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Kapetanaki SM, Fekete Z, Dorlet P, Vos MH, Liebl U, Lukacs A. Molecular insights into the role of heme in the transcriptional regulatory system AppA/PpsR. Biophys J 2022; 121:2135-2151. [PMID: 35488435 DOI: 10.1016/j.bpj.2022.04.031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 03/07/2022] [Accepted: 04/26/2022] [Indexed: 11/30/2022] Open
Abstract
Heme has been shown to have a crucial role in the signal transduction mechanism of the facultative photoheterotrophic bacterium Rhodobacter sphaeroides. It interacts with the transcriptional regulatory complex AppA/PpsR in which AppA and PpsR function as the antirepressor and repressor, respectively of photosynthesis gene expression. The mechanism, however of this interaction remains incompletely understood. In this study, we combined EPR spectroscopy and FRET to demonstrate the ligation of heme in PpsR with a proposed cysteine residue. We show that heme binding in AppA affects the fluorescent properties of the dark-adapted state of the protein, suggesting a less constrained flavin environment compared to the absence of heme and the light-adapted state. We performed ultrafast transient absorption measurements in order to reveal potential differences in the dynamic processes in the full-length AppA and its heme-binding domain alone. Comparison of the CO-binding dynamics demonstrates a more open heme pocket in the holo-protein, qualitatively similar to what has been observed in the CO sensor RcoM-2, and suggests a communication path between the BLUF and SCHIC domains of AppA. We have also examined quantitatively, the affinity of PpsR to bind to individual DNA fragments of the puc promoter using fluorescence anisotropy assays. We conclude that oligomerization of PpsR is initially triggered by binding of one of the two DNA fragments and observe a ∼10-fold increase in the dissociation constant Kd for DNA binding upon heme binding to PpsR. Our study provides significant new insight at the molecular level on the regulatory role of heme that modulates the complex transcriptional regulation in R. sphaeroides and supports the two levels of heme signaling, via its binding to AppA and PpsR and via the sensing of gases like oxygen.
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Affiliation(s)
- Sofia M Kapetanaki
- Department of Biophysics, Medical School, University of Pécs, 7624 Pécs, Hungary; Szentagothai Research Center, University of Pecs, 7624 Pécs, Hungary.
| | - Zsuzsanna Fekete
- Department of Biophysics, Medical School, University of Pécs, 7624 Pécs, Hungary
| | - Pierre Dorlet
- Aix Marseille Univ, CNRS, BIP, IMM, Marseille, France
| | - Marten H Vos
- LOB, CNRS, INSERM, Ecole Polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Ursula Liebl
- LOB, CNRS, INSERM, Ecole Polytechnique, Institut Polytechnique de Paris, 91128 Palaiseau Cedex, France
| | - Andras Lukacs
- Department of Biophysics, Medical School, University of Pécs, 7624 Pécs, Hungary; Szentagothai Research Center, University of Pecs, 7624 Pécs, Hungary.
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2
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Wang H, Sha X, Li R, Li Y, Khaleque HN, Zhang Y, Bohu T, Bai Z, Zhuang X. Comparative Genome Analysis Provides Molecular Evidence for Reclassification of the Photosynthetic Bacterium Rhodobacter sphaeroides EBL0706 as a Strain of Luteovulum azotoformans. Microorganisms 2021; 9:microorganisms9081754. [PMID: 34442833 PMCID: PMC8398827 DOI: 10.3390/microorganisms9081754] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2021] [Revised: 08/04/2021] [Accepted: 08/11/2021] [Indexed: 12/04/2022] Open
Abstract
In this study, we conducted a genome-wide comparative analysis of a former Rhodobacter sphaeroides strain EBL0706, which is now recorded as Luteovulum sphaeroides EBL0706. The genome of EBL0706 was compared with that of Luteovulum azotoformans ATCC 17025, Luteovulum azotoformans KA25, and Luteovulum sphaeroides 2.4.1. The average nucleotide identity (ANI), tetra nucleotide signatures (Tetra), digital DNA–DNA hybridization (dDDH) values, comparative genome, and phylogenetic analysis proposed that EBL0706 is a strain of Luteovulum azotoformans. Functional annotations identified a total of 4034 protein-coding genes in the genome of EBL0706, including a complete photosynthetic gene cluster. This study provides genomic molecular verification for the strain EBL0706 to be reclassified to Luteovulum azotoformans.
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Affiliation(s)
- Haoyu Wang
- School of Chemical and Environmental Engineering, China University of Mining & Technology (Beijing), Beijing 100083, China;
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; (X.S.); (R.L.); (Y.L.); (Z.B.); (X.Z.)
| | - Xiaoling Sha
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; (X.S.); (R.L.); (Y.L.); (Z.B.); (X.Z.)
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Rui Li
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; (X.S.); (R.L.); (Y.L.); (Z.B.); (X.Z.)
- University of Chinese Academy of Sciences, Beijing 100049, China
- Beijing Huachen Jiguang Technology, Co. Ltd., Beijing 101407, China
| | - Yijing Li
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; (X.S.); (R.L.); (Y.L.); (Z.B.); (X.Z.)
- University of Chinese Academy of Sciences, Beijing 100049, China
| | | | - Yuxiu Zhang
- School of Chemical and Environmental Engineering, China University of Mining & Technology (Beijing), Beijing 100083, China;
- Correspondence: (Y.Z.); (T.B.); Tel.: +86-10-6233-1792 (Y.Z.); +853-6855-7877 (T.B.)
| | - Tsing Bohu
- State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology, Taipa 999078, Macao
- CSIRO Mineral Resources, Australian Resources and Research Centre, Kensington, WA 6151, Australia
- Correspondence: (Y.Z.); (T.B.); Tel.: +86-10-6233-1792 (Y.Z.); +853-6855-7877 (T.B.)
| | - Zhihui Bai
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; (X.S.); (R.L.); (Y.L.); (Z.B.); (X.Z.)
- University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xuliang Zhuang
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; (X.S.); (R.L.); (Y.L.); (Z.B.); (X.Z.)
- University of Chinese Academy of Sciences, Beijing 100049, China
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3
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Papiz MZ, Bellini D, Evans K, Grossmann JG, Fordham‐Skelton T. Light-induced complex formation of bacteriophytochrome RpBphP1 and gene repressor RpPpsR2 probed by SAXS. FEBS J 2019; 286:4261-4277. [PMID: 31243889 PMCID: PMC6899989 DOI: 10.1111/febs.14973] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 03/04/2019] [Accepted: 06/24/2019] [Indexed: 11/28/2022]
Abstract
Bacteriophytochrome proteins (BphPs) are molecular light switches that enable organisms to adapt to changing light conditions through the control of gene expression. Canonical type 1 BphPs have histidine kinase output domains, but type 3 RpBphP1, in the bacterium Rhodopseudomonas palustris (Rps. palustris), has a C terminal PAS9 domain and a two-helix output sensor (HOS) domain. Type 1 BphPs form head-to-head parallel dimers; however, the crystal structure of RpBphP1ΔHOS, which does not contain the HOS domain, revealed pseudo anti-parallel dimers. HOS domains are homologs of Dhp dimerization domains in type 1 BphPs. We show, by applying the small angle X-ray scattering (SAXS) technique on full-length RpBphP1, that HOS domains fulfill a similar role in the formation of parallel dimers. On illumination with far-red light, RpBphP1 forms a complex with gene repressor RpPpsR2 through light-induced structural changes in its HOS domains. An RpBphP1:RpPpsR2 complex is formed in the molecular ratio of 2 : 1 such that one RpBphP1 dimer binds one RpPpsR2 monomer. Molecular dimers have been modeled with Pfr and Pr SAXS data, suggesting that, in the Pfr state, stable dimeric four α-helix bundles are formed between HOS domains, rendering RpBphP1functionally inert. On illumination with light of 760 nm wavelength, four α-helix bundles formed by HOS dimers are disrupted, rendering helices available for binding with RpPpsR2.
