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Effects of Fe 2+ addition to sugarcane molasses on poly-γ-glutamic acid production in Bacillus licheniformis CGMCC NO. 23967. Microb Cell Fact 2023; 22:37. [PMID: 36829191 PMCID: PMC9960700 DOI: 10.1186/s12934-023-02042-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Accepted: 02/12/2023] [Indexed: 02/26/2023] Open
Abstract
BACKGROUND Poly-γ-glutamic acid (γ-PGA) is biodegradable, water-soluble, environment-friendly, and edible. Consequently, it has a variety of industrial applications. It is crucial to control production cost and increase output for industrial production γ-PGA. RESULTS Here γ-PGA production from sugarcane molasses by Bacillus licheniformis CGMCC NO. 23967 was studied in shake-flasks and bioreactors, the results indicate that the yield of γ-PGA could reach 40.668 g/L in a 5L stirred tank fermenter. Further study found that γ-PGA production reached 70.436 g/L, γ-PGA production and cell growth increased by 73.20% and 55.44%, respectively, after FeSO4·7H2O was added. Therefore, we investigated the metabolomic and transcriptomic changes following FeSO4·7H2O addition. This addition resulted in increased abundance of intracellular metabolites, including amino acids, organic acids, and key TCA cycle intermediates, as well as upregulation of the glycolysis pathway and TCA cycle. CONCLUSIONS These results compare favorably with those obtained from glucose and other forms of biomass feedstock, confirming that sugarcane molasses can be used as an economical substrate without any pretreatment. The addition of FeSO4·7H2O to sugarcane molasses may increase the efficiency of γ-PGA production in intracellular.
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2
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Mathew LG, Haja DK, Pritchett C, McCormick W, Zeineddine R, Fontenot LS, Rivera ME, Glushka J, Adams MWW, Lanzilotta WN. An unprecedented function for a tungsten-containing oxidoreductase. J Biol Inorg Chem 2022; 27:747-758. [PMID: 36269456 DOI: 10.1007/s00775-022-01965-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 09/30/2022] [Indexed: 01/05/2023]
Abstract
Five tungstopterin-containing oxidoreductases were characterized from the hyperthermophile Pyrococcus furiosus. Each enzyme catalyzes the reversible conversion of one or more aldehydes to the corresponding carboxylic acid, but they have different specificities. The physiological functions of only two of these enzymes are known: one, termed GAPOR, is a glycolytic enzyme that oxidizes glyceraldehyde-3-phosphate, while the other, termed AOR, oxidizes multiple aldehydes generated during peptide fermentation. Two of the enzymes have known structures (AOR and FOR). Herein, we focus on WOR5, the fifth tungstopterin enzyme to be discovered in P. furiosus. Expression of WOR5 was previously shown to be increased during cold shock (growth at 72 ℃), although the physiological substrate is not known. To gain insight into WOR5 function, we sought to determine both its structure and identify its intracellular substrate. Crystallization experiments were performed with a concentrated cytoplasmic extract of P. furiosus grown at 72 ℃ and the structure of WOR5 was deduced from the crystals that were obtained. In contrast to a previous report, WOR5 is heterodimeric containing an additional polyferredoxin-like subunit with four [4Fe-4S] clusters. The active site structure of WOR5 is substantially different from that of AOR and FOR and the significant electron density observed adjacent to the tungsten cofactor of WOR5 was modeled as an aliphatic sulfonate. Biochemical assays and product analysis confirmed that WOR5 is an aliphatic sulfonate ferredoxin oxidoreductase (ASOR). A catalytic mechanism for ASOR is proposed based on the structural information and the potential role of ASOR in the cold-shock response is discussed.
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Affiliation(s)
- Liju G Mathew
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Dominik K Haja
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Clayton Pritchett
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Winston McCormick
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Robbie Zeineddine
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Leo S Fontenot
- Department of Chemistry, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - Mario E Rivera
- Department of Chemistry, Louisiana State University, Baton Rouge, LA, 70803, USA
| | - John Glushka
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA.
| | - William N Lanzilotta
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA.
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3
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Ou YF, Dong HP, McIlroy SJ, Crowe SA, Hallam SJ, Han P, Kallmeyer J, Simister RL, Vuillemin A, Leu AO, Liu Z, Zheng YL, Sun QL, Liu M, Tyson GW, Hou LJ. Expanding the phylogenetic distribution of cytochrome b-containing methanogenic archaea sheds light on the evolution of methanogenesis. THE ISME JOURNAL 2022; 16:2373-2387. [PMID: 35810262 PMCID: PMC9478090 DOI: 10.1038/s41396-022-01281-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 06/20/2022] [Accepted: 06/22/2022] [Indexed: 05/28/2023]
Abstract
Methane produced by methanogenic archaea has an important influence on Earth's changing climate. Methanogenic archaea are phylogenetically diverse and widespread in anoxic environments. These microorganisms can be divided into two subgroups based on whether or not they use b-type cytochromes for energy conservation. Methanogens with b-type cytochromes have a wider substrate range and higher growth yields than those without them. To date, methanogens with b-type cytochromes were found exclusively in the phylum "Ca. Halobacteriota" (formerly part of the phylum Euryarchaeota). Here, we present the discovery of metagenome-assembled genomes harboring methyl-coenzyme M reductase genes reconstructed from mesophilic anoxic sediments, together with the previously reported thermophilic "Ca. Methylarchaeum tengchongensis", representing a novel archaeal order, designated the "Ca. Methylarchaeales", of the phylum Thermoproteota (formerly the TACK superphylum). These microorganisms contain genes required for methyl-reducing methanogenesis and the Wood-Ljundahl pathway. Importantly, the genus "Ca. Methanotowutia" of the "Ca. Methylarchaeales" encode a cytochrome b-containing heterodisulfide reductase (HdrDE) and methanophenazine-reducing hydrogenase complex that have similar gene arrangements to those found in methanogenic Methanosarcinales. Our results indicate that members of the "Ca. Methylarchaeales" are methanogens with cytochromes and can conserve energy via membrane-bound electron transport chains. Phylogenetic and amalgamated likelihood estimation analyses indicate that methanogens with cytochrome b-containing electron transfer complexes likely evolved before diversification of Thermoproteota or "Ca. Halobacteriota" in the early Archean Eon. Surveys of public sequence databases suggest that members of the lineage are globally distributed in anoxic sediments and may be important players in the methane cycle.
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Affiliation(s)
- Ya-Fei Ou
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China
| | - Hong-Po Dong
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China.
| | - Simon J McIlroy
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, QLD, 4102, Australia
| | - Sean A Crowe
- Ecosystem Services, Commercialization Platforms, and Entrepreneurship (ECOSCOPE) Training Program, University of British Columbia, Vancouver, BC, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Steven J Hallam
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Ping Han
- Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University, Shanghai, 200241, China
| | - Jens Kallmeyer
- GFZ German Research Centre for Geosciences, Section Geomicrobiology, Potsdam, Germany
| | - Rachel L Simister
- Ecosystem Services, Commercialization Platforms, and Entrepreneurship (ECOSCOPE) Training Program, University of British Columbia, Vancouver, BC, Canada
- Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - Aurele Vuillemin
- GFZ German Research Centre for Geosciences, Section Geomicrobiology, Potsdam, Germany
| | - Andy O Leu
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, QLD, 4102, Australia
| | - Zhanfei Liu
- Marine Science Institute, The University of Texas at Austin, Port Aransas, TX, 78373, USA
| | - Yan-Ling Zheng
- Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University, Shanghai, 200241, China
| | - Qian-Li Sun
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China
| | - Min Liu
- Key Laboratory of Geographic Information Science, Ministry of Education, East China Normal University, Shanghai, 200241, China
| | - Gene W Tyson
- Centre for Microbiome Research, School of Biomedical Sciences, Queensland University of Technology (QUT), Translational Research Institute, Woolloongabba, QLD, 4102, Australia
| | - Li-Jun Hou
- State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China.
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4
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A novel strategy of feeding nitrate for cost-effective production of poly-γ-glutamic acid from crude glycerol by Bacillus licheniformis WX-02. Biochem Eng J 2021. [DOI: 10.1016/j.bej.2021.108156] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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5
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Duarte AG, Barbosa ACC, Ferreira D, Manteigas G, Domingos RM, Pereira IAC. Redox loops in anaerobic respiration - The role of the widespread NrfD protein family and associated dimeric redox module. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2021; 1862:148416. [PMID: 33753023 DOI: 10.1016/j.bbabio.2021.148416] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 11/15/2020] [Revised: 02/25/2021] [Accepted: 03/11/2021] [Indexed: 02/06/2023]
Abstract
In prokaryotes, the proton or sodium motive force required for ATP synthesis is produced by respiratory complexes that present an ion-pumping mechanism or are involved in redox loops performed by membrane proteins that usually have substrate and quinone-binding sites on opposite sides of the membrane. Some respiratory complexes include a dimeric redox module composed of a quinone-interacting membrane protein of the NrfD family and an iron‑sulfur protein of the NrfC family. The QrcABCD complex of sulfate reducers, which includes the QrcCD module homologous to NrfCD, was recently shown to perform electrogenic quinone reduction providing the first conclusive evidence for energy conservation among this family. Similar redox modules are present in multiple respiratory complexes, which can be associated with electroneutral, energy-driven or electrogenic reactions. This work discusses the presence of the NrfCD/PsrBC dimeric redox module in different bioenergetics contexts and its role in prokaryotic energy conservation mechanisms.
