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Bennett MR, Jain A, Kovacs K, Hill PJ, Alexander C, Rawson FJ. Engineering bacteria to control electron transport altering the synthesis of non-native polymer. RSC Adv 2021; 12:451-457. [PMID: 35424487 PMCID: PMC8978702 DOI: 10.1039/d1ra06403g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Accepted: 12/03/2021] [Indexed: 11/21/2022] Open
Abstract
The use of bacteria as catalysts for radical polymerisations of synthetic monomers has recently been established. However, the role of trans Plasma Membrane Electron Transport (tPMET) in modulating these processes is not well understood. We sort to study this by genetic engineering a part of the tPMET system NapC in E. coli. We show that this engineering altered the rate of extracellular electron transfer coincided with an effect on cell-mediated polymerisation using a model monomer. A plasmid with arabinose inducible PBAD promoters were shown to upregulate NapC protein upon induction at total arabinose concentrations of 0.0018% and 0.18%. These clones (E. coli(IP_0.0018%) and E. coli(IP_0.18%), respectively) were used in iron-mediated atom transfer radical polymerisation (Fe ATRP), affecting the nature of the polymerisation, than cultures containing suppressed or empty plasmids (E. coli(IP_S) and E. coli(E), respectively). These results lead to the hypothesis that EET (Extracellular Electron Transfer) in part modulates cell instructed polymerisations. The use of bacteria as catalysts for radical polymerisations of synthetic monomers has recently been established.![]()
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Affiliation(s)
- Mechelle R Bennett
- Division of Regenerative Medicine and Cellular Therapies, Biodiscovery Institute, School of Pharmacy, University of Nottingham University Park Nottingham NG7 2RD UK
| | - Akhil Jain
- Division of Regenerative Medicine and Cellular Therapies, Biodiscovery Institute, School of Pharmacy, University of Nottingham University Park Nottingham NG7 2RD UK .,Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham University Park, Nottingham NG7 2RD UK
| | - Katalin Kovacs
- Synthetic Biology Research Centre, School of Life Sciences, University of Nottingham University Park, Nottingham NG7 2RD UK
| | - Phil J Hill
- Division of Microbiology, Brewing and Biotechnology, School of Bioscience, University of Nottingham Sutton Bonington Campus Nottingham LE15 5RD UK
| | - Cameron Alexander
- Division of Molecular Therapeutics and Formulation, Boots Science Building, School of Pharmacy, University of Nottingham University Park Nottingham NG7 2RD UK
| | - Frankie J Rawson
- Division of Regenerative Medicine and Cellular Therapies, Biodiscovery Institute, School of Pharmacy, University of Nottingham University Park Nottingham NG7 2RD UK
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Dietrich HM, Edel M, Bursac T, Meier M, Sturm-Richter K, Gescher J. Soluble versions of outer membrane cytochromes function as exporters for heterologously produced cargo proteins. Microb Cell Fact 2019; 18:216. [PMID: 31870378 PMCID: PMC6929479 DOI: 10.1186/s12934-019-1270-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2019] [Accepted: 12/13/2019] [Indexed: 11/13/2022] Open
Abstract
This study reveals that it is possible to secrete truncated versions of outer membrane cytochromes into the culture supernatant and that these proteins can provide a basis for the export of heterologously produced proteins. Different soluble and truncated versions of the outer membrane cytochrome MtrF were analyzed for their suitability to be secreted. A protein version with a very short truncation of the N-terminus to remove the recognition sequence for the addition of a lipid anchor is secreted efficiently to the culture supernatant, and moreover this protein could be further truncated by a deletion of 160 amino acid and still is detectable in the supernatant. By coupling a cellulase to this soluble outer membrane cytochrome, the export efficiency was measured by means of relative cellulase activity. We conclude that outer membrane cytochromes of S. oneidensis can be applied as transporters for the export of target proteins into the medium using the type II secretion pathway.
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Affiliation(s)
- Helge M Dietrich
- Department of Molecular Microbiology and Bioenergetics, Goethe University, Frankfurt, Germany
| | - Miriam Edel
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Thea Bursac
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Manfred Meier
- Institute for Biological Interfaces, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany
| | - Katrin Sturm-Richter
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Johannes Gescher
- Department of Applied Biology, Institute for Applied Biosciences, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.
- Institute for Biological Interfaces, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany.
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Paquete CM, Rusconi G, Silva AV, Soares R, Louro RO. A brief survey of the "cytochromome". Adv Microb Physiol 2019; 75:69-135. [PMID: 31655743 DOI: 10.1016/bs.ampbs.2019.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Multihaem cytochromes c are widespread in nature where they perform numerous roles in diverse anaerobic metabolic pathways. This is achieved in two ways: multihaem cytochromes c display a remarkable diversity of ways to organize multiple hemes within the protein frame; and the hemes possess an intrinsic reactive versatility derived from diverse spin, redox and coordination states. Here we provide a brief survey of multihaem cytochromes c that have been characterized in the context of their metabolic role. The contribution of multihaem cytochromes c to dissimilatory pathways handling metallic minerals, nitrogen compounds, sulfur compounds, organic compounds and phototrophism are described. This aims to set the stage for the further exploration of the vast unknown "cytochromome" that can be anticipated from genomic databases.
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Yu X, Jiang Y, Huang H, Shi J, Wu K, Zhang P, Lv J, Li H, He H, Liu P, Li X. Simultaneous aerobic denitrification and Cr(VI) reduction by Pseudomonas brassicacearum LZ-4 in wastewater. BIORESOURCE TECHNOLOGY 2016; 221:121-129. [PMID: 27639231 DOI: 10.1016/j.biortech.2016.09.037] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 09/07/2016] [Accepted: 09/08/2016] [Indexed: 06/06/2023]
Abstract
Inorganic nitrogen and heavy metals pervasively co-exist in industrial and domestic wastewaters. In this work, Pseudomonas brassicacearum LZ-4 was tested for the simultaneous reduction of Cr(VI) and nitrate. Nitrate was found to be the best inorganic nitrogen source for strain LZ-4, and could promote Cr(VI) reduction. Cr(VI) had a low degree of inhibition on denitrification, and even 50mgL-1 Cr(VI) did not inhibit reduction of 100mgL-1 NO3--N. The capability of simultaneous reduction of Cr(VI) and nitrate was illustrated by the reductase genes contained in the LZ-4 genome. Application in a batch membrane bioreactor showed that the immobilized strain LZ-4 could remove over 95% of 500mgL-1 NO3--N, 80% of 10mgL-1 Cr(VI), and 96% of 5000mgL-1 COD in each batch of 46days. In summary, the strain LZ-4 is an ideal candidate for remediation of co-contaminants.