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Affiliation(s)
- Miroslav Z. Papiz
- Institute of Integrative BiologyUniversity of LiverpoolUK
- STFC Daresbury LaboratoryWarringtonUK
| | - Dom Bellini
- Institute of Integrative BiologyUniversity of LiverpoolUK
| | - Kate Evans
- Pharmacy and Biomolecular SciencesLiverpool John Moores UniversityUK
| | - J Günter Grossmann
- Institute of Integrative BiologyUniversity of LiverpoolUK
- STFC Daresbury LaboratoryWarringtonUK
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Nohr D, Rodriguez R, Weber S, Schleicher E. How can EPR spectroscopy help to unravel molecular mechanisms of flavin-dependent photoreceptors? Front Mol Biosci 2015; 2:49. [PMID: 26389123 PMCID: PMC4555020 DOI: 10.3389/fmolb.2015.00049] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 08/10/2015] [Indexed: 11/25/2022] Open
Abstract
Electron paramagnetic resonance (EPR) spectroscopy is a well-established spectroscopic method for the examination of paramagnetic molecules. Proteins can contain paramagnetic moieties in form of stable cofactors, transiently formed intermediates, or spin labels artificially introduced to cysteine sites. The focus of this review is to evaluate potential scopes of application of EPR to the emerging field of optogenetics. The main objective for EPR spectroscopy in this context is to unravel the complex mechanisms of light-active proteins, from their primary photoreaction to downstream signal transduction. An overview of recent results from the family of flavin-containing, blue-light dependent photoreceptors is given. In detail, mechanistic similarities and differences are condensed from the three classes of flavoproteins, the cryptochromes, LOV (Light-oxygen-voltage), and BLUF (blue-light using FAD) domains. Additionally, a concept that includes spin-labeled proteins and examination using modern pulsed EPR is introduced, which allows for a precise mapping of light-induced conformational changes.
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Affiliation(s)
- Daniel Nohr
- Department of Physical Chemistry, Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg Freiburg, Germany
| | - Ryan Rodriguez
- Department of Physical Chemistry, Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg Freiburg, Germany
| | - Stefan Weber
- Department of Physical Chemistry, Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg Freiburg, Germany
| | - Erik Schleicher
- Department of Physical Chemistry, Institut für Physikalische Chemie, Albert-Ludwigs-Universität Freiburg Freiburg, Germany
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5
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Endres S, Granzin J, Circolone F, Stadler A, Krauss U, Drepper T, Svensson V, Knieps-Grünhagen E, Wirtz A, Cousin A, Tielen P, Willbold D, Jaeger KE, Batra-Safferling R. Structure and function of a short LOV protein from the marine phototrophic bacterium Dinoroseobacter shibae. BMC Microbiol 2015; 15:30. [PMID: 25887755 PMCID: PMC4335406 DOI: 10.1186/s12866-015-0365-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2014] [Accepted: 01/29/2015] [Indexed: 12/29/2022] Open
Abstract
Background Light, oxygen, voltage (LOV) domains are widely distributed in plants, algae, fungi, bacteria, and represent the photo-responsive domains of various blue-light photoreceptor proteins. Their photocycle involves the blue-light triggered adduct formation between the C(4a) atom of a non-covalently bound flavin chromophore and the sulfur atom of a conserved cysteine in the LOV sensor domain. LOV proteins show considerable variation in the structure of N- and C-terminal elements which flank the LOV core domain, as well as in the lifetime of the adduct state. Results Here, we report the photochemical, structural and functional characterization of DsLOV, a LOV protein from the photoheterotrophic marine α-proteobacterium Dinoroseobacter shibae which exhibits an average adduct state lifetime of 9.6 s at 20°C, and thus represents the fastest reverting bacterial LOV protein reported so far. Mutational analysis in D. shibae revealed a unique role of DsLOV in controlling the induction of photopigment synthesis in the absence of blue-light. The dark state crystal structure of DsLOV determined at 1.5 Å resolution reveals a conserved core domain with an extended N-terminal cap. The dimer interface in the crystal structure forms a unique network of hydrogen bonds involving residues of the N-terminus and the β-scaffold of the core domain. The structure of photoexcited DsLOV suggests increased flexibility in the N-cap region and a significant shift in the Cα backbone of β strands in the N- and C-terminal ends of the LOV core domain. Conclusions The results presented here cover the characterization of the unusual short LOV protein DsLOV from Dinoroseobacter shibae including its regulatory function, extremely fast dark recovery and an N-terminus mediated dimer interface. Due to its unique photophysical, structural and regulatory properties, DsLOV might thus serve as an alternative model system for studying light perception by LOV proteins and physiological responses in bacteria. Electronic supplementary material The online version of this article (doi:10.1186/s12866-015-0365-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Stephan Endres
- Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Joachim Granzin
- Institute of Complex Systems, ICS-6: Structural Biochemistry, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Franco Circolone
- Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Andreas Stadler
- Juelich Centre for Neutron Science JCNS (JCNS-1) & Institute for Complex Systems (ICS-1), Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Ulrich Krauss
- Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Thomas Drepper
- Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Vera Svensson
- Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Esther Knieps-Grünhagen
- Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Astrid Wirtz
- Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Anneliese Cousin
- Institute of Complex Systems, ICS-6: Structural Biochemistry, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Petra Tielen
- Institute for Microbiology, Technische Universität Braunschweig, D-38106, Braunschweig, Germany.
| | - Dieter Willbold
- Institute of Complex Systems, ICS-6: Structural Biochemistry, Forschungszentrum Jülich, D-52425, Jülich, Germany. .,Institute of Physical Biology, Heinrich-Heine-Universität Düsseldorf, D-40225, Düsseldorf, Germany.
| | - Karl-Erich Jaeger
- Institute of Molecular Enzyme Technology, Heinrich-Heine-Universität Düsseldorf, Forschungszentrum Jülich, D-52425, Jülich, Germany. .,Institute of Bio- and Geosciences, IBG-1: Biotechnology, Forschungszentrum Jülich, D-52425, Jülich, Germany.
| | - Renu Batra-Safferling
- Institute of Complex Systems, ICS-6: Structural Biochemistry, Forschungszentrum Jülich, D-52425, Jülich, Germany.
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6
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Jun D, Saer RG, Madden JD, Beatty JT. Use of new strains of Rhodobacter sphaeroides and a modified simple culture medium to increase yield and facilitate purification of the reaction centre. PHOTOSYNTHESIS RESEARCH 2014; 120:197-205. [PMID: 23765434 DOI: 10.1007/s11120-013-9866-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/26/2013] [Accepted: 05/24/2013] [Indexed: 06/02/2023]
Abstract
A new gene expression system was developed in Rhodobacter sphaeroides, replacing a pRK415-based system used previously. The broad host-range IPTG-inducible plasmid pIND4 was used to create the plasmid pIND4-RC1 for expression of the puhA and pufQBALMX genes, encoding the reaction centre (RC) and light-harvesting complex 1 (LH1) proteins. The strain R. sphaeroides ΔRCLH was used to make a knockout of the rshI restriction endonuclease gene, enabling electroporation of DNA into the bacterium; a subsequent knockout of ppsR was made, creating the strain R. sphaeroides RCx lacking this oxygen-sensing repressor of the photosynthesis gene cluster. Using pIND4-RC1, LH1 levels were increased by a factor of about 8 over pRS1 per cell in cultures grown semi-aerobically. In addition, the ppsR knockout allowed for photosynthetic pigment-protein complex synthesis in the presence of high concentrations of molecular oxygen; here, LH1 levels per cell increased by 20 % when grown under high aeration conditions. A new medium (called RLB) is the E. coli medium LB supplemented with MgCl2 and CaCl2, which was found to increase growth rates and final cell culture densities, with an increase of 30 % of LH1 per cell detected in R. sphaeroides RCx(pIND4-RC1) grown in RLB versus LB medium. Furthermore, cell density was about three times greater in RLB compared to semi-aerobic conditions. The combination of all the modifications resulted in an increase of LH1 and RC per mL of culture volume by approximately 35-fold, and a decrease in the length of culture incubation time from about 5 days to ~36 h.
