title: The PedR transcriptional regulator interacts with thioredoxin to connect photosynthesis with gene expression in cyanobacteria.
abstract: The redox state of the photosynthetic electron transport chain acts as a critical sensing mechanism by regulating the transcription of key genes involved in the acclimation response to a change in the environment. In the present study we show that the small LuxR-type regulator PedR interacts with Trx (thioredoxin) to achieve photosynthetic electron-transport-dependent transcriptional regulation in the cyanobacterium Synechocystis sp. PCC 6803. TrxM, an isoform of Trx, was isolated as an interacting factor of PedR by pull-down assays. In vitro analysis revealed that the intermolecular disulfide bond formed between Cys80 residues of the PedR homodimer was reduced by both TrxM and TrxX. It has been shown previously that, although PedR is active under low-light conditions, it becomes transiently inactivated following a shift to high-light conditions, with a concomitant conformational change [Nakamura and Hihara (2006) J. Biol. Chem. 281, 36758-36766]. In the present study, we found that the conformational change of PedR and the change in the transcript level of its target gene were minimal when mutants of Synechocystis that lack ferredoxin-Trx reductase or NADPH-Trx reductase were exposed to high levels of light. These results indicate that the reduction of PedR by Trx causes transient inactivation of PedR upon the shift of cyanobacterial cells to high-light conditions.
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: Mayumi
authors.initials: M
authors.lastname: Horiuchi
authors.forename: Kinu
authors.initials: K
authors.lastname: Nakamura
authors.forename: Kouji
authors.initials: K
authors.lastname: Kojima
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nishiyama
authors.forename: Wakako
authors.initials: W
authors.lastname: Hatakeyama
authors.forename: Toru
authors.initials: T
authors.lastname: Hisabori
authors.forename: Yukako
authors.initials: Y
authors.lastname: Hihara
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000458:Cyanobacteria / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000235:genetics; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D046939:Synechocystis / Q000235:genetics / Q000378:metabolism; D013879:Thioredoxins / Q000737:chemistry / Q000378:metabolism*; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D001426:Bacterial Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D013879:Thioredoxins