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Affiliation(s)
- Xuan Yu
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Tianshuinanlu #222, Lanzhou, Gansu 730000, PR China; Gansu Academy of Membrane Science and Technology, Duanjiatanlu #1272, Lanzhou, Gansu 730020, PR China; School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, Jiangsu 221116, PR China
| | - Yiming Jiang
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Tianshuinanlu #222, Lanzhou, Gansu 730000, PR China
| | - Haiying Huang
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Tianshuinanlu #222, Lanzhou, Gansu 730000, PR China
| | - Juanjuan Shi
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Tianshuinanlu #222, Lanzhou, Gansu 730000, PR China
| | - Kejia Wu
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Tianshuinanlu #222, Lanzhou, Gansu 730000, PR China
| | - Pengyun Zhang
- Gansu Academy of Membrane Science and Technology, Duanjiatanlu #1272, Lanzhou, Gansu 730020, PR China
| | - Jianguo Lv
- Gansu Academy of Membrane Science and Technology, Duanjiatanlu #1272, Lanzhou, Gansu 730020, PR China
| | - Hongli Li
- PetroChina Lanzhou Petrochemical Company, Yumenjie #10, Lanzhou, Gansu 730060, PR China
| | - Huan He
- School of Chemical Engineering and Technology, China University of Mining and Technology, Xuzhou, Jiangsu 221116, PR China
| | - Pu Liu
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Tianshuinanlu #222, Lanzhou, Gansu 730000, PR China
| | - Xiangkai Li
- Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Science, Lanzhou University, Tianshuinanlu #222, Lanzhou, Gansu 730000, PR China.
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Abstract
Nitrate reduction to ammonia via nitrite occurs widely as an anabolic process through which bacteria, archaea, and plants can assimilate nitrate into cellular biomass. Escherichia coli and related enteric bacteria can couple the eight-electron reduction of nitrate to ammonium to growth by coupling the nitrate and nitrite reductases involved to energy-conserving respiratory electron transport systems. In global terms, the respiratory reduction of nitrate to ammonium dominates nitrate and nitrite reduction in many electron-rich environments such as anoxic marine sediments and sulfide-rich thermal vents, the human gastrointestinal tract, and the bodies of warm-blooded animals. This review reviews the regulation and enzymology of this process in E. coli and, where relevant detail is available, also in Salmonella and draws comparisons with and implications for the process in other bacteria where it is pertinent to do so. Fatty acids may be present in high levels in many of the natural environments of E. coli and Salmonella in which oxygen is limited but nitrate is available to support respiration. In E. coli, nitrate reduction in the periplasm involves the products of two seven-gene operons, napFDAGHBC, encoding the periplasmic nitrate reductase, and nrfABCDEFG, encoding the periplasmic nitrite reductase. No bacterium has yet been shown to couple a periplasmic nitrate reductase solely to the cytoplasmic nitrite reductase NirB. The cytoplasmic pathway for nitrate reduction to ammonia is restricted almost exclusively to a few groups of facultative anaerobic bacteria that encounter high concentrations of environmental nitrate.
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Sparacino-Watkins C, Stolz JF, Basu P. Nitrate and periplasmic nitrate reductases. Chem Soc Rev 2014; 43:676-706. [PMID: 24141308 DOI: 10.1039/c3cs60249d] [Citation(s) in RCA: 184] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The nitrate anion is a simple, abundant and relatively stable species, yet plays a significant role in global cycling of nitrogen, global climate change, and human health. Although it has been known for quite some time that nitrate is an important species environmentally, recent studies have identified potential medical applications. In this respect the nitrate anion remains an enigmatic species that promises to offer exciting science in years to come. Many bacteria readily reduce nitrate to nitrite via nitrate reductases. Classified into three distinct types--periplasmic nitrate reductase (Nap), respiratory nitrate reductase (Nar) and assimilatory nitrate reductase (Nas), they are defined by their cellular location, operon organization and active site structure. Of these, Nap proteins are the focus of this review. Despite similarities in the catalytic and spectroscopic properties Nap from different Proteobacteria are phylogenetically distinct. This review has two major sections: in the first section, nitrate in the nitrogen cycle and human health, taxonomy of nitrate reductases, assimilatory and dissimilatory nitrate reduction, cellular locations of nitrate reductases, structural and redox chemistry are discussed. The second section focuses on the features of periplasmic nitrate reductase where the catalytic subunit of the Nap and its kinetic properties, auxiliary Nap proteins, operon structure and phylogenetic relationships are discussed.
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Gonzalez PJ, Rivas MG, Mota CS, Brondino CD, Moura I, Moura JJ. Periplasmic nitrate reductases and formate dehydrogenases: Biological control of the chemical properties of Mo and W for fine tuning of reactivity, substrate specificity and metabolic role. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2012.05.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Characterization of axial and proximal histidine mutations of the decaheme cytochrome MtrA from Shewanella sp. strain ANA-3 and implications for the electron transport system. J Bacteriol 2012; 194:5840-7. [PMID: 22923588 DOI: 10.1128/jb.00890-12] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Extracellular respiration of solid-phase electron acceptors in some microorganisms requires a complex chain of multiheme c-type cytochromes that span the inner and outer membranes. In Shewanella species, MtrA, an ~35-kDa periplasmic decaheme c-type cytochrome, is an essential component for extracellular respiration of iron(III). The exact mechanism of electron transport has not yet been resolved, but the arrangement of the polypeptide chain may have a strong influence on the capability of the MtrA cytochrome to transport electrons. The iron hemes of MtrA are bound to its polypeptide chain via proximal (CXXCH) and distal histidine residues. In this study, we show the effects of mutating histidine residues of MtrA to arginine on protein expression and extracellular respiration using Shewanella sp. strain ANA-3 as a model organism. Individual mutations to six out of nine proximal histidines in CXXCH of MtrA led to decreased protein expression. However, distal histidine mutations resulted in various degrees of protein expression. In addition, the effects of histidine mutations on extracellular respiration were tested using ferrihydrite and current production in microbial fuel cells. These results show that proximal histidine mutants were unable to reduce ferrihydrite. Mutations to the distal histidine residues resulted in various degrees of ferrihydrite reduction. These findings indicate that mutations to the proximal histidine residues affect MtrA expression, leading to loss of extracellular respiration ability. In contrast, mutations to the distal histidine residues are less detrimental to protein expression, and extracellular respiration can proceed.