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Affiliation(s)
- Américo G Duarte
- Instituto de Tecnologia Química e Biológica António Xavier/Universidade Nova de Lisboa, Av. da República, Estação Agronómica Nacional, 2780-157 Oeiras, Portugal.
| | - Ana C C Barbosa
- Instituto de Tecnologia Química e Biológica António Xavier/Universidade Nova de Lisboa, Av. da República, Estação Agronómica Nacional, 2780-157 Oeiras, Portugal
| | - Delfim Ferreira
- Instituto de Tecnologia Química e Biológica António Xavier/Universidade Nova de Lisboa, Av. da República, Estação Agronómica Nacional, 2780-157 Oeiras, Portugal
| | - Gonçalo Manteigas
- Instituto de Tecnologia Química e Biológica António Xavier/Universidade Nova de Lisboa, Av. da República, Estação Agronómica Nacional, 2780-157 Oeiras, Portugal
| | - Renato M Domingos
- Instituto de Tecnologia Química e Biológica António Xavier/Universidade Nova de Lisboa, Av. da República, Estação Agronómica Nacional, 2780-157 Oeiras, Portugal
| | - Inês A C Pereira
- Instituto de Tecnologia Química e Biológica António Xavier/Universidade Nova de Lisboa, Av. da República, Estação Agronómica Nacional, 2780-157 Oeiras, Portugal.
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6
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Calisto F, Sousa FM, Sena FV, Refojo PN, Pereira MM. Mechanisms of Energy Transduction by Charge Translocating Membrane Proteins. Chem Rev 2021; 121:1804-1844. [PMID: 33398986 DOI: 10.1021/acs.chemrev.0c00830] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Life relies on the constant exchange of different forms of energy, i.e., on energy transduction. Therefore, organisms have evolved in a way to be able to harvest the energy made available by external sources (such as light or chemical compounds) and convert these into biological useable energy forms, such as the transmembrane difference of electrochemical potential (Δμ̃). Membrane proteins contribute to the establishment of Δμ̃ by coupling exergonic catalytic reactions to the translocation of charges (electrons/ions) across the membrane. Irrespectively of the energy source and consequent type of reaction, all charge-translocating proteins follow two molecular coupling mechanisms: direct- or indirect-coupling, depending on whether the translocated charge is involved in the driving reaction. In this review, we explore these two coupling mechanisms by thoroughly examining the different types of charge-translocating membrane proteins. For each protein, we analyze the respective reaction thermodynamics, electron transfer/catalytic processes, charge-translocating pathways, and ion/substrate stoichiometries.
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Affiliation(s)
- Filipa Calisto
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal.,BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Faculty of Sciences, Campo Grande, 1749-016 Lisboa, Portugal
| | - Filipe M Sousa
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal.,BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Faculty of Sciences, Campo Grande, 1749-016 Lisboa, Portugal
| | - Filipa V Sena
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal.,BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Faculty of Sciences, Campo Grande, 1749-016 Lisboa, Portugal
| | - Patricia N Refojo
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal
| | - Manuela M Pereira
- Instituto de Tecnologia Química e Biológica-António Xavier, Universidade Nova de Lisboa, Av. da República EAN, 2780-157, Oeiras, Portugal.,BioISI-Biosystems & Integrative Sciences Institute, University of Lisboa, Faculty of Sciences, Campo Grande, 1749-016 Lisboa, Portugal
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7
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Pandey CB, Kumar U, Kaviraj M, Minick KJ, Mishra AK, Singh JS. DNRA: A short-circuit in biological N-cycling to conserve nitrogen in terrestrial ecosystems. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 738:139710. [PMID: 32544704 DOI: 10.1016/j.scitotenv.2020.139710] [Citation(s) in RCA: 111] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 05/21/2020] [Accepted: 05/23/2020] [Indexed: 06/11/2023]
Abstract
This paper reviews dissimilatory nitrate reduction to ammonium (DNRA) in soils - a newly appreciated pathway of nitrogen (N) cycling in the terrestrial ecosystems. The reduction of NO3- occurs in two steps; in the first step, NO3- is reduced to NO2-; and in the second, unlike denitrification, NO2- is reduced to NH4+ without intermediates. There are two sets of NO3-/NO2- reductase enzymes, i.e., Nap/Nrf and Nar/Nir; the former occurs on the periplasmic-membrane and energy conservation is respiratory via electron-transport-chain, whereas the latter is cytoplasmic and energy conservation is both respiratory and fermentative (Nir, substrate-phosphorylation). Since, Nir catalyzes both assimilatory- and dissimilatory-nitrate reduction, the nrfA gene, which transcribes the NrfA protein, is treated as a molecular-marker of DNRA; and a high nrfA/nosZ (N2O-reductase) ratio favours DNRA. Recently, several crystal structures of NrfA have been presumed to producee N2O as a byproduct of DNRA via the NO (nitric-oxide) pathway. Meta-analyses of about 200 publications have revealed that DNRA is regulated by oxidation state of soils and sediments, carbon (C)/N and NO2-/NO3- ratio, and concentrations of ferrous iron (Fe2+) and sulfide (S2-). Under low-redox conditions, a high C/NO3- ratio selects for DNRA while a low ratio selects for denitrification. When the proportion of both C and NO3- are equal, the NO2-/NO3- ratio modulates partitioning of NO3-, and a high NO2-/NO3- ratio favours DNRA. A high S2-/NO3- ratio also promotes DNRA in coastal-ecosystems and saline sediments. Soil pH, temperature, and fine soil particles are other factors known to influence DNRA. Since, DNRA reduces NO3- to NH4+, it is essential for protecting NO3- from leaching and gaseous (N2O) losses and enriches soils with readily available NH4+-N to primary producers and heterotrophic microorganisms. Therefore, DNRA may be treated as a tool to reduce ground-water NO3- pollution, enhance soil health and improve environmental quality.
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Affiliation(s)
- C B Pandey
- ICAR-Central Arid Zone Research Institute, Jodhpur 342003, Rajasthan, India.
| | - Upendra Kumar
- ICAR-National Rice Research Institute, Cuttack 753006, Odisha, India.
| | - Megha Kaviraj
- ICAR-National Rice Research Institute, Cuttack 753006, Odisha, India
| | - K J Minick
- Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695, USA
| | - A K Mishra
- International Rice Research Institute, New Delhi 110012, India
| | - J S Singh
- Ecosystem Analysis Lab, Centre of Advanced Study in Botany, Banaras Hindu University (BHU), Varanasi 221005, India
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8
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Yang J, Feng L, Pi S, Cui D, Ma F, Zhao HP, Li A. A critical review of aerobic denitrification: Insights into the intracellular electron transfer. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 731:139080. [PMID: 32417477 DOI: 10.1016/j.scitotenv.2020.139080] [Citation(s) in RCA: 96] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 04/04/2020] [Accepted: 04/26/2020] [Indexed: 05/23/2023]
Abstract
Aerobic denitrification is a novel biological nitrogen removal technology, which has been widely investigated as an alternative to the conventional denitrification and for its unique advantages. To fully comprehend aerobic denitrification, it is essential to clarify the regulatory mechanisms of intracellular electron transfer during aerobic denitrification. However, reports on intracellular electron transfer during aerobic denitrification are rather limited. Thus, the purpose of this review is to discuss the molecular mechanism of aerobic denitrification from the perspective of electron transfer, by summarizing the advancements in current research on electron transfer based on conventional denitrification. Firstly, the implication of aerobic denitrification is briefly discussed, and the status of current research on aerobic denitrification is summarized. Then, the occurring foundation and significance of aerobic denitrification are discussed based on a brief review of the key components involved in the electron transfer of denitrifying enzymes. Moreover, a strategy for enhancing the efficiency of aerobic denitrification is proposed on the basis of the regulatory mechanisms of denitrification enzymes. Finally, scientific outlooks are given for further investigation on aerobic denitrification in the future. This review could help clarify the mechanism of aerobic denitrification from the perspective of electron transfer.
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Affiliation(s)
- Jixian Yang
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, People's Republic of China
| | - Liang Feng
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, People's Republic of China
| | - Shanshan Pi
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, People's Republic of China
| | - Di Cui
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, People's Republic of China; Engineering Research Center for Medicine, College of Pharmacy, Harbin University of Commerce, Harbin 150076, People's Republic of China
| | - Fang Ma
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, People's Republic of China
| | - He-Ping Zhao
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, People's Republic of China
| | - Ang Li
- State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, People's Republic of China.
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9
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Nitrate-Utilizing Microorganisms Resistant to Multiple Metals from the Heavily Contaminated Oak Ridge Reservation. Appl Environ Microbiol 2019; 85:AEM.00896-19. [PMID: 31253673 DOI: 10.1128/aem.00896-19] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Accepted: 06/20/2019] [Indexed: 11/20/2022] Open
Abstract
Contamination of environments with nitrate generated by industrial processes and the use of nitrogen-containing fertilizers is a growing problem worldwide. While nitrate can be removed from contaminated areas by microbial denitrification, nitrate frequently occurs with other contaminants, such as heavy metals, that have the potential to impede the process. Here, nitrate-reducing microorganisms were enriched and isolated from both groundwater and sediments at the Oak Ridge Reservation (ORR) using concentrations of nitrate and metals (Al, Mn, Fe, Co, Ni, Cu, Cd, and U) similar to those observed in a contaminated environment at ORR. Seven new metal-resistant, nitrate-reducing strains were characterized, and their distribution across both noncontaminated and contaminated areas at ORR was examined. While the seven strains have various pH ranges for growth, carbon source preferences, and degrees of resistance to individual and combinations of metals, all were able to reduce nitrate at similar rates both in the presence and absence of the mixture of metals found in the contaminated ORR environment. Four strains were identified in groundwater samples at different ORR locations by exact 16S RNA sequence variant analysis, and all four were found in both noncontaminated and contaminated areas. By using environmentally relevant metal concentrations, we successfully isolated multiple organisms from both ORR noncontaminated and contaminated environments that are capable of reducing nitrate in the presence of extreme mixed-metal contamination.IMPORTANCE Nitrate contamination is a global issue that affects groundwater quality. In some cases, cocontamination of groundwater with nitrate and mixtures of heavy metals could decrease microbially mediated nitrate removal, thereby increasing the duration of nitrate contamination. Here, we used metal and nitrate concentrations that are present in a contaminated site at the Oak Ridge Reservation to isolate seven metal-resistant strains. All were able to reduce nitrate in the presence of high concentrations of a mixture of heavy metals. Four of seven strains were located in pristine as well as contaminated sites at the Oak Ridge Reservation. Further study of these nitrate-reducing strains will uncover mechanisms of resistance to multiple metals that will increase our understanding of the effect of nitrate and metal contamination on groundwater microbial communities.
