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Query: EC:6.1.1.10 (methionyl-tRNA synthetase)
 387 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The DNA sequence and transcriptional organization around the Escherichia coli methionyl-tRNA synthetase gene, metG, were resolved. This gene can be transcribed in vivo and in vitro from two distinct promoters separated by 510 nucleotides. The upstream promoter is located within the coding sequence of a divergent gene expressing a protein of Mr 39 kDa of unknown function. Transcription originating from this upstream promoter is attenuated by a Rho-independent terminator before entering the structural gene. This leader RNA contains several potentially stable secondary structures, one of which shows striking similarity to tRNA(Met), but no methionine-rich coding sequence. The regulation of metG expression was investigated by means of fusions to the lacZ gene. Transcription of a metG::lacZ fusion is induced in a metG mutant and, reciprocally, repression is observed in a methionyl-tRNA synthetase overproducing strain. A model of metG expression control is proposed.
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PMID:Transcription and regulation of expression of the Escherichia coli methionyl-tRNA synthetase gene. 225 34

Besides their central role in protein synthesis, aminoacyl-tRNA synthetases have been found or thought to be involved in other processes. We present here a study showing that tryptophanyl-tRNA synthetase has a surprising tissular distribution. Indeed, immunochemical determinations showed that in several bovine organs such as liver, kidney and heart, tryptophanyl-tRNA synthetase constitutes, as expected, about 0.02% of soluble proteins. In spleen, brain cortex, stomach, cerebellum or duodenum, this amount is about 10-times higher, and in pancreas it is 100-fold. There is no correlation between these amounts and the RNA content of the organs. Moreover, the concentration of another aminoacyl-tRNA synthetase (methionyl-tRNA synthetase) is higher in liver than in pancreas, while the amount of tRNATrp is not higher in pancreas than in liver as compared to other tRNAs. Among several interpretations, it is possible that tryptophanyl-tRNA synthetase is involved in a function other than tRNA aminoacylation. This unknown function would be specific to the differentiated organs, since fetal cerebellum and fetal pancreas contain the same amount of tryptophanyl-tRNA synthetase as adult liver.
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PMID:Tryptophanyl-tRNA synthetase is a major soluble protein species in bovine pancreas. 351 5

Biofilm infections exhibit high tolerance against antibiotic treatment. The study of biofilms is complicated by phenotypic heterogeneity; biofilm subpopulations differ in their metabolic activities and their responses to antibiotics. Here, we describe the use of the bio-orthogonal noncanonical amino acid tagging (BONCAT) method to enable selective proteomic analysis of a Pseudomonas aeruginosa biofilm subpopulation. Through controlled expression of a mutant methionyl-tRNA synthetase, we targeted BONCAT labeling to cells in the regions of biofilm microcolonies that showed increased tolerance to antibiotics. We enriched and identified proteins synthesized by cells in these regions. Compared to the entire biofilm proteome, the labeled subpopulation was characterized by a lower abundance of ribosomal proteins and was enriched in proteins of unknown function. We performed a pulse-labeling experiment to determine the dynamic proteomic response of the tolerant subpopulation to supra-MIC treatment with the fluoroquinolone antibiotic ciprofloxacin. The adaptive response included the upregulation of proteins required for sensing and repairing DNA damage and substantial changes in the expression of enzymes involved in central carbon metabolism. We differentiated the immediate proteomic response, characterized by an increase in flagellar motility, from the long-term adaptive strategy, which included the upregulation of purine synthesis. This targeted, selective analysis of a bacterial subpopulation demonstrates how the study of proteome dynamics can enhance our understanding of biofilm heterogeneity and antibiotic tolerance.IMPORTANCE Bacterial growth is frequently characterized by behavioral heterogeneity at the single-cell level. Heterogeneity is especially evident in the physiology of biofilms, in which distinct cellular subpopulations can respond differently to stresses, including subpopulations of pathogenic biofilms that are more tolerant to antibiotics. Global proteomic analysis affords insights into cellular physiology but cannot identify proteins expressed in a particular subpopulation of interest. Here, we report a chemical biology method to selectively label, enrich, and identify proteins expressed by cells within distinct regions of biofilm microcolonies. We used this approach to study changes in protein synthesis by the subpopulation of antibiotic-tolerant cells throughout a course of treatment. We found substantial differences between the initial response and the long-term adaptive strategy that biofilm cells use to cope with antibiotic stress. The method we describe is readily applicable to investigations of bacterial heterogeneity in diverse contexts.
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PMID:Selective Proteomic Analysis of Antibiotic-Tolerant Cellular Subpopulations in Pseudomonas aeruginosa Biofilms. 2906 49