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Simon J, Klotz MG. Diversity and evolution of bioenergetic systems involved in microbial nitrogen compound transformations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1827:114-35. [PMID: 22842521 DOI: 10.1016/j.bbabio.2012.07.005] [Citation(s) in RCA: 210] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 07/10/2012] [Accepted: 07/19/2012] [Indexed: 11/18/2022]
Abstract
Nitrogen is an essential element of life that needs to be assimilated in its most reduced form, ammonium. On the other hand, nitrogen exists in a multitude of oxidation states and, consequently, nitrogen compounds (NCs) serve as electron donor and/or acceptors in many catabolic pathways including various forms of microbial respiration that contribute to the global biogeochemical nitrogen cycle. Some of these NCs are also known as reactive nitrogen species able to cause nitrosative stress because of their high redox reactivity. The best understood processes of the nitrogen cycle are denitrification and ammonification (both beginning with nitrate reduction to nitrite), nitrification (aerobic oxidation of ammonium and nitrite) and anaerobic ammonium oxidation (anammox). This review presents examples of the diverse architecture, either elucidated or anticipated, and the high degree of modularity of the corresponding respiratory electron transport processes found in Bacteria and Archaea, and relates these to their respective bioenergetic mechanisms of proton motive force generation. In contrast to the multiplicity of enzymes that catalyze NC transformations, the number of proteins or protein modules involved in connecting electron transport to and from these enzymes with the quinone/quinol pool is comparatively small. These quinone/quinol-reactive protein modules consist of cytochromes b and c and iron-sulfur proteins. Conclusions are drawn towards the evolutionary relationships of bioenergetic systems involved in NC transformation and deduced aspects of the evolution of the biogeochemical nitrogen cycle are presented. This article is part of a Special Issue entitled: The evolutionary aspects of bioenergetic systems.
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Affiliation(s)
- Jörg Simon
- Microbial Energy Conversion and Biotechnology, Department of Biology, Technische Universität Darmstadt, Schnittspahnstr. 10, 64287 Darmstadt, Germany.
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10
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Marritt SJ, Lowe TG, Bye J, McMillan DGG, Shi L, Fredrickson J, Zachara J, Richardson DJ, Cheesman MR, Jeuken LJC, Butt JN. A functional description of CymA, an electron-transfer hub supporting anaerobic respiratory flexibility in Shewanella. Biochem J 2012; 444:465-74. [PMID: 22458729 DOI: 10.1042/bj20120197] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2023]
Abstract
CymA (tetrahaem cytochrome c) is a member of the NapC/NirT family of quinol dehydrogenases. Essential for the anaerobic respiratory flexibility of shewanellae, CymA transfers electrons from menaquinol to various dedicated systems for the reduction of terminal electron acceptors including fumarate and insoluble minerals of Fe(III). Spectroscopic characterization of CymA from Shewanella oneidensis strain MR-1 identifies three low-spin His/His co-ordinated c-haems and a single high-spin c-haem with His/H(2)O co-ordination lying adjacent to the quinol-binding site. At pH 7, binding of the menaquinol analogue, 2-heptyl-4-hydroxyquinoline-N-oxide, does not alter the mid-point potentials of the high-spin (approximately -240 mV) and low-spin (approximately -110, -190 and -265 mV) haems that appear biased to transfer electrons from the high- to low-spin centres following quinol oxidation. CymA is reduced with menadiol (E(m) = -80 mV) in the presence of NADH (E(m) = -320 mV) and an NADH-menadione (2-methyl-1,4-naphthoquinone) oxidoreductase, but not by menadiol alone. In cytoplasmic membranes reduction of CymA may then require the thermodynamic driving force from NADH, formate or H2 oxidation as the redox poise of the menaquinol pool in isolation is insufficient. Spectroscopic studies suggest that CymA requires a non-haem co-factor for quinol oxidation and that the reduced enzyme forms a 1:1 complex with its redox partner Fcc3 (flavocytochrome c3 fumarate reductase). The implications for CymA supporting the respiratory flexibility of shewanellae are discussed.
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Affiliation(s)
- Sophie J Marritt
- Centre for Molecular and Structural Biochemistry, School of Chemistry and School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K
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Bueno E, Mesa S, Bedmar EJ, Richardson DJ, Delgado MJ. Bacterial adaptation of respiration from oxic to microoxic and anoxic conditions: redox control. Antioxid Redox Signal 2012; 16:819-52. [PMID: 22098259 PMCID: PMC3283443 DOI: 10.1089/ars.2011.4051] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Revised: 11/16/2011] [Accepted: 11/18/2011] [Indexed: 12/22/2022]
Abstract
Under a shortage of oxygen, bacterial growth can be faced mainly by two ATP-generating mechanisms: (i) by synthesis of specific high-affinity terminal oxidases that allow bacteria to use traces of oxygen or (ii) by utilizing other substrates as final electron acceptors such as nitrate, which can be reduced to dinitrogen gas through denitrification or to ammonium. This bacterial respiratory shift from oxic to microoxic and anoxic conditions requires a regulatory strategy which ensures that cells can sense and respond to changes in oxygen tension and to the availability of other electron acceptors. Bacteria can sense oxygen by direct interaction of this molecule with a membrane protein receptor (e.g., FixL) or by interaction with a cytoplasmic transcriptional factor (e.g., Fnr). A third type of oxygen perception is based on sensing changes in redox state of molecules within the cell. Redox-responsive regulatory systems (e.g., ArcBA, RegBA/PrrBA, RoxSR, RegSR, ActSR, ResDE, and Rex) integrate the response to multiple signals (e.g., ubiquinone, menaquinone, redox active cysteine, electron transport to terminal oxidases, and NAD/NADH) and activate or repress target genes to coordinate the adaptation of bacterial respiration from oxic to anoxic conditions. Here, we provide a compilation of the current knowledge about proteins and regulatory networks involved in the redox control of the respiratory adaptation of different bacterial species to microxic and anoxic environments.
