The Redox State of EF-G under High-light Conditions in Synechocystis sp. PCC 6803.

Abstract

Elongation factor G (EF-G), a key protein in translational elongation, is inactivated by reactive oxygen species (ROS) upon the formation of an intramolecular disulfide bond between two specific cysteine residues of EF-G in Synechocystis sp. PCC 6803. We monitored the redox state of EF-G in vivo under high-light conditions using an SH-modifying reagent. Levels of the reduced form of EF-G were increased during the shift from low to high light. However, under excess high light, levels of the oxidized form were increased, suggesting that ROS interrupted the reduction of EF-G. Levels of the oxidized EF-G in a mutant that lacks NADPH-thioredoxin reductase were higher than those in wild type, suggesting that EF-G might be reduced by reducing power that is generated by the photosynthetic electron transport and transmitted by thioredoxin.