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Caldas Nogueira ML, Pastore AJ, Davidson VL. Diversity of structures and functions of oxo-bridged non-heme diiron proteins. Arch Biochem Biophys 2021; 705:108917. [PMID: 33991497 PMCID: PMC8165033 DOI: 10.1016/j.abb.2021.108917] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Revised: 05/04/2021] [Accepted: 05/06/2021] [Indexed: 02/07/2023]
Abstract
Oxo-bridged diiron proteins are a distinct class of non-heme iron proteins. Their active sites are composed of two irons that are coordinated by amino acid side chains, and a bridging oxygen that interacts with each iron. These proteins are members of the ferritin superfamily and share the structural feature of a four α-helix bundle that provides the residues that coordinate the irons. The different proteins also display a wide range of structures and functions. A prototype of this family is hemerythrin, which functions as an oxygen transporter. Several other hemerythrin-like proteins have been described with a diversity of functions including oxygen and iron sensing, and catalytic activities. Rubrerythrins react with hydrogen peroxide and rubrerythrin-like proteins possess a rubredoxin domain, in addition to the oxo-bridged diiron center. Other redox enzymes with oxo-bridged irons include flavodiiron proteins that act as O2 or NO reductases, ribonucleotide reductase and methane monooxygenase. Ferritins have an oxo-bridged diiron in the ferroxidase center of the protein, which plays a role in the iron storage function of these proteins. There are also bacterial ferritins that exhibit catalytic activities. The structures and functions of this broad class of oxo-bridged diiron proteins are described and compared in this review.
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Affiliation(s)
- Maria Luiza Caldas Nogueira
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32827, United States
| | - Anthony J Pastore
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32827, United States
| | - Victor L Davidson
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, 32827, United States.
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2
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Folgosa F, Martins MC, Teixeira M. Diversity and complexity of flavodiiron NO/O2 reductases. FEMS Microbiol Lett 2019; 365:4733271. [PMID: 29240952 DOI: 10.1093/femsle/fnx267] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 12/11/2017] [Indexed: 11/14/2022] Open
Abstract
Flavodiiron proteins (FDPs) are a family of enzymes endowed with nitric oxide (NO) or oxygen reductase activities, forming the innocuous nitrous oxide (N2O) or water molecules, respectively. FDPs are widespread in the three life kingdoms, and have a modular nature, being each monomer minimally constituted by a metallo-β-lactamase-like domain containing a catalytic diiron centre, followed by a flavodoxin one, with a flavin mononucleotide. Since their discovery, additional domains have been found in FDPs, attached to the C-terminus, and containing either extra metal (iron) centers or extra flavin binding modules. Following an extensive analysis of genomic databases, we identified novel domain compositions, and proposed a new classification of FDPs in eight classes based on the nature and number of extra domains.
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3
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Jokel M, Nagy V, Tóth SZ, Kosourov S, Allahverdiyeva Y. Elimination of the flavodiiron electron sink facilitates long-term H 2 photoproduction in green algae. BIOTECHNOLOGY FOR BIOFUELS 2019; 12:280. [PMID: 31827608 PMCID: PMC6894204 DOI: 10.1186/s13068-019-1618-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Accepted: 11/23/2019] [Indexed: 05/14/2023]
Abstract
BACKGROUND The development of renewable and sustainable biofuels to cover the future energy demand is one of the most challenging issues of our time. Biohydrogen, produced by photosynthetic microorganisms, has the potential to become a green biofuel and energy carrier for the future sustainable world, since it provides energy without CO2 emission. The recent development of two alternative protocols to induce hydrogen photoproduction in green algae enables the function of the O2-sensitive [FeFe]-hydrogenases, located at the acceptor side of photosystem I, to produce H2 for several days. These protocols prevent carbon fixation and redirect electrons toward H2 production. In the present work, we employed these protocols to a knockout Chlamydomonas reinhardtii mutant lacking flavodiiron proteins (FDPs), thus removing another possible electron competitor with H2 production. RESULTS The deletion of the FDP electron sink resulted in the enhancement of H2 photoproduction relative to wild-type C. reinhardtii. Additionally, the lack of FDPs leads to a more effective obstruction of carbon fixation even under elongated light pulses. CONCLUSIONS We demonstrated that the rather simple adjustment of cultivation conditions together with genetic manipulation of alternative electron pathways of photosynthesis results in efficient re-routing of electrons toward H2 photoproduction. Furthermore, the introduction of a short recovery phase by regular switching from H2 photoproduction to biomass accumulation phase allows to maintain cell fitness and use photosynthetic cells as long-term H2-producing biocatalysts.
