title: Characterization of an aerobic repressor that coordinately regulates bacteriochlorophyll, carotenoid, and light harvesting-II expression in Rhodobacter capsulatus.
abstract: For most species of purple photosynthetic bacteria, the presence of molecular oxygen represses synthesis of carotenoids and bacteriochlorophyll. In this study we characterize a strain of Rhodobacter capsulatus, DB469, which contains a genomic disruption of an open reading frame in the photosynthesis gene cluster termed ORF469. Characterization of the steady-state level of bacteriochlorophyll synthesis demonstrates that disruption of ORF469 results in a 2.5-fold increase in aerobic synthesis of bacteriochlorophyll over that observed with the parent strain. Utilizing reporter plasmids that contain transcriptional fusions of lacZ to various carotenoid and bacteriochlorophyll biosynthesis genes, we also demonstrate that disruption of ORF469 leads to an approximate twofold increase in bacteriochlorophyll and carotenoid gene expression under anaerobic growth conditions. Similar analysis with reporter plasmids that contain translational fusions of lacZ to the puf, puh, and puc operons demonstrates that disruption of ORF469 leads to elevated levels of aerobic transcription of light harvesting-II genes (puc), without affecting light harvesting-I or reaction center gene expression (puf and puh, respectively). Gel mobility analysis demonstrates that DB469 cells lack a DNA-binding protein that interacts with a palindromic sequence in the bchC promoter region. The results of this study indicate that ORF469 codes for a DNA-binding protein that acts as an aerobic repressor of promoters for bacteriochlorophyll, carotenoid, and light harvesting-II gene expression.
authors.affiliation: Department of Chemistry, Indiana University, Bloomington 47405, USA.
authors.forename: S N
authors.initials: SN
authors.lastname: Ponnampalam
authors.forename: J J
authors.initials: JJ
authors.lastname: Buggy
authors.forename: C E
authors.initials: CE
authors.lastname: Bauer
mesh_terms: D000332:Aerobiosis; D001426:Bacterial Proteins; D001429:Bacteriochlorophylls / Q000235:genetics*; D001483:Base Sequence; D002338:Carotenoids / Q000235:genetics*; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial / Q000235:genetics; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D009876:Operon; D010788:Photosynthesis; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins / Q000502:physiology*; D016354:Rhodobacter capsulatus / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid
chemical_list: D001426:Bacterial Proteins; D001429:Bacteriochlorophylls; D017931:DNA Primers; D004268:DNA-Binding Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; C094744:light-harvesting complex 1, Rhodospirillum; D002338:Carotenoids