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Ke N, Bauer CE. The Response Regulator RegA Is a Copper Binding Protein That Covalently Dimerizes When Exposed to Oxygen. Microorganisms 2022; 10:microorganisms10050934. [PMID: 35630378 PMCID: PMC9147068 DOI: 10.3390/microorganisms10050934] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/25/2022] [Accepted: 04/28/2022] [Indexed: 01/27/2023] Open
Abstract
In Rhodobacter capsulatus, the histidine kinase RegB is believed to phosphorylate its cognate transcriptional factor RegA only under anaerobic conditions. However, transcriptome evidence indicates that RegA regulates 47 genes involved in energy storage, energy production, signaling and transcription, under aerobic conditions. In this study, we provide evidence that RegA is a copper binding protein and that copper promotes the dimerization of RegA under aerobic conditions. Inductively coupled plasma mass spectrometry (ICP-MS) analysis indicates that RegA binds Cu1+ and Cu2+ in a 1:1 and 2:1 ratio, respectively. Through LC-MS/MS, ESI-MS and non-reducing SDS-PAGE gels, we show that Cu2+ stimulates disulfide bond formation in RegA at Cys156 in the presence of oxygen. Finally, we used DNase I footprint analysis to demonstrate that Cu2+-mediated covalent dimerized RegA is capable of binding to the ccoN promoter, which drives the expression of cytochrome cbb3 oxidase subunits. This study provides a new model of aerobic regulation of gene expression by RegA involving the formation of an intermolecular disulfide bond.
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2
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Kullapanich C, Dubbs JM, Mongkolsuk S. Inactivation of the Agrobacterium tumefaciens ActSR system affects resistance to multiple stresses with increased H 2O 2 sensitivity due to reduced expression of hemH. MICROBIOLOGY-SGM 2020; 165:1117-1134. [PMID: 31339484 DOI: 10.1099/mic.0.000838] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The Agrobacterium tumefaciens ActSR two-component regulatory system is a member of a homologous group of global redox-responsive regulatory systems that adjust the expression of energy-consuming and energy-supplying metabolic pathways in order to maintain cellular redox balance. In this study, the transcriptional organization of the hrpB-actSR locus was determined and the effect of actSR system inactivation on stress resistance was investigated. It was found that hrpB is transcribed as a monocistronic mRNA and actS is transcribed along with actR as a bicistronic mRNA, while actR is also transcribed as a monocistronic message. Each message is initiated from a separate promoter. Inactivation of actR resulted in decreased resistance to membrane stress (sodium dodecyl sulfate), acid stress (pH 5.5), iron starvation (bipyridyl) and iron excess (FeCl3), and antibiotic stress (tetracycline and ciprofloxacin). Resistance to oxidative stress in the form of organic peroxide (cumene hydroperoxide) increased, while resistance to inorganic peroxide (H2O2) decreased. An actR insertion mutant displayed reduced catalase activity, even though transcription of katA and catE remained unchanged. Complementation of the actR inactivation mutant with plasmid-encoded actR or overexpression of hemH, encoding ferrochelatase, restored wild-type catalase activity and H2O2 resistance levels. Gel mobility shift and hemH promoter-lacZ fusion results indicated that ActR is a positive regulator of hemH that binds directly to the hemH promoter region. Thus, inactivation of the A. tumefaciens ActSR system affects resistance to multiple stresses, including reduced resistance to H2O2 resulting from a reduction in catalase activity due to reduced expression of hemH.
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Affiliation(s)
- Chitrasak Kullapanich
- Program in Applied Biological Sciences, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, Bangkok, Thailand
| | - James M Dubbs
- Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, Thailand.,Program in Applied Biological Sciences, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, Bangkok, Thailand
| | - Skorn Mongkolsuk
- Center of Excellence on Environmental Health and Toxicology, EHT Ministry of Education, Bangkok, Thailand.,Laboratory of Biotechnology, Chulabhorn Research Institute, Bangkok, Thailand.,Program in Applied Biological Sciences, Chulabhorn Graduate Institute, Chulabhorn Royal Academy, Bangkok, Thailand
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3
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Reyes Ruiz LM, Fiebig A, Crosson S. Regulation of bacterial surface attachment by a network of sensory transduction proteins. PLoS Genet 2019; 15:e1008022. [PMID: 31075103 PMCID: PMC6530869 DOI: 10.1371/journal.pgen.1008022] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2019] [Revised: 05/22/2019] [Accepted: 04/26/2019] [Indexed: 11/25/2022] Open
Abstract
Bacteria are often attached to surfaces in natural ecosystems. A surface-associated lifestyle can have advantages, but shifts in the physiochemical state of the environment may result in conditions in which attachment has a negative fitness impact. Therefore, bacteria employ numerous mechanisms to control the transition from an unattached to a sessile state. The Caulobacter crescentus protein HfiA is a potent developmental inhibitor of the secreted polysaccharide adhesin known as the holdfast, which enables permanent attachment to surfaces. Multiple environmental cues influence expression of hfiA, but mechanisms of hfiA regulation remain largely undefined. Through a forward genetic selection, we have discovered a multi-gene network encoding a suite of two-component system (TCS) proteins and transcription factors that coordinately control hfiA transcription, holdfast development and surface adhesion. The hybrid HWE-family histidine kinase, SkaH, is central among these regulators and forms heteromeric complexes with the kinases, LovK and SpdS. The response regulator SpdR indirectly inhibits hfiA expression by activating two XRE-family transcription factors that directly bind the hfiA promoter to repress its transcription. This study provides evidence for a model in which a consortium of environmental sensors and transcriptional regulators integrate environmental cues at the hfiA promoter to control the attachment decision. Living on a surface within a community of cells confers a number of advantages to a bacterium. However, the transition from a free-living, planktonic state to a surface-attached lifestyle should be tightly regulated to ensure that cells avoid adhering to toxic or resource-limited niches. Many bacteria build adhesive structures on the surface of their cell envelopes that enable attachment. We sought to discover genes that control development of the Caulobacter crescentus surface adhesin known as the holdfast. Our studies uncovered a network of signal transduction proteins that coordinately control the biosynthesis of the holdfast by regulating transcription of the holdfast inhibitor, hfiA. We conclude that C. crescentus uses a multi-component regulatory system to sense and integrate environmental information to determine whether to attach to a surface, or to remain in an unattached state.
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Affiliation(s)
- Leila M Reyes Ruiz
- Committee on Genetics, Genomics and Systems Biology, University of Chicago, Chicago, Illinois, United States of America
| | - Aretha Fiebig
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois United States of America
| | - Sean Crosson
- Committee on Genetics, Genomics and Systems Biology, University of Chicago, Chicago, Illinois, United States of America.,Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois United States of America.,Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
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4
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Kumka JE, Schindel H, Fang M, Zappa S, Bauer CE. Transcriptomic analysis of aerobic respiratory and anaerobic photosynthetic states in Rhodobacter capsulatus and their modulation by global redox regulators RegA, FnrL and CrtJ. Microb Genom 2017; 3:e000125. [PMID: 29114403 PMCID: PMC5643017 DOI: 10.1099/mgen.0.000125] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2017] [Accepted: 06/19/2017] [Indexed: 01/09/2023] Open
Abstract
Anoxygenicphotosynthetic prokaryotes have simplified photosystems that represent ancient lineages that predate the more complex oxygen evolving photosystems present in cyanobacteria and chloroplasts. These organisms thrive under illuminated anaerobic photosynthetic conditions, but also have the ability to grow under dark aerobic respiratory conditions. This study provides a detailed snapshot of transcription ground states of both dark aerobic and anaerobic photosynthetic growth modes in the purple photosynthetic bacterium Rhodobactercapsulatus. Using 18 biological replicates for aerobic and photosynthetic states, we observed that 1834 genes (53 % of the genome) exhibited altered expression between aerobic and anaerobic growth. In comparison with aerobically grown cells, photosynthetically grown anaerobic cells showed decreased transcription of genes for cobalamin biosynthesis (-45 %), iron transport and homeostasis (-42 %), motility (-32 %), and glycolysis (-34 %). Conversely and more intuitively, the expression of genes involved in carbon fixation (547 %), bacteriochlorophyll biosynthesis (162 %) and carotenogenesis (114 %) were induced. We also analysed the relative contributions of known global redox transcription factors RegA, FnrL and CrtJ in regulating aerobic and anaerobic growth. Approximately 50 % of differentially expressed genes (913 of 1834) were affected by a deletion of RegA, while 33 % (598 out of 1834) were affected by FnrL, and just 7 % (136 out of 1834) by CrtJ. Numerous genes were also shown to be controlled by more than one redox responding regulator.