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Affiliation(s)
- Martina Jokel
- Molecular Plant Biology, Department of Biochemistry, University of Turku, 20014 Turku, Finland
| | - Valéria Nagy
- Molecular Plant Biology, Department of Biochemistry, University of Turku, 20014 Turku, Finland
| | - Szilvia Z. Tóth
- Institute of Plant Biology, Biological Research Centre, Szeged, Temesvári krt. 62, Szeged, 6726 Hungary
| | - Sergey Kosourov
- Molecular Plant Biology, Department of Biochemistry, University of Turku, 20014 Turku, Finland
| | - Yagut Allahverdiyeva
- Molecular Plant Biology, Department of Biochemistry, University of Turku, 20014 Turku, Finland
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Romão CV, Vicente JB, Borges PT, Victor BL, Lamosa P, Silva E, Pereira L, Bandeiras TM, Soares CM, Carrondo MA, Turner D, Teixeira M, Frazão C. Structure of Escherichia coli Flavodiiron Nitric Oxide Reductase. J Mol Biol 2016; 428:4686-4707. [PMID: 27725182 DOI: 10.1016/j.jmb.2016.10.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 10/02/2016] [Accepted: 10/04/2016] [Indexed: 01/08/2023]
Abstract
Flavodiiron proteins (FDPs) are present in organisms from all domains of life and have been described so far to be involved in the detoxification of oxygen or nitric oxide (NO), acting as O2 and/or NO reductases. The Escherichia coli FDP, named flavorubredoxin (FlRd), is the most extensively studied FDP. Biochemical and in vivo studies revealed that FlRd is involved in NO detoxification as part of the bacterial defense mechanisms against reactive nitrogen species. E. coli FlRd has a clear preference for NO as a substrate in vitro, exhibiting a very low reactivity toward O2. To contribute to the understanding of the structural features defining this substrate selectivity, we determined the crystallographic structure of E. coli FlRd, both in the isolated and reduced states. The overall tetrameric structure revealed a highly conserved flavodiiron core domain, with a metallo-β-lactamase-like domain containing a diiron center, and a flavodoxin domain with a flavin mononucleotide cofactor. The metal center in the oxidized state has a μ-hydroxo bridge coordinating the two irons, while in the reduced state, this moiety is not detected. Since only the flavodiiron domain was observed in these crystal structures, the structure of the rubredoxin domain was determined by NMR. Tunnels for the substrates were identified, and through molecular dynamics simulations, no differences for O2 or NO permeation were found. The present data represent the first structure for a NO-selective FDP.
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Affiliation(s)
- Célia V Romão
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - João B Vicente
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - Patrícia T Borges
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - Bruno L Victor
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - Pedro Lamosa
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - Elísio Silva
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - Luís Pereira
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - Tiago M Bandeiras
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal; Instituto de Biologia Experimental e Tecnológica, Apartado 12, 2781-901 Oeiras, Portugal
| | - Cláudio M Soares
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - Maria A Carrondo
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - David Turner
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal
| | - Miguel Teixeira
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal.
| | - Carlos Frazão
- Instituto de Tecnologia Química e Biológica António Xavier, ITQB NOVA, Av. da República, 2780-157 Oeiras, Portugal.
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5
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Romão CV, Vicente JB, Borges PT, Frazão C, Teixeira M. The dual function of flavodiiron proteins: oxygen and/or nitric oxide reductases. J Biol Inorg Chem 2016; 21:39-52. [PMID: 26767750 DOI: 10.1007/s00775-015-1329-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 12/28/2015] [Indexed: 12/27/2022]
Abstract
Flavodiiron proteins have emerged in the last two decades as a newly discovered family of oxygen and/or nitric oxide reductases widespread in the three life domains, and present in both aerobic and anaerobic organisms. Herein we present the main features of these fascinating enzymes, with a particular emphasis on the metal sites, as more appropriate for this special issue in memory of the exceptional bioinorganic scientist R. J. P. Williams who pioneered the notion of (metal) element availability-driven evolution. We also compare the flavodiiron proteins with the other oxygen and nitric oxide reductases known until now, highlighting how throughout evolution Nature arrived at different solutions for similar functions, in some cases adding extra features, such as energy conservation. These enzymes are an example of the (bioinorganic) unpredictable diversity of the living world.
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Affiliation(s)
- Célia V Romão
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal
| | - João B Vicente
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal
| | - Patrícia T Borges
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal
| | - Carlos Frazão
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal
| | - Miguel Teixeira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal.
