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Villarreal DG, Rao G, Tao L, Liu L, Rauchfuss TB, Britt RD. Characterizing the Biosynthesis of the [Fe(II)(CN)(CO) 2(cysteinate)] - Organometallic Product of the Radical-SAM Enzyme HydG by EPR and Mössbauer Spectroscopy. J Phys Chem B 2023; 127:9295-9302. [PMID: 37861415 DOI: 10.1021/acs.jpcb.3c05495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2023]
Abstract
[FeFe]-hydrogenases employ a catalytic H-cluster, consisting of a [4Fe-4S]H cluster linked to a [2Fe]H subcluster with CO, CN- ligands, and an azadithiolate bridge, which mediates the rapid redox interconversion of H+ and H2. In the biosynthesis of this H-cluster active site, the radical S-adenosyl-l-methionine (radical SAM, RS) enzyme HydG plays the crucial role of generating an organometallic [Fe(II)(CN)(CO)2(cysteinate)]- product that is en route to forming the H-cluster. Here, we report direct observation of this diamagnetic organometallic Fe(II) complex through Mössbauer spectroscopy, revealing an isomer shift of δ = 0.10 mm s-1 and quadrupole splitting of ΔEQ = 0.66 mm s-1. These Mössbauer values are a change from the starting values of δ = 1.15 mm s-1 and ΔEQ = 3.23 mm s-1 for the ferrous "dangler" Fe in HydG. These values of the observed product complex B are in good agreement with Mössbauer parameters for the low-spin Fe2+ ions in synthetic analogues, such as 57Fe Syn-B, which we report here. These results highlight the essential role that HydG plays in converting a resting-state high-spin Fe(II) to a low-spin organometallic Fe(II) product that can be transferred to the downstream maturase enzymes.
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Affiliation(s)
- David G Villarreal
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| | - Guodong Rao
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| | - Lizhi Tao
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
| | - Liang Liu
- School of Chemical Sciences, University of Illinois at Urbana─Champaign, Urbana, Illinois 61801, United States
| | - Thomas B Rauchfuss
- School of Chemical Sciences, University of Illinois at Urbana─Champaign, Urbana, Illinois 61801, United States
| | - R David Britt
- Department of Chemistry, University of California Davis, Davis, California 95616, United States
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2
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Brown AC, Suess DLM. An Open-Cuboidal [Fe 3S 4] Cluster Characterized in Both Biologically Relevant Redox States. J Am Chem Soc 2023; 145:2075-2080. [PMID: 36688844 DOI: 10.1021/jacs.2c13126] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Synthetic analogues of the three common types of Fe-S clusters found in biology─diamond-core [Fe2S2] clusters, open-cuboidal [Fe3S4] clusters, and cuboidal [Fe4S4] clusters─have been reported in each biologically relevant redox state with one exception: the open-cuboidal [Fe3S4]+ cluster. Here, we describe the synthesis and characterization of an open-cuboidal [Fe3S4] cluster in both biologically relevant redox states: [Fe3S4]+ and [Fe3S4]0. Like their biological counterparts, the oxidized cluster has a spin-canted, S = 1/2 ground state, and the reduced cluster has an S = 2 ground state. Structural analysis reveals that the [Fe3S4] core undergoes substantial contraction upon oxidation, in contrast to the minimal structural changes observed for the only [Fe3S4] protein for which high-resolution structures are available in both redox states (Azotobacter vinelandii ferredoxin I; Av FdI). This difference between the synthetic models and Av FdI is discussed in the context of electron transfer by [Fe3S4] proteins.
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Affiliation(s)
- Alexandra C Brown
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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3
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Abstract
57Fe Mӧssbauer spectroscopy is unparalleled in the study of Fe-S cluster-containing proteins because of its unique ability to detect all forms of iron. Enrichment of biological samples with the 57Fe isotope and manipulation of experimental parameters such as temperature and magnetic field allow for elucidation of the number of Fe-S clusters present in a given protein, their nuclearity, oxidation state, geometry, and ligation environment, as well as any transient states relevant to enzyme chemistry. This chapter is arranged in five sections to help navigate an experimentalist to utilize 57Fe Mӧssbauer spectroscopy for delineating the role and structure of biological Fe-S clusters. The first section lays out the tools and technical considerations for the preparation of 57Fe-labeled samples. The choice of experimental parameters and their effects on the Mӧssbauer spectra are presented in the following two sections. The last two sections provide a theoretical and practical guide on spectral acquisition and analysis relevant to Fe-S centers.