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10
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Duarte AG, Catarino T, White GF, Lousa D, Neukirchen S, Soares CM, Sousa FL, Clarke TA, Pereira IAC. An electrogenic redox loop in sulfate reduction reveals a likely widespread mechanism of energy conservation. Nat Commun 2018; 9:5448. [PMID: 30575735 PMCID: PMC6303296 DOI: 10.1038/s41467-018-07839-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 11/27/2018] [Indexed: 02/02/2023] Open
Abstract
The bioenergetics of anaerobic metabolism frequently relies on redox loops performed by membrane complexes with substrate- and quinone-binding sites on opposite sides of the membrane. However, in sulfate respiration (a key process in the biogeochemical sulfur cycle), the substrate- and quinone-binding sites of the QrcABCD complex are periplasmic, and their role in energy conservation has not been elucidated. Here we show that the QrcABCD complex of Desulfovibrio vulgaris is electrogenic, as protons and electrons required for quinone reduction are extracted from opposite sides of the membrane, with a H+/e− ratio of 1. Although the complex does not act as a H+-pump, QrcD may include a conserved proton channel leading from the N-side to the P-side menaquinone pocket. Our work provides evidence of how energy is conserved during dissimilatory sulfate reduction, and suggests mechanisms behind the functions of related bacterial respiratory complexes in other bioenergetic contexts. The bacterial complex QrcABCD plays a key role in the bioenergetics of sulfate respiration. Here, Duarte et al. show that this complex is electrogenic, with protons and electrons required for quinone reduction being extracted from opposite sides of the membrane.
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Affiliation(s)
- Américo G Duarte
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157, Oeiras, Portugal
| | - Teresa Catarino
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157, Oeiras, Portugal.,Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal
| | - Gaye F White
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Diana Lousa
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157, Oeiras, Portugal
| | - Sinje Neukirchen
- Division of Archaea Biology and Ecogenomics, Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14 UZA I, 1090, Vienna, Austria
| | - Cláudio M Soares
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157, Oeiras, Portugal
| | - Filipa L Sousa
- Division of Archaea Biology and Ecogenomics, Department of Ecogenomics and Systems Biology, University of Vienna, Althanstrasse 14 UZA I, 1090, Vienna, Austria
| | - Thomas A Clarke
- Centre for Molecular and Structural Biochemistry, School of Biological Sciences and School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, UK
| | - Inês A C Pereira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157, Oeiras, Portugal.
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11
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Insight into Energy Conservation via Alternative Carbon Monoxide Metabolism in Carboxydothermus pertinax Revealed by Comparative Genome Analysis. Appl Environ Microbiol 2018; 84:AEM.00458-18. [PMID: 29728389 DOI: 10.1128/aem.00458-18] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Accepted: 04/28/2018] [Indexed: 11/20/2022] Open
Abstract
Carboxydothermus species are some of the most studied thermophilic carboxydotrophs. Their varied carboxydotrophic growth properties suggest distinct strategies for energy conservation via carbon monoxide (CO) metabolism. In this study, we used comparative genome analysis of the genus Carboxydothermus to show variations in the CO dehydrogenase-energy-converting hydrogenase gene cluster, which is responsible for CO metabolism with H2 production (hydrogenogenic CO metabolism). Indeed, the ability or inability to produce H2 with CO oxidation is explained by the presence or absence of this gene cluster in Carboxydothermus hydrogenoformans, Carboxydothermus islandicus, and Carboxydothermus ferrireducens Interestingly, despite its hydrogenogenic CO metabolism, Carboxydothermus pertinax lacks the Ni-CO dehydrogenase catalytic subunit (CooS-I) and its transcriptional regulator-encoding genes in this gene cluster, probably due to inversion. Transcriptional analysis in C. pertinax showed that the Ni-CO dehydrogenase gene (cooS-II) and distantly encoded energy-converting-hydrogenase-related genes were remarkably upregulated with 100% CO. In addition, when thiosulfate was available as a terminal electron acceptor in 100% CO, the maximum cell density and maximum specific growth rate of C. pertinax were 3.1-fold and 1.5-fold higher, respectively, than when thiosulfate was absent. The amount of H2 produced was only 62% of the amount of CO consumed, less than expected according to hydrogenogenic CO oxidation (CO + H2O → CO2 + H2). Accordingly, C. pertinax would couple CO oxidation by Ni-CO dehydrogenase II with simultaneous reduction of not only H2O but also thiosulfate when grown in 100% CO.IMPORTANCE Anaerobic hydrogenogenic carboxydotrophs are thought to fill a vital niche by scavenging potentially toxic CO and producing H2 as an available energy source for thermophilic microbes. This hydrogenogenic carboxydotrophy relies on a Ni-CO dehydrogenase-energy-converting hydrogenase gene cluster. This feature is thought to be common to these organisms. However, the hydrogenogenic carboxydotroph Carboxydothermus pertinax lacks the gene for the Ni-CO dehydrogenase catalytic subunit encoded in the gene cluster. Here, we performed a comparative genome analysis of the genus Carboxydothermus, a transcriptional analysis, and a cultivation study in 100% CO to prove the hydrogenogenic CO metabolism. Results revealed that C. pertinax could couple Ni-CO dehydrogenase II alternatively to the distal energy-converting hydrogenase. Furthermore, C. pertinax represents an example of the functioning of Ni-CO dehydrogenase that does not always correspond to its genomic context, owing to the versatility of CO metabolism and the low redox potential of CO.
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12
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The Aerobic and Anaerobic Respiratory Chain of Escherichia coli and Salmonella enterica: Enzymes and Energetics. EcoSal Plus 2015; 6. [PMID: 26442941 DOI: 10.1128/ecosalplus.esp-0005-2013] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Escherichia coli contains a versatile respiratory chain that oxidizes 10 different electron donor substrates and transfers the electrons to terminal reductases or oxidases for the reduction of six different electron acceptors. Salmonella is able to use two more electron acceptors. The variation is further increased by the presence of isoenzymes for some substrates. A large number of respiratory pathways can be established by combining different electron donors and acceptors. The respiratory dehydrogenases use quinones as the electron acceptors that are oxidized by the terminal reductase and oxidases. The enzymes vary largely with respect to their composition, architecture, membrane topology, and the mode of energy conservation. Most of the energy-conserving dehydrogenases (FdnGHI, HyaABC, HybCOAB, and others) and the terminal reductases (CydAB, NarGHI, and others) form a proton potential (Δp) by a redox-loop mechanism. Two enzymes (NuoA-N and CyoABCD) couple the redox energy to proton translocation by proton pumping. A large number of dehydrogenases and terminal reductases do not conserve the redox energy in a proton potential. For most of the respiratory enzymes, the mechanism of proton potential generation is known or can be predicted. The H+/2e- ratios for most respiratory chains are in the range from 2 to 6 H+/2e-. The energetics of the individual redox reactions and the respiratory chains is described and related to the H+/2e- ratios.
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13
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The Aerobic and Anaerobic Respiratory Chain of Escherichia coli and Salmonella enterica: Enzymes and Energetics. EcoSal Plus 2015; 3. [PMID: 26443736 DOI: 10.1128/ecosalplus.3.2.2] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Escherichia coli contains a versatile respiratory chain which oxidizes ten different electron donor substrates and transfers the electrons to terminal reductases or oxidases for the reduction of six different electron acceptors. Salmonella is able to use even two more electron acceptors. The variation is further increased by the presence of isoenzymes for some substrates. Various respiratory pathways can be established by combining the oxidation of different electron donors and acceptors which are linked by respiratory quinones. The enzymes vary largely with respect to architecture, membrane topology, and mode of energy conservation. Most of the energy-conserving dehydrogenases (e.g., FdnGHI, HyaABC, and HybCOAB) and of the terminal reductases (CydAB, NarGHI, and others) form a proton potential (Δp) by a redox loop mechanism. Only two enzymes (NuoA-N and CyoABCD) couple the redox energy to proton translocation by proton pumping. A large number of dehydrogenases (e.g., Ndh, SdhABCD, and GlpD) and of terminal reductases (e.g., FrdABCD and DmsABC) do not conserve the redox energy in a proton potential. For most of the respiratory enzymes, the mechanism of proton potential generation is known from structural and biochemical studies or can be predicted from sequence information. The H+/2e- ratios of proton translocation for most respiratory chains are in the range from 2 to 6 H+/2e-. The energetics of the individual redox reactions and of the respiratory chains is described. In contrast to the knowledge on enzyme function are physiological aspects of respiration such as organization and coordination of the electron transport and the use of alternative respiratory enzymes, not well characterized.
