Regulation of Translation via the Redox State of EF-G in Synechocystis sp. PCC 6803

Abstract

Elongation factor G (EF-G) is a key protein responsible for translational elongation. We have recently found that EF-G is a primary target, by reactive oxygen species (ROS), of inhibition of the translational machinery in Synechocystis sp. PCC 6803. In the present study, we found that inactivation of EF-G by ROS was attributed to oxidation of two specific cysteine residues and formation of a disulfide bond. The disulfide bond in the oxidized EF-G was reduced by thioredoxin. Substitution of the target cysteine residues by serine in EF-G resulted in the increased tolerance to ROS of EF-G as well as of the translation system in vitro. These observations suggest that the activity of translation might be regulated by the redox state of EF-G, which is determined by a redox signal that is emitted by photosynthetic electron transport and mediated by thioredoxin.