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Affiliation(s)
- Joseph E. Kumka
- Molecular and Cellular Biochemistry, Indiana University, Bloomington, USA
| | - Heidi Schindel
- Molecular and Cellular Biochemistry, Indiana University, Bloomington, USA
| | - Mingxu Fang
- Molecular and Cellular Biochemistry, Indiana University, Bloomington, USA
| | - Sebastien Zappa
- Molecular and Cellular Biochemistry, Indiana University, Bloomington, USA
| | - Carl E. Bauer
- Biochemistry, Indiana University Bloomington, Simon Hall MSB, 212 S Hawthorne Dr, Bloomington, IN 47405-7003, USA
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5
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Schindel HS, Bauer CE. The RegA regulon exhibits variability in response to altered growth conditions and differs markedly between Rhodobacter species. Microb Genom 2016; 2:e000081. [PMID: 28348828 PMCID: PMC5359404 DOI: 10.1099/mgen.0.000081] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 07/21/2016] [Indexed: 01/01/2023] Open
Abstract
The RegB/RegA two-component system from Rhodobacter capsulatus regulates global changes in gene expression in response to alterations in oxygen levels. Studies have shown that RegB/RegA controls many energy-generating and energy-utilizing systems such as photosynthesis, nitrogen fixation, carbon fixation, hydrogen utilization, respiration, electron transport and denitrification. In this report, we utilized RNA-seq and ChIP-seq to analyse the breadth of genes indirectly and directly regulated by RegA. A comparison of mRNA transcript levels in wild type cells relative to a RegA deletion strain shows that there are 257 differentially expressed genes under photosynthetic defined minimal growth medium conditions and 591 differentially expressed genes when grown photosynthetically in a complex rich medium. ChIP-seq analysis also identified 61 unique RegA binding sites with a well-conserved recognition sequence, 33 of which exhibit changes in neighbouring gene expression. These transcriptome results define new members of the RegA regulon including genes involved in iron transport and motility. These results also reveal that the set of genes that are regulated by RegA are growth medium specific. Similar analyses under dark aerobic conditions where RegA is thought not to be phosphorylated by RegB reveal 40 genes that are differentially expressed in minimal medium and 20 in rich medium. Finally, a comparison of the R. capsulatus RegA regulon with the orthologous PrrA regulon in Rhodobacter sphaeroides shows that the number of photosystem genes regulated by RegA and PrrA are similar but that the identity of genes regulated by RegA and PrrA beyond those involved in photosynthesis are quite distinct.
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Affiliation(s)
- Heidi S. Schindel
- Biochemistry, Indiana University Bloomington, Simon Hall MSB, 212 S. Hawthorne Dr., Bloomington, IN 47405-7003, USA
| | - Carl E. Bauer
- Biochemistry, Indiana University Bloomington, Simon Hall MSB, 212 S. Hawthorne Dr., Bloomington, IN 47405-7003, USA
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6
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Willett JW, Crosson S. Atypical modes of bacterial histidine kinase signaling. Mol Microbiol 2016; 103:197-202. [PMID: 27618209 DOI: 10.1111/mmi.13525] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/07/2016] [Indexed: 11/28/2022]
Abstract
The environment of a cell has a profound influence on its physiology, development and evolution. Accordingly, the capacity to sense and respond to physical and chemical signals in the environment is an important feature of cellular biology. In bacteria, environmental sensory perception is often regulated by two-component signal transduction systems (TCSTs). Canonical TCST entails signal-induced autophosphorylation of a sensor histidine kinase (HK) followed by phosphoryl transfer to a cognate response regulator (RR) protein, which may affect gene expression at multiple levels. Recent studies provide evidence for systems that do not adhere to this archetypal TCST signaling model. We present selected examples of atypical modes of signal transduction including inactivation of HK activity via homo- and hetero oligomerization, and cross-phosphorylation between HKs. These examples highlight mechanisms bacteria use to integrate environmental signals to control complex adaptive processes.
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Affiliation(s)
- Jonathan W Willett
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.,Howard Taylor Ricketts Laboratory, University of Chicago, Argonne National Laboratory, Argonne, IL, USA
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, USA.,Howard Taylor Ricketts Laboratory, University of Chicago, Argonne National Laboratory, Argonne, IL, USA.,Department of Microbiology, University of Chicago, Chicago, IL, USA
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7
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Tsygankov AA, Khusnutdinova AN. Hydrogen in metabolism of purple bacteria and prospects of practical application. Microbiology (Reading) 2015. [DOI: 10.1134/s0026261715010154] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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8
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Amino acid residues of RegA important for interactions with the CbbR-DNA complex of Rhodobacter sphaeroides. J Bacteriol 2014; 196:3179-90. [PMID: 24957624 DOI: 10.1128/jb.01842-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
CbbR and RegA (PrrA) are transcriptional regulators of the Calvin-Benson-Bassham (CBB) CO2 fixation pathway (cbbI and cbbII) operons of Rhodobacter sphaeroides. The CbbR and RegA proteins interact, but CbbR must be bound to the promoter DNA in order for RegA-CbbR protein-protein interactions to occur. RegA greatly enhances the ability of CbbR to bind the cbbI promoter or greatly enhances the stability of the CbbR/promoter complex. The N-terminal receiver domain and the DNA binding domain of RegA were shown to interact with CbbR. Residues in α-helix 7 and α-helix 8 of the DNA binding domain (helix-turn-helix) of RegA directly interacted with CbbR, with α-helix 7 positioned immediately above the DNA and α-helix 8 located in the major groove of the DNA. A CbbR protein containing only the DNA binding motif and the linker helix was capable of binding to RegA. In contrast, a truncated CbbR containing only the linker helix and recognition domains I and II (required for effector binding) was not able to interact with RegA. The accumulated results strongly suggest that the DNA binding domains of both proteins interact to facilitate optimal transcriptional control over the cbb operons. In vivo analysis, using constitutively active mutant CbbR proteins, further indicated that CbbR must interact with phosphorylated RegA in order to accomplish transcriptional activation.
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Dziewit L, Czarnecki J, Wibberg D, Radlinska M, Mrozek P, Szymczak M, Schlüter A, Pühler A, Bartosik D. Architecture and functions of a multipartite genome of the methylotrophic bacterium Paracoccus aminophilus JCM 7686, containing primary and secondary chromids. BMC Genomics 2014; 15:124. [PMID: 24517536 PMCID: PMC3925955 DOI: 10.1186/1471-2164-15-124] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 02/07/2014] [Indexed: 11/10/2022] Open
Abstract
Background Paracoccus aminophilus JCM 7686 is a methylotrophic α-Proteobacterium capable of utilizing reduced one-carbon compounds as sole carbon and energy source for growth, including toxic N,N-dimethylformamide, formamide, methanol, and methylamines, which are widely used in the industry. P. aminophilus JCM 7686, as many other Paracoccus spp., possesses a genome representing a multipartite structure, in which the genomic information is split between various replicons, including chromids, essential plasmid-like replicons, with properties of both chromosomes and plasmids. In this study, whole-genome sequencing and functional genomics approaches were applied to investigate P. aminophilus genome information. Results The P. aminophilus JCM 7686 genome has a multipartite structure, composed of a single circular chromosome and eight additional replicons ranging in size between 5.6 and 438.1 kb. Functional analyses revealed that two of the replicons, pAMI5 and pAMI6, are essential for host viability, therefore they should be considered as chromids. Both replicons carry housekeeping genes, e.g. responsible for de novo NAD biosynthesis and ammonium transport. Other mobile genetic elements have also been identified, including 20 insertion sequences, 4 transposons and 10 prophage regions, one of which represents a novel, functional serine recombinase-encoding bacteriophage, ϕPam-6. Moreover, in silico analyses allowed us to predict the transcription regulatory network of the JCM 7686 strain, as well as components of the stress response, recombination, repair and methylation machineries. Finally, comparative genomic analyses revealed that P. aminophilus JCM 7686 has a relatively distant relationship to other representatives of the genus Paracoccus. Conclusions P. aminophilus genome exploration provided insights into the overall structure and functions of the genome, with a special focus on the chromids. Based on the obtained results we propose the classification of bacterial chromids into two types: “primary” chromids, which are indispensable for host viability and “secondary” chromids, which are essential, but only under some environmental conditions and which were probably formed quite recently in the course of evolution. Detailed genome investigation and its functional analysis, makes P. aminophilus JCM 7686 a suitable reference strain for the genus Paracoccus. Moreover, this study has increased knowledge on overall genome structure and composition of members within the class Alphaproteobacteria.
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Affiliation(s)
- Lukasz Dziewit
- Department of Bacterial Genetics, Institute of Microbiology, Faculty of Biology, University of Warsaw, Miecznikowa 1, 02-096 Warsaw, Poland.
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10
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Aussel L, Pierrel F, Loiseau L, Lombard M, Fontecave M, Barras F. Biosynthesis and physiology of coenzyme Q in bacteria. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1004-11. [PMID: 24480387 DOI: 10.1016/j.bbabio.2014.01.015] [Citation(s) in RCA: 102] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 01/23/2014] [Accepted: 01/24/2014] [Indexed: 11/24/2022]
Abstract
Ubiquinone, also called coenzyme Q, is a lipid subject to oxido-reduction cycles. It functions in the respiratory electron transport chain and plays a pivotal role in energy generating processes. In this review, we focus on the biosynthetic pathway and physiological role of ubiquinone in bacteria. We present the studies which, within a period of five decades, led to the identification and characterization of the genes named ubi and involved in ubiquinone production in Escherichia coli. When available, the structures of the corresponding enzymes are shown and their biological function is detailed. The phenotypes observed in mutants deficient in ubiquinone biosynthesis are presented, either in model bacteria or in pathogens. A particular attention is given to the role of ubiquinone in respiration, modulation of two-component activity and bacterial virulence. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
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Affiliation(s)
- Laurent Aussel
- Laboratoire de Chimie Bactérienne, UMR 7283 Aix-Marseille Université - CNRS, Institut de Microbiologie de la Méditerranée, 31 Chemin Joseph Aiguier 13009 Marseille, France
| | - Fabien Pierrel
- Laboratoire de Chimie et Biologie des Métaux, UMR 5249 CEA - Université Grenoble I - CNRS, 17 Rue des Martyrs, 38054 Grenoble Cedex France
| | - Laurent Loiseau
- Laboratoire de Chimie Bactérienne, UMR 7283 Aix-Marseille Université - CNRS, Institut de Microbiologie de la Méditerranée, 31 Chemin Joseph Aiguier 13009 Marseille, France
| | - Murielle Lombard
- Laboratoire de Chimie des Processus Biologiques, UMR 8229 CNRS, UPMC, Collège de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05 France
| | - Marc Fontecave
- Laboratoire de Chimie des Processus Biologiques, UMR 8229 CNRS, UPMC, Collège de France, 11 Place Marcellin Berthelot, 75231 Paris Cedex 05 France
| | - Frédéric Barras
- Laboratoire de Chimie Bactérienne, UMR 7283 Aix-Marseille Université - CNRS, Institut de Microbiologie de la Méditerranée, 31 Chemin Joseph Aiguier 13009 Marseille, France.
