title: Regulation of translation by the redox state of elongation factor G in the cyanobacterium Synechocystis sp. PCC 6803.
abstract: Elongation factor G (EF-G), a key protein in translational elongation, was identified as a primary target of inactivation by reactive oxygen species within the translational machinery of the cyanobacterium Synechocystis sp. PCC 6803 (Kojima, K., Oshita, M., Nanjo, Y., Kasai, K., Tozawa, Y., Hayashi, H., and Nishiyama, Y. (2007) Mol. Microbiol. 65, 936-947). In the present study, we found that inactivation of EF-G (Slr1463) by H(2)O(2) was attributable to the oxidation of two specific cysteine residues and formation of a disulfide bond. Substitution of these cysteine residues by serine residues protected EF-G from inactivation by H(2)O(2) and allowed the EF-G to mediate translation in a translation system in vitro that had been prepared from Synechocystis. The disulfide bond in oxidized EF-G was reduced by thioredoxin, and the resultant reduced form of EF-G regained the activity to mediate translation in vitro. Western blotting analysis showed that levels of the oxidized form of EF-G increased under strong light in a mutant that lacked NADPH-thioredoxin reductase, indicating that EF-G is reduced by thioredoxin in vivo. These observations suggest that the translational machinery is regulated by the redox state of EF-G, which is oxidized by reactive oxygen species and reduced by thioredoxin, a transmitter of reducing signals generated by the photosynthetic transport of electrons.
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Kojima
authors.forename: Ken
authors.initials: K
authors.lastname: Motohashi
authors.forename: Takuya
authors.initials: T
authors.lastname: Morota
authors.forename: Masaru
authors.initials: M
authors.lastname: Oshita
authors.forename: Toru
authors.initials: T
authors.lastname: Hisabori
authors.forename: Hidenori
authors.initials: H
authors.lastname: Hayashi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nishiyama
mesh_terms: D003545:Cysteine / Q000737:chemistry; D004220:Disulfides / Q000737:chemistry; D004583:Electrons; D015964:Gene Expression Regulation, Bacterial; D006861:Hydrogen Peroxide / Q000737:chemistry; D009154:Mutation; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D020653:Peptide Elongation Factor G / Q000737:chemistry / Q000378:metabolism*; D010788:Photosynthesis; D014176:Protein Biosynthesis; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds / Q000737:chemistry; D046939:Synechocystis / Q000378:metabolism*; D013880:Thioredoxin-Disulfide Reductase / Q000737:chemistry
chemical_list: D004220:Disulfides; D020653:Peptide Elongation Factor G; D017382:Reactive Oxygen Species; D013438:Sulfhydryl Compounds; D006861:Hydrogen Peroxide; D013880:Thioredoxin-Disulfide Reductase; D003545:Cysteine; D010100:Oxygen