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Affiliation(s)
- D Jun
- Department of Microbiology and Immunology, The University of British Columbia, 2350 Health Sciences Mall, Vancouver, BC, V6T 1Z3, Canada
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7
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Heintz U, Meinhart A, Winkler A. Multi-PAS domain-mediated protein oligomerization of PpsR from Rhodobacter sphaeroides. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:863-76. [PMID: 24598755 PMCID: PMC3949515 DOI: 10.1107/s1399004713033634] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 12/12/2013] [Indexed: 01/04/2023]
Abstract
Per-ARNT-Sim (PAS) domains are essential modules of many multi-domain signalling proteins that mediate protein interaction and/or sense environmental stimuli. Frequently, multiple PAS domains are present within single polypeptide chains, where their interplay is required for protein function. Although many isolated PAS domain structures have been reported over the last decades, only a few structures of multi-PAS proteins are known. Therefore, the molecular mechanism of multi-PAS domain-mediated protein oligomerization and function is poorly understood. The transcription factor PpsR from Rhodobacter sphaeroides is such a multi-PAS domain protein that, in addition to its three PAS domains, contains a glutamine-rich linker and a C-terminal helix-turn-helix DNA-binding motif. Here, crystal structures of two N-terminally and C-terminally truncated PpsR variants that comprise a single (PpsRQ-PAS1) and two (PpsRN-Q-PAS1) PAS domains, respectively, are presented and the multi-step strategy required for the phasing of a triple PAS domain construct (PpsRΔHTH) is illustrated. While parts of the biologically relevant dimerization interface can already be observed in the two shorter constructs, the PpsRΔHTH structure reveals how three PAS domains enable the formation of multiple oligomeric states (dimer, tetramer and octamer), highlighting that not only the PAS cores but also their α-helical extensions are essential for protein oligomerization. The results demonstrate that the long helical glutamine-rich linker of PpsR results from a direct fusion of the N-cap of the PAS1 domain with the C-terminal extension of the N-domain that plays an important role in signal transduction.
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Affiliation(s)
- Udo Heintz
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Anton Meinhart
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Heidelberg, Germany
| | - Andreas Winkler
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Heidelberg, Germany
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8
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Winkler A, Heintz U, Lindner R, Reinstein J, Shoeman RL, Schlichting I. A ternary AppA-PpsR-DNA complex mediates light regulation of photosynthesis-related gene expression. Nat Struct Mol Biol 2013; 20:859-67. [PMID: 23728293 PMCID: PMC3702404 DOI: 10.1038/nsmb.2597] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2012] [Accepted: 04/10/2013] [Indexed: 11/09/2022]
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.
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Affiliation(s)
- Andreas Winkler
- Department of Biomolecular Mechanisms, Max Planck Institute for Medical Research, Heidelberg, Germany.
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9
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Metz S, Haberzettl K, Frühwirth S, Teich K, Hasewinkel C, Klug G. Interaction of two photoreceptors in the regulation of bacterial photosynthesis genes. Nucleic Acids Res 2012; 40:5901-9. [PMID: 22434878 PMCID: PMC3401432 DOI: 10.1093/nar/gks243] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The expression of photosynthesis genes in the facultatively photosynthetic bacterium Rhodobacter sphaeroides is controlled by the oxygen tension and by light quantity. Two photoreceptor proteins, AppA and CryB, have been identified in the past, which are involved in this regulation. AppA senses light by its N-terminal BLUF domain, its C-terminal part binds heme and is redox-responsive. Through its interaction to the transcriptional repressor PpsR the AppA photoreceptor controls expression of photosynthesis genes. The cryptochrome-like protein CryB was shown to affect regulation of photosynthesis genes, but the underlying signal chain remained unknown. Here we show that CryB interacts with the C-terminal domain of AppA and modulates the binding of AppA to the transcriptional repressor PpsR in a light-dependent manner. Consequently, binding of the transcription factor PpsR to its DNA target is affected by CryB. In agreement with this, all genes of the PpsR regulon showed altered expression levels in a CryB deletion strain after blue-light illumination. These results elucidate for the first time how a bacterial cryptochrome affects gene expression.
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Affiliation(s)
- Sebastian Metz
- Institut für Mikrobiologie und Molekularbiologie, Universität Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany
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10
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Metz S, Jäger A, Klug G. Role of a short light, oxygen, voltage (LOV) domain protein in blue light- and singlet oxygen-dependent gene regulation in Rhodobacter sphaeroides. Microbiology (Reading) 2012; 158:368-379. [DOI: 10.1099/mic.0.054700-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Affiliation(s)
- Sebastian Metz
- Institut für Mikro- und Molekularbiologie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 26-32, D-35392 Gießen, Germany
| | - Andreas Jäger
- Institut für Mikro- und Molekularbiologie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 26-32, D-35392 Gießen, Germany
| | - Gabriele Klug
- Institut für Mikro- und Molekularbiologie, Justus-Liebig-Universität Gießen, Heinrich-Buff-Ring 26-32, D-35392 Gießen, Germany
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11
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Krapf S, Weber S, Koslowski T. The road not taken: a theoretical view of an unexpected cryptochrome charge transfer path. Phys Chem Chem Phys 2012; 14:11518-24. [DOI: 10.1039/c2cp40793k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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12
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Weber S, Schroeder C, Kacprzak S, Mathes T, Kowalczyk RM, Essen LO, Hegemann P, Schleicher E, Bittl R. Light-generated paramagnetic intermediates in BLUF domains. Photochem Photobiol 2011; 87:574-83. [PMID: 21198648 DOI: 10.1111/j.1751-1097.2010.00885.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Blue-light sensitive photoreceptory BLUF domains are flavoproteins, which regulate various, mostly stress-related processes in bacteria and eukaryotes. The photoreactivity of the flavin adenine dinucleotide (FAD) cofactor in three BLUF domains from Rhodobacter sphaeroides, Synechocystis sp. PCC 6803 and Escherichia coli have been studied at low temperature using time-resolved electron paramagnetic resonance. Photoinduced flavin triplet states and radical-pair species have been detected on a microsecond time scale. Differences in the electronic structures of the FAD cofactors as reflected by altered zero-field splitting parameters of the triplet states could be correlated with changes in the amino-acid composition of the various BLUF domains' cofactor binding pockets. For the generation of the light-induced, spin-correlated radical-pair species in the BLUF domain from Synechocystis sp. PCC 6803, a tyrosine residue near the flavin's isoalloxazine moiety plays a critical role.
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Affiliation(s)
- Stefan Weber
- Albert-Ludwigs-Universität Freiburg, Institut für Physikalische Chemie, Freiburg, Germany
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13
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Metz S, Hendriks J, Jäger A, Hellingwerf K, Klug G. In vivo effects on photosynthesis gene expression of base pair exchanges in the gene encoding the light-responsive BLUF domain of AppA in Rhodobacter sphaeroides. Photochem Photobiol 2010; 86:882-9. [PMID: 20497366 DOI: 10.1111/j.1751-1097.2010.00749.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Rhodobacter sphaeroides protein AppA has the unique quality of sensing and transmitting light and redox signals. By acting as antirepressor to the PpsR protein, it acts as a major regulator in photosynthesis gene expression. In this study, we show that by introducing amino acid exchanges into the AppA protein, the in vivo activity as an antirepressor can be greatly altered. The tryptophan 104 to phenylalanine (W104F) base exchange greatly diminished blue-light sensitivity of the BLUF domain. From the obtained in vivo data, the difference in thermal recovery rate of the signaling state of the BLUF domain between the wild type and mutated protein was calculated, predicting an about 10-fold faster recovery in the mutant, which is consistent with in vitro data. Introduction of a tyrosine 21 to phenylalanine (Y21F) or to cysteine (Y21C) mutation led to a complete loss of AppA antirepressor activity, while additionally leading to an increase of photosynthesis gene expression after illumination with high blue-light quantities. Interestingly, this effect is not visible in a W104F/Y21F double mutant that again shows a wild-type-like behavior of the BLUF domain after blue-light illumination, thus restoring the activity of AppA.