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11
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Cheng Z, Li K, Hammad LA, Karty JA, Bauer CE. Vitamin B12 regulates photosystem gene expression via the CrtJ antirepressor AerR in Rhodobacter capsulatus. Mol Microbiol 2014; 91:649-64. [PMID: 24329562 DOI: 10.1111/mmi.12491] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/08/2013] [Indexed: 12/29/2022]
Abstract
The tetrapyrroles haem, bacteriochlorophyll and cobalamin (B12 ) exhibit a complex interrelationship regarding their synthesis. In this study, we demonstrate that AerR functions as an antirepressor of the tetrapyrrole regulator CrtJ. We show that purified AerR contains B12 that is bound to a conserved histidine (His145) in AerR. The interaction of AerR to CrtJ was further demonstrated in vitro by pull down experiments using AerR as bait and quantified using microscale thermophoresis. DNase I DNA footprint assays show that AerR containing B12 inhibits CrtJ binding to the bchC promoter. We further show that bchC expression is greatly repressed in a B12 auxotroph of Rhodobacter capsulatus and that B12 regulation of gene expression is mediated by AerR's ability to function as an antirepressor of CrtJ. This study thus provides a mechanism for how the essential tetrapyrrole, cobalamin controls the synthesis of bacteriochlorophyll, an essential component of the photosystem.
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Affiliation(s)
- Zhuo Cheng
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, IN, 47405, USA
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12
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Li RF, Lu GT, Li L, Su HZ, Feng GF, Chen Y, He YQ, Jiang BL, Tang DJ, Tang JL. Identification of a putative cognate sensor kinase for the two-component response regulator HrpG, a key regulator controlling the expression of the hrp genes in Xanthomonas campestris pv. campestris. Environ Microbiol 2013; 16:2053-71. [PMID: 23906314 DOI: 10.1111/1462-2920.12207] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2013] [Revised: 06/10/2013] [Accepted: 06/30/2013] [Indexed: 11/29/2022]
Abstract
The bacterial phytopathogen Xanthomonas campestris pv. campestris (Xcc) relies on the hrp (hypersensitive response and pathogenicity) genes to cause disease and induce hypersensitive response (HR). The hrp genes of bacterial phytopathogens are divided into two groups. Xcc hrp genes belong to group II. It has long been known that the group II hrp genes are activated by an AraC-type transcriptional regulator whose expression is controlled by a two-component system (TCS) response regulator (named HrpG in Xcc). However, no cognate sensor kinase has yet been identified. Here, we present evidence showing that the Xcc open-reading frame XC_3670 encodes a TCS sensor kinase (named HpaS). Mutation of hpaS almost completely abolished the HR induction and virulence. Bacterial two-hybrid and protein pull-down assays revealed that HpaS physically interacted with HrpG. Phos-tag™ SDS-PAGE analysis showed that mutation in hpaS reduced markedly the phosphorylation of HrpG in vivo. These data suggest that HpaS and HrpG are most likely to form a TCS. We also showed that XC_3669 (named hpaR2), which is adjacent to hpaS and encodes a putative TCS response regulator, is required for full virulence but not HR induction. HpaR2 also physically interacted with HpaS, suggesting that HpaS may also form another TCS with HpaR2.
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Affiliation(s)
- Rui-Fang Li
- State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, 530004, China
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13
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Wu J, Cheng Z, Reddie K, Carroll K, Hammad LA, Karty JA, Bauer CE. RegB kinase activity is repressed by oxidative formation of cysteine sulfenic acid. J Biol Chem 2013; 288:4755-62. [PMID: 23306201 DOI: 10.1074/jbc.m112.413492] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
RegB/RegA comprise a global redox-sensing signal transduction system utilized by a wide range of proteobacteria to sense environmental changes in oxygen tension. The conserved cysteine 265 in the sensor kinase RegB was previously reported to form an intermolecular disulfide bond under oxidizing conditions that converts RegB from an active dimer into an inactive tetramer. In this study, we demonstrate that a stable sulfenic acid (-SOH) derivative also forms at Cys-265 in vitro and in vivo when RegB is exposed to oxygen. This sulfenic acid modification is reversible and stable in the air. Autophosphorylation assay shows that reduction of the SOH at Cys-265 to a free thiol (SH) can increase RegB kinase activity in vitro. Our results suggest that a sulfenic acid modification at Cys-265 performs a regulatory role in vivo and that it may be the major oxidation state of Cys-265 under aerobic conditions. Cys-265 thus functions as a complex redox switch that can form multiple thiol modifications in response to different redox signals to control the kinase activity of RegB.
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Affiliation(s)
- Jiang Wu
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana 47405, USA
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14
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Mercer RG, Quinlan M, Rose AR, Noll S, Beatty JT, Lang AS. Regulatory systems controlling motility and gene transfer agent production and release in Rhodobacter capsulatus. FEMS Microbiol Lett 2012; 331:53-62. [PMID: 22443140 DOI: 10.1111/j.1574-6968.2012.02553.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 03/14/2012] [Accepted: 03/16/2012] [Indexed: 11/30/2022] Open
Abstract
Production of the gene transfer agent of Rhodobacter capsulatus, RcGTA, is dependent upon several cellular regulatory systems, including a putative phosphorelay involving the CtrA and CckA proteins. These proteins are also involved in flagellar motility in R. capsulatus. The interactions of proteins in this system are best understood in Caulobacter crescentus where CtrA is activated by phosphorylation by the CckA-ChpT phosphorelay. CtrA~P activity is further controlled by SciP, which represses ctrA transcription and CtrA activation of transcription. We show that R. capsulatus chpT and cckA mutants both have greatly reduced motility and RcGTA activity. Unlike the ctrA mutant where RcGTA gene transcription is absent, the decrease in RcGTA activity is because of reduced release of RcGTA from the cells. The sciP mutant is not affected for RcGTA production but our results support the C. crescentus model of SciP repression of flagellar motility genes. We show that both unphosphorylated and phosphorylated CtrA can activate RcGTA gene expression, while CtrA~P seems to be required for release of the particle and expression of motility genes. This has led us to a new model of how this regulatory system controls motility and production of RcGTA in R. capsulatus.
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Affiliation(s)
- Ryan G Mercer
- Department of Biology, Memorial University of Newfoundland, St. John's, NL, Canada
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15
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Wu J, Bauer CE. RegB kinase activity is controlled in part by monitoring the ratio of oxidized to reduced ubiquinones in the ubiquinone pool. mBio 2010; 1:e00272-10. [PMID: 21157513 PMCID: PMC3000548 DOI: 10.1128/mbio.00272-10] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Accepted: 11/10/2010] [Indexed: 01/08/2023] Open
Abstract
RegB is a membrane-spanning sensor kinase responsible for redox regulation of a wide variety of metabolic processes in numerous proteobacterial species. Here we show that full-length RegB purified from Escherichia coli membranes contains bound ubiquinone. Four conserved residues in the membrane-spanning domain of RegB are shown to have important roles in ubiquinone binding in vitro and redox sensing in vivo. Isothermal titration calorimetry measurements, coupled with kinase assays under oxidizing and reducing conditions, indicate that RegB weakly binds both oxidized ubiquinone and reduced ubiquinone (ubiquinol) with nearly equal affinity and that oxidized ubiquinone inhibits kinase activity without promoting a redox reaction. We propose a model in which ubiquinone/ubiquinol bound to RegB readily equilibrates with ubiquinones/ubiquinols in the membrane, allowing the kinase activity to be tuned by the redox state of the ubiquinone pool. This noncatalytic role of ubiquinone in controlling RegB activity is distinct from that of other known ubiquinone-binding proteins, which use ubiquinone as an electron donor or acceptor.
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Affiliation(s)
- Jiang Wu
- Department of Molecular and Cellular Biochemistry, Indiana University, Bloomington, Indiana, USA
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Regulation of gene expression by PrrA in Rhodobacter sphaeroides 2.4.1: role of polyamines and DNA topology. J Bacteriol 2009; 191:4341-52. [PMID: 19411327 DOI: 10.1128/jb.00243-09] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
In the present study, we show in vitro binding of PrrA, a global regulator in Rhodobacter sphaeroides 2.4.1, to the PrrA site 2, within the RSP3361 locus. Specific binding, as shown by competition experiments, requires the phosphorylation of PrrA. The binding affinity of PrrA for site 2 was found to increase 4- to 10-fold when spermidine was added to the binding reaction. The presence of extracellular concentrations of spermidine in growing cultures of R. sphaeroides gave rise to a twofold increase in the expression of the photosynthesis genes pucB and pufB, as well as the RSP3361 gene, under aerobic growth conditions, as shown by the use of lacZ transcriptional fusions, and led to the production of light-harvesting spectral complexes. In addition, we show that negative supercoiling positively regulates the expression of the RSP3361 gene, as well as pucB. We show the importance of supercoiling through an evaluation of the regulation of gene expression in situ by supercoiling, in the case of the former gene, as well as using the DNA gyrase inhibitor novobiocin. We propose that polyamines and DNA supercoiling act synergistically to regulate expression of the RSP3361 gene, partly by affecting the affinity of PrrA binding to the PrrA site 2 within the RSP3361 gene.