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Affiliation(s)
- Emilio Bueno
- Estación Experimental del Zaidín, CSIC, Granada, Spain
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Magalon A, Fedor JG, Walburger A, Weiner JH. Molybdenum enzymes in bacteria and their maturation. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2010.12.031] [Citation(s) in RCA: 87] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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Kim HJ, Zatsman A, Upadhyay AK, Whittaker M, Bergmann D, Hendrich MP, Hooper AB. Membrane tetraheme cytochrome c(m552) of the ammonia-oxidizing nitrosomonas europaea: a ubiquinone reductase. Biochemistry 2010; 47:6539-51. [PMID: 18505274 DOI: 10.1021/bi8001264] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome c(m552) (cyt c(m552)) from the ammonia-oxidizing Nitrosomonas europaea is encoded by the cycB gene, which is preceded in a gene cluster by three genes encoding proteins involved in the oxidation of hydroxylamine: hao, hydroxylamine oxidoreductase; orf2, a putative membrane protein; cycA, cyt c(554). By amino acid sequence alignment of the core tetraheme domain, cyt c(m552) belongs to the NapC/TorC family of tetra- or pentaheme cytochrome c species involved in electron transport from membrane quinols to a variety of periplasmic electron shuttles leading to terminal reductases. However, cyt c(m552) is thought to reduce quinone with electrons originating from HAO. In this work, the tetrahemic 27 kDa cyt c(m552) from N. europaea was purified after extraction from membranes using Triton X-100 with subsequent exchange into n-dodecyl beta-d-maltoside. The cytochrome had a propensity to form strong SDS-resistant dimers likely mediated by a conserved GXXXG motif present in the putative transmembrane segment. Optical spectra of the ferric protein contained a broad ligand-metal charge transfer band at approximately 625 nm indicative of a high-spin heme. Mossbauer spectroscopy of the reduced (57)Fe-enriched protein revealed the presence of high-spin and low-spin hemes in a 1:3 ratio. Multimode EPR spectroscopy of the native state showed signals from an electronically interacting high-spin/low-spin pair of hemes. Upon partial reduction, a typical high-spin heme EPR signal was observed. No EPR signals were observed from the other two low-spin hemes, indicating an electronic interaction between these hemes as well. UV-vis absorption data indicate that CO (ferrous enzyme) or CN(-) (ferric or ferrous enzyme) bound to more than one and possibly all hemes. Other anionic ligands did not bind. The four ferrous hemes of the cytochrome were rapidly oxidized in the presence of oxygen. Comparative modeling, based on the crystal structure and conserved residues of the homologous NrfH protein from Desulfovibrio of cyt c(m552), predicted some structural elements, including a Met-ligated high-spin heme in a quinone-binding pocket, and likely axial ligands to all four hemes.
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Affiliation(s)
- Hyung J Kim
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, St. Paul, Minnesota 55106, USA
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14
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Simpson PJL, Richardson DJ, Codd R. The periplasmic nitrate reductase in Shewanella: the resolution, distribution and functional implications of two NAP isoforms, NapEDABC and NapDAGHB. MICROBIOLOGY-SGM 2009; 156:302-312. [PMID: 19959582 DOI: 10.1099/mic.0.034421-0] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In the bacterial periplasm, the reduction of nitrate to nitrite is catalysed by a periplasmic nitrate reductase (NAP) system, which is a species-dependent assembly of protein subunits encoded by the nap operon. The reduction of nitrate catalysed by NAP takes place in the 90 kDa NapA subunit, which contains a Mo-bis-molybdopterin guanine dinucleotide cofactor and one [4Fe-4S] iron-sulfur cluster. A review of the nap operons in the genomes of 19 strains of Shewanella shows that most genomes contain two nap operons. This is an unusual feature of this genus. The two NAP isoforms each comprise three isoform-specific subunits - NapA, a di-haem cytochrome NapB, and a maturation chaperone NapD - but have different membrane-intrinsic subunits, and have been named NAP-alpha (NapEDABC) and NAP-beta (NapDAGHB). Sixteen Shewanella genomes encode both NAP-alpha and NAP-beta. The genome of the vigorous denitrifier Shewanella denitrificans OS217 encodes only NAP-alpha and the genome of the respiratory nitrate ammonifier Shewanella oneidensis MR-1 encodes only NAP-beta. This raises the possibility that NAP-alpha and NAP-beta are associated with physiologically distinct processes in the environmentally adaptable genus Shewanella.
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Affiliation(s)
- Philippa J L Simpson
- Centre for Heavy Metals Research, School of Chemistry, University of Sydney, New South Wales 2006, Australia
| | - David J Richardson
- School of Biological Sciences, University of East Anglia, Norwich NR4 TJ7, UK
| | - Rachel Codd
- School of Medical Sciences (Pharmacology) and Bosch Institute, University of Sydney, New South Wales 2006, Australia.,Centre for Heavy Metals Research, School of Chemistry, University of Sydney, New South Wales 2006, Australia
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Zajicek RS, Bali S, Arnold S, Brindley AA, Warren MJ, Ferguson SJ. d(1) haem biogenesis - assessing the roles of three nir gene products. FEBS J 2009; 276:6399-411. [PMID: 19796169 DOI: 10.1111/j.1742-4658.2009.07354.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The synthesis of the modified tetrapyrrole known as d(1) haem requires several dedicated proteins which are coded for by a set of genes that are often found adjacent to the structural gene, nirS, for cytochrome cd(1) nitrite reductase. NirE, the product of the first gene in the nir biogenesis operon, was anticipated to catalyse the conversion of uroporphyrinogen III into precorrin-2; this was confirmed, but it was shown that this enzyme is less sensitive to product inhibition than similar enzymes that function in other biosynthetic pathways. Sequence analysis suggesting that one of these proteins, NirN, is a c-type cytochrome, and has similarity to the part of cytochrome cd(1) that binds d(1), was validated by recombinant production and characterization of NirN. A NirN-d(1) haem complex was demonstrated to release the cofactor to a semi-apo form of cytochrome cd(1) from which d(1) was extracted, suggesting a role for NirN in the assembly of cytochrome cd(1) (NirS). However, inactivation of nirN surprisingly led to only a marginal attenuation of growth of Paracoccus pantotrophus under anaerobic denitrifying conditions. As predicted, NirC is a c-type cytochrome; it was shown in vitro to be an electron donor to the NirN-d(1) complex.
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16
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Quinone-reactive proteins devoid of haem b form widespread membrane-bound electron transport modules in bacterial respiration. Biochem Soc Trans 2008; 36:1011-6. [DOI: 10.1042/bst0361011] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Many quinone-reactive enzyme complexes that are part of membrane-integral eukaryotic or prokaryotic respiratory electron transport chains contain one or more haem b molecules embedded in the membrane. In recent years, various novel proteins have emerged that are devoid of haem b but are thought to fulfil a similar function in bacterial anaerobic respiratory systems. These proteins are encoded by genes organized in various genomic arrangements and are thought to form widespread membrane-bound quinone-reactive electron transport modules that exchange electrons with redox partner proteins located at the outer side of the cytoplasmic membrane. Prototypic representatives are the multihaem c-type cytochromes NapC, NrfH and TorC (NapC/NrfH family), the putative iron–sulfur protein NapH and representatives of the NrfD/PsrC family. Members of these protein families vary in the number of their predicted transmembrane segments and, consequently, diverse quinone-binding sites are expected. Only a few of these enzymes have been isolated and characterized biochemically and high-resolution structures are limited. This mini-review briefly summarizes predicted and experimentally demonstrated properties of the proteins in question and discusses their role in electron transport and bioenergetics of anaerobic respiration.