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 559] [Impact Index Per Article: 55.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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15
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Affiliation(s)
- Russ Hille
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - James Hall
- Department of Biochemistry, University of California, Riverside, Riverside, California 92521, United States
| | - Partha Basu
- Department of Chemistry and Biochemistry, Duquesne University, Pittsburgh, Pennsylvania 15282, United States
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Beller HR, Zhou P, Legler TC, Chakicherla A, Kane S, Letain TE, A O'Day P. Genome-enabled studies of anaerobic, nitrate-dependent iron oxidation in the chemolithoautotrophic bacterium Thiobacillus denitrificans. Front Microbiol 2013; 4:249. [PMID: 24065960 PMCID: PMC3753534 DOI: 10.3389/fmicb.2013.00249] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2013] [Accepted: 08/06/2013] [Indexed: 01/15/2023] Open
Abstract
Thiobacillus denitrificans is a chemolithoautotrophic bacterium capable of anaerobic, nitrate-dependent U(IV) and Fe(II) oxidation, both of which can strongly influence the long-term efficacy of in situ reductive immobilization of uranium in contaminated aquifers. We previously identified two c-type cytochromes involved in nitrate-dependent U(IV) oxidation in T. denitrificans and hypothesized that c-type cytochromes would also catalyze Fe(II) oxidation, as they have been found to play this role in anaerobic phototrophic Fe(II)-oxidizing bacteria. Here we report on efforts to identify genes associated with nitrate-dependent Fe(II) oxidation, namely (a) whole-genome transcriptional studies [using FeCO3, Fe(2) (+), and U(IV) oxides as electron donors under denitrifying conditions], (b) Fe(II) oxidation assays performed with knockout mutants targeting primarily highly expressed or upregulated c-type cytochromes, and (c) random transposon-mutagenesis studies with screening for Fe(II) oxidation. Assays of mutants for 26 target genes, most of which were c-type cytochromes, indicated that none of the mutants tested were significantly defective in nitrate-dependent Fe(II) oxidation. The non-defective mutants included the c 1-cytochrome subunit of the cytochrome bc 1 complex (complex III), which has relevance to a previously proposed role for this complex in nitrate-dependent Fe(II) oxidation and to current concepts of reverse electron transfer. A transposon mutant with a disrupted gene associated with NADH:ubiquinone oxidoreductase (complex I) was ~35% defective relative to the wild-type strain; this strain was similarly defective in nitrate reduction with thiosulfate as the electron donor. Overall, our results indicate that nitrate-dependent Fe(II) oxidation in T. denitrificans is not catalyzed by the same c-type cytochromes involved in U(IV) oxidation, nor have other c-type cytochromes yet been implicated in the process.
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Affiliation(s)
- Harry R Beller
- Earth Sciences Division, Lawrence Berkeley National Laboratory Berkeley, CA, USA
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17
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Lancaster CRD. The di-heme family of respiratory complex II enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:679-87. [PMID: 23466335 DOI: 10.1016/j.bbabio.2013.02.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/26/2012] [Revised: 02/22/2013] [Accepted: 02/22/2013] [Indexed: 01/28/2023]
Abstract
The di-heme family of succinate:quinone oxidoreductases is of particular interest, because its members support electron transfer across the biological membranes in which they are embedded. In the case of the di-heme-containing succinate:menaquinone reductase (SQR) from Gram-positive bacteria and other menaquinone-containing bacteria, this results in an electrogenic reaction. This is physiologically relevant in that it allows the transmembrane electrochemical proton potential Δp to drive the endergonic oxidation of succinate by menaquinone. In the case of the reverse reaction, menaquinol oxidation by fumarate, catalysed by the di-heme-containing quinol:fumarate reductase (QFR), evidence has been obtained that this electrogenic electron transfer reaction is compensated by proton transfer via a both novel and essential transmembrane proton transfer pathway ("E-pathway"). Although the reduction of fumarate by menaquinol is exergonic, it is obviously not exergonic enough to support the generation of a Δp. This compensatory "E-pathway" appears to be required by all di-heme-containing QFR enzymes and results in the overall reaction being electroneutral. In addition to giving a brief overview of progress in the characterization of other members of this diverse family, this contribution summarizes key evidence and progress in identifying constituents of the "E-pathway" within the framework of the crystal structure of the QFR from the anaerobic epsilon-proteobacterium Wolinella succinogenes at 1.78Å resolution. This article is part of a Special Issue entitled: Respiratory complex II: Role in cellular physiology and disease.
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Affiliation(s)
- C Roy D Lancaster
- Department of Structural Biology, Saarland University, Homburg, Germany.
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18
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Schoepp-Cothenet B, van Lis R, Atteia A, Baymann F, Capowiez L, Ducluzeau AL, Duval S, ten Brink F, Russell MJ, Nitschke W. On the universal core of bioenergetics. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1827:79-93. [PMID: 22982447 DOI: 10.1016/j.bbabio.2012.09.005] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 09/06/2012] [Accepted: 09/07/2012] [Indexed: 01/05/2023]
Abstract
Living cells are able to harvest energy by coupling exergonic electron transfer between reducing and oxidising substrates to the generation of chemiosmotic potential. Whereas a wide variety of redox substrates is exploited by prokaryotes resulting in very diverse layouts of electron transfer chains, the ensemble of molecular architectures of enzymes and redox cofactors employed to construct these systems is stunningly small and uniform. An overview of prominent types of electron transfer chains and of their characteristic electrochemical parameters is presented. We propose that basic thermodynamic considerations are able to rationalise the global molecular make-up and functioning of these chemiosmotic systems. Arguments from palaeogeochemistry and molecular phylogeny are employed to discuss the evolutionary history leading from putative energy metabolisms in early life to the chemiosmotic diversity of extant organisms. Following the Occam's razor principle, we only considered for this purpose origin of life scenarios which are contiguous with extant life. This article is part of a Special Issue entitled: The evolutionary aspects of bioenergetic systems.
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Affiliation(s)
- Barbara Schoepp-Cothenet
- Laboratoire de Bioénergétique et Ingénierie des Protéines UMR 7281 CNRS/AMU, FR3479, F-13402 Marseille Cedex 20, France.
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19
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Grein F, Ramos AR, Venceslau SS, Pereira IAC. Unifying concepts in anaerobic respiration: insights from dissimilatory sulfur metabolism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1827:145-60. [PMID: 22982583 DOI: 10.1016/j.bbabio.2012.09.001] [Citation(s) in RCA: 125] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 09/03/2012] [Accepted: 09/04/2012] [Indexed: 10/27/2022]
Abstract
Behind the versatile nature of prokaryotic energy metabolism is a set of redox proteins having a highly modular character. It has become increasingly recognized that a limited number of redox modules or building blocks appear grouped in different arrangements, giving rise to different proteins and functionalities. This modularity most likely reveals a common and ancient origin for these redox modules, and is obviously reflected in similar energy conservation mechanisms. The dissimilation of sulfur compounds was probably one of the earliest biological strategies used by primitive organisms to obtain energy. Here, we review some of the redox proteins involved in dissimilatory sulfur metabolism, focusing on sulfate reducing organisms, and highlight links between these proteins and others involved in different processes of anaerobic respiration. Noteworthy are links to the complex iron-sulfur molybdoenzyme family, and heterodisulfide reductases of methanogenic archaea. We discuss how chemiosmotic and electron bifurcation/confurcation may be involved in energy conservation during sulfate reduction, and how introduction of an additional module, multiheme cytochromes c, opens an alternative bioenergetic strategy that seems to increase metabolic versatility. Finally, we highlight new families of heterodisulfide reductase-related proteins from non-methanogenic organisms, which indicate a widespread distribution for these protein modules and may indicate a more general involvement of thiol/disulfide conversions in energy metabolism. This article is part of a Special Issue entitled: The evolutionary aspects of bioenergetic systems.
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Affiliation(s)
- Fabian Grein
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal
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20
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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: 111] [Impact Index Per Article: 9.3] [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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21
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Stoffels L, Krehenbrink M, Berks BC, Unden G. Thiosulfate reduction in Salmonella enterica is driven by the proton motive force. J Bacteriol 2012; 194:475-85. [PMID: 22081391 PMCID: PMC3256639 DOI: 10.1128/jb.06014-11] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2011] [Accepted: 11/01/2011] [Indexed: 11/20/2022] Open
Abstract
Thiosulfate respiration in Salmonella enterica serovar Typhimurium is catalyzed by the membrane-bound enzyme thiosulfate reductase. Experiments with quinone biosynthesis mutants show that menaquinol is the sole electron donor to thiosulfate reductase. However, the reduction of thiosulfate by menaquinol is highly endergonic under standard conditions (ΔE°' = -328 mV). Thiosulfate reductase activity was found to depend on the proton motive force (PMF) across the cytoplasmic membrane. A structural model for thiosulfate reductase suggests that the PMF drives endergonic electron flow within the enzyme by a reverse loop mechanism. Thiosulfate reductase was able to catalyze the combined oxidation of sulfide and sulfite to thiosulfate in a reverse of the physiological reaction. In contrast to the forward reaction the exergonic thiosulfate-forming reaction was PMF independent. Electron transfer from formate to thiosulfate in whole cells occurs predominantly by intraspecies hydrogen transfer.