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Half-Site DNA sequence and spacing length contributions to PrrA binding to PrrA site 2 of RSP3361 in Rhodobacter sphaeroides 2.4.1. J Bacteriol 2009; 191:4353-64. [PMID: 19411326 DOI: 10.1128/jb.00244-09] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The consensus DNA binding sequence for PrrA, a global regulator in Rhodobacter sphaeroides 2.4.1, is poorly defined. We have performed mutational analysis of PrrA site 2, of the RSP3361 gene, to which PrrA binds in vitro (J. M. Eraso and S. Kaplan, J. Bacteriol. 191:4341-4352, 2009), to further define the consensus sequence for DNA binding. Two half-sites of equal length, containing 6 nucleotides each, were required for PrrA binding to this DNA sequence. Systematic nucleotide substitutions in both inverted half-sites led to a decrease in binding affinity of phosphorylated PrrA in vitro, the level of which was dependent on the substitution. The reduced binding affinities were confirmed by competition experiments and led to proportional decreases in the expression of lacZ transcriptional fusions to the RSP3361 gene in vivo. The 5-nucleotide spacer region between the half-sites was found to be optimal for PrrA binding to the wild-type half-sites, as shown by decreased PrrA DNA binding affinities to synthetic DNA sequences without spacer regions or with spacer regions ranging from 1 to 10 nucleotides. The synthetic spacer region alleles also showed decreased gene expression in vivo when analyzed using lacZ transcriptional fusions. We have studied three additional DNA sequences to which PrrA binds in vitro. They are located in the regulatory regions of genes positively regulated by PrrA and contain spacer regions with 5 or 8 nucleotides. We demonstrate that PrrA can bind in vitro to DNA sequences with different lengths in the spacer regions between the half-sites.
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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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RegB/RegA, A Global Redox-Responding Two-Component System. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 631:131-48. [DOI: 10.1007/978-0-387-78885-2_9] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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21
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Thomas SA, Brewster JA, Bourret RB. Two variable active site residues modulate response regulator phosphoryl group stability. Mol Microbiol 2008; 69:453-65. [PMID: 18557815 DOI: 10.1111/j.1365-2958.2008.06296.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Many signal transduction networks control their output by switching regulatory elements on or off. To synchronize biological response with environmental stimulus, switching kinetics must be faster than changes in input. Two-component regulatory systems (used for signal transduction by bacteria, archaea and eukaryotes) switch via phosphorylation or dephosphorylation of the receiver domain in response regulator proteins. Although receiver domains share conserved active site residues and similar three-dimensional structures, rates of self-catalysed dephosphorylation span a >or= 40,000-fold range in response regulators that control diverse biological processes. For example, autodephosphorylation of the chemotaxis response regulator CheY is 640-fold faster than Spo0F, which controls sporulation. Here we demonstrate that substitutions at two variable active site positions decreased CheY autodephosphorylation up to 40-fold and increased the Spo0F rate up to 110-fold. Particular amino acids had qualitatively similar effects in different response regulators. However, mutant proteins matched to other response regulators at the two key variable positions did not always exhibit similar autodephosphorylation kinetics. Therefore, unknown factors also influence absolute rates. Understanding the effects that particular active site amino acid compositions have on autodephosphorylation rate may allow manipulation of phosphoryl group stability for useful purposes, as well as prediction of signal transduction kinetics from amino acid sequence.
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Affiliation(s)
- Stephanie A Thomas
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, NC 27599-7290, USA
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Swem LR, Swem DL, Wu J, Bauer CE. Purification and assays of Rhodobacter capsulatus RegB-RegA two-component signal transduction system. Methods Enzymol 2008; 422:171-83. [PMID: 17628139 PMCID: PMC2774727 DOI: 10.1016/s0076-6879(06)22008-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Two-component signal-transduction systems, composed of a histidine-sensor kinase and a DNA-binding response regulator, allow bacteria to detect environmental changes and adjust cellular physiology to live more efficiently in a broad distribution of niches. Although many two-component signal-transduction systems are known, a limited number of signals that stimulate these systems have been discovered. This chapter describes the purification and characterization of the predominant two-component signal-transduction system utilized by Rhodobacter capsulatus, a nonsulfur purple photosynthetic bacterium. Specifically, we explain the overexpression, detergent solubilization, and purification of the full-length membrane-spanning histidine-sensor kinase RegB. We also provide a method to measure autophosphorylation of RegB and discern the effect of its signal molecule, ubiquinone, on autophosphorylation levels. In addition we describe the overexpression and purification of the cognate response regulator RegA and a technique used to visualize the phosphotransfer reaction from RegB to RegA.
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Affiliation(s)
- Lee R Swem
- Department of Molecular Biology, Princeton University, Princeton, New Jersey, USA
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Willett J, Smart JL, Bauer CE. RegA control of bacteriochlorophyll and carotenoid synthesis in Rhodobacter capsulatus. J Bacteriol 2007; 189:7765-73. [PMID: 17616588 PMCID: PMC2168725 DOI: 10.1128/jb.00853-07] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2007] [Accepted: 06/29/2007] [Indexed: 11/20/2022] Open
Abstract
We provide in vivo genetic and in vitro biochemical evidence that RegA directly regulates bacteriochlorophyll and carotenoid biosynthesis in Rhodobacter capsulatus. beta-Galactosidase expression assays with a RegA-disrupted strain containing reporter plasmids for Mg-protoporphyrin IX monomethyl ester oxidative cyclase (bchE), Mg-protoporphyrin IX chelatase (bchD), and phytoene dehydrogenase (crtI) demonstrate RegA is responsible for fourfold anaerobic induction of bchE, threefold induction of bchD, and twofold induction of crtI. Promoter mapping studies, coupled with DNase I protection assays, map the region of RegA binding to three sites in the bchE promoter region. Similar studies at the crtA and crtI promoters indicate that RegA binds to a single region equidistant from these divergent promoters. These results demonstrate that RegA is directly responsible for anaerobic induction of bacteriochlorophyll biosynthesis genes bchE, bchD, bchJ, bchI, bchG, and bchP and carotenoid biosynthesis genes crtI, crtB, and crtA.
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Gregor J, Zeller T, Balzer A, Haberzettl K, Klug G. Bacterial Regulatory Networks Include Direct Contact of Response Regulator Proteins: Interaction of RegA and NtrX in Rhodobacter capsulatus. J Mol Microbiol Biotechnol 2007; 13:126-39. [PMID: 17693720 DOI: 10.1159/000103604] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The formation of photosynthetic complexes in facultatively photosynthetic bacteria is controlled by the oxygen tension in the environment. In Rhodobacter capsulatus the two-component system RegB/RegA plays a major role in the redox control of photosynthesis genes but also controls other redox-dependent systems. The response regulator RegA is phosphorylated under low oxygen tension and activates the puf and puc operons, which encode pigment binding proteins, by binding to their promoter regions. Data from a yeast two-hybrid analysis as well as an in vitroanalysis indicate that RegA interacts with the NtrX protein, the response regulator of the NtrY/NtrX two-component system which is believed to be involved in regulation of nitrogen fixation genes. Our further analysis revealed that NtrX is indeed involved in the regulation of the puf and puc operons. Furthermore, we showed that an altered NtrX protein, which is predicted to adopt the conformation of phosphorylated NtrX protein, binds within the puf promoter region close to the RegA binding sites. We conclude that a direct interaction of two response regulators connects the regulatory systems for redox control and nitrogen control.
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Affiliation(s)
- Jutta Gregor
- Institut für Mikrobiologie und Molekularbiologie, University of Giessen, Giessen, Germany
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25
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Stolov A, Valverde A, Ronald P, Burdman S. Purification of soluble and active RaxH, a transmembrane histidine protein kinase from Xanthomonas oryzae pv. oryzae required for AvrXa21 activity. MOLECULAR PLANT PATHOLOGY 2007; 8:93-101. [PMID: 20507481 DOI: 10.1111/j.1364-3703.2006.00374.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
SUMMARY The RaxHR two-component regulatory system (TCS) of the rice pathogen Xanthomonas oryzae pv. oryzae is required for AvrXa21 activity. RaxH is a typical transmembrane histidine protein kinase (HK), whereas RaxR is its concomitant response regulator (RR). Here, we report the isolation of soluble, active amounts of recombinant His-tagged full-length RaxH and RaxR following growth of Escherichia coli over-expressing strains in the presence of sorbitol and glycine betaine. Full-length His-RaxH showed similar autophosphorylation activities to that of a truncated version of the protein (His-t-RaxH), lacking the N-terminal transmembrane region. Transphosphorylation assays revealed that only full-length RaxH was able to induce phosphorylation of His-RaxR, indicating that the N-terminal region of RaxH may be required for transphosphorylation of RaxR. Using site-directed mutagenesis we also demonstrated that residues histidine 222 in RaxH and aspartate 51 in RaxR are essential for phosphorylation activities of these proteins. Utilization of compatible solutes may be widely applied for purification of soluble, active recombinant transmembrane proteins, and in particular for purification of transmembrane HKs.
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Affiliation(s)
- Avital Stolov
- Department of Plant Pathology and Microbiology, Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, PO Box 12, Rehovot 76100, Israel
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Seok JS, Kaplan S, Oh JI. Interacting specificity of a histidine kinase and its cognate response regulator: the PrrBA system of Rhodobacter sphaeroides. MICROBIOLOGY-SGM 2006; 152:2479-2490. [PMID: 16849810 DOI: 10.1099/mic.0.28961-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Using a yeast two-hybrid assay system, it was demonstrated that the four-helix bundle of the Rhodobacter sphaeroides PrrB histidine kinase both serves as the interaction site for the regulatory domain of its cognate response regulator PrrA and is the primary determinant of the interaction specificity. The alpha-helix 1 and its flanking turn region within the dimerization domain (DD) of the PrrB histidine kinase appear to play an important role in conferring the recognition specificity for the PrrA response regulator on the DD. The catalytic ATP-binding domain of the histidine kinase, which functions as the catalytic unit for the phosphotransfer reaction from ATP to the conserved histidine residue in the DD, also appears to contribute to the enhancement of the recognition specificity conferred by the DD. It was also revealed that replacement of Asp-63 and Lys-113 of the PrrA response regulator by alanine abolished protein-protein interactions between PrrA and its cognate histidine kinase PrrB, whereas mutations of Asp-19, Asp-20 and Thr-87 to alanine did not affect protein-protein interactions, indicating that among the active site residues of PrrA, Asp-63 and Lys-113 are important not only in the function of PrrA but also for protein-protein interactions between PrrA and PrrB.