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Affiliation(s)
- Sebastian Metz
- Institut für Mikro- und Molekularbiologie, University of Giessen, Giessen, Germany
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14
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Bacteriophytochromes Control Photosynthesis in Rhodopseudomonas palustris. ACTA ACUST UNITED AC 2009. [DOI: 10.1007/978-1-4020-8815-5_40] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
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15
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Bauer CE, Setterdahl A, Wu J, Robinson BR. Regulation of Gene Expression in Response to Oxygen Tension. THE PURPLE PHOTOTROPHIC BACTERIA 2009. [DOI: 10.1007/978-1-4020-8815-5_35] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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16
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Ayers RA, Moffat K. Changes in quaternary structure in the signaling mechanisms of PAS domains. Biochemistry 2008; 47:12078-86. [PMID: 18942854 DOI: 10.1021/bi801254c] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
FixL from Bradyrhizobium japonicum is a PAS sensor protein in which two PAS domains covalently linked to a histidine kinase domain are responsible for regulating nitrogen fixation in an oxygen-dependent manner. The more C-terminal PAS domain, denoted bjFixLH, contains a heme cofactor that binds diatomic molecules such as carbon monoxide and oxygen and regulates the activity of the FixL histidine kinase as part of a two-component signaling system. We present the structures of ferric, deoxy, and carbon monoxide-bound bjFixLH in a new space group ( P1) and at resolutions (1.5-1.8 A) higher than the resolutions of those previously obtained. Interestingly, bjFixLH can form two different dimers (in P1 and R32 crystal forms) in the same crystallization solution, where the monomers in one dimer are rotated approximately 175 degrees relative to the second. This suggests that PAS monomers are plastic and that two quite distinct quaternary structures are closely similar in free energy. We use screw rotation analysis to carry out a quantitative pairwise comparison of PAS quaternary structures, which identifies five different relative orientations adopted by isolated PAS monomers. We conclude that PAS monomer arrangement is context-dependent and could differ depending on whether the PAS domains are isolated or are part of a full-length protein. Structurally homologous residues comprise a conserved dimer interface. Using network analysis, we find that the architecture of the PAS dimer interface is continuous rather than modular; the network of residues comprising the interface is strongly connected. A continuous dimer interface is consistent with the low dimer-monomer dissociation equilibrium constant. Finally, we quantitate quaternary structural changes induced by carbon monoxide binding to a bjFixLH dimer, in which monomers rotate by up to approximately 2 degrees relative to each other. We relate these changes to those in other dimeric PAS domains and discuss the role of quaternary structural changes in the signaling mechanisms of PAS sensor proteins.
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Affiliation(s)
- Rebecca A Ayers
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, Illinois 60637, USA
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17
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Hierarchical regulation of photosynthesis gene expression by the oxygen-responsive PrrBA and AppA-PpsR systems of Rhodobacter sphaeroides. J Bacteriol 2008; 190:8106-14. [PMID: 18931128 DOI: 10.1128/jb.01094-08] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the facultatively phototrophic proteobacterium Rhodobacter sphaeroides, formation of the photosynthetic apparatus is oxygen dependent. When oxygen tension decreases, the response regulator PrrA of the global two-component PrrBA system is believed to directly activate transcription of the puf, puh, and puc operons, encoding structural proteins of the photosynthetic complexes, and to indirectly upregulate the photopigment biosynthesis genes bch and crt. Decreased oxygen also results in inactivation of the photosynthesis-specific repressor PpsR, bringing about derepression of the puc, bch, and crt operons. We uncovered a hierarchical relationship between these two regulatory systems, earlier thought to function independently. We also more accurately assessed the spectrum of gene targets of the PrrBA system. First, expression of the appA gene, encoding the PpsR antirepressor, is PrrA dependent, which establishes one level of hierarchical dominance of the PrrBA system over AppA-PpsR. Second, restoration of the appA transcript to the wild-type level is insufficient for rescuing phototrophic growth impairment of the prrA mutant, whereas inactivation of ppsR is sufficient. This suggests that in addition to controlling appA transcription, PrrA affects the activity of the AppA-PpsR system via an as yet unidentified mechanism(s). Third, PrrA directly activates several bch and crt genes, traditionally considered to be the PpsR targets. Therefore, in R. sphaeroides, the global PrrBA system regulates photosynthesis gene expression (i) by rigorous control over the photosynthesis-specific AppA-PpsR regulatory system and (ii) by extensive direct transcription activation of genes encoding structural proteins of photosynthetic complexes as well as genes encoding photopigment biosynthesis enzymes.
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18
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The use of chromatin immunoprecipitation to define PpsR binding activity in Rhodobacter sphaeroides 2.4.1. J Bacteriol 2008; 190:6817-28. [PMID: 18689484 DOI: 10.1128/jb.00719-08] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The expression of genes involved in photosystem development in Rhodobacter sphaeroides is dependent upon three major regulatory networks: FnrL, the PrrBA (RegBA) two-component system, and the transcriptional repressor/antirepressor PpsR/AppA. Of the three regulators, PpsR appears to have the narrowest range of physiological effects, which are limited to effects on the structural and pigment biosynthetic activities involved in photosynthetic membrane function. Although a PrrA(-) mutant is unable to grow under photosynthetic conditions, when a ppsR mutation was present, photosynthetic growth occurred. An examination of the double mutant under anaerobic-dark-dimethyl sulfoxide conditions using microarray analysis revealed the existence of an "extended" PpsR regulon and new physiological roles. To characterize the PpsR regulon and to better ascertain the significance of degeneracy within the PpsR binding sequence in vivo, we adapted the chromatin immunoprecipitation technique to R. sphaeroides. We demonstrated that in vivo there was direct and significant binding by PpsR to newly identified genes involved in microaerobic respiration and periplasmic stress resistance, as well as to photosynthesis genes. The new members of the PpsR regulon are located outside the photosynthesis gene cluster and have degenerate PpsR binding sequences. The possible interaction under physiologic conditions with degenerate binding sequences in the presence of other biologically relevant molecules is discussed with respect to its importance in physiological processes and to the existence of complex phenotypes associated with regulatory mutants. This study further defines the DNA structure necessary for PpsR binding in situ.
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19
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Yamazaki Y, Fukusumi H, Kamikubo H, Kataoka M. Role of the N-terminal region in the function of the photosynthetic bacterium transcription regulator PpsR. Photochem Photobiol 2008; 84:839-44. [PMID: 18282179 DOI: 10.1111/j.1751-1097.2008.00306.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PpsR is a transcription repressor for the gene cluster encoding photosystem genes in Rhodobacter sphaeroides. Repression activity is accomplished by DNA binding on the promoter regions of the photosystem gene clusters, and depends on both the redox potential and the presence of antirepressor protein AppA. To understand DNA repression regulation by PpsR, we investigated the function of PpsR domains in self-association for DNA binding. We constructed domain-deletion mutants and verified DNA-binding activity and dimer formation. Gel shift assay for measuring the DNA-binding activity of three sequential N-terminal deletion mutants revealed that N-terminal deletions (of minimum 121 residues) caused loss of binding activity. Size-exclusion gel chromatography revealed that deletion mutant which lacks the N-terminal 121-amino acid deletion mutant to exist as a dimer, although it was less stable than the intact PpsR. The mutants lacking the adjacent regions, Q-linker region and the first Per-Ant-Sim domain, did not form dimers, suggesting the involvement of the N-terminal region in dimer formation. This region is thus considered to be a functional domain in self-association, although not yet identified as a structural domain. Circular dichroism spectrum of the N-terminal region fragment exhibited a alpha/beta structure. We conclude that this region is a structural and functional domain, contributing to PpsR repression through dimer stabilization.
