title: Oxidation of elongation factor G inhibits the synthesis of the D1 protein of photosystem II.
abstract: Oxidative stress inhibits the repair of photodamaged photosystem II (PSII). This inhibition is due initially to the suppression, by reactive oxygen species (ROS), of the synthesis de novo of proteins that are required for the repair of PSII, such as the D1 protein, at the level of translational elongation. To investigate in vitro the mechanisms whereby ROS inhibit translational elongation, we developed a translation system in vitro from the cyanobacterium Synechocystis sp. PCC 6803. The synthesis of the D1 protein in vitro was inhibited by exogenous H2O2. However, the addition of reduced forms of elongation factor G (EF-G), which is known to be particularly sensitive to oxidation, was able to reverse the inhibition of translation. By contrast, the oxidized forms of EF-G failed to restore translational activity. Furthermore, the overexpression of EF-G of Synechocystis in another cyanobacterium Synechococcus sp. PCC 7942 increased the tolerance of cells to H2O2 in terms of protein synthesis. These observations suggest that EF-G might be the primary target, within the translational machinery, of inhibition by ROS.
authors.affiliation: Cell-Free Science and Technology Research Center, and Venture Business Laboratory, Ehime University, Bunkyo-cho, Matsuyama 790-8577, Japan.
authors.forename: Kouji
authors.initials: K
authors.lastname: Kojima
authors.forename: Masaru
authors.initials: M
authors.lastname: Oshita
authors.forename: Yohei
authors.initials: Y
authors.lastname: Nanjo
authors.forename: Koji
authors.initials: K
authors.lastname: Kasai
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Tozawa
authors.forename: Hidenori
authors.initials: H
authors.lastname: Hayashi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nishiyama
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism; D003545:Cysteine / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D005816:Genetic Complementation Test; D006861:Hydrogen Peroxide / Q000494:pharmacology; D010084:Oxidation-Reduction / Q000187:drug effects; D020653:Peptide Elongation Factor G / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000096:biosynthesis*; D014176:Protein Biosynthesis / Q000187:drug effects; D046939:Synechocystis / Q000187:drug effects / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D020653:Peptide Elongation Factor G; D045332:Photosystem II Protein Complex; D006861:Hydrogen Peroxide; D003545:Cysteine