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Affiliation(s)
- Jin-Sook Seok
- Department of Microbiology, Pusan National University, 609-735 Busan, South Korea
| | - Samuel Kaplan
- Department of Microbiology and Molecular Genetics, The University of Texas Health Science Center Medical School, 6431 Fannin, Houston, TX 77030, USA
| | - Jeong-Il Oh
- Department of Microbiology, Pusan National University, 609-735 Busan, South Korea
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Laguri C, Stenzel RA, Donohue TJ, Phillips-Jones MK, Williamson MP. Activation of the global gene regulator PrrA (RegA) from Rhodobacter sphaeroides. Biochemistry 2006; 45:7872-81. [PMID: 16784239 PMCID: PMC2517121 DOI: 10.1021/bi060683g] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PrrA is a global transcription regulator activated upon phosphorylation by its cognate kinase PrrB in response to low oxygen levels in Rhodobacter sphaeroides. Here we show by gel filtration, analytical ultracentrifugation, and NMR diffusion measurements that treatment of PrrA with a phosphate analogue, BeF(3)(-), results in dimerization of the protein, producing a protein that binds DNA. No dimeric species was observed in the absence of BeF(3)(-). Upon addition of BeF(3)(-), the inhibitory activity of the N-terminal domain on the C-terminal DNA-binding domain is relieved, after which PrrA becomes capable of binding DNA as a dimer. The interaction surface of the DNA-binding domain with the regulatory domain of PrrA is identified by NMR as being a well-conserved region centered on helix alpha6, which is on the face opposite from the DNA recognition helix. This suggests that there is no direct blockage of DNA binding in the inactive state but rather that PrrA dimerization promotes a correct arrangement of two adjacent DNA-binding domains that recognizes specific DNA binding sequences.
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Affiliation(s)
- Cédric Laguri
- Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Western Bank, UK
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Jones DF, Stenzel RA, Donohue TJ. Mutational analysis of the C-terminal domain of the Rhodobacter sphaeroides response regulator PrrA. MICROBIOLOGY-SGM 2006; 151:4103-4110. [PMID: 16339955 PMCID: PMC2800098 DOI: 10.1099/mic.0.28300-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Rhodobacter sphaeroides response regulator PrrA directly activates transcription of genes necessary for energy conservation at low O2 tensions and under anaerobic conditions. It is proposed that PrrA homologues contain a C-terminal DNA-binding domain (PrrA-CTD) that lacks significant amino acid sequence similarity to those found in other response regulators. To test this hypothesis, single amino acid substitutions were created at 12 residues in the PrrA-CTD. These mutant PrrA proteins were purified and tested for the ability to be phosphorylated by the low-molecular-mass phosphate donor acetyl phosphate, to activate transcription and to bind promoter DNA. Each mutant PrrA protein accepted phosphate from 32P-labelled acetyl phosphate. At micromolar concentrations of acetyl phosphate-treated wild-type PrrA, a single 20 bp region in the PrrA-dependent cycA P2 promoter was protected from DNase I digestion. Of the mutant PrrA proteins tested, only acetyl phosphate-treated PrrA-N168A and PrrA-I177A protected cycA P2 from DNase I digestion at similar protein concentrations compared to wild-type PrrA. The use of in vitro transcription assays with the PrrA-dependent cycA P2 and puc promoters showed that acetyl phosphate-treated PrrA-N168A produced transcript levels similar to that of wild-type PrrA at comparable protein concentrations. Using concentrations of acetyl phosphate-treated PrrA that are saturating for the wild-type protein, PrrA-H170A and PrrA-I177A produced <45 % as much transcript as wild-type PrrA. Under identical conditions, the remaining mutant PrrA proteins produced little or no detectable transcripts from either promoter in vitro. Explanations are presented for why these amino acid side chains in the PrrA-CTD are important for its ability to activate transcription.
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Affiliation(s)
- Denise F Jones
- Department of Bacteriology, University of Wisconsin-Madison, Room 390B, 420 Henry Mall, Madison, WI 53706, USA
| | - Rachelle A Stenzel
- Department of Bacteriology, University of Wisconsin-Madison, Room 390B, 420 Henry Mall, Madison, WI 53706, USA
| | - Timothy J Donohue
- Department of Bacteriology, University of Wisconsin-Madison, Room 390B, 420 Henry Mall, Madison, WI 53706, USA
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Swem LR, Gong X, Yu CA, Bauer CE. Identification of a ubiquinone-binding site that affects autophosphorylation of the sensor kinase RegB. J Biol Chem 2006; 281:6768-75. [PMID: 16407278 PMCID: PMC2776112 DOI: 10.1074/jbc.m509687200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rhodobacter capsulatus regulates many metabolic processes in response to the level of environmental oxygen and the energy state of the cell. One of the key global redox regulators of the cell's metabolic physiology is the sensor kinase RegB that controls the synthesis of numerous energy generation and utilization processes. In this study, we have succeeded in purifying full-length RegB containing six transmembrane-spanning elements. Exogenous addition of excess oxidized coenzyme Q1 is capable of inhibiting RegB autophosphorylation approximately 6-fold. However, the addition of reduced coenzyme Q1 exhibits no inhibitory effect on kinase activity. A ubiquinone-binding site, as defined by azidoquinone photo affinity cross-linking, was determined to lie within a periplasmic loop between transmembrane helices 3 and 4 that contains a fully conserved heptapeptide sequence of GGXXNPF. Mutation of the phenylalanine in this heptapeptide renders RegB constitutively active in vivo, indicating that this domain is responsible for sensing the redox state of the ubiquinone pool and subsequently controlling RegB autophosphorylation.
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Affiliation(s)
- Lee R. Swem
- Department of Biology, Indiana University, Bloomington, Indiana 47405
| | - Xing Gong
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078
| | - Chang-An Yu
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, Oklahoma 74078
| | - Carl E. Bauer
- Department of Biology, Indiana University, Bloomington, Indiana 47405
- To whom correspondence should be addressed. Tel.: 812-855-6595; Fax: 812-856-4178;
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Wei JR, Tsai YH, Soo PC, Horng YT, Hsieh SC, Ho SW, Lai HC. Biochemical characterization of RssA-RssB, a two-component signal transduction system regulating swarming behavior in Serratia marcescens. J Bacteriol 2005; 187:5683-90. [PMID: 16077114 PMCID: PMC1196059 DOI: 10.1128/jb.187.16.5683-5690.2005] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Our previous study had identified a pair of potential two-component signal transduction proteins, RssA-RssB, involved in the regulation of Serratia marcescens swarming. When mutated, both rssA and rssB mutants showed precocious swarming phenotypes on LB swarming agar, whereby swarming not only occurred at 37 degrees C but also initiated on a surface of higher agar concentration and more rapidly than did the parent strain at 30 degrees C. In this study, we further show that the predicted sensor kinase RssA and the response regulator RssB bear characteristics of components of the phosphorelay signaling system. In vitro phosphorylation and site-directed mutagenesis assays showed that phosphorylated RssA transfers the phosphate group to RssB and that histidine 248 and aspartate 51 are essential amino acid residues involved in the phosphotransfer reactions in RssA and RssB, respectively. Accordingly, while wild-type rssA could, the mutated rssA(H248A) in trans could not complement the precocious swarming phenotype of the rssA mutant. Although RssA-RssB regulates expressions of shlA and ygfF of S. marcescens (ygfF(Sm)), in vitro DNA-binding assays showed that the phosphorylated RssB did not bind directly to the promoter regions of these two genes but bound to its own rssB promoter. Subsequent assays located the RssB binding site within a 63-bp rssB promoter DNA region and confirmed a direct negative autoregulation of the RssA-RssB signaling pathway. These results suggest that when activated, RssA-RssB acts as a negative regulator for controlling the initiation of S. marcescens swarming.
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Affiliation(s)
- Jun-Rong Wei
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University College of Medicine, No. 1. Chang-Der Street, Taipei 100, Taiwan, Republic of China
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Kovács AT, Rákhely G, Balogh J, Maróti G, Fülöp A, Kovács KL. Anaerobic regulation of hydrogenase transcription in different bacteria. Biochem Soc Trans 2005; 33:36-8. [PMID: 15667258 DOI: 10.1042/bst0330036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Hydrogen metabolism is closely related to other important metabolic and energetic processes of bacterial cells, such as photosynthesis, anaerobic respiration and sulphur metabolism. Even small environmental changes influence these networks through different regulatory systems. The presence or absence of oxygen is one of the most important signals; how the cascades evolved to transmit this signal in different bacteria is summarized. In many instances, hydrogen is released only under anoxic conditions, because of bioenergetic considerations. Most [NiFe] hydrogenases are inactivated by oxygen, but many of them can be re-activated under reducing conditions. In addition to direct inactivation of the hydrogenases, oxygen can also regulate their expression. The global regulatory systems [FNR (fumarate and nitrate reduction regulator), ArcAB (aerobic respiratory control) and RegAB], which respond to alterations in oxygen content and redox conditions of the environment, have an important role in hydrogenase regulation of several bacteria. FNR-like proteins were shown to be important for the regulation of hydrogenases in Escherichia coli, Thiocapsa roseopersicina and Rhizobium leguminosarum, whereas RegA protein modulates the expression of hupSL genes in Rhodobacter capsulatus.
