and the third letter U36 to other nucleotides led to a remarkable decrease of threonine charging activity. Charging experiments with a series of anticodon-deletion transcripts also suggest the importance of the G35U36 sequence. A mutation at either the G1-C72 or C2-G71 base pair in the acceptor stem seriously affected the threonine charging activity. These results indicate that the second and third positions of the anticodon and the first and second base pairs in the acceptor stem are the recognition sites of E. coli tRNA(THR) for threonyl-tRNA synthetase. Discriminator base, A73, is not involved in threonine charging activity.
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PMID:Identity determinants of E. coli threonine tRNA. 156 50

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

The Deinococcus-Thermus group of species is currently recognized as a distinct phylum solely on the basis of their branching in 16S rRNA trees. No unique biochemical or molecular characteristics that can distinguish this group from all other bacteria are known at present. In this work, we describe eight conserved indels (viz., inserts or deletions) in seven widely distributed proteins that are distinctive characteristics of the Deinococcus-Thermus phylum but are not found in any other group of bacteria. The identified signatures include a 7-amino-acid (aa) insert in threonyl-tRNA synthetase, 1- and 3-aa inserts in the RNA polymerase beta' subunit, a 5-aa deletion in signal recognition particle (Ffh/SR54), a 2-aa insert in major sigma factor 70 (sigma70), a 2-aa insert in seryl-tRNA synthetase (SerRS), a 1-aa insert in ribosomal protein L1, and a 2-aa insert in UvrA homologs. By using PCR primers for conserved regions, fragments of these genes were amplified from a number of Deinococcus-Thermus species, and all such fragments (except SerRS in Deinococcus proteolyticus) were found to contain the indicated signatures. The presence of these signatures in various species from all three known genera within this phylum, viz., Deinococcus, Thermus, and Meiothermus, provide evidence that they are likely distinctive characteristics of the entire phylum which were introduced in a common ancestor of this group. The signature in SerRS, which is absent in D. proteolyticus, was likely introduced after the branching of this species. Phylogenetic studies as well as the nature of the inserts in some of these proteins (viz., sigma70 and SerRS) also support a sister group relationship between the Thermus and the Meiothermus genera. The identified signatures provide strong evidence for the monophyletic nature of the Deinococcus-Thermus phylum. These molecular markers should prove very useful in the identification of new species related to this group.
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PMID:Distinctive protein signatures provide molecular markers and evidence for the monophyletic nature of the deinococcus-thermus phylum. 1512 71