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Affiliation(s)
- Yoichi Yamazaki
- Graduate School of Materials Science, Nara Institute of Science and Technology, Ikoma, Nara, Japan
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20
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Han Y, Meyer MHF, Keusgen M, Klug G. A haem cofactor is required for redox and light signalling by the AppA protein of Rhodobacter sphaeroides. Mol Microbiol 2007; 64:1090-104. [PMID: 17501930 DOI: 10.1111/j.1365-2958.2007.05724.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The AppA protein of Rhodobacter sphaeroides is unique in its ability to sense and transmit redox signals as well as light signals. By functioning as antagonist to the PpsR transcriptional repressor, it regulates the expression of photosynthesis genes in response to these environmental stimuli. Here we show binding of the cofactor haem to a domain in the C-terminal part of AppA and redox activity of bound haem. This is supported by the findings that: (i) the C-terminal domain of AppA (AppADeltaN) binds to haemin agarose, (ii) AppADeltaN isolated from Escherichia coli shows absorbance at 411 nm and absorbances at 424 nm and 556 nm after reduction with dithionite and (iii) AppADeltaN can be reconstituted with haem in vitro. Expression of AppA variants in R. sphaeroides reveals that the haem binding domain is important for normal expression levels of photosynthesis genes and for normal light regulation in the presence of oxygen. The haem cofactor affects the interaction of the C-terminal part of AppA to PpsR but also its interaction to the N-terminal light sensing AppA-BLUF domain. Based on this we present a model for the transmission of light and redox signals by AppA.
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Affiliation(s)
- Yuchen Han
- Institut für Mikrobiologie und Molekularbiologie, University of Giessen, D-35392 Giessen, Germany
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21
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Braatsch S, Bernstein JR, Lessner F, Morgan J, Liao JC, Harwood CS, Beatty JT. Rhodopseudomonas palustris CGA009 has two functional ppsR genes, each of which encodes a repressor of photosynthesis gene expression. Biochemistry 2007; 45:14441-51. [PMID: 17128983 DOI: 10.1021/bi061074b] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The PpsR protein is a regulator of redox-dependent photosystem development in purple phototrophic bacteria. In contrast to most species, Rhodopseudomonas palustris contains two ppsR genes. We show that the inactivation of each of the R. palustris strain CGA009 ppsR genes results in an elevated level of formation of the photosystem under dark aerobic conditions. Absorption spectra of the two PpsR mutants revealed qualitative and quantitative differences in light-harvesting peak amplitude increases. A sequence difference in the helix-turn-helix DNA binding motif of PpsR2 (Arg 439 to Cys) between R. palustris strains CEA001 and CGA009 is shown to be a natural polymorphism that does not inactivate the repressor activity of the protein. To evaluate which photosynthesis genes are regulated by the two PpsR proteins, transcriptome profiles of the CGA009 and PpsR mutant strains were analyzed in microarray experiments. Transcription of most but not all photosystem genes was derepressed in the mutant strains to levels consistent with the in vivo absorption spectra, mathematical analyses of peak shapes and amplitudes, reaction center protein levels, and real-time PCR of selected mRNAs. Closely spaced PpsR binding motif repeats were identified 5' of genes that were derepressed in the transcriptome analysis of PpsR mutants. This work shows that both the PpsR1 and PpsR2 proteins from R. palustris strain CGA009 function as oxygen-responsive transcriptional repressors.
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Affiliation(s)
- Stephan Braatsch
- Department of Microbiology and Immunology, University of British Columbia, 2350 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
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22
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Abstract
The importance of chlorophyll (Chl) to the process of photosynthesis is obvious, and there is clear evidence that the regulation of Chl biosynthesis has a significant role in the regulation of assembly of the photosynthetic apparatus. The understanding of Chl biosynthesis has rapidly advanced in recent years. The identification of genetic loci associated with each of the biochemical steps has been accompanied by a greater appreciation of the role of Chl biosynthesis intermediates in intracellular signaling. The purpose of this review is to provide a source of information for all the steps in Chl and bacteriochlorophyll a biosynthesis, with an emphasis on steps that are believed to be key regulation points.
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Affiliation(s)
- David W Bollivar
- Department of Biology, Illinois Wesleyan University, Bloomington, IL 61702-2900, USA.
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23
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Ukaegbu UE, Henery S, Rosenzweig AC. Biochemical characterization of MmoS, a sensor protein involved in copper-dependent regulation of soluble methane monooxygenase. Biochemistry 2006; 45:10191-8. [PMID: 16922494 DOI: 10.1021/bi060693h] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Methane monooxygenase (MMO) enzymes catalyze the oxidation of methane to methanol in methanotrophic bacteria. Several strains of methanotrophs, including Methylococcus capsulatus (Bath), express a membrane-bound or particulate MMO (pMMO) at high copper-to-biomass ratios and a soluble MMO (sMMO) form when copper is limited. The mechanism of this "copper switch" is not understood. The mmoS gene, located downstream of the sMMO operon, encodes a sensor protein that is part of a two-component signaling system and has been proposed to play a role in the copper switch. MmoS from M. capsulatus (Bath) has been cloned, expressed, and purified. The purified protein is a tetramer of molecular mass 480 kDa. Optical spectra indicate that MmoS contains a flavin cofactor, identified as flavin adenine dinucleotide (FAD) by fluorescence spectroscopy and chromatographic analysis. The redox potential of the MmoS-bound FAD, which binds within the N-terminal PAS-PAC domains, is -290 +/- 2 mV at pH 8.0 and 25 degrees C. Despite extensive efforts, MmoS could not be loaded with Cu(I) or Cu(II), indicating that MmoS does not sense copper directly. These data suggest that MmoS functions as a redox sensor and provide new insight into the copper-mediated regulation of sMMO expression.
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Affiliation(s)
- Uchechi E Ukaegbu
- Department of Biochemistry, Molecular Biology, and Cell Biology and Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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24
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Abstract
Isoprenoids represent the oldest class of known low molecular-mass natural products synthesized by plants. Their biogenesis in plastids, mitochondria and the endoplasmic reticulum-cytosol proceed invariably from the C5 building blocks, isopentenyl diphosphate and/or dimethylallyl diphosphate according to complex and reiterated mechanisms. Compounds derived from the pathway exhibit a diverse spectrum of biological functions. This review centers on advances obtained in the field based on combined use of biochemical, molecular biology and genetic approaches. The function and evolutionary implications of this metabolism are discussed in relation with seminal informations gathered from distantly but related organisms.
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Affiliation(s)
- Florence Bouvier
- Institut de Biologie Moléculaire des Plantes du CNRS (UPR2357) et Université Louis Pasteur, 12 rue du Général Zimmer, 67084 Strasbourg Cedex, France
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25
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Mao L, Mackenzie C, Roh JH, Eraso JM, Kaplan S, Resat H. Combining microarray and genomic data to predict DNA binding motifs. Microbiology (Reading) 2005; 151:3197-3213. [PMID: 16207904 DOI: 10.1099/mic.0.28167-0] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The ability to detect regulatory elements within genome sequences is important in understanding how gene expression is controlled in biological systems. In this work, microarray data analysis is combined with genome sequence analysis to predict DNA sequences in the photosynthetic bacterium Rhodobacter sphaeroides that bind the regulators PrrA, PpsR and FnrL. These predictions were made by using hierarchical clustering to detect genes that share similar expression patterns. The DNA sequences upstream of these genes were then searched for possible transcription factor recognition motifs that may be involved in their co-regulation. The approach used promises to be widely applicable for the prediction of cis-acting DNA binding elements. Using this method the authors were independently able to detect and extend the previously described consensus sequences that have been suggested to bind FnrL and PpsR. In addition, sequences that may be recognized by the global regulator PrrA were predicted. The results support the earlier suggestions that the DNA binding sequence of PrrA may have a variable-sized gap between its conserved block elements. Using the predicted DNA binding sequences, a whole-genome-scale analysis was performed to determine the relative importance of the interplay between the three regulators PpsR, FnrL and PrrA. Results of this analysis showed that, compared to the regulation by PpsR and FnrL, a much larger number of genes are candidates to be regulated by PrrA. The study demonstrates by example that integration of multiple data types can be a powerful approach for inferring transcriptional regulatory patterns in microbial systems, and it allowed the detection of photosynthesis-related regulatory patterns in R. sphaeroides.