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Affiliation(s)
- A T Kovács
- Institute of Biophysics, Biological Research Center, Hungarian Academy of Sciences and Department of Biotechnology, University of Szeged, H-6726 Szeged, Temesvári krt. 62, Hungary
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Dubbs P, Dubbs JM, Tabita FR. Effector-mediated interaction of CbbRI and CbbRII regulators with target sequences in Rhodobacter capsulatus. J Bacteriol 2004; 186:8026-35. [PMID: 15547275 PMCID: PMC529060 DOI: 10.1128/jb.186.23.8026-8035.2004] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Rhodobacter capsulatus, genes encoding enzymes of the Calvin-Benson-Bassham reductive pentose phosphate pathway are located in the cbb(I) and cbb(II) operons. Each operon contains a divergently transcribed LysR-type transcriptional activator (CbbR(I) and CbbR(II)) that regulates the expression of its cognate cbb promoter in response to an as yet unidentified effector molecule(s). Both CbbR(I) and CbbR(II) were purified, and the ability of a variety of potential effector molecules to induce changes in their DNA binding properties at their target promoters was assessed. The responses of CbbR(I) and CbbR(II) to potential effectors were not identical. In gel mobility shift assays, the affinity of both CbbR(I) and CbbR(II) for their target promoters was enhanced in the presence of ribulose-1,5-bisphosphate (RuBP), phosphoenolpyruvate, 3-phosphoglycerate, 2-phosphoglycolate. ATP, 2-phosphoglycerate, and KH(2)PO(4) were found to enhance only CbbR(I) binding, while fructose-1,6-bisphosphate enhanced the binding of only CbbR(II). The DNase I footprint of CbbR(I) was reduced in the presence of RuBP, while reductions in the CbbR(II) DNase I footprint were induced by fructose-1,6-bisphosphate, 3-phosphoglycerate, and KH(2)PO(4). The current in vitro results plus recent in vivo studies suggest that CbbR-mediated regulation of cbb transcription is controlled by multiple metabolic signals in R. capsulatus. This control reflects not only intracellular levels of Calvin-Benson-Bassham cycle metabolic intermediates but also the fixed (organic) carbon status and energy charge of the cell.
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Affiliation(s)
- Padungsri Dubbs
- Department of Microbiology, Mahidol University, Payathai, Thailand
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Dubbs JM, Tabita FR. Regulators of nonsulfur purple phototrophic bacteria and the interactive control of CO2 assimilation, nitrogen fixation, hydrogen metabolism and energy generation. FEMS Microbiol Rev 2004; 28:353-76. [PMID: 15449608 DOI: 10.1016/j.femsre.2004.01.002] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
For the metabolically diverse nonsulfur purple phototrophic bacteria, maintaining redox homeostasis requires balancing the activities of energy supplying and energy-utilizing pathways, often in the face of drastic changes in environmental conditions. These organisms, members of the class Alphaproteobacteria, primarily use CO2 as an electron sink to achieve redox homeostasis. After noting the consequences of inactivating the capacity for CO2 reduction through the Calvin-Benson-Bassham (CBB) pathway, it was shown that the molecular control of many additional important biological processes catalyzed by nonsulfur purple bacteria is linked to expression of the CBB genes. Several regulator proteins are involved, with the two component Reg/Prr regulatory system playing a major role in maintaining redox poise in these organisms. Reg/Prr was shown to be a global regulator involved in the coordinate control of a number of metabolic processes including CO2 assimilation, nitrogen fixation, hydrogen metabolism and energy-generation pathways. Accumulating evidence suggests that the Reg/Prr system senses the oxidation/reduction state of the cell by monitoring a signal associated with electron transport. The response regulator RegA/PrrA activates or represses gene expression through direct interaction with target gene promoters where it often works in concert with other regulators that can be either global or specific. For the key CO2 reduction pathway, which clearly triggers whether other redox balancing mechanisms are employed, the ability to activate or inactivate the specific regulator CbbR is of paramount importance. From these studies, it is apparent that a detailed understanding of how diverse regulatory elements integrate and control metabolism will eventually be achieved.
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Affiliation(s)
- James M Dubbs
- Laboratory of Biotechnology, Chulabhorn Research Institute, Lak Si, Bangkok 10210, Thailand
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Elsen S, Swem LR, Swem DL, Bauer CE. RegB/RegA, a highly conserved redox-responding global two-component regulatory system. Microbiol Mol Biol Rev 2004; 68:263-79. [PMID: 15187184 PMCID: PMC419920 DOI: 10.1128/mmbr.68.2.263-279.2004] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Reg regulon from Rhodobacter capsulatus and Rhodobacter sphaeroides encodes proteins involved in numerous energy-generating and energy-utilizing processes such as photosynthesis, carbon fixation, nitrogen fixation, hydrogen utilization, aerobic and anaerobic respiration, denitrification, electron transport, and aerotaxis. The redox signal that is detected by the membrane-bound sensor kinase, RegB, appears to originate from the aerobic respiratory chain, given that mutations in cytochrome c oxidase result in constitutive RegB autophosphorylation. Regulation of RegB autophosphorylation also involves a redox-active cysteine that is present in the cytosolic region of RegB. Both phosphorylated and unphosphorylated forms of the cognate response regulator RegA are capable of activating or repressing a variety of genes in the regulon. Highly conserved homologues of RegB and RegA have been found in a wide number of photosynthetic and nonphotosynthetic bacteria, with evidence suggesting that RegB/RegA plays a fundamental role in the transcription of redox-regulated genes in many bacterial species.
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Affiliation(s)
- Sylvie Elsen
- Laboratoire de Biochimie et de Biophysique des Systèmes Intégrés (UMR 5092 CNRS-CEA-UJF), Grenoble, France
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35
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Fenner BJ, Tiwari RP, Reeve WG, Dilworth MJ, Glenn AR. Sinorhizobium medicaegenes whose regulation involves the ActS and/or ActR signal transduction proteins. FEMS Microbiol Lett 2004. [DOI: 10.1111/j.1574-6968.2004.tb09622.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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Swem LR, Kraft BJ, Swem DL, Setterdahl AT, Masuda S, Knaff DB, Zaleski JM, Bauer CE. Signal transduction by the global regulator RegB is mediated by a redox-active cysteine. EMBO J 2003; 22:4699-708. [PMID: 12970182 PMCID: PMC212728 DOI: 10.1093/emboj/cdg461] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
All living organisms alter their physiology in response to changes in oxygen tension. The photosynthetic bacterium uses the RegB-RegA signal transduction cascade to control a wide variety of oxygen-responding processes such as respiration, photosynthesis, carbon fixation and nitrogen fixation. We demonstrate that a highly conserved cysteine has a role in controlling the activity of the sensor kinase, RegB. In vitro studies indicate that exposure of RegB to oxidizing conditions results in the formation of an intermolecular disulfide bond and that disulfide bond formation is metal-dependent, with the metal fulfilling a structural role. Formation of a disulfide bond in vitro is also shown to convert the kinase from an active dimer into an inactive tetramer state. Mutational analysis indicates that a cysteine residue flanked by cationic amino acids is involved in redox sensing in vitro and in vivo. These residues appear to constitute a novel 'redox-box' that is present in sensor kinases from diverse species of bacteria.
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Affiliation(s)
- Lee R Swem
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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37
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Dubbs JM, Tabita FR. Interactions of the cbbII promoter-operator region with CbbR and RegA (PrrA) regulators indicate distinct mechanisms to control expression of the two cbb operons of Rhodobacter sphaeroides. J Biol Chem 2003; 278:16443-50. [PMID: 12601011 DOI: 10.1074/jbc.m211267200] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In a previous study (Dubbs, J. M., Bird, T. H., Bauer, C. E., and Tabita, F. R. (2000) J. Biol. Chem. 275, 19224-19230), it was demonstrated that the regulators CbbR and RegA (PrrA) interacted with both promoter proximal and promoter distal regions of the form I (cbb(I)) promoter operon specifying genes of the Calvin-Benson-Bassham cycle of Rhodobacter sphaeroides. To determine how these regulators interact with the form II (cbb(II)) promoter, three cbbF(II)::lacZ translational fusion plasmids were constructed containing various lengths of sequence 5' to the cbb(II) operon of R. sphaeroides CAC. Expression of beta-galactosidase was monitored under a variety of growth conditions in both the parental strain and knock-out strains that contain mutations that affect synthesis of CbbR and RegA. The binding sites for both CbbR and RegA were determined by DNase I footprinting. A region of the cbb(II) promoter from +38 to -227 bp contained a CbbR binding site and conferred low level regulated cbb(II) expression. The region from -227 to -1025 bp contained six RegA binding sites and conferred enhanced cbb(II) expression under all growth conditions. Unlike the cbb(I) operon, the region between -227 and -545 bp that contains one RegA binding site, was responsible for the majority of the observed enhancement. Both RegA and CbbR were required for maximal cbb(II) expression. Two potentially novel and specific cbb(II) promoter-binding proteins that did not interact with the cbb(I) promoter region were detected in crude extracts of R. sphaeroides. These results, combined with the observation that chemoautotrophic expression of the cbb(I) operon is RegA independent, indicated that the mechanisms controlling cbb(I) and cbb(II) operon expression during chemoautotrophic growth are quite different.
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Affiliation(s)
- James M Dubbs
- Department of Microbiology, Plant Molecular Biology/Biotechnology Program, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210-1292, USA
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Carmany DO, Hollingsworth K, McCleary WR. Genetic and biochemical studies of phosphatase activity of PhoR. J Bacteriol 2003; 185:1112-5. [PMID: 12533489 PMCID: PMC142828 DOI: 10.1128/jb.185.3.1112-1115.2003] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Escherichia coli, PhoR is the histidine kinase of the phosphate regulon. It has been postulated that PhoR may function as a phospho-PhoB phosphatase. Experiments with four precise phoR deletion mutants supported this hypothesis and suggested that this activity resides within the histidine phosphorylation domain. This biochemical activity was confirmed by using a separately expressed histidine phosphorylation domain.