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4
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Stich TA. Characterization of Paramagnetic Iron-Sulfur Clusters Using Electron Paramagnetic Resonance Spectroscopy. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2021; 2353:259-280. [PMID: 34292554 DOI: 10.1007/978-1-0716-1605-5_14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Continuous-wave (CW) electron paramagnetic resonance (EPR) spectroscopy is a powerful ally in characterizing the multitude of redox-active iron-sulfur cluster-containing ([Fe-S]) species present in biological samples. The technique detects only those clusters that are paramagnetic-having a nonzero total electron spin (S > 0)-thus, it can discriminate between clusters in different oxidation states. The low-temperature CW-EPR spectrum of an [Fe-S] yields the three magnetic g-values that serve as a fingerprint of its electronic structure. This chapter briefly describes the underlying theory that defines this electronic structure and provides a recipe for the acquisition and analysis of EPR spectra of [Fe-S] proteins.
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Affiliation(s)
- Troy A Stich
- Department of Chemistry, Wake Forest University, Winston-Salem, NC, USA.
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5
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Postbiosynthetic modification of a precursor to the nitrogenase iron-molybdenum cofactor. Proc Natl Acad Sci U S A 2021; 118:2015361118. [PMID: 33836573 DOI: 10.1073/pnas.2015361118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nitrogenases utilize Fe-S clusters to reduce N2 to NH3 The large number of Fe sites in their catalytic cofactors has hampered spectroscopic investigations into their electronic structures, mechanisms, and biosyntheses. To facilitate their spectroscopic analysis, we are developing methods for incorporating 57Fe into specific sites of nitrogenase cofactors, and we report herein site-selective 57Fe labeling of the L-cluster-a carbide-containing, [Fe8S9C] precursor to the Mo nitrogenase catalytic cofactor. Treatment of the isolated L-cluster with the chelator ethylenediaminetetraacetate followed by reconstitution with 57Fe2+ results in 57Fe labeling of the terminal Fe sites in high yield and with high selectivity. This protocol enables the generation of L-cluster samples in which either the two terminal or the six belt Fe sites are selectively labeled with 57Fe. Mössbauer spectroscopic analysis of these samples bound to the nitrogenase maturase Azotobacter vinelandii NifX reveals differences in the primary coordination sphere of the terminal Fe sites and that one of the terminal sites of the L-cluster binds to H35 of Av NifX. This work provides molecular-level insights into the electronic structure and biosynthesis of the L-cluster and introduces postbiosynthetic modification as a promising strategy for studies of nitrogenase cofactors.
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RirA of Dinoroseobacter shibae senses iron via a [3Fe-4S]1+ cluster co-ordinated by three cysteine residues. Biochem J 2020; 477:191-212. [PMID: 31860023 DOI: 10.1042/bcj20180734] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2018] [Revised: 12/17/2019] [Accepted: 12/19/2019] [Indexed: 12/15/2022]
Abstract
In the marine bacterium, Dinoroseobacter shibae the transcription factor rhizobial iron regulator A (RirA) is involved in the adaptation to iron-limited growth conditions. In vitro iron and sulfide content determinations in combination with UV/Vis and electron paramagnetic resonance (EPR) spectroscopic analyses using anaerobically purified, recombinant RirA protein suggested a [3Fe-4S]1+ cluster as a cofactor. In vivo Mössbauer spectroscopy also corroborated the presence of a [3Fe-4S]1+ cluster in RirA. Moreover, the cluster was found to be redox stable. Three out of four highly conserved cysteine residues of RirA (Cys 91, Cys 99, Cys 105) were found essential for the [3Fe-4S]1+ cluster coordination. The dimeric structure of the RirA protein was independent of the presence of the [3Fe-4S]1+ cluster. Electro mobility shift assays demonstrated the essential role of an intact [3Fe-4S]1+ cluster for promoter binding by RirA. The DNA binding site was identified by DNase I footprinting. Mutagenesis studies in combination with DNA binding assays confirmed the promoter binding site as 3'-TTAAN10AATT-5'. This work describes a novel mechanism for the direct sensing of cellular iron levels in bacteria by an iron-responsive transcriptional regulator using the integrity of a redox-inactive [3Fe-4S]1+ cluster, and further contributes to the general understanding of iron regulation in marine bacteria.
