Metabolism of D-aminoacyl-tRNAs in Escherichia coli and Saccharomyces cerevisiae cells.
In Escherichia coli, tyrosyl-tRNA synthetase is known to esterify tRNA(Tyr) with tyrosine. Resulting d-Tyr-tRNA(Tyr) can be hydrolyzed by a d-Tyr-tRNA(Tyr) deacylase. By monitoring E. coli growth in liquid medium, we systematically searched for other d-amino acids, the toxicity of which might be exacerbated by the inactivation of the gene encoding d-Tyr-tRNA(Tyr) deacylase. In addition to the already documented case of d-tyrosine, positive responses were obtained with d-tryptophan, d-aspartate, d-serine, and d-glutamine. In agreement with this observation, production of d-Asp-tRNA(Asp) and d-Trp-tRNA(Trp) by aspartyl-tRNA synthetase and tryptophanyl-tRNA synthetase, respectively, was established in vitro. Furthermore, the two d-aminoacylated tRNAs behaved as substrates of purified E. coli d-Tyr-tRNA(Tyr) deacylase. These results indicate that an unexpected high number of d-amino acids can impair the bacterium growth through the accumulation of d-aminoacyl-tRNA molecules and that d-Tyr-tRNA(Tyr) deacylase has a specificity broad enough to recycle any of these molecules. The same strategy of screening was applied using Saccharomyces cerevisiae, the tyrosyl-tRNA synthetase of which also produces d-Tyr-tRNA(Tyr), and which, like E. coli, possesses a d-Tyr-tRNA(Tyr) deacylase activity. In this case, inhibition of growth by the various 19 d-amino acids was followed on solid medium. Two isogenic strains containing or not the deacylase were compared. Toxic effects of d-tyrosine and d-leucine were reinforced upon deprivation of the deacylase. This observation suggests that, in yeast, at least two d-amino acids succeed in being transferred onto tRNAs and that, like in E. coli, the resulting two d-aminoacyl-tRNAs are substrates of a same d-aminoacyl-tRNA deacylase.
Laboratoire de Biochimie, Unité Mixte de Recherche 7654, CNRS-Ecole Polytechnique, 91128 Palaiseau Cedex, France.
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Soutourina
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Plateau
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Blanquet
D000604:Amino Acyl-tRNA Synthetases / Q000378:metabolism*; D001226:Aspartate-tRNA Ligase / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D005838:Genotype; D010957:Plasmids; D012345:RNA, Transfer, Amino Acid-Specific / Q000378:metabolism*; D012349:RNA, Transfer, Asp / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D013237:Stereoisomerism; D013379:Substrate Specificity; D014364:Tryptophan / Q000378:metabolism*; D014369:Tryptophan-tRNA Ligase / Q000378:metabolism*; D014448:Tyrosine-tRNA Ligase / Q000378:metabolism*
D012345:RNA, Transfer, Amino Acid-Specific; D012349:RNA, Transfer, Asp; D014364:Tryptophan; D000604:Amino Acyl-tRNA Synthetases; D014448:Tyrosine-tRNA Ligase; D001226:Aspartate-tRNA Ligase; D014369:Tryptophan-tRNA Ligase