Knowledge Bank

Translation is a highly accurate process with an overall error rate of only about 10-4. The fidelity of translation is determined by two main events: synthesis of cognate amino acid:tRNA pairs by aminoacyl-tRNA synthetases (aaRSs) and accurate selection of aminoacyl-tRNAs (aa-tRNAs) by the ribosome. To ensure correct pairing between amino acids and tRNA molecules, some aminoacyl-tRNA synthetases (aaRSs) possess editing mechanisms, whereby non-cognate amino acids can be hydrolyzed, thereby preventing the incorrect amino acid from being transferred to the ribosome and incorporated into the polypeptide chain. Such editing abilities augment the fidelity of the translation machinery. To correct errors occurring in amino acid selection, phenylalanyl-tRNA synthetase (PheRS) possesses a post-transfer editing activity, which targets misacylated Tyr-tRNAPhe. Although the mechanism of hydrolysis of Tyr-tRNAPhe has been examined, the impact of editing at the cellular level remains unclear; however, editing may be especially important when cells are experiencing physiological stress and/or when the relative concentration of tyrosine is elevated. To investigate these issues, the growth of four mutant strains of Escherichia coli was examined. To do so, the strains were grown under a set of four different conditions with varying concentrations of phenylalanine and tyrosine, and growth curves were established and analyzed. The implications of this study are relevant to understanding the survival strategies of pathogens in limiting environments and to understanding diseases which result from errors in editing pathways. Future work in this area may include quantifying intracellular amino acid pools to better understand their impact on the quality control of translation.