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Wittenborn EC, Cohen SE, Merrouch M, Léger C, Fourmond V, Dementin S, Drennan CL. Structural insight into metallocofactor maturation in carbon monoxide dehydrogenase. J Biol Chem 2019; 294:13017-13026. [PMID: 31296570 DOI: 10.1074/jbc.ra119.009610] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Revised: 07/10/2019] [Indexed: 12/11/2022] Open
Abstract
The nickel-dependent carbon monoxide dehydrogenase (CODH) employs a unique heterometallic nickel-iron-sulfur cluster, termed the C-cluster, to catalyze the interconversion of CO and CO2 Like other complex metalloenzymes, CODH requires dedicated assembly machinery to form the fully intact and functional C-cluster. In particular, nickel incorporation into the C-cluster depends on the maturation factor CooC; however, the mechanism of nickel insertion remains poorly understood. Here, we compare X-ray structures (1.50-2.48 Å resolution) of CODH from Desulfovibrio vulgaris (DvCODH) heterologously expressed in either the absence (DvCODH-CooC) or presence (DvCODH+CooC) of co-expressed CooC. We find that the C-cluster of DvCODH-CooC is fully loaded with iron but does not contain any nickel. Interestingly, the so-called unique iron ion (Feu) occupies both its canonical site (80% occupancy) and the nickel site (20% occupancy), with addition of reductant causing further mismetallation of the nickel site (60% iron occupancy). We also demonstrate that a DvCODH variant that lacks a surface-accessible iron-sulfur cluster (the D-cluster) has a C-cluster that is also replete in iron but lacks nickel, despite co-expression with CooC. In this variant, all Feu is in its canonical location, and the nickel site is empty. This D-cluster-deficient CODH is inactive despite attempts to reconstitute it with nickel. Taken together, these results suggest that an empty nickel site is not sufficient for nickel incorporation. Based on our findings, we propose a model for C-cluster assembly that requires both CooC and a functioning D-cluster, involves precise redox-state control, and includes a two-step nickel-binding process.
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Affiliation(s)
- Elizabeth C Wittenborn
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Steven E Cohen
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Mériem Merrouch
- CNRS, Aix-Marseille Université, Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Marseille, France
| | - Christophe Léger
- CNRS, Aix-Marseille Université, Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Marseille, France
| | - Vincent Fourmond
- CNRS, Aix-Marseille Université, Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Marseille, France
| | - Sébastien Dementin
- CNRS, Aix-Marseille Université, Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Marseille, France.
| | - Catherine L Drennan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; Bio-inspired Solar Energy Program, Canadian Institute for Advanced Research, Toronto, Ontario M5G 1M1, Canada.