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Affiliation(s)
- Linyong Mao
- Pacific Northwest National Laboratory, Computational Biology and Bioinformatics Group, PO Box 999, MS: K7-90, Richland, WA 99352, USA
| | - Chris Mackenzie
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center, Medical School, Houston, TX 77030, USA
| | - Jung H Roh
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center, Medical School, Houston, TX 77030, USA
| | - Jesus M Eraso
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center, Medical School, Houston, TX 77030, USA
| | - Samuel Kaplan
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center, Medical School, Houston, TX 77030, USA
| | - Haluk Resat
- Pacific Northwest National Laboratory, Computational Biology and Bioinformatics Group, PO Box 999, MS: K7-90, Richland, WA 99352, USA
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26
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Elsen S, Jaubert M, Pignol D, Giraud E. PpsR: a multifaceted regulator of photosynthesis gene expression in purple bacteria. Mol Microbiol 2005; 57:17-26. [PMID: 15948946 DOI: 10.1111/j.1365-2958.2005.04655.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Purple bacteria control the level of expression and the composition of their photosystem according to light and redox conditions. This control involves several regulatory systems that have been now well characterized. Among them, the PpsR regulator plays a central role, because it directly or indirectly controls the synthesis of all of the different components of the photosystem. In this review, we report our knowledge of the PpsR protein, highlighting the diversity of its mode of action and focusing on the proteins identified in four model purple bacteria (Rhodobacter capsulatus, Rhodobacter sphaeroides, Rubrivivax gelatinosus, Bradyrhizobium ORS278). This regulator exhibits unique regulatory features in each bacterium: it can activate and/or repress the expression of photosynthesis genes, its activity can be modulated or not by the redox conditions, it can interact with other specific regulators and therefore be involved differently in light and/or redox regulatory circuits.
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Affiliation(s)
- Sylvie Elsen
- Laboratoire de Biochimie et Biophysique des Systèmes Intégrés (UMR 5092 CNRS-CEA-UJF), CEA-Grenoble, 38054 Grenoble Cedex 9, France
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27
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Moskvin OV, Gomelsky L, Gomelsky M. Transcriptome analysis of the Rhodobacter sphaeroides PpsR regulon: PpsR as a master regulator of photosystem development. J Bacteriol 2005; 187:2148-56. [PMID: 15743963 PMCID: PMC1064034 DOI: 10.1128/jb.187.6.2148-2156.2005] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PpsR from the anoxygenic phototrophic bacterium Rhodobacter sphaeroides has been known as an oxygen- and light-dependent repressor of bacteriochlorophyll and carotenoid biosynthesis genes and puc operons involved in photosystem development. However, the putative PpsR-binding sites, TGTN12ACA, are also located upstream of numerous nonphotosystem genes, thus raising the possibility that the role of PpsR is broader. To characterize the PpsR regulon, transcriptome profiling was performed on the wild-type strain grown at high and low oxygen tensions, on the strain overproducing PpsR, and on the ppsR mutant. Transcriptome analysis showed that PpsR primarily regulates photosystem genes; the consensus PpsR binding sequence is TGTcN10gACA (lowercase letters indicate lesser conservation); the presence of two binding sites is required for repression in vivo. These findings explain why numerous single TGTN12ACA sequences are nonfunctional. In addition to photosystem genes, the hemC and hemE genes involved in the early steps of tetrapyrrole biosynthesis were identified as new direct targets of PpsR repression. Unexpectedly, PpsR was found to indirectly repress the puf and puhA operons encoding photosystem core proteins. The upstream regions of these operons contain no PpsR binding sites. Involvement in regulation of these operons suggests that PpsR functions as a master regulator of photosystem development. Upregulation of the puf and puhA operons that resulted from ppsR inactivation was sufficient to restore the ability to grow phototrophically to the prrA mutant. PrrA, the global redox-dependent activator, was previously considered indispensable for phototrophic growth. It is revealed that the PrrBA and AppA-PpsR systems, believed to work independently, in fact interact and coordinately regulate photosystem development.
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Affiliation(s)
- Oleg V Moskvin
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071, USA
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28
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Kovács AT, Rákhely G, Kovács KL. The PpsR regulator family. Res Microbiol 2005; 156:619-25. [PMID: 15950121 DOI: 10.1016/j.resmic.2005.02.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Revised: 02/04/2005] [Accepted: 02/04/2005] [Indexed: 10/25/2022]
Abstract
Under aerobic conditions, phototrophic bacteria repress the formation of pigments to protect cells in the presence of light from the damaging effects of reactive oxygen species and consume oxygen through respiratory complexes. Members of the PpsR family regulate the transcription of bch, crt, puc, and hem genes in respond to redox or light conditions. This mini-review focuses on the function and distribution of PpsR proteins.
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Affiliation(s)
- Akos T Kovács
- Institute of Biophysics, Biological Research Center, Hungarian Academy of Sciences and Department of Biotechnology, University of Szeged, Szeged, Temesvári krt. 62, Hungary
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29
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Phadwal K. Carotenoid biosynthetic pathway: molecular phylogenies and evolutionary behavior of crt genes in eubacteria. Gene 2005; 345:35-43. [PMID: 15716108 DOI: 10.1016/j.gene.2004.11.038] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2004] [Revised: 11/11/2004] [Accepted: 11/15/2004] [Indexed: 10/26/2022]
Abstract
Phylogenetic analysis of carotenoid biosynthetic pathway genes and their evolutionary rate variations were studied among eubacterial taxa. The gene sequences for the enzymes involved in this pathway were obtained for major phylogenetic groups of eubacteria (green sulfur bacteria, green nonsulphur bacteria, Gram-positive bacteria, proteobacteria, flavobacteria, cyanobacteria) and archeabacteria. These gene datasets were distributed under five major steps of carotenoid biosynthesis in eubacteria; isoprenoid precursor biosynthesis, phytoene synthesis, dehydrogenation of phytoene, lycopene cyclization, formation of acyclic xanthophylls, formation of cyclic xanthophylls and carotenoid biosynthesis regulation. The NJ algorithm was used on protein coding DNA sequences to deduce the evolutionary relationship for the respective crt genes among different eubacterial lineages. The rate of nonsynonymous nucleotide substitutions per nonsynonymous site (d(N)) and synonymous nucleotide substitutions per synonymous site (d(S)) were calculated for different clades of the respective phylogenetic tree for specific crt genes. The phylogenetic analysis suggests that evolutionary pattern of crt genes in eubacteria is characterized by lateral gene transfer and gene duplication events. The d(N) values indicate that carotenoid biosynthetic genes are more conserved in proteobacteria than in any other eubacterial phyla. Furthermore, of the genes involved in carotenoid biosynthesis pathway, structural genes evolve slowly than the regulatory genes in eubacteria.
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Affiliation(s)
- Kanchan Phadwal
- Department of Biotechnology, Birla Institute of Technology, Ranchi 835215, India.
