title: Gene cloning and regulation of gene expression of the puc operon from Rhodovulum sulfidophilum.
abstract: Rhodovulum (Rhv.) sulfidophilum, unlike other nonsulfur purple bacteria, is able to synthesize the peripheral antenna complex even under fully aerobic conditions in the dark. We have obtained strong evidence that Rhv. sulfidophilum encodes only one copy of the puc operon, comprising pucB, pucA and pucC. pucB and pucA encode the beta- and alpha-polypeptides. The third ORF (pucC), downstream of pucA, has a strong homology to pucC of Rhodobacter (Rb.) capsulatus. Deletion mutation analysis indicated that the requirement for the pucC gene product for LH II expression was less strict than in Rb. capsulatus. Comparison of the deduced alpha and beta polypeptide sequences with the directly determined primary structure revealed a C-terminal processing of the alpha-subunit. Primer extension analysis showed that the pucBAC is transcribed from a sigma70-type promoter 130 bases upstream of the translational start of pucB. Transcriptional expression of the pucBAC operon in Rhv. sulfidophilum is higher, the lower the light intensity is, and is not reduced to a ground-level by the presence of oxygen. Based on lacZ fusions the relative promoter activities were, for dark aerobic:dark semiaerobic:low light anaerobic:medium light anaerobic:high light anaerobic, 5.5:7.0:2.0:1.0:0.78. Still unidentified cis-regulatory elements or binding sites of trans-regulatory elements are apparently localized in two distinct upstream regions. Furthermore, comparison of the promoter region of the Rhv. sulfidophilum pucBAC with the promoter regions of puc operons in related species showed distinct differences in the regulatory elements. The significance of these results with respect to the regulation of transcription and the oxygen-independent synthesis of LH II from Rhv. sulfidophilum is discussed.
authors.affiliation: Institute for Biology II/Microbiology, University of Freiburg, Germany.
authors.forename: G E
authors.initials: GE
authors.lastname: Hagemann
authors.forename: E
authors.initials: E
authors.lastname: Katsiou
authors.forename: H
authors.initials: H
authors.lastname: Forkl
authors.forename: A C
authors.initials: AC
authors.lastname: Steindorf
authors.forename: M H
authors.initials: MH
authors.lastname: Tadros
mesh_terms: D000595:Amino Acid Sequence; D001419:Bacteria / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D001426:Bacterial Proteins; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D045342:Light-Harvesting Protein Complexes; D008969:Molecular Sequence Data; D009154:Mutation; D016366:Open Reading Frames; D009876:Operon / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D045332:Photosystem II Protein Complex; D011401:Promoter Regions, Genetic; D014176:Protein Biosynthesis; D012329:RNA, Bacterial / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
chemical_list: C081521:B800-850 light-harvesting complex, bacteria; D001426:Bacterial Proteins; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045332:Photosystem II Protein Complex; C100892:PucC protein, Rhodobacter; D012329:RNA, Bacterial; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D001616:beta-Galactosidase