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8
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Holm RH, Lo W. Structural Conversions of Synthetic and Protein-Bound Iron–Sulfur Clusters. Chem Rev 2016; 116:13685-13713. [DOI: 10.1021/acs.chemrev.6b00276] [Citation(s) in RCA: 83] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- R. H. Holm
- Department
of Chemistry and
Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
| | - Wayne Lo
- Department
of Chemistry and
Chemical Biology, Harvard University, Cambridge, Massachusetts 02138, United States
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9
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Roncaroli F, Bill E, Friedrich B, Lenz O, Lubitz W, Pandelia ME. Cofactor composition and function of a H 2-sensing regulatory hydrogenase as revealed by Mössbauer and EPR spectroscopy. Chem Sci 2015; 6:4495-4507. [PMID: 29142700 PMCID: PMC5665086 DOI: 10.1039/c5sc01560j] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Accepted: 05/26/2015] [Indexed: 01/22/2023] Open
Abstract
The regulatory hydrogenase (RH) from Ralstonia eutropha H16 acts as a sensor for the detection of environmental H2 and regulates gene expression related to hydrogenase-mediated cellular metabolism. In marked contrast to prototypical energy-converting [NiFe] hydrogenases, the RH is apparently insensitive to inhibition by O2 and CO. While the physiological function of regulatory hydrogenases is well established, little is known about the redox cycling of the [NiFe] center and the nature of the iron-sulfur (FeS) clusters acting as electron relay. The absence of any FeS cluster signals in EPR had been attributed to their particular nature, whereas the observation of essentially only two active site redox states, namely Ni-SI and Ni-C, invoked a different operant mechanism. In the present work, we employ a combination of Mössbauer, FTIR and EPR spectroscopic techniques to study the RH, and the results are consistent with the presence of three [4Fe-4S] centers in the small subunit. In the as-isolated, oxidized RH all FeS clusters reside in the EPR-silent 2+ state. Incubation with H2 leads to reduction of two of the [4Fe-4S] clusters, whereas only strongly reducing agents lead to reduction of the third cluster, which is ascribed to be the [4Fe-4S] center in 'proximal' position to the [NiFe] center. In the two different active site redox states, the low-spin FeII exhibits distinct Mössbauer features attributed to changes in the electronic and geometric structure of the catalytic center. The results are discussed with regard to the spectral characteristics and physiological function of H2-sensing regulatory hydrogenases.
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Affiliation(s)
- Federico Roncaroli
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , 45470 Mülheim an der Ruhr , Germany . ; .,Department of Condensed Matter Physics , Centro Atómico Constituyentes , Comisión Nacional de Energía Atómica (CNEA) , Argentina
| | - Eckhard Bill
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , 45470 Mülheim an der Ruhr , Germany . ;
| | - Bärbel Friedrich
- Institut für Biologie/Mikrobiologie , Humboldt-Universität zu Berlin , Chausseestraße 117 , 10115 Berlin , Germany
| | - Oliver Lenz
- Institut für Biologie/Mikrobiologie , Humboldt-Universität zu Berlin , Chausseestraße 117 , 10115 Berlin , Germany.,Institut für Chemie , Technische Universität Berlin , Max-Volmer-Laboratorium , Straße des 17. Juni 135 , 10623 Berlin , Germany
| | - Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , 45470 Mülheim an der Ruhr , Germany . ;
| | - Maria-Eirini Pandelia
- The Pennsylvania State University , Department of Chemistry , State College , PA 16802 , USA . .,Max-Planck-Institut für Chemische Energiekonversion , Stiftstraße 34-36 , 45470 Mülheim an der Ruhr , Germany . ;
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10
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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: 549] [Impact Index Per Article: 54.9] [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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Martic M, Jakab-Simon IN, Haahr LT, Hagen WR, Christensen HEM. Heterometallic [AgFe(3)S (4)] ferredoxin variants: synthesis, characterization, and the first crystal structure of an engineered heterometallic iron-sulfur protein. J Biol Inorg Chem 2013; 18:261-276. [PMID: 23296387 DOI: 10.1007/s00775-012-0971-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2012] [Accepted: 12/04/2012] [Indexed: 01/12/2023]
Abstract
Heterometallic [AgFe(3)S(4)] iron-sulfur clusters assembled in wild-type Pyrococcus furiosus ferredoxin and two variants, D14C and D14H, are characterized. The crystal structure of the [AgFe(3)S(4)] D14C variant shows that the silver(I) ion is indeed part of the cluster and is coordinated to the thiolate group of residue 14. Cyclic voltammetry shows one redox pair with a reduction potential of +220 mV versus the standard hydrogen electrode which is assigned to the [AgFe(3)S(4)](2+/+) couple. The oxidized form of the [AgFe(3)S(4)] D14C variant is stable in the presence of dioxygen, whereas the oxidized forms of the [AgFe(3)S(4)] wild type and D14H variants convert to the [Fe(3)S(4)] ferredoxin form. The monovalent d (10) silver(I) ion stabilizes the [Fe(3)S(4)](+/0) cluster fragment, as opposed to divalent d (10) metal ions, resulting in more than 0.4 V difference in reduction potentials between the silver(I) and, e.g., zinc(II) heterometallic [MFe(3)S(4)] ferredoxins. The trend in reduction potentials for the variants containing the [AgFe(3)S(4)] cluster is wild type ≤ D14C < D14H and shows the same trend as reported for the variants containing the [Fe(3)S(4)] cluster, but is different from the D14C < D14H < wild type trend reported for the [Fe(4)S(4)] ferredoxin. The similarity in the reduction potential trend for the variants containing the heterometallic [AgFe(3)S(4)] cluster and the [Fe(3)S(4)] cluster can be rationalized in terms of the electrostatic influence of the residue 14 side chains, rather than the dissociation constant of this residue, as is the case for [Fe(4)S(4)] ferredoxins. The trends in reduction potentials are in line with there being no electronic coupling between the silver(I) ion and the Fe(3)S(4) fragment.