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Affiliation(s)
- Laura Stoffels
- Institute for Microbiology and Wine Research, Johannes Gutenberg-University of Mainz, Mainz, Germany
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Martin Krehenbrink
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Ben C. Berks
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Gottfried Unden
- Institute for Microbiology and Wine Research, Johannes Gutenberg-University of Mainz, Mainz, Germany
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22
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Frielingsdorf S, Schubert T, Pohlmann A, Lenz O, Friedrich B. A Trimeric Supercomplex of the Oxygen-Tolerant Membrane-Bound [NiFe]-Hydrogenase from Ralstonia eutropha H16. Biochemistry 2011; 50:10836-43. [DOI: 10.1021/bi201594m] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stefan Frielingsdorf
- Institut für Biologie-Mikrobiologie, Humboldt-Universität zu Berlin, Chausseestraβe
117, 10115 Berlin, Germany
| | - Torsten Schubert
- Institut für Biologie-Mikrobiologie, Humboldt-Universität zu Berlin, Chausseestraβe
117, 10115 Berlin, Germany
| | - Anne Pohlmann
- Institut für Biologie-Mikrobiologie, Humboldt-Universität zu Berlin, Chausseestraβe
117, 10115 Berlin, Germany
| | - Oliver Lenz
- Institut für Biologie-Mikrobiologie, Humboldt-Universität zu Berlin, Chausseestraβe
117, 10115 Berlin, Germany
| | - Bärbel Friedrich
- Institut für Biologie-Mikrobiologie, Humboldt-Universität zu Berlin, Chausseestraβe
117, 10115 Berlin, Germany
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Khan ZI, Ahmad K, Ashraf M, Raza N, Sher M. Assessment of molybdenum status in soil and forage for ruminant production under semiarid environmental conditions in Sargodha, Pakistan. Biol Trace Elem Res 2011; 142:465-70. [PMID: 20734241 DOI: 10.1007/s12011-010-8808-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2010] [Accepted: 08/05/2010] [Indexed: 11/25/2022]
Abstract
The present investigation was carried out to determine the molybdenum (Mo) status of soil and forage at the Livestock Experimental Station, Khizer abad, Sargodha, Pakistan. This site falls under semiarid climatic conditions. Soil and forage samples were collected on a monthly basis during the winter season (from October through January) and analyzed after wet digestion to determine the effect of sampling intervals on Mo content as well as its transfer from soil to forage during the whole study period. The effect of sampling intervals on soil Mo content was found to be highly significant, but in contrast, this effect on forage Mo was nonsignificant. The Mo content of soil was found to be highly sufficient to meet the requirement of forage crops, whereas those of forage at the borderline of the ruminant requirement is insufficient. It is expected that with time, further depletion of Mo in the pasture soil due to interaction with Cu and other antagonistic elements may take place, which could finally lower Mo levels in the forage being used for rearing livestock. Thus, at some stage in the future, addition of standard fertilizers enriched with Mo to the soils may be required at the livestock farm.
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Affiliation(s)
- Zafar Iqbal Khan
- Department of Biological Sciences, University of Sargodha, Sargodha 40100, Pakistan.
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24
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Sezer M, Frielingsdorf S, Millo D, Heidary N, Utesch T, Mroginski MA, Friedrich B, Hildebrandt P, Zebger I, Weidinger IM. Role of the HoxZ Subunit in the Electron Transfer Pathway of the Membrane-Bound [NiFe]-Hydrogenase from Ralstonia eutropha Immobilized on Electrodes. J Phys Chem B 2011; 115:10368-74. [DOI: 10.1021/jp204665r] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Murat Sezer
- Insitut für Chemie, Technische Universität Berlin, Strasse des 17, Juni 135, 10623 Berlin, Germany
| | | | - Diego Millo
- Insitut für Chemie, Technische Universität Berlin, Strasse des 17, Juni 135, 10623 Berlin, Germany
| | - Nina Heidary
- Insitut für Chemie, Technische Universität Berlin, Strasse des 17, Juni 135, 10623 Berlin, Germany
| | - Tillman Utesch
- Insitut für Chemie, Technische Universität Berlin, Strasse des 17, Juni 135, 10623 Berlin, Germany
| | - Maria-Andrea Mroginski
- Insitut für Chemie, Technische Universität Berlin, Strasse des 17, Juni 135, 10623 Berlin, Germany
| | - Bärbel Friedrich
- Humboldt-Universität zu Berlin, Chausseestrasse 117, 10115 Berlin, Germany
| | - Peter Hildebrandt
- Insitut für Chemie, Technische Universität Berlin, Strasse des 17, Juni 135, 10623 Berlin, Germany
| | - Ingo Zebger
- Insitut für Chemie, Technische Universität Berlin, Strasse des 17, Juni 135, 10623 Berlin, Germany
| | - Inez M. Weidinger
- Insitut für Chemie, Technische Universität Berlin, Strasse des 17, Juni 135, 10623 Berlin, Germany
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25
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McHatton SC, Barry JP, Jannasch HW, Nelson DC. High Nitrate Concentrations in Vacuolate, Autotrophic Marine Beggiatoa spp. Appl Environ Microbiol 2010; 62:954-8. [PMID: 16535282 PMCID: PMC1388807 DOI: 10.1128/aem.62.3.954-958.1996] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Massive accumulations of very large Beggiatoa spp. are found at a Monterey Canyon cold seep and at Guaymas Basin hydrothermal vents. Both environments are characterized by high sediment concentrations of soluble sulfide and low levels of dissolved oxygen in surrounding waters. These filamentous, sulfur-oxidizing bacteria accumulate nitrate intracellularly at concentrations of 130 to 160 mM, 3,000- to 4,000-fold higher than ambient levels. Average filament widths range from 24 to 122 (mu)m, and individual cells of all widths possess a central vacuole. These findings plus recent parallel discoveries for Thioploca spp. (H. Fossing, V. A. Gallardo, B. B. Jorgensen, M. Huttel, L. P. Nielsen, H. Schulz, D. E. Canfield, S. Forster, R. N. Glud, J. K. Gundersen, J. Kuver, N. B. Ramsing, A. Teske, B. Thamdrup, and O. Ulloa, Nature (London) 374:713-715, 1995) suggest that nitrate accumulation may be a universal property of vacuolate, filamentous sulfur bacteria. Ribulose bisphosphate carboxylase-oxygenase and 2-oxoglutarate dehydrogenase activities in the Beggiatoa sp. from Monterey Canyon suggest in situ autotrophic growth of these bacteria. Nitrate reductase activity is much higher in the Monterey Beggiatoa sp. than in narrow, laboratory-grown strains of Beggiatoa spp., and the activity is found primarily in the membrane fraction, suggesting that the vacuolate Beggiatoa sp. can reduce nitrate coupled to electron flow through an electron transport system. Nitrate-concentrating and respiration potentials of these chemolithoautotrophs suggest that the Beggiatoa spp. described here are an important link between the sulfur, nitrogen, and carbon cycles at the Monterey Canyon seeps and the Guaymas Basin hydrothermal vents where they are found.
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26
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Price CE, Driessen AJM. Biogenesis of membrane bound respiratory complexes in Escherichia coli. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:748-66. [PMID: 20138092 DOI: 10.1016/j.bbamcr.2010.01.019] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 01/21/2010] [Accepted: 01/27/2010] [Indexed: 11/19/2022]
Abstract
Escherichia coli is one of the preferred bacteria for studies on the energetics and regulation of respiration. Respiratory chains consist of primary dehydrogenases and terminal reductases or oxidases linked by quinones. In order to assemble this complex arrangement of protein complexes, synthesis of the subunits occurs in the cytoplasm followed by assembly in the cytoplasm and/or membrane, the incorporation of metal or organic cofactors and the anchoring of the complex to the membrane. In the case of exported metalloproteins, synthesis, assembly and incorporation of metal cofactors must be completed before translocation across the cytoplasmic membrane. Coordination data on these processes is, however, scarce. In this review, we discuss the various processes that respiratory proteins must undergo for correct assembly and functional coupling to the electron transport chain in E. coli. Targeting to and translocation across the membrane together with cofactor synthesis and insertion are discussed in a general manner followed by a review of the coordinated biogenesis of individual respiratory enzyme complexes. Lastly, we address the supramolecular organization of respiratory enzymes into supercomplexes and their localization to specialized domains in the membrane.
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Affiliation(s)
- Claire E Price
- Department of Molecular Microbiology, University of Groningen, 9751 NN Haren, The Netherlands
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Schwarz C, Poss Z, Hoffmann D, Appel J. Hydrogenases and Hydrogen Metabolism in Photosynthetic Prokaryotes. RECENT ADVANCES IN PHOTOTROPHIC PROKARYOTES 2010; 675:305-48. [DOI: 10.1007/978-1-4419-1528-3_18] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Blank CE. Phylogenomic dating--the relative antiquity of archaeal metabolic and physiological traits. ASTROBIOLOGY 2009; 9:193-219. [PMID: 19371161 DOI: 10.1089/ast.2008.0248] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Ancestral trait reconstruction was used to identify the relative ancestry of metabolic and physiological traits in the archaeal domain of life. First, well-resolved phylogenetic trees were inferred with multiple gene sequences obtained from whole genome sequences. Next, metabolic and physiological traits were coded into characters, and ancestral state reconstruction was used to identify ancient and derived traits. Traits inferred to be ancient included sulfur reduction, methanogenesis, and hydrogen oxidation. By using the articulation of the "oxygen age constraint," several other traits were inferred to have arisen at or after 2.32 Ga: aerobic respiration, nitrate reduction, sulfate reduction, thiosulfate reduction, sulfur oxidation, and sulfide oxidation. Complex organic metabolism appeared to be nearly as ancient as autotrophy. Hyperthermophily was ancestral, while hyperacidophily and extreme halophily likely arose after 2.32 Ga. The ancestral euryarchaeote was inferred to have been a hyperthermophilic marine methanogen that lived in a deep-sea hydrothermal vent. In contrast, the ancestral crenarchaeote was most likely a hyperthermophilic sulfur reducer that lived in a slightly acidic terrestrial environment, perhaps a fumarole. Cross-colonization of these habitats may not have occurred until after 2.32 Ga, which suggests that both archaeal lineages exhibited niche specialization on early Earth for a protracted period of time.