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30
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Braatsch S, Moskvin OV, Klug G, Gomelsky M. Responses of the Rhodobacter sphaeroides transcriptome to blue light under semiaerobic conditions. J Bacteriol 2004; 186:7726-35. [PMID: 15516587 PMCID: PMC524910 DOI: 10.1128/jb.186.22.7726-7735.2004] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2004] [Accepted: 08/10/2004] [Indexed: 11/20/2022] Open
Abstract
Exposure to blue light of the facultative phototrophic proteobacterium Rhodobacter sphaeroides grown semiaerobically results in repression of the puc and puf operons involved in photosystem formation. To reveal the genome-wide effects of blue light on gene expression and the underlying photosensory mechanisms, transcriptome profiles of R. sphaeroides during blue-light irradiation (for 5 to 135 min) were analyzed. Expression of most photosystem genes was repressed upon irradiation. Downregulation of photosystem development may be used to prevent photooxidative damage occurring when the photosystem, oxygen, and high-intensity light are present simultaneously. The photoreceptor of the BLUF-domain family, AppA, which belongs to the AppA-PpsR antirepressor-repressor system, is essential for maintenance of repression upon prolonged irradiation (S. Braatsch et al., Mol. Microbiol. 45:827-836, 2002). Transcriptome data suggest that the onset of repression is also mediated by the AppA-PpsR system, albeit via an apparently different sensory mechanism. Expression of several genes, whose products may participate in photooxidative damage defense, including deoxypyrimidine photolyase, glutathione peroxidase, and quinol oxidoreductases, was increased. Among the genes upregulated were genes encoding two sigma factors: sigmaE and sigma38. The consensus promoter sequences for these sigma factors were predicted in the upstream sequences of numerous upregulated genes, suggesting that coordinated action of sigmaE and sigma38 is responsible for the upregulation. Based on the dynamics of upregulation, the anti-sigmaE factor ChrR or its putative upstream partner is proposed to be the primary sensor. The identified transcriptome responses provided a framework for deciphering blue-light-dependent signal transduction pathways in R. sphaeroides.
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Affiliation(s)
- Stephan Braatsch
- Institut für Mikrobiologie und Molekularbiologie, Universität Giessen, Giesse, Germany
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Jaubert M, Zappa S, Fardoux J, Adriano JM, Hannibal L, Elsen S, Lavergne J, Verméglio A, Giraud E, Pignol D. Light and Redox Control of Photosynthesis Gene Expression in Bradyrhizobium. J Biol Chem 2004; 279:44407-16. [PMID: 15304477 DOI: 10.1074/jbc.m408039200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The two closely related bacteria Bradyrhizobium and Rhodopseudomonas palustris show an unusual mechanism of regulation of photosystem formation by light thanks to a bacteriophytochrome that antirepresses the regulator PpsR. In these two bacteria, we found out, unexpectedly, that two ppsR genes are present. We show that the two Bradyrhizobium PpsR proteins exert antagonistic effects in the regulation of photosystem formation with a classical repressor role for PpsR2 and an unexpected activator role for PpsR1. DNase I footprint analysis show that both PpsR bind to the same DNA TGTN12ACA motif that is present in tandem in the bchC promoter and the crtED intergenic region. Interestingly, the cycA and aerR promoter regions that contain only one conserved palindrome are recognized by PpsR2, but not PpsR1. Further biochemical analyses indicate that PpsR1 only is redox sensitive through the formation of an intermolecular disulfide bond, which changes its oligomerization state from a tetramer to an octamer under oxidizing conditions. Moreover, PpsR1 presents a higher DNA affinity under its reduced form in contrast to what has been previously found for PpsR or its homolog CrtJ from the Rhodobacter species. These results suggest that regulation of photosystem synthesis in Bradyrhizobium involves two PpsR competing for the binding to the same photosynthesis genes and this competition might be modulated by two factors: light via the antagonistic action of a bacteriophytochrome on PpsR2 and redox potential via the switch of PpsR1 oligomerization state.
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Affiliation(s)
- Marianne Jaubert
- Laboratoire des Symbioses Tropicales et Méditerranéennes (UMR113-IRD-CIRAD-AGRO-M-INRA-UM2), TA 10/J, Campus de Baillarguet, 34398 Montpellier 5, France
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Cho SH, Youn SH, Lee SR, Yim HS, Kang SO. Redox property and regulation of PpsR, a transcriptional repressor of photosystem gene expression in Rhodobacter sphaeroides. MICROBIOLOGY-SGM 2004; 150:697-706. [PMID: 14993319 DOI: 10.1099/mic.0.26777-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
PpsR from Rhodobacter sphaeroides is involved in the repression of photosystem gene expression. The PpsR protein was heterologously overexpressed and purified to homogeneity. Gel mobility shift assay showed that the purified PpsR has DNA-binding activity. SDS-PAGE analysis showed that some portions of PpsR were oxidized, indicating that intramolecular or intermolecular disulphide bonds were formed between the two cysteines in each subunit. When the disulphide bond of PpsR was reduced by DTT, the binding activity of PpsR to the puc promoter region distinctly increased. The changes in protein level and DNA-binding activity of PpsR were observed in a conjugant with an extra copy of the ppsR gene and in a PpsR-null mutant (PPS1), respectively. Both cysteines in PpsR existed in their reduced form under aerobic, anaerobic-dark and anaerobic-light growth conditions, as determined using thiol-specific chemical modification. In an AppA-null mutant (APP11), the binding activity and the amount of PpsR decreased compared to those of the wild-type and an appA-complemented strain, and decreased even more under anaerobic-dark conditions than under aerobic conditions. PpsR had a redox-sensitive property but retained its reduced state in the cell, and its amount was reduced by disruption of AppA.
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Affiliation(s)
- Seung-Hyun Cho
- Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea
| | - Sang-Hee Youn
- Laboratory of Biophysics, School of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea
| | - Seung-Rock Lee
- Center for Cell Signalling Research, Division of Molecular Life Sciences, Ewha Women's University, Seoul 120-750, Korea
| | - Hyung-Soon Yim
- Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea
| | - Sa-Ouk Kang
- Institute of Microbiology, Seoul National University, Seoul 151-742, Republic of Korea
- Laboratory of Biophysics, School of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea
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Kho DH, Yoo SB, Kim JS, Kim EJ, Lee JK. Characterization of Cu- and Zn-containing superoxide dismutase ofRhodobacter sphaeroides. FEMS Microbiol Lett 2004. [DOI: 10.1111/j.1574-6968.2004.tb09542.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Roh JH, Smith WE, Kaplan S. Effects of Oxygen and Light Intensity on Transcriptome Expression in Rhodobacter sphaeroides 2.4.1. J Biol Chem 2004; 279:9146-55. [PMID: 14662761 DOI: 10.1074/jbc.m311608200] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The roles of oxygen and light on the regulation of photosynthesis gene expression in Rhodobacter sphaeroides 2.4.1 have been well studied over the past 50 years. More recently, the effects of oxygen and light on gene regulation have been shown to involve the interacting redox chains present in R. sphaeroides under diverse growth conditions, and many of the redox carriers comprising these chains have been well studied. However, the expression patterns of those genes encoding these redox carriers, under aerobic and anaerobic photosynthetic growth, have been less well studied. Here, we provide a transcriptional analysis of many of the genes comprising the photosynthesis lifestyle, including genes corresponding to many of the known regulatory elements controlling the response of this organism to oxygen and light. The observed patterns of gene expression are evaluated and discussed in light of our knowledge of the physiology of R. sphaeroides under aerobic and photosynthetic growth conditions. Finally, this analysis has enabled to us go beyond the traditional patterns of gene expression associated with the photosynthesis lifestyle and to consider, for the first time, the full complement of genes responding to oxygen, and variations in light intensity when growing photosynthetically. The data provided here should be considered as a first step in enabling one to model electron flow in R. sphaeroides 2.4.1.
