title: A ternary AppA-PpsR-DNA complex mediates light regulation of photosynthesis-related gene expression.
abstract: The anoxygenic phototrophic bacterium Rhodobacter sphaeroides uses different energy sources, depending on environmental conditions including aerobic respiration or, in the absence of oxygen, photosynthesis. Photosynthetic genes are repressed at high oxygen tension, but at intermediate levels their partial expression prepares the bacterium for using light energy. Illumination, however, enhances repression under semiaerobic conditions. Here, we describe molecular details of two proteins mediating oxygen and light control of photosynthesis-gene expression: the light-sensing antirepressor AppA and the transcriptional repressor PpsR. Our crystal structures of both proteins and their complex and hydrogen/deuterium-exchange data show that light activation of AppA-PpsR2 affects the PpsR effector region within the complex. DNA binding studies demonstrate the formation of a light-sensitive ternary AppA-PpsR-DNA complex. We discuss implications of these results for regulation by light and oxygen, highlighting new insights into blue light-mediated signal transduction.
authors.affiliation: Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Heidelberg, Germany. andreas.winkler@mpimf-heidelberg.mpg.de
authors.forename: Andreas
authors.initials: A
authors.lastname: Winkler
authors.forename: Udo
authors.initials: U
authors.lastname: Heintz
authors.forename: Robert
authors.initials: R
authors.lastname: Lindner
authors.forename: Jochen
authors.initials: J
authors.lastname: Reinstein
authors.forename: Robert L
authors.initials: RL
authors.lastname: Shoeman
authors.forename: Ilme
authors.initials: I
authors.lastname: Schlichting
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D002850:Chromatography, Gel; D017124:Conserved Sequence; D004269:DNA, Bacterial / Q000737:chemistry* / Q000378:metabolism; D005420:Flavoproteins / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D015964:Gene Expression Regulation, Bacterial / Q000528:radiation effects*; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D062105:Molecular Docking Simulation; D008969:Molecular Sequence Data; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000528:radiation effects; D011485:Protein Binding; D011487:Protein Conformation; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D012242:Rhodobacter sphaeroides / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: C116785:AppA protein, Rhodobacter sphaeroides; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D005420:Flavoproteins; D045322:Photosynthetic Reaction Center Complex Proteins; D010100:Oxygen