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Affiliation(s)
- Daniel O Carmany
- Microbiology and Molecular Biology Department, Brigham Young University, Provo, UT 84602-5253, 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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40
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Romagnoli S, Packer HL, Armitage JP. Tactic responses to oxygen in the phototrophic bacterium Rhodobacter sphaeroides WS8N. J Bacteriol 2002; 184:5590-8. [PMID: 12270816 PMCID: PMC139605 DOI: 10.1128/jb.184.20.5590-5598.2002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The temporal and spatial behavior of a number of mutants of the photosynthetic, facultative anaerobe Rhodobacter sphaeroides to both step changes and to gradients of oxygen was analyzed. Wild-type cells, grown under a range of conditions, showed microaerophilic behavior, accumulating in a 1.3-mm band about 1.3 mm from the meniscus of capillaries. Evidence suggests this is the result of two signaling pathways. The strength of any response depended on the growth and incubation conditions. Deletion of either the complete chemosensory operons 1 and 2 plus the response regulator genes cheY(4) and cheY(5) or cheA(2) alone led to the loss of all aerotactic responses, although the cells still swam normally. The Prr system of R. sphaeroides responds to electron flow through the alternative high-affinity cytochrome oxidase, cbb(3), controlling expression of a wide range of metabolic pathways. Mutants with deletions of either the complete Prr operon or the histidine kinase, PrrB, accumulated up to the meniscus but still formed a thick band 1.3 mm from the aerobic interface. This indicates that the negative aerotactic response to high oxygen levels depends on PrrB, but the mutant cells still retain the positive response. Tethered PrrB(-) cells also showed no response to a step-down in oxygen concentration, although those with deletions of the whole operon showed some response. In gradients of oxygen where the concentration was reduced at 0.4 micro M/s, tethered wild-type cells showed two different phases of response, with an increase in stopping frequency when the oxygen concentration fell from 80 to 50% dissolved oxygen and a decrease in stopping at 50 to 20% dissolved oxygen, with cells returning to their normal stopping frequency in 0% oxygen. PrrB and CheA(2) mutants showed no response, while PrrCBA mutants still showed some response.
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Affiliation(s)
- Simona Romagnoli
- Microbiology Unit, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
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41
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Janausch IG, Garcia-Moreno I, Unden G. Function of DcuS from Escherichia coli as a fumarate-stimulated histidine protein kinase in vitro. J Biol Chem 2002; 277:39809-14. [PMID: 12167640 DOI: 10.1074/jbc.m204482200] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The two-component regulatory system DcuSR of Escherichia coli controls the expression of genes of C(4)-dicarboxylate metabolism in response to extracellular C(4)- dicarboxylates such as fumarate or succinate. DcuS is a membrane-integral sensor kinase, and the sensory and kinase domains are located on opposite sides of the cytoplasmic membrane. The intact DcuS protein (His(6)-DcuS) was overproduced and isolated in detergent containing buffer. His(6)-DcuS was reconstituted into liposomes made from E. coli phospholipids. Reconstituted His(6)-DcuS catalyzed, in contrast to the detergent-solubilized sensor, autophosphorylation by [gamma-(33)P]ATP with an approximate K(D) of 0.16 mm for ATP. Up to 7% of the reconstituted DcuS was phosphorylated. Phosphorylation was stimulated up to 5.9-fold by C(4)-dicarboxylates, but not by other carboxylates. The phosphoryl group of DcuS was rapidly transferred to the response regulator DcuR. Upon phosphorylation, DcuR bound specifically to dcuB promoter DNA. The reconstituted DcuSR system therefore represents a defined in vitro system, which is capable of the complete transmembrane signal transduction by the DcuSR two-component system from the stimulus (fumarate) to the DNA, including signal transfer across the phospholipid membrane.
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Affiliation(s)
- Ingo G Janausch
- Institut für Mikrobiologie und Weinforschung, Johannes Gutenberg-Universität Mainz, Becherweg 15, 55099 Mainz, Germany
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42
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Potter CA, Ward A, Laguri C, Williamson MP, Henderson PJF, Phillips-Jones MK. Expression, purification and characterisation of full-length histidine protein kinase RegB from Rhodobacter sphaeroides. J Mol Biol 2002; 320:201-13. [PMID: 12079379 DOI: 10.1016/s0022-2836(02)00424-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The global redox switch between aerobic and anaerobic growth in Rhodobacter sphaeroides is controlled by the RegA/RegB two-component system, in which RegB is the integral membrane histidine protein kinase, and RegA is the cytosolic response regulator. Despite the global regulatory importance of this system and its many homologues, there have been no reported examples to date of heterologous expression of full-length RegB or any histidine protein kinases. Here, we report the amplified expression of full-length functional His-tagged RegB in Escherichia coli, its purification, and characterisation of its properties. Both the membrane-bound and purified solubilised RegB protein demonstrate autophosphorylation activity, and the purified protein autophosphorylates at the same rate under both aerobic and anaerobic conditions confirming that an additional regulator is required to control/inhibit autophosphorylation. The intact protein has similar activity to previously characterised soluble forms, but is dephosphorylated more rapidly than the soluble form (half-life ca 30 minutes) demonstrating that the transmembrane segment present in the full-length RegB may be an important regulator of RegB activity. Phosphotransfer from RegB to RegA (overexpressed and purified from E. coli) by RegB is very rapid, as has been reported for the soluble domain. Dephosphorylation of active RegA by full-length RegB has a rate similar to that observed previously for soluble RegB.
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Affiliation(s)
- Christopher A Potter
- Division of Microbiology, School of Biochemistry and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
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Comolli JC, Carl AJ, Hall C, Donohue T. Transcriptional activation of the Rhodobacter sphaeroides cytochrome c(2) gene P2 promoter by the response regulator PrrA. J Bacteriol 2002; 184:390-9. [PMID: 11751815 PMCID: PMC139555 DOI: 10.1128/jb.184.2.390-399.2002] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Anoxygenic photosynthetic growth of Rhodobacter sphaeroides, a member of the alpha subclass of the class Proteobacteria, requires the response regulator PrrA. PrrA and the sensor kinase PrrB are part of a two-component signaling pathway that influences a wide range of processes under oxygen-limited conditions. In this work we characterized the pathway of transcription activation by PrrB and PrrA by purifying these proteins, analyzing them in vitro, and characterizing a mutant PrrA protein in vivo and in vitro. When purified, a soluble transmitter domain of PrrB (cPrrB) could autophosphorylate, rapidly transfer phosphate to PrrA, and stimulate dephosphorylation of phospho-PrrA. Unphosphorylated PrrA activated transcription from a target cytochrome c(2) gene (cycA) promoter, P2, which contained sequences from -73 to +22 relative to the transcription initiation site. However, phosphorylation of PrrA increased its activity since activation of cycA P2 was enhanced up to 15-fold by treatment with the low-molecular-weight phosphodonor acetyl phosphate. A mutant PrrA protein containing a single amino acid substitution in the presumed phosphoacceptor site (PrrA-D63A) was not phosphorylated in vitro but also was not able to stimulate cycA P2 transcription. PrrA-D63A also had no apparent in vivo activity, demonstrating that aspartate 63 is necessary both for the function of PrrA and for its phosphorylation-dependent activation. The cellular level of wild-type PrrA was negatively autoregulated so that less PrrA was present in the absence of oxygen, conditions in which the activities of many PrrA target genes increase. PrrA-D63A failed to repress expression of the prrA gene under anaerobic conditions, suggesting that this single amino acid change also eliminated PrrA function in vivo.
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Affiliation(s)
- James C Comolli
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Oh JI, Ko IJ, Kaplan S. The default state of the membrane-localized histidine kinase PrrB of Rhodobacter sphaeroides 2.4.1 is in the kinase-positive mode. J Bacteriol 2001; 183:6807-14. [PMID: 11698369 PMCID: PMC95521 DOI: 10.1128/jb.183.23.6807-6814.2001] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The PrrBA two-component activation system of Rhodobacter sphaeroides plays a major role in the induction of photosynthesis gene expression under oxygen-limiting or anaerobic conditions. The PrrB histidine kinase is composed of two structurally identifiable regions, the conserved C-terminal kinase/phosphatase domain and the N-terminal membrane-spanning domain with six transmembrane helices framing three periplasmic and two cytoplasmic loops. Using a set of PrrB mutants with lesions in the transmembrane domain, we demonstrate that the central portion of the PrrB transmembrane domain including the second periplasmic loop plays an important role in both sensing and signal transduction. Signal transduction via the transmembrane domain is ultimately manifested by controlling the activity of the C-terminal kinase/phosphatase domain. The extent of signal transduction is determined by the ability of the transmembrane domain to sense the strength of the inhibitory signal received from the cbb(3) terminal oxidase (J.-I Oh, and S. Kaplan, EMBO J. 19:4237-4247, 2000). Therefore, the intrinsic ("default") state of PrrB is in the kinase-dominant mode. It is also demonstrated that the extent of prrB gene expression is subject to the negative autoregulation of the PrrBA system.
