Evolutionarily conserved cysteines in plant cytosolic seryl-tRNA synthetase are important for its resistance to oxidation

We have previously identified a unique disulfide bond in the crystal structure of Arabidopsis cytosolic seryl-tRNA synthetase involving cysteines evolutionarily conserved in all green plants. Here, we discovered that both cysteines are important for protein stability, but with opposite effects, and that their microenvironment may promote disulfide bond formation in oxidizing conditions. The crystal structure of the C244S mutant exhibited higher rigidity and an extensive network of noncovalent interactions correlating with its higher thermal stability. The activity of the wild-type showed resistance to oxidation with H2O2, while the activities of cysteine-to-serine mutants were impaired, indicating that the disulfide link may enable the protein to function under oxidative stress conditions which can be beneficial for an efficient plant stress response.

Automated summary

A unique disulfide bond involving cysteines that are conserved in all green plants has been identified in the crystal structure of Arabidopsis cytosolic seryl-tRNA synthetase. Both cysteines are important for protein stability, but with opposite effects, and their microenvironment may promote disulfide bond formation under oxidizing conditions. The presence of the disulfide bond may enable the protein to function under oxidative stress conditions, benefiting efficient plant stress response.