Fine-Tuning of Alanyl-tRNA Synthetase Quality Control Alleviates Global Dysregulation of the Proteome.

Paul Kelly,Arundhati Kavoor,Michael Ibba

doi:10.3390/genes11101222

Abstract

One integral step in the transition from a nucleic acid encoded-genome to functional proteins is the aminoacylation of tRNA molecules. To perform this activity, aminoacyl-tRNA synthetases (aaRSs) activate free amino acids in the cell forming an aminoacyl-adenylate before transferring the amino acid on to its cognate tRNA. These newly formed aminoacyl-tRNA (aa-tRNA) can then be used by the ribosome during mRNA decoding. In Escherichia coli, there are twenty aaRSs encoded in the genome, each of which corresponds to one of the twenty proteinogenic amino acids used in translation. Given the shared chemicophysical properties of many amino acids, aaRSs have evolved mechanisms to prevent erroneous aa-tRNA formation with non-cognate amino acid substrates. Of particular interest is the post-transfer proofreading activity of alanyl-tRNA synthetase (AlaRS) which prevents the accumulation of Ser-tRNAAla and Gly-tRNAAla in the cell. We have previously shown that defects in AlaRS proofreading of Ser-tRNAAla lead to global dysregulation of the E. coli proteome, subsequently causing defects in growth, motility, and antibiotic sensitivity. Here we report second-site AlaRS suppressor mutations that alleviate the aforementioned phenotypes, revealing previously uncharacterized residues within the AlaRS proofreading domain that function in quality control.

Highlights

Across all domains of life, protein-coding sequences have evolved to maintain activity of essential biological processes
Translational fidelity is maintained at several distinct stages of protein synthesis, with one of the key steps being the accuracy of aminoacyl-tRNA synthesis by aminoacyl-tRNA synthetases (aaRSs)
It has been previously observed that perturbation of alanyl-tRNA synthetase (AlaRS) proofreading in E. coli leads to growth defects when compared to wild-type E. coli [13]

Summary

Introduction

Across all domains of life, protein-coding sequences have evolved to maintain activity of essential biological processes. Translational fidelity is maintained at several distinct stages of protein synthesis, with one of the key steps being the accuracy of aminoacyl-tRNA synthesis by aaRSs. AaRSs are responsible for pairing free amino acids in the cell to their cognate tRNAs, with the product released for participation in ternary complex formation with elongation factor and GTP [4]. AaRSs are responsible for pairing free amino acids in the cell to their cognate tRNAs, with the product released for participation in ternary complex formation with elongation factor and GTP [4] This complex is recruited to the A-site of the ribosome to facilitate peptide bond formation. In complex with ATP, aaRSs bind to free cognate amino acids leading to the synthesis of an aminoacyl-adenylate This activated amino acid will be transferred to the 30 end of the tRNA to

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Discussion

Conclusion