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Variants of the tetrahaem cytochrome c quinol dehydrogenase NrfH characterize the menaquinol-binding site, the haem c-binding motifs and the transmembrane segment. Biochem J 2008; 414:73-9. [DOI: 10.1042/bj20080475] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Members of the NapC/NrfH family are multihaem c-type cytochromes that exchange electrons with oxidoreductases situated at the outside of the cytoplasmic membrane or in the periplasmic space of many proteobacteria. They form a group of membrane-bound quinol dehydrogenases that are essential components of several electron transport chains, for example those of periplasmic nitrate respiration and respiratory nitrite ammonification. Knowledge of the structure–function relationships of NapC/NrfH proteins is scarce and only one high-resolution structure (Desulfovibrio vulgaris NrfH) is available. In the present study, several Wolinella succinogenes mutants that produce variants of NrfH, the membrane anchor of the cytochrome c nitrite reductase complex, were constructed and characterized in order to improve the understanding of the putative menaquinol-binding site, the maturation and function of the four covalently bound haem c groups and the importance of the N-terminal transmembrane segment. Based on amino acid sequence alignments, a homology model for W. succinogenes NrfH was constructed that underlines the overall conservation of tertiary structure in spite of a low sequence homology. The results support the proposed architecture of the menaquinol-binding site in D. vulgaris NrfH, demonstrate that each histidine residue arranged in one of the four CX2CH haem c-binding motifs is essential for NrfH maturation in W. succinogenes, and indicate a limited flexibility towards the length and structure of the transmembrane region.
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Martinez-Espinosa RM, Dridge EJ, Bonete MJ, Butt JN, Butler CS, Sargent F, Richardson DJ. Look on the positive side! The orientation, identification and bioenergetics of 'Archaeal' membrane-bound nitrate reductases. FEMS Microbiol Lett 2007; 276:129-39. [PMID: 17888006 DOI: 10.1111/j.1574-6968.2007.00887.x] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Many species of Bacteria and Archaea respire nitrate using a molybdenum-dependent membrane-bound respiratory system called Nar. Classically, the 'Bacterial' Nar system is oriented such that nitrate reduction takes place on the inside of this membrane. However, the active site subunit of the 'Archaeal' Nar systems has a twin arginine ('RR') motif, which is a suggestion of translocation to the outside of the cytoplasmic membrane. These 'Archaeal' type of nitrate reductases are part of a group of molybdoenzymes with an 'RR' motif that are predicted to have an aspartate ligand to the molybdenum ion. This group includes selenate reductases and possible sequence signatures are described that serve to distinguish the Nar nitrate reductases from the selenate reductases. The 'RR' sequences of nitrate reductases of Archaea and some that have recently emerged in Bacteria are also considered and it is concluded that there is good evidence for there being both Archaeal and Bacterial examples of Nar-type nitrate reductases with an active site on the outside of the cytoplasmic membrane. Finally, the bioenergetic consequences of nitrate reduction on the outside of the cytoplasmic membrane have been explored.
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Dementin S, Arnoux P, Frangioni B, Grosse S, Léger C, Burlat B, Guigliarelli B, Sabaty M, Pignol D. Access to the Active Site of Periplasmic Nitrate Reductase: Insights from Site-Directed Mutagenesis and Zinc Inhibition Studies. Biochemistry 2007; 46:9713-21. [PMID: 17676770 DOI: 10.1021/bi700928m] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The periplasmic nitrate reductase (NapAB), a member of the DMSO reductase superfamily, catalyzes the first step of the denitrification process in bacteria. In this heterodimer, a di-heme NapB subunit is associated to the catalytic NapA subunit that binds a [4Fe-4S] cluster and a bis(molybdopterin guanine dinucleotide) cofactor. Here, we report the kinetic characterization of purified mutated heterodimers from Rhodobacter sphaeroides. By combining site-directed mutagenesis, redox potentiometry, EPR spectroscopy, and enzymatic characterization, we investigate the catalytic role of two conserved residues (M153 and R392) located in the vicinity of the molybdenum active site. We demonstrate that M153 and R392 are involved in nitrate binding: the Vm measured on the M153A and R392A mutants are similar to that measured on the wild-type enzyme, whereas the Km for nitrate is increased 10-fold and 200-fold, respectively. The use of an alternative enzymatic assay led us to discover that NapAB is uncompetitively inhibited by Zn2+ ions (Ki' = 1 microM). We used this property to further probe the active site access in the mutant enzymes. It is proposed that R392 acts as a filter by preventing a direct reduction of the Mo atom by small reducing molecules and partially protecting the active site against zinc inhibition. In addition, we show that M153 is a key residue mediating this inhibition likely by coordinating Zn2+ ions via its sulfur atom. This residue is not conserved in the DMSO reductase superfamily while it is conserved in the periplasmic nitrate reductase family. Zinc inhibition is therefore likely to be specific and restricted to periplasmic nitrate reductases.
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Affiliation(s)
- Sébastien Dementin
- Laboratoire de Bioénergétique Cellulaire, CEA/Cadarache, DSV/IBEB/SBVME, 13108 St Paul lez Durance Cedex, France.
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20
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Murphy JN, Saltikov CW. The cymA gene, encoding a tetraheme c-type cytochrome, is required for arsenate respiration in Shewanella species. J Bacteriol 2007; 189:2283-90. [PMID: 17209025 PMCID: PMC1899399 DOI: 10.1128/jb.01698-06] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In Shewanella sp. strain ANA-3, utilization of arsenate as a terminal electron acceptor is conferred by a two-gene operon, arrAB, which lacks a gene encoding a membrane-anchoring subunit for the soluble ArrAB protein complex. Analysis of the genome sequence of Shewanella putrefaciens strain CN-32 showed that it also contained the same arrAB operon with 100% nucleotide identity. Here, we report that CN-32 respires arsenate and that this metabolism is dependent on arrA and an additional gene encoding a membrane-associated tetraheme c-type cytochrome, cymA. Deletion of cymA in ANA-3 also eliminated growth on and reduction of arsenate. The DeltacymA strains of CN-32 and ANA-3 negatively affected the reduction of Fe(III) and Mn(IV) but not growth on nitrate. Unlike the CN-32 DeltacymA strain, growth on fumarate was absent in the DeltacymA strain of ANA-3. Both homologous and heterologous complementation of cymA in trans restored growth on arsenate in DeltacymA strains of both CN-32 and ANA-3. Transcription patterns of cymA showed that it was induced under anaerobic conditions in the presence of fumarate and arsenate. Nitrate-grown cells exhibited the greatest level of cymA expression in both wild-type strains. Lastly, site-directed mutagenesis of the first Cys to Ser in each of the four CXXCH c-heme binding motifs of the CN-32 CymA nearly eliminated growth on and reduction of arsenate. Together, these results indicate that the biochemical mechanism of arsenate respiration and reduction requires the interactions of ArrAB with a membrane-associated tetraheme cytochrome, which in the non-arsenate-respiring Shewanella species Shewanella oneidensis strain MR-1, has pleiotropic effects on Fe(III), Mn(IV), dimethyl sulfoxide, nitrate, nitrite, and fumarate respiration.
