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.
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. https://doi.org/10.1002/1873-3468.14287