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To ensure correct amino acids are incorporated during protein synthesis, aminoacyl-tRNA synthetases (aaRSs) employ proofreading mechanisms collectively referred to as editing. Although editing is important for viability, editing-deficient aaRSs have been identified in host-dependent organisms. In Mycoplasma mobile, editing-deficient PheRS and LeuRS have been identified. We characterized the amino acid activation site of MmPheRS and identified a previously unknown hyperaccurate mutation, L287F. Additionally, we report that m-Tyr, an oxidation byproduct of Phe which is toxic to editing-deficient cells, is poorly discriminated by MmPheRS activation and is not subjected to editing. Furthermore, expressing MmPheRS and the hyperaccurate variants renders Escherichia coli susceptible to m-Tyr stress, indicating that active site discrimination is insufficient in tolerating excess m-Tyr.


This is the accepted version of the following article:

Han, N.-C., Kavoor, A. and Ibba, M. (2022), Characterizing the amino acid activation center of the naturally editing-deficient aminoacyl-tRNA synthetase PheRS in Mycoplasma mobile. FEBS Lett. 596: 947-957.

which has been published in final form at This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.

feb214287-sup-0001-supinfo.pdf (6667 kB)
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