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Affiliation(s)
- Julie N Murphy
- Department of Environmental Toxicology, University of California, Santa Cruz, Santa Cruz, CA 95064, USA
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21
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Rodrigues ML, Oliveira TF, Pereira IAC, Archer M. X-ray structure of the membrane-bound cytochrome c quinol dehydrogenase NrfH reveals novel haem coordination. EMBO J 2006; 25:5951-60. [PMID: 17139260 PMCID: PMC1698886 DOI: 10.1038/sj.emboj.7601439] [Citation(s) in RCA: 127] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2006] [Accepted: 10/10/2006] [Indexed: 11/09/2022] Open
Abstract
Oxidation of membrane-bound quinol molecules is a central step in the respiratory electron transport chains used by biological cells to generate ATP by oxidative phosphorylation. A novel family of cytochrome c quinol dehydrogenases that play an important role in bacterial respiratory chains was recognised in recent years. Here, we describe the first structure of a cytochrome from this family, NrfH from Desulfovibrio vulgaris, which forms a stable complex with its electron partner, the cytochrome c nitrite reductase NrfA. One NrfH molecule interacts with one NrfA dimer in an asymmetrical manner, forming a large membrane-bound complex with an overall alpha(4)beta(2) quaternary arrangement. The menaquinol-interacting NrfH haem is pentacoordinated, bound by a methionine from the CXXCHXM sequence, with an aspartate residue occupying the distal position. The NrfH haem that transfers electrons to NrfA has a lysine residue from the closest NrfA molecule as distal ligand. A likely menaquinol binding site, containing several conserved and essential residues, is identified.
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Affiliation(s)
- Maria Luisa Rodrigues
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Oeiras, Portugal
| | - Tânia F Oliveira
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Oeiras, Portugal
| | - Inês A C Pereira
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Oeiras, Portugal
| | - Margarida Archer
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Oeiras, Portugal
- Membrane Protein Crystallography, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Apt. 127, Av. Republica, EAN, Oeiras 2780-157, Portugal. Tel.: +351 214469762; Fax: +351 21433644; E-mail:
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22
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Rodrigues ML, Oliveira T, Matias PM, Martins IC, Valente FMA, Pereira IAC, Archer M. Crystallization and preliminary structure determination of the membrane-bound complex cytochrome c nitrite reductase from Desulfovibrio vulgaris Hildenborough. Acta Crystallogr Sect F Struct Biol Cryst Commun 2006; 62:565-8. [PMID: 16754983 PMCID: PMC2243080 DOI: 10.1107/s1744309106016629] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2006] [Accepted: 05/05/2006] [Indexed: 11/10/2022]
Abstract
The cytochrome c nitrite reductase (cNiR) isolated from Desulfovibrio vulgaris Hildenborough is a membrane-bound complex formed of NrfA and NrfH subunits. The catalytic subunit NrfA is a soluble pentahaem cytochrome c that forms a physiological dimer of about 120 kDa. The electron-donor subunit NrfH is a membrane-anchored tetrahaem cytochrome c of about 18 kDa molecular weight and belongs to the NapC/NirT family of quinol dehydrogenases, for which no structures are known. Crystals of the native cNiR membrane complex, solubilized with dodecylmaltoside detergent (DDM), were obtained using PEG 4K as precipitant. Anomalous diffraction data were measured at the Swiss Light Source to 2.3 A resolution. Crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 79.5, b = 256.7, c = 578.2 A. Molecular-replacement and MAD methods were combined to solve the structure. The data presented reveal that D. vulgaris cNiR contains one NrfH subunit per NrfA dimer.
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Affiliation(s)
- M. L. Rodrigues
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Av. República, Apt. 127, 2781-901 Oeiras, Portugal
| | - T. Oliveira
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Av. República, Apt. 127, 2781-901 Oeiras, Portugal
| | - P. M. Matias
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Av. República, Apt. 127, 2781-901 Oeiras, Portugal
| | - I. C. Martins
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Av. República, Apt. 127, 2781-901 Oeiras, Portugal
| | - F. M. A. Valente
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Av. República, Apt. 127, 2781-901 Oeiras, Portugal
| | - I. A. C. Pereira
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Av. República, Apt. 127, 2781-901 Oeiras, Portugal
| | - M. Archer
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, ITQB-UNL, Av. República, Apt. 127, 2781-901 Oeiras, Portugal
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González PJ, Correia C, Moura I, Brondino CD, Moura JJG. Bacterial nitrate reductases: Molecular and biological aspects of nitrate reduction. J Inorg Biochem 2006; 100:1015-23. [PMID: 16412515 DOI: 10.1016/j.jinorgbio.2005.11.024] [Citation(s) in RCA: 152] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2005] [Revised: 11/10/2005] [Accepted: 11/11/2005] [Indexed: 11/30/2022]
Abstract
Nitrogen is a vital component in living organisms as it participates in the making of essential biomolecules such as proteins, nucleic acids, etc. In the biosphere, nitrogen cycles between the oxidation states +V and -III producing many species that constitute the biogeochemical cycle of nitrogen. All reductive branches of this cycle involve the conversion of nitrate to nitrite, which is catalyzed by the enzyme nitrate reductase. The characterization of nitrate reductases from prokaryotic organisms has allowed us to gain considerable information on the molecular basis of nitrate reduction. Prokaryotic nitrate reductases are mononuclear Mo-containing enzymes sub-grouped as respiratory nitrate reductases, periplasmic nitrate reductases and assimilatory nitrate reductases. We review here the biological and molecular properties of these three enzymes along with their gene organization and expression, which are necessary to understand the biological processes involved in nitrate reduction.
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Affiliation(s)
- P J González
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica, Portugal
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24
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Gross R, Eichler R, Simon J. Site-directed modifications indicate differences in axial haem c iron ligation between the related NrfH and NapC families of multihaem c-type cytochromes. Biochem J 2006; 390:689-93. [PMID: 15907193 PMCID: PMC1199662 DOI: 10.1042/bj20050448] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
During the last decade, a number of related bacterial membrane-bound multihaem c-type cytochromes, collectively referred to as the NapC/NirT family, were identified. These proteins are generally thought to catalyse electron transport between the quinone/quinol pool and periplasmic oxidoreductases. The best-characterized members, the tetrahaem c-type cytochromes NrfH and NapC, mediate electron transport to NrfA and NapA respectively. Amino acid sequence alignments suggest that the nature and position of distal haem c iron ligands differs in NrfH and NapC proteins. Site-directed modification of potential haem c iron-ligating histidine, lysine and methionine residues in Wolinella succinogenes NrfH was performed to determine the implication in electron transport from formate to nitrite. Two histidine, one lysine and one methionine residues were found to be essential, whereas the replacement of three other conserved histidine residues, one methionine and two lysines did not prevent growth by nitrite respiration. The results contrast those previously obtained for Paracoccus pantotrophus NapC, in which four essential histidine residues have been identified that are highly likely to serve as distal haem c iron ligands. The combined experimental evidence suggests different haem ligation patterns within NapC and NrfH proteins, which might reflect their different functions in the bacterial electron transfer.
