Regulation of Translation by the Redox State of Elongation Factor G in Synechocystis sp. PCC 6803

Abstract

The elongation step of translation is sensitive to oxidative stress. We have recently found that elongation factor G (EF-G) is the primary target of inhibition by reactive oxygen species (ROS) within the translational machinery. In the present study, we investigated the redox properties of EF-G (Slr1463) in Synechocystis sp. PCC 6803. The presence of H₂O₂ oxidized two Cys residues in EF-G, suggesting that inactivation of EF-G by ROS is due to the formation of a disulfide bond between two Cys residues. Substitution of Cys105 by Ser rendered Slr1463 insensitive to H₂O₂, suggesting that Cys105 is a target of ROS. The oxidized Cys residues were reduced by thioredoxin, suggesting that thioredoxin reduced the disulfide bond. These results suggest that the redox state of EF-G regulates the activity of translation.