A metal ion mediated functional dichotomy encodes plasticity during translation quality control

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Genetic code translation requires proofreading for quality control and stress adaptation.
• Alanyl-tRNA synthetase (AlaRS-Ed) and threonyl-tRNA synthetase (ThrRS-Ed) editing domains share a common structure and Zn²⁺ binding motif.
• Functional divergence in these domains, particularly metal ion usage, is critical.

Purpose of the Study:

• To elucidate the structural and functional basis for the operational dichotomy of AlaRS-Ed and ThrRS-Ed proofreading modules.
• To understand the role of Zn²⁺ in protecting translation fidelity against reactive oxygen species (ROS).
• To investigate the evolutionary divergence of these proofreading mechanisms.

Main Methods:

• Structural analysis of tRNA synthetase editing domains.
• Biochemical assays to assess enzyme activity and fidelity.
• Comparative evolutionary analysis.

Main Results:

• Zn²⁺ in AlaRS-Ed protects against ROS, ensuring high-fidelity translation of Ala-codons for cell survival.
• ThrRS-Ed activity is modulated by ROS, allowing for tolerance of Thr-codon mistranslation.
• A single amino acid change accounts for the functional divergence between AlaRS-Ed and ThrRS-Ed.

Conclusions:

• Protein quality control is integrated with redox signaling via tunable metal-binding sites.
• Evolutionary divergence in metal ion utilization by tRNA synthetases impacts cellular fitness under stress.
• This study highlights a conserved mechanism for adapting genetic translation to environmental conditions since the Last Universal Common Ancestor (LUCA).