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Affiliation(s)
- Roland Gross
- *Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität, Marie-Curie-Str. 9, D-60439 Frankfurt am Main, Germany
| | - Robert Eichler
- *Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität, Marie-Curie-Str. 9, D-60439 Frankfurt am Main, Germany
| | - Jörg Simon
- *Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität, Marie-Curie-Str. 9, D-60439 Frankfurt am Main, Germany
- †School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K
- To whom correspondence should be addressed, at School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K. (email or )
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Garman EF, Grime GW. Elemental analysis of proteins by microPIXE. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2005; 89:173-205. [PMID: 15910917 DOI: 10.1016/j.pbiomolbio.2004.09.005] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The identification and quantification of metals bound to proteins is a crucial problem to be solved in structural biology. This paper describes the technique of particle induced X-ray emission with a microfocused beam (microPIXE) as a tool for analysing the elemental composition of liquid and crystalline protein samples. The proton beam induces characteristic X-ray emission from all elements in the protein, which can be interpreted in terms of the metal content of the protein molecule with a relative accuracy of between 10% and 20%. The compelling advantage of this method is that the sulphur atoms in the methionines and cysteines of the protein provide an internal calibration of the number of protein molecules present so that systematic errors are minimised and the technique is entirely internally self-consistent. This is achieved by the simultaneous measurement of the energy of backscattered protons (Rutherford backscattering), to enable us to determine the matrix composition and thickness, and so correct the PIXE data for the self-absorption of X-rays in the sample. The theoretical background to the technique is described, and the technical and experimental procedures are outlined. Examples of recent measurements are given which have informed a range of investigations in structural biology. The use of the technique is increasing and we envisage that future developments will enable it to become a routine high-throughput method.
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Affiliation(s)
- Elspeth F Garman
- Laboratory of Molecular Biophysics, Department of Biochemistry, University of Oxford, Oxford OX1 3QU, UK.
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Marietou A, Richardson D, Cole J, Mohan S. Nitrate reduction byDesulfovibrio desulfuricans: A periplasmic nitrate reductase system that lacks NapB, but includes a unique tetrahemec-type cytochrome, NapM. FEMS Microbiol Lett 2005; 248:217-25. [PMID: 15972253 DOI: 10.1016/j.femsle.2005.05.042] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2005] [Revised: 05/20/2005] [Accepted: 05/20/2005] [Indexed: 11/24/2022] Open
Abstract
Many sulphate reducing bacteria can also reduce nitrite, but relatively few isolates are known to reduce nitrate. Although nitrate reductase genes are absent from Desulfovibrio vulgaris strain Hildenborough, for which the complete genome sequence has been reported, a single subunit periplasmic nitrate reductase, NapA, was purified from Desulfovibrio desulfuricans strain 27774, and the structural gene was cloned and sequenced. Chromosome walking methods have now been used to determine the complete sequence of the nap gene cluster from this organism. The data confirm the absence of a napB homologue, but reveal a novel six-gene organisation, napC-napM-napA-napD-napG-napH. The NapC polypeptide is more similar to the NrfH subgroup of tetraheme cytochromes than to NapC from other bacteria. NapM is predicted to be a tetra-heme c-type cytochrome with similarity to the small tetraheme cytochromes from Shewanella oneidensis. The operon is located close to a gene encoding a lysyl-tRNA synthetase that is also found in D. vulgaris. We suggest that electrons might be transferred to NapA either from menaquinol via NapC, or from other electron donors such as formate or hydrogen via the small tetraheme cytochrome, NapM. We also suggest that, despite the absence of a twin-arginine targeting sequence, NapG might be located in the periplasm where it would provide an alternative direct electron donor to NapA.
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Affiliation(s)
- Angeliki Marietou
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
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Lucana DODO, Schaa T, Schrempf H. The novel extracellular Streptomyces reticuli haem-binding protein HbpS influences the production of the catalase-peroxidase CpeB. MICROBIOLOGY-SGM 2004; 150:2575-2585. [PMID: 15289554 DOI: 10.1099/mic.0.27091-0] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The Gram-positive soil bacterium and cellulose degrader Streptomyces reticuli synthesizes the mycelium-associated enzyme CpeB, which displays haem-dependent catalase and peroxidase activity, as well as haem-independent manganese-peroxidase activity. Downstream of the cpeB gene, a so far unknown gene was identified. The new gene and its mutated derivatives were cloned in Escherichia coli as well as in Streptomyces lividans and a gene-disruption mutant within the chromosome of the original S. reticuli host was constructed, comparative physiological, biochemical and immunological studies then allowed the deduction of the following characteristics of the novel gene product. (i) The protein was found extracellularly; the substitution of twin arginines within the signal peptide abolished its secretion. (ii) The highly purified protein interacted specifically with haem and hence was designated HbpS (haem-binding protein of Streptomyces). (iii) HbpS contained three histidine residues surrounded by hydrophobic amino acids; one of them was located within the motif LX(3)THLX(10)AA, which is related to the motif within the yeast cytochrome c peroxidase LX(2)THLX(10)AA whose histidine residue interacts with haem. (iv) The addition of haemin (Fe(3+) oxidized form of haem) to the Streptomyces cultures led to enhanced levels of HbpS which correlated with increased haemin-resistance. (v) The presence of HbpS increased synthesis of the highly active catalase-peroxidase CpeB containing haem. In this process HbpS could act as a chaperone that binds haem and then delivers it to the mycelium-associated CpeB; HbpS could also interact with membrane-associated proteins involved in a signal transduction cascade regulating the expression of cpeB. (vi) HbpS shared varying degrees of amino acid identities with bacterial proteins of so far unknown function. This report contributes to the elucidation of the biological function of these proteins.