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6
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Belevich NP, Bertsova YV, Verkhovskaya ML, Baykov AA, Bogachev AV. Identification of the coupling step in Na(+)-translocating NADH:quinone oxidoreductase from real-time kinetics of electron transfer. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1857:141-149. [PMID: 26655930 DOI: 10.1016/j.bbabio.2015.12.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Revised: 11/02/2015] [Accepted: 12/03/2015] [Indexed: 10/22/2022]
Abstract
Bacterial Na(+)-translocating NADH:quinone oxidoreductase (Na(+)-NQR) uses a unique set of prosthetic redox groups-two covalently bound FMN residues, a [2Fe-2S] cluster, FAD, riboflavin and a Cys4[Fe] center-to catalyze electron transfer from NADH to ubiquinone in a reaction coupled with Na(+) translocation across the membrane. Here we used an ultra-fast microfluidic stopped-flow instrument to determine rate constants and the difference spectra for the six consecutive reaction steps of Vibrio harveyi Na(+)-NQR reduction by NADH. The instrument, with a dead time of 0.25 ms and optical path length of 1 cm allowed collection of visible spectra in 50-μs intervals. By comparing the spectra of reaction steps with the spectra of known redox transitions of individual enzyme cofactors, we were able to identify the chemical nature of most intermediates and the sequence of electron transfer events. A previously unknown spectral transition was detected and assigned to the Cys4[Fe] center reduction. Electron transfer from the [2Fe-2S] cluster to the Cys4[Fe] center and all subsequent steps were markedly accelerated when Na(+) concentration was increased from 20 μM to 25 mM, suggesting coupling of the former step with tight Na(+) binding to or occlusion by the enzyme. An alternating access mechanism was proposed to explain electron transfer between subunits NqrF and NqrC. According to the proposed mechanism, the Cys4[Fe] center is alternatively exposed to either side of the membrane, allowing the [2Fe-2S] cluster of NqrF and the FMN residue of NqrC to alternatively approach the Cys4[Fe] center from different sides of the membrane.
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Affiliation(s)
- Nikolai P Belevich
- Institute of Biotechnology, University of Helsinki, PO Box 65, Viikinkaari 1, FIN-00014, Finland
| | - Yulia V Bertsova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia
| | - Marina L Verkhovskaya
- Institute of Biotechnology, University of Helsinki, PO Box 65, Viikinkaari 1, FIN-00014, Finland
| | - Alexander A Baykov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia
| | - Alexander V Bogachev
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow 119992, Russia.
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7
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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: 560] [Impact Index Per Article: 56.0] [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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8
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Vicente JB, Testa F, Mastronicola D, Forte E, Sarti P, Teixeira M, Giuffrè A. Redox properties of the oxygen-detoxifying flavodiiron protein from the human parasite Giardia intestinalis. Arch Biochem Biophys 2009; 488:9-13. [PMID: 19545535 DOI: 10.1016/j.abb.2009.06.011] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Revised: 06/17/2009] [Accepted: 06/18/2009] [Indexed: 10/20/2022]
Abstract
Flavodiiron proteins (FDPs) are enzymes identified in prokaryotes and a few pathogenic protozoa, which protect microorganisms by reducing O(2) to H(2)O and/or NO to N(2)O. Unlike most prokaryotic FDPs, the protozoan enzymes from the human pathogens Giardia intestinalis and Trichomonas vaginalis are selective towards O(2). UV/vis and EPR spectroscopy showed that, differently from the NO-consuming bacterial FDPs, the Giardia FDP contains an FMN with reduction potentials for the formation of the single and the two-electron reduced forms very close to each other (E(1)=-66+/-15mV and E(2)=-83+/-15mV), a condition favoring destabilization of the semiquinone radical. Giardia FDP contains also a non-heme diiron site with significantly up-shifted reduction potentials (E(1)=+163+/-20mV and E(2)=+2+/-20mV). These properties are common to the Trichomonas hydrogenosomal FDP, and likely reflect yet undetermined subtle structural differences in the protozoan FDPs, accounting for their marked O(2) specificity.
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Affiliation(s)
- João B Vicente
- Instituto de Tecnologia Quimica e Biologica, Universidade Nova de Lisboa, Oeiras, Portugal
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9
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Petoukhov MV, Vicente JB, Crowley PB, Carrondo MA, Teixeira M, Svergun DI. Quaternary structure of flavorubredoxin as revealed by synchrotron radiation small-angle X-ray scattering. Structure 2008; 16:1428-36. [PMID: 18786405 DOI: 10.1016/j.str.2008.06.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 06/01/2008] [Accepted: 06/03/2008] [Indexed: 10/21/2022]
Abstract
Flavodiiron proteins (FDP) are modular enzymes which function as NO and/or O(2) reductases. Although the majority is composed of two structural domains, the homolog found in Escherichia coli, flavorubredoxin, possesses an extra C-terminal module consisting of a linker and a rubredoxin (Rd) domain necessary for interprotein redox processes. In order to investigate the location of the Rd domain with respect to the flavodiiron structural core, small-angle X-ray scattering was used to construct low-resolution structural models of flavorubredoxin. Scattering patterns from the Rd domain, the FDP core, and full-length flavorubredoxin were collected. The latter two species were found to be tetrameric in solution. Ab initio shape reconstruction and rigid-body modeling indicate a peripheral location for the Rd domains, which appear to have weak contacts with the FDP core. This finding suggests that Rd behaves as an independent domain and is freely available to participate in redox reactions with protein partners.
