Abstract
Oxidative stress inhibits the repair of photosystem II by suppressing the synthesis de novo of proteins in the elongation step of translation. We examined effects of oxidative stress on elongation factor G (EF-G), which is known to be particularly sensitive to oxidative stress, in Synechocystis sp. PCC 6803. EF-G (Slr1463) protein was oxidized by H2O2 and subsequently reduced by different concentrations of dithiothreitol (DTT). Analysis of reduced Cys residues with a SH-modifying reagent revealed that the reduction of Cys residues occurred stepwise. Addition of thioredoxin promoted the reduction of oxidized EF-G, suggesting that EF-G interacts with thioredoxin. Substitution of Cys105 by Ser resulted in the insensitivity of EF-G to oxidation by H2O2 and to thioredoxin, indicating that Cys105 is involved in the formation of disulfide bond and is also a target of thioredoxin.