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Affiliation(s)
- Maja Martic
- Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800, Kongens Lyngby, Denmark
| | - Ida Noémi Jakab-Simon
- Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800, Kongens Lyngby, Denmark
| | - Lærke Tvedebrink Haahr
- Department of Chemistry, Technical University of Denmark, Kemitorvet 207, 2800, Kongens Lyngby, Denmark
| | - Wilfred Raymond Hagen
- Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, Delft, The Netherlands
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Esrafili MD, Rezaei S, Eftekhari E. A theoretical investigation on geometry and electronic structure of small FemSn nanoclusters (1⩽m,n⩽4). COMPUT THEOR CHEM 2012. [DOI: 10.1016/j.comptc.2012.09.034] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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13
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Hoppe A, Pandelia ME, Gärtner W, Lubitz W. [Fe4S4]- and [Fe3S4]-cluster formation in synthetic peptides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1807:1414-22. [DOI: 10.1016/j.bbabio.2011.06.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 06/24/2011] [Accepted: 06/27/2011] [Indexed: 12/31/2022]
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Abstract
Mössbauer spectroscopy has contributed significantly to the studies of Fe-containing proteins. Early applications yielded detailed electronic characterizations of hemeproteins, and thus enhanced our understanding of the chemical properties of this important class of proteins. The next stage of the applications was marked by major discoveries of several novel Fe clusters of complex structures, including the 8Fe7S P cluster and the mixed metal 1Mo7Fe M center in nitrogenase. Since early 1990 s, rapid kinetic techniques have been used to arrest enzymatic reactions for Mössbauer studies. A number of reaction intermediates were discovered and characterized, both spectroscopically and kinetically, providing unprecedented detailed molecular-level mechanistic information. This chapter gives a brief summary of the historical accounts and a concise description of some experimental and theoretical elements in Mössbauer spectroscopy that are essential for understanding Mössbauer spectra. Major biological applications are summarized at the end.
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15
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Grazina R, de Sousa PMP, Brondino CD, Carepo MSP, Moura I, Moura JJG. Structural redox control in a 7Fe ferredoxin isolated from Desulfovibrio alaskensis. Bioelectrochemistry 2011; 82:22-8. [PMID: 21600857 DOI: 10.1016/j.bioelechem.2011.04.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Revised: 04/05/2011] [Accepted: 04/19/2011] [Indexed: 10/18/2022]
Abstract
The redox behaviour of a ferredoxin (Fd) from Desulfovibrio alaskensis was characterized by electrochemistry. The protein was isolated and purified, and showed to be a tetramer containing one [3Fe-4S] and one [4Fe-4S] centre. This ferredoxin has high homology with FdI from Desulfovibrio vulgaris Miyazaki and Hildenborough and FdIII from Desulfovibrio africanus. From differential pulse voltammetry the following signals were identified: [3Fe-4S](+1/0) (E(0')=-158±5mV); [4Fe-4S](+2/+1) (E(0')=-474±5mV) and [3Fe-4S](0/-2) (E(0')=-660±5mV). The effect of pH on these signals showed that the reduced [3Fe-4S](0) cluster has a pK'(red)(')=5.1±0.1, the [4Fe-4S](+2/+1) centre is pH independent, and the [3Fe-4S](0/-2) reduction is accompanied by the binding of two protons. The ability of the [3Fe-4S](0) cluster to be converted into a new [4Fe-4S] cluster was proven. The redox potential of the original [4Fe-4S] centre showed to be dependent on the formation of the new [4Fe-4S] centre, which results in a positive shift (ca. 70mV) of the redox potential of the original centre. Being most [Fe-S] proteins involved in electron transport processes, the electrochemical characterization of their clusters is essential to understand their biological function. Complementary EPR studies were performed.
