The physiological target for LeuRS translational quality control is norvaline

Area of Science:

• Molecular Biology
• Biochemistry
• Bacterial Physiology

Background:

• Protein synthesis fidelity relies on aminoacyl-tRNA synthetases (AARSs) accurately pairing amino acids with cognate tRNAs.
• AARSs possess inherent editing activity to hydrolyze mischarged tRNAs, ensuring translational accuracy when amino acid selectivity is compromised.

Purpose of the Study:

• To investigate the primary biological function of the editing activity of Escherichia coli leucyl-tRNA synthetase (EcLeuRS).
• To determine if EcLeuRS editing is essential for preventing isoleucine misincorporation or if it serves another critical role.

Main Methods:

• Kinetic analysis of EcLeuRS activity.
• Structural studies of EcLeuRS.
• In vivo experiments using an EcLeuRS editing-deficient E. coli strain.
• Growth assays under varying amino acid concentrations and oxygen deprivation conditions.

Main Results:

• EcLeuRS editing is not essential for preventing isoleucine misincorporation.
• The prime function of LeuRS editing is to prevent the misincorporation of the non-standard amino acid norvaline.
• LeuRS editing-deficient E. coli strains grow normally in high isoleucine but not under oxygen deprivation, where norvaline accumulates.

Conclusions:

• Bacterial adaptive response to oxygen deprivation relies on AARS-based translational quality control.
• LeuRS editing plays a critical role in bacterial survival under specific stress conditions, particularly oxygen deprivation.
• The non-essential role of LeuRS editing during normal growth has implications for developing antimicrobial agents targeting this site.