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Affiliation(s)
- Carrine E Blank
- Department of Geosciences, University of Montana, Missoula, Montana 59808-1296, USA.
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A molybdopterin oxidoreductase is involved in H2 oxidation in Desulfovibrio desulfuricans G20. J Bacteriol 2009; 191:2675-82. [PMID: 19233927 DOI: 10.1128/jb.01814-08] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Three mutants deficient in hydrogen/formate uptake were obtained through screening of a transposon mutant library containing 5,760 mutants of Desulfovibrio desulfuricans G20. Mutations were in the genes encoding the type I tetraheme cytochrome c(3) (cycA), Fe hydrogenase (hydB), and molybdopterin oxidoreductase (mopB). Mutations did not decrease the ability of cells to produce H(2) or formate during growth. Complementation of the cycA and mopB mutants with a plasmid carrying the intact cycA and/or mopB gene and the putative promoter from the parental strain allowed the recovery of H(2) uptake ability, showing that these specific genes are involved in H(2) oxidation. The mop operon encodes a periplasm-facing transmembrane protein complex which may shuttle electrons from periplasmic cytochrome c(3) to the menaquinone pool. Electrons can then be used for sulfate reduction in the cytoplasm.
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Simon J, van Spanning RJ, Richardson DJ. The organisation of proton motive and non-proton motive redox loops in prokaryotic respiratory systems. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2008; 1777:1480-90. [DOI: 10.1016/j.bbabio.2008.09.008] [Citation(s) in RCA: 106] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 09/08/2008] [Accepted: 09/09/2008] [Indexed: 10/21/2022]
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Bis-histidine-coordinated hemes in four-helix bundles: how the geometry of the bundle controls the axial imidazole plane orientations in transmembrane cytochromes of mitochondrial complexes II and III and related proteins. J Biol Inorg Chem 2008; 13:481-98. [PMID: 18418633 DOI: 10.1007/s00775-008-0372-9] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2008] [Accepted: 03/27/2008] [Indexed: 10/22/2022]
Abstract
Early investigation of the electron paramagnetic resonance spectra of bis-histidine-coordinated membrane-bound ferriheme proteins led to the description of a spectral signal that had only one resolved feature. These became known as "highly anisotropic low-spin" or "large g(max)" ferriheme centers. Extensive work with small-molecule model heme complexes showed that this spectroscopic signature occurs in bis-imidazole ferrihemes in which the planes of the imidazole ligands are nearly perpendicular, deltaphi = 57-90 degrees. In the last decade protein crystallographic studies have revealed the atomic structures of a number of examples of bis-histidine heme proteins. A frequent characteristic of these large g(max) ferrihemes in membrane-bound proteins is the occurrence of the heme within a four-helix bundle with a left-handed twist. The histidine ligands occur at the same level on two diametrically opposed helices of the bundle. These ligands have the same side-chain conformation and ligate heme iron on the bundle axis, resulting in a quasi-twofold symmetric structure. The two non-ligand-bearing helices also obey this symmetry, and have a conserved small residue, usually glycine, where the edge of the heme ring makes contact with the helix backbones. In many cases this small residue is preceded by a threonine or serine residue whose side-chain hydroxyl oxygen acts as a hydrogen-bond acceptor from the N(delta1) atom of the heme-ligating histidine. The deltaphi angle is thus determined by the common histidine side-chain conformation and the crossing angle of the ligand-bearing helices, in some cases constrained by hydrogen bonds to the serine/threonine residues on the non-ligand-bearing helices.
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Goddard AD, Moir JWB, Richardson DJ, Ferguson SJ. Interdependence of two NarK domains in a fused nitrate/nitrite transporter. Mol Microbiol 2008; 70:667-81. [PMID: 18823285 DOI: 10.1111/j.1365-2958.2008.06436.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitrate uptake is essential for various bacterial processes and combines with nitrite export to form the usual initial steps of denitrification, a process that reduces nitrate to dinitrogen gas. Although many bacterial species contain NarK-like transporters that are proposed to function as either nitrate/proton symporters or nitrate/nitrite antiporters based on sequence homology, these transporters remain, in general, poorly characterized. Several bacteria appear to contain a transporter that is a fusion of two NarK-like proteins, although the significance of this arrangement remains elusive. We demonstrate that NarK from Paracoccus denitrificans is expressed as a fusion of two NarK-like transporters. NarK1 and NarK2 are separately capable of supporting anaerobic denitrifying growth but with growth defects that are partially mitigated by coexpression of the two domains. NarK1 appears to be a nitrate/proton symporter with high affinity for nitrate and NarK2 a nitrate/nitrite antiporter with lower affinity for nitrate. Each transporter requires two conserved arginine residues for activity. A transporter consisting of inactivated NarK1 fused to active NarK2 has a dramatically increased affinity for nitrate compared with NarK2 alone, implying a functional interaction between the two domains. A potential model for nitrate and nitrite transport in P. denitrificans is proposed.
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Affiliation(s)
- Alan D Goddard
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford, UK
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Jormakka M, Yokoyama K, Yano T, Tamakoshi M, Akimoto S, Shimamura T, Curmi P, Iwata S. Molecular mechanism of energy conservation in polysulfide respiration. Nat Struct Mol Biol 2008; 15:730-7. [PMID: 18536726 DOI: 10.1038/nsmb.1434] [Citation(s) in RCA: 121] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2008] [Accepted: 04/23/2008] [Indexed: 11/09/2022]
Abstract
Bacterial polysulfide reductase (PsrABC) is an integral membrane protein complex responsible for quinone-coupled reduction of polysulfide, a process important in extreme environments such as deep-sea vents and hot springs. We determined the structure of polysulfide reductase from Thermus thermophilus at 2.4-A resolution, revealing how the PsrA subunit recognizes and reduces its unique polyanionic substrate. The integral membrane subunit PsrC was characterized using the natural substrate menaquinone-7 and inhibitors, providing a comprehensive representation of a quinone binding site and revealing the presence of a water-filled cavity connecting the quinone binding site on the periplasmic side to the cytoplasm. These results suggest that polysulfide reductase could be a key energy-conserving enzyme of the T. thermophilus respiratory chain, using polysulfide as the terminal electron acceptor and pumping protons across the membrane via a previously unknown mechanism.
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Affiliation(s)
- Mika Jormakka
- Department of Biophysics, University of New South Wales, Barker Street, Sydney, New South Wales 2052, Australia.
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Morozkina EV, Zvyagilskaya RA. Nitrate reductases: structure, functions, and effect of stress factors. BIOCHEMISTRY (MOSCOW) 2008; 72:1151-60. [PMID: 18021072 DOI: 10.1134/s0006297907100124] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Structural and functional peculiarities of four types of nitrate reductases are considered: assimilatory nitrate reductase of eukaryotes, as well as cytoplasmic assimilatory, membrane-bound respiratory, and periplasmic dissimilatory bacterial nitrate reductases. Arguments are presented showing that eukaryotic organisms are capable of nitrate dissimilation. Data concerning new classes of extremophil nitrate reductases, whose active center does not contain molybdocofactor, are summarized.
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Affiliation(s)
- E V Morozkina
- Bach Institute of Biochemistry, Russian Academy of Sciences, 119071 Moscow, Russia.
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Coelho C, González PJ, Trincão J, Carvalho AL, Najmudin S, Hettman T, Dieckman S, Moura JJG, Moura I, Romão MJ. Heterodimeric nitrate reductase (NapAB) from Cupriavidus necator H16: purification, crystallization and preliminary X-ray analysis. Acta Crystallogr Sect F Struct Biol Cryst Commun 2007; 63:516-9. [PMID: 17554176 PMCID: PMC2335073 DOI: 10.1107/s1744309107022129] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2007] [Accepted: 05/04/2007] [Indexed: 11/10/2022]
Abstract
The periplasmic nitrate reductase from Cupriavidus necator (also known as Ralstonia eutropha) is a heterodimer that is able to reduce nitrate to nitrite. It comprises a 91 kDa catalytic subunit (NapA) and a 17 kDa subunit (NapB) that is involved in electron transfer. The larger subunit contains a molybdenum active site with a bis-molybdopterin guanine dinucleotide cofactor as well as one [4Fe-4S] cluster, while the small subunit is a di-haem c-type cytochrome. Crystals of the oxidized form of this enzyme were obtained using polyethylene glycol 3350 as precipitant. A single crystal grown at the High Throughput Crystallization Laboratory of the EMBL in Grenoble diffracted to beyond 1.5 A at the ESRF (ID14-1), which is the highest resolution reported to date for a nitrate reductase. The unit-cell parameters are a = 142.2, b = 82.4, c = 96.8 A, beta = 100.7 degrees, space group C2, and one heterodimer is present per asymmetric unit.