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Affiliation(s)
- Raquel Grazina
- REQUIMTE/CQFB, Departamento de Química, Universidade Nova de Lisboa, Caparica, Portugal.
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Hsieh YC, Liu MY, Wang VCC, Chiang YL, Liu EH, Wu WG, Chan SI, Chen CJ. Structural insights into the enzyme catalysis from comparison of three forms of dissimilatory sulphite reductase from Desulfovibrio gigas. Mol Microbiol 2010; 78:1101-16. [DOI: 10.1111/j.1365-2958.2010.07390.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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17
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Bröcker MJ, Schomburg S, Heinz DW, Jahn D, Schubert WD, Moser J. Crystal structure of the nitrogenase-like dark operative protochlorophyllide oxidoreductase catalytic complex (ChlN/ChlB)2. J Biol Chem 2010; 285:27336-27345. [PMID: 20558746 PMCID: PMC2930732 DOI: 10.1074/jbc.m110.126698] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Revised: 04/15/2010] [Indexed: 11/06/2022] Open
Abstract
During (bacterio)chlorophyll biosynthesis of many photosynthetically active organisms, dark operative protochlorophyllide oxidoreductase (DPOR) catalyzes the two-electron reduction of ring D of protochlorophyllide to form chlorophyllide. DPOR is composed of the subunits ChlL, ChlN, and ChlB. Homodimeric ChlL(2) bearing an intersubunit [4Fe-4S] cluster is an ATP-dependent reductase transferring single electrons to the heterotetrameric (ChlN/ChlB)(2) complex. The latter contains two intersubunit [4Fe-4S] clusters and two protochlorophyllide binding sites, respectively. Here we present the crystal structure of the catalytic (ChlN/ChlB)(2) complex of DPOR from the cyanobacterium Thermosynechococcus elongatus at a resolution of 2.4 A. Subunits ChlN and ChlB exhibit a related architecture of three subdomains each built around a central, parallel beta-sheet surrounded by alpha-helices. The (ChlN/ChlB)(2) crystal structure reveals a [4Fe-4S] cluster coordinated by an aspartate oxygen alongside three cysteine ligands. Two equivalent substrate binding sites enriched in aromatic residues for protochlorophyllide substrate binding are located at the interface of each ChlN/ChlB half-tetramer. The complete octameric (ChlN/ChlB)(2)(ChlL(2))(2) complex of DPOR was modeled based on the crystal structure and earlier functional studies. The electron transfer pathway via the various redox centers of DPOR to the substrate is proposed.
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Affiliation(s)
- Markus J Bröcker
- Institut für Mikrobiologie, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
| | - Sebastian Schomburg
- Institut für Mikrobiologie, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
| | - Dirk W Heinz
- Division of Structural Biology, Helmholtz-Centre for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
| | - Dieter Jahn
- Institut für Mikrobiologie, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
| | - Wolf-Dieter Schubert
- Division of Structural Biology, Helmholtz-Centre for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany; Department of Biotechnology, University of the Western Cape, Private Bag X17, Bellville 7535, Cape Town, South Africa.