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Affiliation(s)
| | - Tanja Schaa
- Universität Osnabrück, FB Biologie/Chemie, Barbarastraße 11, D-49069 Osnabrück, Germany
| | - Hildgund Schrempf
- Universität Osnabrück, FB Biologie/Chemie, Barbarastraße 11, D-49069 Osnabrück, Germany
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Zajicek RS, Allen JWA, Cartron ML, Richardson DJ, Ferguson SJ. Paracoccus pantotrophusNapC can reductively activate cytochromecd1nitrite reductase. FEBS Lett 2004; 565:48-52. [PMID: 15135051 DOI: 10.1016/j.febslet.2004.03.072] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2004] [Revised: 03/23/2004] [Accepted: 03/25/2004] [Indexed: 11/24/2022]
Abstract
The oxidized "as isolated" form of Paracoccus pantotrophus cytochrome cd1 nitrite reductase has a bis-histidinyl coordinated c heme and a histidine/tyrosine coordinated d1 heme. This form of the enzyme has previously been shown to be kinetically incompetent. Upon reduction, the coordination of both hemes changes and the enzyme is kinetically activated. Here, we show that P. pantotrophus NapC, a tetraheme c-type cytochrome belonging to a large family of such proteins, is capable of reducing, and hence activating, "as isolated" cytochrome cd1. NapC is the first protein from P. pantotrophus identified as being capable of this activation step and, given the periplasmic co-location and co-expression of the two proteins, is a strong candidate to be a physiological activation partner.
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Affiliation(s)
- Richard S Zajicek
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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29
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Arnoux P, Sabaty M, Alric J, Frangioni B, Guigliarelli B, Adriano JM, Pignol D. Structural and redox plasticity in the heterodimeric periplasmic nitrate reductase. Nat Struct Mol Biol 2003; 10:928-34. [PMID: 14528294 DOI: 10.1038/nsb994] [Citation(s) in RCA: 112] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2003] [Accepted: 09/04/2003] [Indexed: 11/09/2022]
Abstract
The structure of the respiratory nitrate reductase (NapAB) from Rhodobacter sphaeroides, the periplasmic heterodimeric enzyme responsible for the first step in the denitrification process, has been determined at a resolution of 3.2 A. The di-heme electron transfer small subunit NapB binds to the large subunit with heme II in close proximity to the [4Fe-4S] cluster of NapA. A total of 57 residues at the N- and C-terminal extremities of NapB adopt an extended conformation, embracing the NapA subunit and largely contributing to the total area of 5,900 A(2) buried in the complex. Complex formation was studied further by measuring the variation of the redox potentials of all the cofactors upon binding. The marked effects observed are interpreted in light of the three-dimensional structure and depict a plasticity that contributes to an efficient electron transfer in the complex from the heme I of NapB to the molybdenum catalytic site of NapA.
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Affiliation(s)
- Pascal Arnoux
- CEA/Cadarache, DSV, DEVM, Laboratoire de Bioénergétique Cellulaire, 13108 St Paul lez Durance Cedex, France.
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Pitts KE, Dobbin PS, Reyes-Ramirez F, Thomson AJ, Richardson DJ, Seward HE. Characterization of the Shewanella oneidensis MR-1 decaheme cytochrome MtrA: expression in Escherichia coli confers the ability to reduce soluble Fe(III) chelates. J Biol Chem 2003; 278:27758-65. [PMID: 12732647 DOI: 10.1074/jbc.m302582200] [Citation(s) in RCA: 174] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Shewanella oneidensis MR-1 has the metabolic capacity to grow anaerobically using Fe(III) as a terminal electron acceptor. Growth under these conditions results in the de novo synthesis of a number of periplasmic c-type cytochromes, many of which are multiheme in nature and are thought to be involved in the Fe(III) respiratory process. To begin a biochemical study of these complex cytochromes, the mtrA gene that encodes an approximate 32-kDa periplasmic decaheme cytochrome has been heterologously expressed in Escherichia coli. Co-expression of mtrA with a plasmid that contains cytochrome c maturation genes leads to the assembly of a correctly targeted holoprotein, which covalently binds ten hemes. The recombinant MtrA protein has been characterized by magnetic circular dichroism, which shows that all ten hemes have bis-histidine axial ligation. EPR spectroscopy detected only eight of these hemes, all of which are low spin and provides evidence for a spin-coupled pair of hemes in the oxidized state. Redox titrations of MtrA have been carried out with optical- and EPR-monitored methods, and the hemes are shown to reduce over the potential range -100 to -400 mV. In intact cells of E. coli, MtrA is shown to obtain electrons from the host electron transport chain and pass these onto host oxidoreductases or a range of soluble Fe(III) species. This demonstrates the promiscuous nature of this decaheme cytochrome and its potential to serve as a soluble Fe(III) reductase in intact cells.
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Affiliation(s)
- Katy E Pitts
- Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences and School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ, United Kingdom
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Simon J, Sänger M, Schuster SC, Gross R. Electron transport to periplasmic nitrate reductase (NapA) of Wolinella succinogenes is independent of a NapC protein. Mol Microbiol 2003; 49:69-79. [PMID: 12823811 DOI: 10.1046/j.1365-2958.2003.03544.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The rumen bacterium Wolinella succinogenes grows by respiratory nitrate ammonification with formate as electron donor. Whereas the enzymology and coupling mechanism of nitrite respiration is well known, nitrate reduction to nitrite has not yet been examined. We report here that intact cells and cell fractions catalyse nitrate and chlorate reduction by reduced viologen dyes with high specific activities. A gene cluster encoding components of a putative periplasmic nitrate reductase system (napA, G, H, B, F, L, D) was sequenced. The napA gene was inactivated by inserting a kanamycin resistance gene cassette. The resulting mutant did not grow by nitrate respiration and did not reduce nitrate during growth by fumarate respiration, in contrast to the wild type. An antigen was detected in wild-type cells using an antiserum raised against the periplasmic nitrate reductase (NapA) from Paracoccus pantotrophus. This antigen was absent in the W. succinogenes napA mutant. It is concluded that the periplasmic nitrate reductase NapA is the only respiratory nitrate reductase in W. succinogenes, although a second nitrate-reducing enzyme is apparently induced in the napA mutant. The nap cluster of W. succinogenes lacks a napC gene whose product is thought to function in quinol oxidation and electron transfer to NapA in other bacteria. The W. succinogenes genome encodes two members of the NapC/NirT family, NrfH and FccC. Characterization of corresponding deletion mutants indicates that neither of these two proteins is required for nitrate respiration. A mutant lacking the genes encoding respiratory nitrite reductase (nrfHA) had wild-type properties with respect to nitrate respiration. A model of the electron transport chain of nitrate respiration is proposed in which one or more of the napF, G, H and L gene products mediate electron transport from menaquinol to the periplasmic NapAB complex. Inspection of the W. succinogenes genome sequence suggests that ammonia formation from nitrate is catalysed exclusively by periplasmic respiratory enzymes.
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Affiliation(s)
- Jörg Simon
- Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität, Marie-Curie-Str. 9, D-60439 Frankfurt am Main, Germany.
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