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Affiliation(s)
- Catarina Coelho
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Pablo J. González
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - José Trincão
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Ana L. Carvalho
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Shabir Najmudin
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Thomas Hettman
- Institute for Molecular Biotechnology, Beutenbergstrasse 11, 07745 Jena, Germany
| | - Stephan Dieckman
- Institute for Molecular Biotechnology, Beutenbergstrasse 11, 07745 Jena, Germany
| | - José J. G. Moura
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Isabel Moura
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
| | - Maria J. Romão
- REQUIMTE/CQFB, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal
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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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Lalucat J, Bennasar A, Bosch R, García-Valdés E, Palleroni NJ. Biology of Pseudomonas stutzeri. Microbiol Mol Biol Rev 2006; 70:510-47. [PMID: 16760312 PMCID: PMC1489536 DOI: 10.1128/mmbr.00047-05] [Citation(s) in RCA: 325] [Impact Index Per Article: 18.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Pseudomonas stutzeri is a nonfluorescent denitrifying bacterium widely distributed in the environment, and it has also been isolated as an opportunistic pathogen from humans. Over the past 15 years, much progress has been made in elucidating the taxonomy of this diverse taxonomical group, demonstrating the clonality of its populations. The species has received much attention because of its particular metabolic properties: it has been proposed as a model organism for denitrification studies; many strains have natural transformation properties, making it relevant for study of the transfer of genes in the environment; several strains are able to fix dinitrogen; and others participate in the degradation of pollutants or interact with toxic metals. This review considers the history of the discovery, nomenclatural changes, and early studies, together with the relevant biological and ecological properties, of P. stutzeri.
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Affiliation(s)
- Jorge Lalucat
- Department de Biologia, Microbiologia, Universitat de les Illes Balears, 07122 Palma de Mallorca, Spain.
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Argandoña M, Martínez-Checa F, Llamas I, Arco Y, Quesada E, del Moral A. A membrane-bound nitrate reductase encoded by the narGHJI operon is responsible for anaerobic respiration in Halomonas maura. Extremophiles 2006; 10:411-9. [PMID: 16612553 DOI: 10.1007/s00792-006-0515-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Accepted: 01/11/2006] [Indexed: 10/24/2022]
Abstract
The halophilic bacterium Halomonas maura is capable of anaerobic respiration on nitrates. By insertional mutagenesis with the minitransposon Tn-5 we obtained the mutant Tc62, which was incapable of anaerobic respiration on nitrates. An analysis of the regions adjacent to the transposon allowed us to characterize the membrane-bound anaerobic-respiratory nitrate reductase narGHJI gene cluster in H. maura. We identified consensus sequences for fumarate and nitrate reductase regulator (FNR)-like protein-binding sites in the promoter regions of the nar genes and consensus sequences corresponding to the NarL binding sites upstream of the nar genes. RT-PCR analysis showed that the narGHJI operon was expressed in response to anaerobic conditions when nitrate was available as electron acceptor. This membrane-bound nitrate reductase is the only enzyme responsible for anaerobic respiration on nitrate in H. maura. In this article we discuss the possible relationship between this enzyme and a dissimilatory nitrate-reduction-to-ammonia process (DNRA) in H. maura and its role in the colonization of the rhizosphere.
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Affiliation(s)
- Montserrat Argandoña
- Department of Microbiology, Faculty of Pharmacy, University of Granada, Campus Universitario de Cartuja s/n, 18071 Granada, Spain
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Beller HR, Chain PSG, Letain TE, Chakicherla A, Larimer FW, Richardson PM, Coleman MA, Wood AP, Kelly DP. The genome sequence of the obligately chemolithoautotrophic, facultatively anaerobic bacterium Thiobacillus denitrificans. J Bacteriol 2006; 188:1473-88. [PMID: 16452431 PMCID: PMC1367237 DOI: 10.1128/jb.188.4.1473-1488.2006] [Citation(s) in RCA: 225] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2005] [Accepted: 11/30/2005] [Indexed: 11/20/2022] Open
Abstract
The complete genome sequence of Thiobacillus denitrificans ATCC 25259 is the first to become available for an obligately chemolithoautotrophic, sulfur-compound-oxidizing, beta-proteobacterium. Analysis of the 2,909,809-bp genome will facilitate our molecular and biochemical understanding of the unusual metabolic repertoire of this bacterium, including its ability to couple denitrification to sulfur-compound oxidation, to catalyze anaerobic, nitrate-dependent oxidation of Fe(II) and U(IV), and to oxidize mineral electron donors. Notable genomic features include (i) genes encoding c-type cytochromes totaling 1 to 2 percent of the genome, which is a proportion greater than for almost all bacterial and archaeal species sequenced to date, (ii) genes encoding two [NiFe]hydrogenases, which is particularly significant because no information on hydrogenases has previously been reported for T. denitrificans and hydrogen oxidation appears to be critical for anaerobic U(IV) oxidation by this species, (iii) a diverse complement of more than 50 genes associated with sulfur-compound oxidation (including sox genes, dsr genes, and genes associated with the AMP-dependent oxidation of sulfite to sulfate), some of which occur in multiple (up to eight) copies, (iv) a relatively large number of genes associated with inorganic ion transport and heavy metal resistance, and (v) a paucity of genes encoding organic-compound transporters, commensurate with obligate chemolithoautotrophy. Ultimately, the genome sequence of T. denitrificans will enable elucidation of the mechanisms of aerobic and anaerobic sulfur-compound oxidation by beta-proteobacteria and will help reveal the molecular basis of this organism's role in major biogeochemical cycles (i.e., those involving sulfur, nitrogen, and carbon) and groundwater restoration.
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Affiliation(s)
- Harry R Beller
- Lawrence Livermore National Laboratory, P.O. Box 808, L-542, Livermore, California 94551-0808, USA.
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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: 155] [Impact Index Per Article: 8.6] [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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Butler CS, Richardson DJ. The emerging molecular structure of the nitrogen cycle: an introduction to the proceedings of the 10th annual N-cycle meeting. Biochem Soc Trans 2005; 33:113-8. [PMID: 15667280 DOI: 10.1042/bst0330113] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Over the last 10 years, during the lifetime of the nitrogen cycle meetings, structural biology, coupled with spectroscopy, has had a major impact of our understanding enzymology of the nitrogen cycle. The three-dimensional structures for many of the key enzymes have now been resolved and have provided a wealth of information regarding the architecture of redox active metal sites, as well as revealing novel structural folds. Coupled with structure-based spectroscopic analysis, this has led to new insight into the reaction mechanisms of the diverse chemical transformations that together cycle nitrogen in the biosphere. An overview of the some of the key developments in field over the last decade is presented.
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Affiliation(s)
- C S Butler
- Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne, NE2 4HH, UK.
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Jormakka M, Richardson D, Byrne B, Iwata S. Architecture of NarGH reveals a structural classification of Mo-bisMGD enzymes. Structure 2004; 12:95-104. [PMID: 14725769 DOI: 10.1016/j.str.2003.11.020] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
The structure of the catalytic and electron-transfer subunits (NarGH) of the integral membrane protein, respiratory nitrate reductase (Nar) has been determined to 2.0 A resolution revealing the molecular architecture of this Mo-bisMGD (molybdopterin-guanine-dinucleotide) containing enzyme which includes a previously undetected FeS cluster. Nar, together with the related enzyme formate dehydrogenase (Fdh-N), is a key enzyme in the generation of proton motive force across the membrane in Escherichia coli nitrate respiration. A comparative study revealed that Nar and Fdh-N employ different approaches for acquiring substrate, reflecting different catalytic mechanisms. Nar uses a very narrow and nonpolar substrate-conducting cavity with a nonspecific substrate binding site, whereas Fdh-N accommodates a wider, positively charged substrate-conducting cavity with a more specific substrate binding site. The Nar structure also demonstrates the first example of an Asp side chain acting as a Mo ligand providing a structural basis for the classification of Mo-bisMGD enzymes.
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Affiliation(s)
- Mika Jormakka
- Division of Biomedical Sciences, Imperial College London, SW7 2AZ, UK
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Turner RJ, Papish AL, Sargent F. Sequence analysis of bacterial redox enzyme maturation proteins (REMPs). Can J Microbiol 2004; 50:225-38. [PMID: 15213747 DOI: 10.1139/w03-117] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The twin-arginine protein transport (Tat) system is a remarkable molecular machine dedicated to the translocation of fully folded proteins across energy-transducing membranes. Complex cofactor-containing Tat substrates acquire their cofactors prior to export, and substrate proteins actually require to be folded before transport can proceed. Thus, it is very likely that mechanisms exist to prevent wasteful export of immature Tat substrates or to curb competition between immature and mature substrates for the transporter. Here we assess the primary sequence relationships between the accessory proteins implicated in this process during assembly of key respiratory enzymes in the model prokaryote Escherichia coli. For each respiratory enzyme studied, a redox enzyme maturation protein (REMP) was assigned. The main finding from this review was the hitherto unexpected link between the Tat-linked REMP DmsD and the nitrate reductase biosynthetic protein NarJ. The evolutionary link between Tat transport and cofactor insertion processes is discussed.Key words: Tat translocase, twin-arginine leader, hydrogenase, nitrate reductase, TMAO reductase, DMSO reductase, formate dehydrogenase, Tor, Dms, Hya, Hyb, Fdh, Nap.
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Affiliation(s)
- Raymond J Turner
- Department of Biological Sciences, University of Calgary, Alberta, Canada.
