title: Sulfide-responsive transcriptional repressor SqrR functions as a master regulator of sulfide-dependent photosynthesis.
abstract: Sulfide was used as an electron donor early in the evolution of photosynthesis, with many extant photosynthetic bacteria still capable of using sulfur compounds such as hydrogen sulfide (H2S) as a photosynthetic electron donor. Although enzymes involved in H2S oxidation have been characterized, mechanisms of regulation of sulfide-dependent photosynthesis have not been elucidated. In this study, we have identified a sulfide-responsive transcriptional repressor, SqrR, that functions as a master regulator of sulfide-dependent gene expression in the purple photosynthetic bacteriumRhodobacter capsulatusSqrR has three cysteine residues, two of which, C41 and C107, are conserved in SqrR homologs from other bacteria. Analysis with liquid chromatography coupled with an electrospray-interface tandem-mass spectrometer reveals that SqrR forms an intramolecular tetrasulfide bond between C41 and C107 when incubated with the sulfur donor glutathione persulfide. SqrR is oxidized in sulfide-stressed cells, and tetrasulfide-cross-linked SqrR binds more weakly to a target promoter relative to unmodified SqrR. C41S and C107SR. capsulatusSqrRs lack the ability to respond to sulfide, and constitutively repress target gene expression in cells. These results establish that SqrR is a sensor of H2S-derived reactive sulfur species that maintain sulfide homeostasis in this photosynthetic bacterium and reveal the mechanism of sulfide-dependent transcriptional derepression of genes involved in sulfide metabolism.
authors.affiliation: Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Kanagawa 226-8501, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Shimizu
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, IN 47405-7102.|Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405.
authors.forename: Jiangchuan
authors.initials: J
authors.lastname: Shen
authors.affiliation: Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405.
authors.forename: Mingxu
authors.initials: M
authors.lastname: Fang
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, IN 47405-7102.|Laboratory for Biological Mass Spectrometry, Indiana University, Bloomington, IN 47405-7102.
authors.forename: Yixiang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: School of Life Science and Technology, Tokyo Institute of Technology, Kanagawa 226-8501, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Hori
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, IN 47405-7102.|Laboratory for Biological Mass Spectrometry, Indiana University, Bloomington, IN 47405-7102.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Trinidad
authors.affiliation: Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405.
authors.forename: Carl E
authors.initials: CE
authors.lastname: Bauer
authors.affiliation: Department of Chemistry, Indiana University, Bloomington, IN 47405-7102.|Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN 47405.
authors.forename: David P
authors.initials: DP
authors.lastname: Giedroc
authors.affiliation: Center for Biological Resources and Informatics, Tokyo Institute of Technology, Kanagawa 226-8501, Japan; shmasuda@bio.titech.ac.jp.|Earth-Life Science Institute, Tokyo Institute of Technology, Tokyo 152-8551, Japan.
authors.forename: Shinji
authors.identifier: 0000-0002-5349-4927
authors.initials: S
authors.lastname: Masuda
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D005075:Biological Evolution; D003545:Cysteine / Q000737:chemistry / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry; D004579:Electron Transport; D004583:Electrons; D015964:Gene Expression Regulation, Bacterial; D005978:Glutathione / Q000031:analogs & derivatives / Q000737:chemistry; D006862:Hydrogen Sulfide / Q000378:metabolism*; D010084:Oxidation-Reduction; D010788:Photosynthesis / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D000072757:Protein Conformation, beta-Strand; D012097:Repressor Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016354:Rhodobacter capsulatus / Q000235:genetics* / Q000378:metabolism; D040681:Structural Homology, Protein; D013455:Sulfur / Q000378:metabolism
chemical_list: D004220:Disulfides; D012097:Repressor Proteins; C000611742:glutathione persulfide; D013455:Sulfur; D005978:Glutathione; D003545:Cysteine; D006862:Hydrogen Sulfide
keywords: Rhodobacter; photosynthesis regulation; purple bacteria; reactive sulfur species; sulfide sensor