Regulation of translation by the redox state of elongation factor G in the cyanobacterium Synechocystis sp. PCC 6803.
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.
Kojima
Kouji
K
Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan.
Motohashi
Ken
K
Morota
Takuya
T
Oshita
Masaru
M
Hisabori
Toru
T
Hayashi
Hidenori
H
Nishiyama
Yoshitaka
Y
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
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