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Sohaskey CD, Wayne LG. Role of narK2X and narGHJI in hypoxic upregulation of nitrate reduction by Mycobacterium tuberculosis. J Bacteriol 2003; 185:7247-56. [PMID: 14645286 PMCID: PMC296237 DOI: 10.1128/jb.185.24.7247-7256.2003] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2003] [Accepted: 09/25/2003] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis is one of the strongest reducers of nitrate in the genus Mycobacterium: Under microaerobic conditions, whole cells exhibit upregulation of activity, producing approximately eightfold more nitrite than those of aerobic cultures of the same age. Assays of cell extracts from aerobic cultures and hypoxic cultures yielded comparable nitrate reductase activities. Mycobacterium bovis produced only low levels of nitrite, and this activity was not induced by hypoxia. M. tuberculosis has two sets of genes, narGHJI and narX of the narK2X operon, that exhibit some degree of homology to prokaryotic dissimilatory nitrate reductases. Each of these were knocked out by insertional inactivation. The narG mutant showed no nitrate reductase activity in whole culture or in cell-free assays, while the narX mutant showed wild-type levels in both assays. A knockout of the putative nitrite transporter narK2 gene produced a strain that had aerobic levels of nitrate reductase activity but failed to show hypoxic upregulation. Insertion of the M. tuberculosis narGHJI into a nitrate reductase Escherichia coli mutant allowed anaerobic growth in the presence of nitrate. Under aerobic and hypoxic conditions, transcription of narGHJI was constitutive, while the narK2X operon was induced under hypoxia, as measured with a lacZ reporter system and by quantitative real-time reverse PCR. This indicates that nitrate reductase activity in M. tuberculosis is due to the narGHJI locus with no detectable contribution from narX and that the hypoxic upregulation of activity is associated with the induction of the nitrate and nitrite transport gene narK2.
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Affiliation(s)
- Charles D Sohaskey
- Department of Veterans Affairs Medical Center, Long Beach,and Department of Microbiology and Molecular Genetics, College of Medicine, University of California, Irvine, USA.
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Berks BC, Palmer T, Sargent F. The Tat protein translocation pathway and its role in microbial physiology. Adv Microb Physiol 2003; 47:187-254. [PMID: 14560665 DOI: 10.1016/s0065-2911(03)47004-5] [Citation(s) in RCA: 193] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The Tat (twin arginine translocation) protein transport system functions to export folded protein substrates across the bacterial cytoplasmic membrane and to insert certain integral membrane proteins into that membrane. It is entirely distinct from the Sec pathway. Here, we describe our current knowledge of the molecular features of the Tat transport system. In addition, we discuss the roles that the Tat pathway plays in the bacterial cell, paying particular attention to the involvement of the Tat pathway in the biogenesis of cofactor-containing proteins, in cell wall biosynthesis and in bacterial pathogenicity.
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Affiliation(s)
- Ben C Berks
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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Gross R, Pisa R, Sänger M, Lancaster CRD, Simon J. Characterization of the menaquinone reduction site in the diheme cytochrome b membrane anchor of Wolinella succinogenes NiFe-hydrogenase. J Biol Chem 2003; 279:274-81. [PMID: 14576151 DOI: 10.1074/jbc.m310610200] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The majority of bacterial membrane-bound NiFe-hydrogenases and formate dehydrogenases have homologous membrane-integral cytochrome b subunits. The prototypic NiFe-hydrogenase of Wolinella succinogenes (HydABC complex) catalyzes H2 oxidation by menaquinone during anaerobic respiration and contains a membrane-integral cytochrome b subunit (HydC) that carries the menaquinone reduction site. Using the crystal structure of the homologous FdnI subunit of Escherichia coli formate dehydrogenase-N as a model, the HydC protein was modified to examine residues thought to be involved in menaquinone binding. Variant HydABC complexes were produced in W. succinogenes, and several conserved HydC residues were identified that are essential for growth with H2 as electron donor and for quinone reduction by H2. Modification of HydC with a C-terminal Strep-tag II enabled one-step purification of the HydABC complex by Strep-Tactin affinity chromatography. The tagged HydC, separated from HydAB by isoelectric focusing, was shown to contain 1.9 mol of heme b/mol of HydC demonstrating that HydC ligates both heme b groups. The four histidine residues predicted as axial heme b ligands were individually replaced by alanine in Strep-tagged HydC. Replacement of either histidine ligand of the heme b group proximal to HydAB led to HydABC preparations that contained only one heme b group. This remaining heme b could be completely reduced by quinone supporting the view that the menaquinone reduction site is located near the distal heme b group. The results indicate that both heme b groups are involved in electron transport and that the architecture of the menaquinone reduction site near the cytoplasmic side of the membrane is similar to that proposed for E. coli FdnI.
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Affiliation(s)
- Roland Gross
- Institut für Mikrobiologie, Johann Wolfgang Goethe-Universität, Marie-Curie-Str 9, Frankfurt am Main, Germany
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47
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Lancaster CRD. The structure of Wolinella succinogenes quinol: fumarate reductase and its relevance to the superfamily of succinate: quinone oxidoreductases. ADVANCES IN PROTEIN CHEMISTRY 2003; 63:131-49. [PMID: 12629969 DOI: 10.1016/s0065-3233(03)63006-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- C Roy D Lancaster
- Department of Molecular Membrane Biology, Max Planck Institute of Biophysics, D-60528 Frankfurt am Main, Germany
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Hatzixanthis K, Palmer T, Sargent F. A subset of bacterial inner membrane proteins integrated by the twin-arginine translocase. Mol Microbiol 2003; 49:1377-90. [PMID: 12940994 DOI: 10.1046/j.1365-2958.2003.03642.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A group of bacterial exported proteins are synthesized with N-terminal signal peptides containing a SRRxFLK 'twin-arginine' amino acid motif. Proteins bearing twin-arginine signal peptides are targeted post-translationally to the twin-arginine translocation (Tat) system which transports folded substrates across the inner membrane. In Escherichia coli, most integral inner membrane proteins are assembled by a co-translational process directed by SRP/FtsY, the SecYEG translocase, and YidC. In this work we define a novel class of integral membrane proteins assembled by a Tat-dependent mechanism. We show that at least five E. coli Tat substrate proteins contain hydrophobic C-terminal transmembrane helices (or 'C-tails'). Fusions between the identified transmembrane C-tails and the exclusively Tat-dependent reporter proteins TorA and SufI render the resultant chimeras membrane-bound. Export-linked signal peptide processing and membrane integration of the chimeras is shown to be both Tat-dependent and YidC-independent. It is proposed that the mechanism of membrane integration of proteins by the Tat system is fundamentally distinct from that employed for other bacterial inner membrane proteins.
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Affiliation(s)
- Kostas Hatzixanthis
- Centre for Metalloprotein Spectroscopy and Biology, School of Biological Sciences, University of East Anglia, Norwich, NR4 7TJ, UK
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Bertero MG, Rothery RA, Palak M, Hou C, Lim D, Blasco F, Weiner JH, Strynadka NCJ. Insights into the respiratory electron transfer pathway from the structure of nitrate reductase A. Nat Struct Mol Biol 2003; 10:681-7. [PMID: 12910261 DOI: 10.1038/nsb969] [Citation(s) in RCA: 349] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2003] [Accepted: 07/21/2003] [Indexed: 11/08/2022]
Abstract
The facultative anaerobe Escherichia coli is able to assemble specific respiratory chains by synthesis of appropriate dehydrogenases and reductases in response to the availability of specific substrates. Under anaerobic conditions in the presence of nitrate, E. coli synthesizes the cytoplasmic membrane-bound quinol-nitrate oxidoreductase (nitrate reductase A; NarGHI), which reduces nitrate to nitrite and forms part of a redox loop generating a proton-motive force. We present here the crystal structure of NarGHI at a resolution of 1.9 A. The NarGHI structure identifies the number, coordination scheme and environment of the redox-active prosthetic groups, a unique coordination of the molybdenum atom, the first structural evidence for the role of an open bicyclic form of the molybdo-bis(molybdopterin guanine dinucleotide) (Mo-bisMGD) cofactor in the catalytic mechanism and a novel fold of the membrane anchor subunit. Our findings provide fundamental molecular details for understanding the mechanism of proton-motive force generation by a redox loop.
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Affiliation(s)
- Michela G Bertero
- Department of Biochemistry, University of British Columbia, 2146 Health Sciences Mall, Vancouver, British Columbia V6T 1Z3, Canada
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Pires RH, Lourenço AI, Morais F, Teixeira M, Xavier AV, Saraiva LM, Pereira IAC. A novel membrane-bound respiratory complex from Desulfovibrio desulfuricans ATCC 27774. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1605:67-82. [PMID: 12907302 DOI: 10.1016/s0005-2728(03)00065-3] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
In the anaerobic respiration of sulfate, performed by sulfate-reducing prokaryotes, reduction of the terminal electron acceptor takes place in the cytoplasm. The membrane-associated electron transport chain that feeds electrons to the cytoplasmic reductases is still very poorly characterized. In this study we report the isolation and characterization of a novel membrane-bound redox complex from Desulfovibrio desulfuricans ATCC 27774. This complex is formed by three subunits, and contains two hemes b, two FAD groups and several iron-sulfur centers. The two hemes b are low-spin, with macroscopic redox potentials of +75 and -20 mV at pH 7.6. Both hemes are reduced by menadiol, a menaquinone analogue, indicating a function for this complex in the respiratory electron-transport chain. EPR studies of the as-isolated and dithionite-reduced complex support the presence of a [3Fe-4S](1+/0) center and at least four [4Fe-4S](2+/1+) centers. Cloning of the genes coding for the complex subunits revealed that they form a putative transcription unit and have homology to subunits of heterodisulfide reductases (Hdr). The first and second genes code for soluble proteins that have homology to HdrA, whereas the third gene codes for a novel type of membrane-associated protein that contains both a hydrophobic domain with homology to the heme b protein HdrE and a hydrophilic domain with homology to the iron-sulfur protein HdrC. Homologous operons are found in the genomes of other sulfate-reducing organisms and in the genome of the green-sulfur bacterium Chlorobium tepidum TLS. The isolated complex is the first example of a new family of respiratory complexes present in anaerobic prokaryotes.
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Affiliation(s)
- Ricardo H Pires
- Instituto de Tecnologia Qui;mica e Biológica, Universidade Nova de Lisboa, R. da Quinta Grande 6, Oeiras 2780-156, Portugal
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