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Affiliation(s)
- Jung Hyeob Roh
- Department of Microbiology and Molecular Genetics, University of Texas, Health Science Center, Houston, Texas 77030, USA
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Abstract
Thiol-based regulatory switches play central roles in cellular responses to oxidative stress, nitrosative stress, and changes in the overall thiol-disulfide redox balance. Protein sulfhydryls offer a great deal of flexibility in the different types of modification they can undergo and the range of chemical signals they can perceive. For example, recent work on OhrR and OxyR has clearly established that disulfide bonds are not the only cysteine oxidation products that are likely to be relevant to redox sensing in vivo. Furthermore, different stresses can result in distinct modifications to the same protein; in OxyR it seems that distinct modifications can occur at the same cysteine, and in Yap1 a partner protein ensures that the disulfide bond induced by peroxide stress is different from the disulfide bond induced by other stresses. These kinds of discoveries have also led to the intriguing suggestion that different modifications to the same protein can create multiple activation states and thus deliver discrete regulatory outcomes. In this review, we highlight these issues, focusing on seven well-characterized microbial proteins controlled by thiol-based switches, each of which exhibits unique regulatory features.
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Affiliation(s)
- Mark S B Paget
- Department of Biochemistry, School of Life Sciences, University of Sussex, Brighton BN1 9QG, United Kingdom.
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Gomelsky L, Sram J, Moskvin OV, Horne IM, Dodd HN, Pemberton JM, McEwan AG, Kaplan S, Gomelsky M. Identification and in vivo characterization of PpaA, a regulator of photosystem formation in Rhodobacter sphaeroides. MICROBIOLOGY (READING, ENGLAND) 2003; 149:377-388. [PMID: 12624200 DOI: 10.1099/mic.0.25972-0] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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.
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Affiliation(s)
- Larissa Gomelsky
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA
| | - Jakub Sram
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA
| | - Oleg V Moskvin
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA
| | - Irene M Horne
- Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia
| | - Helen N Dodd
- Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia
| | - John M Pemberton
- Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia
| | - Alastair G McEwan
- Department of Microbiology and Parasitology, University of Queensland, Brisbane 4072, Australia
| | - Samuel Kaplan
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, TX 77030, USA
| | - Mark Gomelsky
- Department of Molecular Biology, University of Wyoming, Laramie, WY 82071-3944, USA
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Bauer C, Elsen S, Swem LR, Swem DL, Masuda S. Redox and light regulation of gene expression in photosynthetic prokaryotes. Philos Trans R Soc Lond B Biol Sci 2003; 358:147-53; discussion 153-4. [PMID: 12594923 PMCID: PMC1693112 DOI: 10.1098/rstb.2002.1189] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
All photosynthetic organisms control expression of photosynthesis genes in response to alterations in light intensity as well as to changes in cellular redox potential. Light regulation in plants involves a well-defined set of red- and blue-light absorbing photoreceptors called phytochrome and cryptochrome. Less understood are the factors that control synthesis of the plant photosystem in response to changes in cellular redox. Among a diverse set of photosynthetic bacteria the best understood regulatory systems are those synthesized by the photosynthetic bacterium Rhodobacter capsulatus. This species uses the global two-component signal transduction cascade, RegB and RegA, to anaerobically de-repress anaerobic gene expression. Under reducing conditions, the phosphate on RegB is transferred to RegA, which then activates genes involved in photosynthesis, nitrogen fixation, carbon fixation, respiration and electron transport. In the presence of oxygen, there is a second regulator known as CrtJ, which is responsible for repressing photosynthesis gene expression. CrtJ responds to redox by forming an intramolecular disulphide bond under oxidizing, but not reducing, growth conditions. The presence of the disulphide bond stimulates DNA binding activity of the repressor. There is also a flavoprotein that functions as a blue-light absorbing anti-repressor of CrtJ in the related bacterial species Rhodobacter sphaeroides called AppA. AppA exhibits a novel long-lived photocycle that is initiated by blue-light absorption by the flavin. Once excited, AppA binds to CrtJ thereby inhibiting the repressor activity of CrtJ. Various mechanistic aspects of this photocycle will be discussed.
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Affiliation(s)
- Carl Bauer
- Department of Biology, Indiana University, Bloomington, IN 47405, USA.
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Kaplan S. Photosynthesis genes and their expression in Rhodobacter sphaeroides 2.4.1: a tribute to my students and associates. PHOTOSYNTHESIS RESEARCH 2002; 73:95-108. [PMID: 16245109 DOI: 10.1023/a:1020437317471] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
This minireview traces the photosynthesis genes, their structure, function and expression in Rhodobacter sphaeroides 2.4.1, as applied to our understanding of the inducible photosynthetic intracytoplasmic membrane system or ICM. This focus has represented the research interests of this laboratory from the late 1960s to the present. This opportunity has been used to highlight the contributions of students and postdoctorals to this research effort. The work described here took place in a much greater and much broader context than what can be conveyed here. The 'timeline' begins with a clear acknowledgment of the work of June Lascelles and William Sistrom, whose foresight intuitively recognized the necessity of a 'genetic' approach to the study of photosynthesis in R. sphaeroides. The 'timeline' concludes with the completed genome sequence of R. sphaeroides 2.4.1. However, it is hoped the reader will recognize this event as not just a new beginning, but also as another hallmark describing this continuum.
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Affiliation(s)
- Samuel Kaplan
- Microbiology and Molecular Genetics, The University of Texas Health Science Center, Houston, UT-Houston Medical School, 6431 Fannin St, JFB 1.765, Houston, TX, 77030-1501, USA,
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Zeng X, Kaplan S. TspO as a modulator of the repressor/antirepressor (PpsR/AppA) regulatory system in Rhodobacter sphaeroides 2.4.1. J Bacteriol 2001; 183:6355-64. [PMID: 11591680 PMCID: PMC100131 DOI: 10.1128/jb.183.21.6355-6364.2001] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The TspO outer membrane protein of Rhodobacter sphaeroides has been shown to be involved in controlling the transcription of a number of genes which encode enzymes involved in photopigment biosynthesis and the puc operon. The display of regulated genes appears identical to those genes encompassing the PpsR/AppA repressor/antirepressor regulon, although the effect of TspO is modest relative to that of PpsR/AppA. To directly address the hypothesis that TspO is effective through the PpsR/AppA system, we constructed mutant strains with mutations in both tspO and appA. In all cases, the phenotypes examined resembled those of the appA lesion by itself, leading us to conclude that TspO works through or modulates the PpsR/AppA system and acts upstream of the site of action of these regulatory proteins. In earlier publications, we had suggested that TspO is involved in the efflux of a certain intermediate(s) of the porphyrin biosynthesis pathway and that transcriptional regulation of target gene expression could be explained by the accumulation of a coactivator of AppA function. Although the data reported here do not precisely identify this coactivator, they lend support to this hypothesis. We discuss the importance of this form of gene control as the result of the recent extension of the TspO system to Sinorhizobium meliloti, as described by Davey and de Bruijn (M. E. Davey and F. J. de Bruijn, Appl. Environ. Microbiol. 66:5353-5359, 2000). It is therefore possible that this system constitutes a more widely, although not universally, demonstrated form of gene regulation.
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Affiliation(s)
- X Zeng
- Department of Microbiology and Molecular Genetics, University of Texas Medical School, Houston, Texas 77030, USA
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40
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Abstract
The volume of electron flow through the cbb3 branch of the electron transport chain and the redox state of the quinone pool generate signals that regulate photosynthesis gene expression in Rhodobacter sphaeroides. An inhibitory signal is generated at the level of the catalytic subunit of the cbb3 cytochrome c oxidase and is transduced through the membrane-localized PrrC polypeptide to the PrrBA two-component activation system, which controls the expression of most of the photosynthesis genes in response to O2. The redox state of the quinone pool is monitored by the redox-active AppA antirepressor protein, which determines the functional state of the PpsR repressor protein. The antirepressor/repressor system as well as a modulator of AppA function, TspO, together with FnrL and PrrA stringently control photopigment gene expression. These regulatory elements, together with spectral complex-specific assembly factors, control the ultimate cellular levels and composition of the photosynthetic membrane.
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Affiliation(s)
- J I Oh
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center, Medical School, Houston, TX 77030, USA
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