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Affiliation(s)
- Maxim V Petoukhov
- European Molecular Biology Laboratory, Hamburg Outstation, Notkestrasse 85, 22603 Hamburg, Germany
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10
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Kinetic characterization of the Escherichia coli nitric oxide reductase flavorubredoxin. Methods Enzymol 2008; 437:47-62. [PMID: 18433622 DOI: 10.1016/s0076-6879(07)37003-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
In strict or facultative anaerobic microorganisms, the flavodiiron proteins (FDP) have been recognized to take part in the response mechanism to both nitrosative and oxidative stress. Their function consists of the reduction of nitric oxide and/or oxygen at the diiron center, and specificity for one substrate or the other appears to be characteristic of the corresponding microorganism, possibly depending on the properties of the catalytic site. Particularly focused on the flavorubredoxin, i.e., the Escherichia coli FDP, herein the amperometric and time-resolved spectroscopic approaches are presented, giving access to the study of in vitro reactivity of a complex multi-redox center enzyme.
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Vicente JB, Justino MC, Gonçalves VL, Saraiva LM, Teixeira M. Biochemical, spectroscopic, and thermodynamic properties of flavodiiron proteins. Methods Enzymol 2008; 437:21-45. [PMID: 18433621 DOI: 10.1016/s0076-6879(07)37002-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The flavodiiron proteins (FDPs), present in Archaea, Bacteria, and some protozoan pathogens (mostly anaerobes or microaerophiles), have been proposed to afford protection to microbes against nitric oxide and/or oxygen (toxic for anaerobes). The structural prototype of this protein family is a homodimer assembled in a "head-to-tail" configuration, with each monomer being composed of two domains: an N-terminal metallo-beta-lactamase module harboring a nonheme diiron center (active site of NO/O(2) reduction) and a C-terminal flavodoxin module, where a flavin mononucleotide moiety is embedded. Several FDPs bear C-terminal extra domains, which influence the composition of the respective electron transfer chains that couple NAD(P)H oxidation to NO/O(2) reduction. Herein are described methodologies employed to successfully produce, isolate, and characterize fully operative recombinant flavodiiron proteins. Spectroscopic techniques, namely absorption (visible and near-ultraviolet) and electron paramagnetic resonance spectroscopies, allowed redox-sensitive spectral fingerprints to be obtained, used further in the functional characterization of isolated flavodiiron proteins. Altogether, these studies on pure proteins contribute to understanding the molecular determinants that govern the in vivo function of the FDPs.
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Affiliation(s)
- João B Vicente
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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12
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Di Matteo A, Scandurra FM, Testa F, Forte E, Sarti P, Brunori M, Giuffrè A. The O2-scavenging flavodiiron protein in the human parasite Giardia intestinalis. J Biol Chem 2007; 283:4061-8. [PMID: 18077462 DOI: 10.1074/jbc.m705605200] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The flavodiiron proteins (FDP) are widespread among strict or facultative anaerobic prokaryotes, where they are involved in the response to nitrosative and/or oxidative stress. Unexpectedly, FDPs were fairly recently identified in a restricted group of microaerobic protozoa, including Giardia intestinalis, the causative agent of the human infectious disease giardiasis. The FDP from Giardia was expressed, purified, and extensively characterized by x-ray crystallography, stopped-flow spectroscopy, respirometry, and NO amperometry. Contrary to flavorubredoxin, the FDP from Escherichia coli, the enzyme from Giardia has high O(2)-reductase activity (>40 s(-1)), but very low NO-reductase activity (approximately 0.2 s(-1)); O(2) reacts with the reduced protein quite rapidly (milliseconds) and with high affinity (K(m) < or = 2 microM), producing H(2)O. The three-dimensional structure of the oxidized protein determined at 1.9A resolution shows remarkable similarities with prokaryotic FDPs. Consistent with HPLC analysis, the enzyme is a dimer of dimers with FMN and the non-heme di-iron site topologically close at the monomer-monomer interface. Unlike the FDP from Desulfovibrio gigas, the residue His-90 is a ligand of the di-iron site, in contrast with the proposal that ligation of this histidine is crucial for a preferential specificity for NO. We propose that in G. intestinalis the primary function of FDP is to efficiently scavenge O(2), allowing this microaerobic parasite to survive in the human small intestine, thus promoting its pathogenicity.
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Affiliation(s)
- Adele Di Matteo
- Department of Biochemical Sciences, CNR Institute of Molecular Biology and Pathology and Istituto Pasteur-Fondazione Cenci Bolognetti, Sapienza, University of Rome, Rome I-00185, Italy
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