title: Identification and in vivo characterization of PpaA, a regulator of photosystem formation in Rhodobacter sphaeroides.
abstract: A regulatory protein, PpaA, involved in photosystem formation in the anoxygenic phototrophic proteobacterium Rhodobacter sphaeroides has been identified and characterized in vivo. Based on the phenotypes of cells expressing the ppaA gene in extra copy and on the phenotype of the ppaA null mutant, it was concluded that PpaA activates photopigment production and puc operon expression under aerobic conditions. This is in contrast to the function of the PpaA homologue from Rhodobacter capsulatus, AerR, which acts as a repressor under aerobic conditions [Dong, C., Elsen, S., Swem, L. R. & Bauer, C. E. (2002). J Bacteriol 184, 2805-2814]. The expression of the ppaA gene increases several-fold in response to a decrease in oxygen tension, suggesting that the PpaA protein is active under conditions of low or no oxygen. However, no discernible phenotype of a ppaA null mutant was observed under anaerobic conditions tested thus far. The photosystem gene repressor PpsR mediates repression of ppaA gene expression under aerobic conditions. Sequence analysis of PpaA homologues from several anoxygenic phototrophic bacteria revealed a putative corrinoid-binding domain. It is suggested that PpaA binds a corrinoid cofactor and the availability or structure of this cofactor affects PpaA activity.
authors.affiliation: Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA.
authors.forename: Larissa
authors.initials: L
authors.lastname: Gomelsky
authors.affiliation: Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA.
authors.forename: Jakub
authors.initials: J
authors.lastname: Sram
authors.affiliation: Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA.
authors.forename: Oleg V
authors.initials: OV
authors.lastname: Moskvin
authors.affiliation: Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia.
authors.forename: Irene M
authors.initials: IM
authors.lastname: Horne
authors.affiliation: Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia.
authors.forename: Helen N
authors.initials: HN
authors.lastname: Dodd
authors.affiliation: Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia.
authors.forename: John M
authors.initials: JM
authors.lastname: Pemberton
authors.affiliation: Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia.
authors.forename: Alastair G
authors.initials: AG
authors.lastname: McEwan
authors.affiliation: Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, TX 77030, USA.
authors.forename: Samuel
authors.initials: S
authors.lastname: Kaplan
authors.affiliation: Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Gomelsky
mesh_terms: D000332:Aerobiosis; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001429:Bacteriochlorophylls / Q000378:metabolism; D045728:Corrinoids; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005420:Flavoproteins; D015964:Gene Expression Regulation, Bacterial; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D009154:Mutation; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics* / Q000378:metabolism*; D011166:Porphyrins / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D012242:Rhodobacter sphaeroides / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D017422:Sequence Analysis, DNA; D015534:Trans-Activators / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C116785:AppA protein, Rhodobacter sphaeroides; D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D045728:Corrinoids; D004268:DNA-Binding Proteins; D005420:Flavoproteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D011166:Porphyrins; D012097:Repressor Proteins; D015534:Trans-Activators