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Affiliation(s)
- J I Oh
- Department of Microbiology and Molecular Genetics, Medical School, The University of Texas Health Science Center, 6431 Fannin, Houston, TX 77030, USA
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Swem LR, Elsen S, Bird TH, Swem DL, Koch HG, Myllykallio H, Daldal F, Bauer CE. The RegB/RegA two-component regulatory system controls synthesis of photosynthesis and respiratory electron transfer components in Rhodobacter capsulatus. J Mol Biol 2001; 309:121-38. [PMID: 11491283 DOI: 10.1006/jmbi.2001.4652] [Citation(s) in RCA: 92] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Recently, we demonstrated that the RegB/RegA two-component regulatory system from Rhodobacter capsulatus functions as a global regulator of metabolic processes that either generate or consume reducing equivalents. For example, the RegB/RegA system controls expression of such energy generating processes as photosynthesis and hydrogen utilization. In addition, RegB/RegA also control nitrogen and carbon fixation pathways that utilize reducing equivalents. Here, we use a combination of DNase I protection and plasmid-based reporter expression studies to demonstrate that RegA directly controls synthesis of cytochrome cbb3 and ubiquinol oxidases that function as terminal electron acceptors in a branched respiratory chain. We also demonstrate that RegA controls expression of cytochromes c2, c(y) and the cytochrome bc1 complex that are involved in both photosynthetic and respiratory electron transfer events. These data provide evidence that the RegB/RegA two-component system has a major role in controlling the synthesis of numerous processes that affect reducing equivalents in Rhodobacter capsulatus.
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Affiliation(s)
- L R Swem
- Department of Biology, Indiana University, Bloomington 47405, USA
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46
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Li H, Sherman LA. A redox-responsive regulator of photosynthesis gene expression in the cyanobacterium Synechocystis sp. Strain PCC 6803. J Bacteriol 2000; 182:4268-77. [PMID: 10894737 PMCID: PMC101939 DOI: 10.1128/jb.182.15.4268-4277.2000] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have identified genes in the unicellular cyanobacterium Synechocystis sp. strain PCC 6803 that are involved with redox control of photosynthesis and pigment-related genes. The genes, rppA (sll0797) and rppB (sll0798), represent a two-component regulatory system that controls the synthesis of photosystem II (PSII) and PSI genes, in addition to photopigment-related genes. rppA (regulator of photosynthesis- and photopigment-related gene expression) and rppB exhibit strong sequence similarity to prokaryotic response regulators and histidine kinases, respectively. In the wild type, the steady-state mRNA levels of PSII reaction center genes increased when the plastoquinone (PQ) pool was oxidized and decreased when the PQ pool was reduced, whereas transcription of the PSI reaction center genes was affected in an opposite fashion. Such results suggested that the redox poise of the PQ pool is critical for regulation of the photosystem reaction center genes. In Delta rppA, an insertion mutation of rppA, the PSII gene transcripts were highly up-regulated relative to the wild type under all redox conditions, whereas transcription of phycobilisome-related genes and PSI genes was decreased. The higher transcription of the psbA gene in Delta rppA was manifest by higher translation of the D1 protein and a concomitant increase in O(2) evolution. The results demonstrated that RppA is a regulator of photosynthesis- and photopigment-related gene expression, is involved in the establishment of the appropriate stoichiometry between the photosystems, and can sense changes in the PQ redox poise.
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Affiliation(s)
- H Li
- Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47907, USA
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47
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Vichivanives P, Bird TH, Bauer CE, Robert Tabita F. Multiple regulators and their interactions in vivo and in vitro with the cbb regulons of Rhodobacter capsulatus. J Mol Biol 2000; 300:1079-99. [PMID: 10903856 DOI: 10.1006/jmbi.2000.3914] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The cbb(I) and cbb(II) operons encode structural genes which are important for carbon dioxide fixation via the Calvin-Benson-Bassham reductive pentose phosphate pathway in Rhodobacter capsulatus. Each operon is regulated by cognate LysR-type transcriptional activators, CbbR(I) and CbbR(II), with the product of the cbbR(I) gene, CbbR(I), able to control its own transcription under some growth conditions. Furthermore, CbbR(I) may at least partially regulate the cbb(II) operon, with significant, yet regulated transcription of the cbb(II) operon occurring in the absence of any CbbR. These results suggested the importance of additional regulators. Thus, in addition to the rather specific control exerted by CbbR, a more globally significant regulatory system, the RegA-RegB (PrrA-PrrB) two-component system, was found to contribute to transcriptional regulation of each cbb operon. The regA and regB mutant strains were found to contain constitutive levels of form I and form II RubisCO, the major proteins encoded by the cbb(I) and cbb(II) operons, respectively. In addition, DNaseI footprint analyses indicated that RegA*, a constitutively active mutant form of RegA, binds specifically to cbb(I) and cbb(II) promoter-operator regions. CbbR(I), CbbR(II), and RegA binding loci were localized relative to transcription start sites, leading to a coherent picture of how each of these regulators interacts with specific promoter-operator sequences of the cbb operons.
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Affiliation(s)
- P Vichivanives
- Department of Microbiology and Plant Biotechnology Center, The Ohio State University, 484 West 12th Avenue, Columbus, OH 43210-1292, USA
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48
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Dubbs JM, Bird TH, Bauer CE, Tabita FR. Interaction of CbbR and RegA* transcription regulators with the Rhodobacter sphaeroides cbbIPromoter-operator region. J Biol Chem 2000; 275:19224-30. [PMID: 10748066 DOI: 10.1074/jbc.m002125200] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The form I (cbb(I)) Calvin-Benson-Bassham (CBB) reductive pentose phosphate cycle operon of Rhodobacter sphaeroides is regulated by both the transcriptional activator CbbR and the RegA/PrrA (RegB/PrrB) two-component signal transduction system. DNase I footprint analyses indicated that R. sphaeroides CbbR binds to the cbb(I) promoter between -10 and -70 base pairs (bp) relative to the cbb(I) transcription start. A cosmid carrying the R. capsulatus reg locus was capable of complementing an R. sphaeroides regA-deficient mutant to phototrophic growth with restored regulated synthesis of both photopigments and ribulose-bisphosphate carboxylase/oxygenase (Rubisco). DNase I footprint analyses, using R. capsulatus RegA*, a constitutively active mutant version of RegA, detected four RegA* binding sites within the cbb(I) promoter. Two sites were found within a previously identified cbb(I) promoter proximal regulatory region from -61 to -110 bp. One of these proximal RegA* binding sites overlapped that of CbbR. Two sites were within a previously identified promoter distal positive regulatory region between -301 and -415 bp. Expression from promoter insertion mutants showed that the function of the promoter distal regulatory region was helical phase-dependent. These results indicated that RegA exerts its regulatory affect on cbb(I) expression through direct interaction with the cbb(I) promoter.
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Affiliation(s)
- J M Dubbs
- Department of Microbiology and Plant Biotechnology Center, The Ohio State University, Columbus, Ohio 43210-1292, USA
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Elsen S, Dischert W, Colbeau A, Bauer CE. Expression of uptake hydrogenase and molybdenum nitrogenase in Rhodobacter capsulatus is coregulated by the RegB-RegA two-component regulatory system. J Bacteriol 2000; 182:2831-7. [PMID: 10781552 PMCID: PMC101992 DOI: 10.1128/jb.182.10.2831-2837.2000] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Purple photosynthetic bacteria are capable of generating cellular energy from several sources, including photosynthesis, respiration, and H(2) oxidation. Under nutrient-limiting conditions, cellular energy can be used to assimilate carbon and nitrogen. This study provides the first evidence of a molecular link for the coregulation of nitrogenase and hydrogenase biosynthesis in an anoxygenic photosynthetic bacterium. We demonstrated that molybdenum nitrogenase biosynthesis is under the control of the RegB-RegA two-component regulatory system in Rhodobacter capsulatus. Footprint analyses and in vivo transcription studies showed that RegA indirectly activates nitrogenase synthesis by binding to and activating the expression of nifA2, which encodes one of the two functional copies of the nif-specific transcriptional activator, NifA. Expression of nifA2 but not nifA1 is reduced in the reg mutants up to eightfold under derepressing conditions and is also reduced under repressing conditions. Thus, although NtrC is absolutely required for nifA2 expression, RegA acts as a coactivator of nifA2. We also demonstrated that in reg mutants, [NiFe]hydrogenase synthesis and activity are increased up to sixfold. RegA binds to the promoter of the hydrogenase gene operon and therefore directly represses its expression. Thus, the RegB-RegA system controls such diverse processes as energy-generating photosynthesis and H(2) oxidation, as well as the energy-demanding processes of N(2) fixation and CO(2) assimilation.
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Affiliation(s)
- S Elsen
- Department of Biology, Indiana University, Bloomington, Indiana 47405, USA
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Abstract
This review discusses various mechanisms that regulatory proteins use to control gene expression in response to alterations in redox. The transcription factor SoxR contains stable [2Fe-2S] centers that promote transcription activation when oxidized. FNR contains [4Fe-4S] centers that disassemble under oxidizing conditions, which affects DNA-binding activity. FixL is a histidine sensor kinase that utilizes heme as a cofactor to bind oxygen, which affects its autophosphorylation activity. NifL is a flavoprotein that contains FAD as a redox responsive cofactor. Under oxidizing conditions, NifL binds and inactivates NifA, the transcriptional activator of the nitrogen fixation genes. OxyR is a transcription factor that responds to redox by breaking or forming disulfide bonds that affect its DNA-binding activity. The ability of the histidine sensor kinase ArcB to promote phosphorylation of the response regulator ArcA is affected by multiple factors such as anaerobic metabolites and the redox state of the membrane. The global regulator of anaerobic gene expression in alpha-purple proteobacteria, RegB, appears to directly monitor respiratory activity of cytochrome oxidase. The aerobic repressor of photopigment synthesis, CrtJ, seems to contain a redox responsive cysteine. Finally, oxygen-sensitive rhizobial NifA proteins presumably bind a metal cofactor that senses redox. The functional variability of these regulatory proteins demonstrates that prokaryotes apply many different mechanisms to sense and respond to alterations in redox.
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Affiliation(s)
- C E Bauer
- Department of Biology, Indiana University, Bloomington 47405, USA
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