| | - Jürgen Moser
- Institut für Mikrobiologie, Technische Universität Braunschweig, Spielmannstrasse 7, D-38106 Braunschweig, Germany
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The PqrR transcriptional repressor of Pseudomonas aeruginosa transduces redox signals via an iron-containing prosthetic group. J Bacteriol 2009; 191:6709-21. [PMID: 19717597 DOI: 10.1128/jb.00932-09] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Inducible defenses against oxidative stress are coordinated by redox-sensitive transcription factors that transduce oxidative damage into differential gene expression. The opportunistic human pathogen Pseudomonas aeruginosa has evolved under physiological and host-derived sources of oxidative stress. Previous work showed that the pqrABC and pqrR genes of P. aeruginosa, all lacking known functions, were induced by treatment of three different isolates of P. aeruginosa with paraquat (PQ), a superoxide-producing agent. Insertional mutation of the pqrABCR genes resulted in hypersensitive phenotypes to a variety of oxidants, although the hypersensitivity to PQ was marginal. Mutation of pqrR and complementation assays showed that PqrR regulated the pqrABC genes in response to PQ. PqrR, a member of the MarR family of transcriptional regulators, contains a C-terminal region with four conserved cysteines, which suggested redox-regulated transcriptional activity. Purified PqrR bound to two discrete sites at the pqrA and pqrR regulatory regions. The in vitro DNA binding activity of PqrR was decreased by exposure to air and reconstituted by treatment with dl-dithiothreitol. Elemental analysis and preliminary electron paramagnetic resonance experiments showed that PqrR contains iron. Interestingly, site-directed mutagenesis of C-terminal cysteines demonstrated that the four conserved cysteine residues are essential for in vivo redox sensing by PqrR.
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19
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Frazão C, Aragão D, Coelho R, Leal SS, Gomes CM, Teixeira M, Carrondo MA. Crystallographic analysis of the intact metal centres [3Fe-4S](1+/0) and [4Fe-4S](2+/1+) in a Zn(2+) -containing ferredoxin. FEBS Lett 2008; 582:763-7. [PMID: 18258200 DOI: 10.1016/j.febslet.2008.01.041] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Revised: 01/07/2008] [Accepted: 01/27/2008] [Indexed: 10/22/2022]
Abstract
Detailed structural models of di-cluster seven-iron ferredoxins constitute a valuable resource for folding and stability studies relating the metal cofactors' role in protein stability. The here reported, hemihedric twinned crystal structure at 2.0 A resolution from Acidianus ambivalens ferredoxin, shows an integral 103 residues, physiologically relevant native form composed by a N-terminal extension comprising a His/Asp Zn(2+) site and the ferredoxin (betaalphabeta)(2) core, which harbours intact clusters I and II, a [3Fe-4S](1+/0) and a [4Fe-4S](2+/1+) centres. This is in contrast with the previously available ferredoxin structure from Sulfolofus tokodai, which was obtained from an artificial oxidative conversion with two [3Fe-4S](1+/0) centres and poor definition around cluster II.
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Affiliation(s)
- Carlos Frazão
- Instituto Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av da República, Oeiras, Portugal.
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20
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Barthelme D, Scheele U, Dinkelaker S, Janoschka A, Macmillan F, Albers SV, Driessen AJM, Stagni MS, Bill E, Meyer-Klaucke W, Schünemann V, Tampé R. Structural Organization of Essential Iron-Sulfur Clusters in the Evolutionarily Highly Conserved ATP-binding Cassette Protein ABCE1. J Biol Chem 2007; 282:14598-607. [PMID: 17355973 DOI: 10.1074/jbc.m700825200] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ABC protein ABCE1, formerly named RNase L inhibitor RLI1, is one of the most conserved proteins in evolution and is expressed in all organisms except eubacteria. Because of its fundamental role in translation initiation and/or ribosome biosynthesis, ABCE1 is essential for life. Its molecular mechanism has, however, not been elucidated. In addition to two ABC ATPase domains, ABCE1 contains a unique N-terminal region with eight conserved cysteines, predicted to coordinate iron-sulfur clusters. Here we present detailed information on the type and on the structural organization of the Fe-S clusters in ABCE1. Based on biophysical, biochemical, and yeast genetic analyses, ABCE1 harbors two essential diamagnetic [4Fe-4S](2+) clusters with different electronic environments, one ferredoxin-like (CPX(n)CX(2)CX(2)C; Cys at positions 4-7) and one unique ABCE1-type cluster (CXPX(2)CX(3)CX(n)CP; Cys at positions 1, 2, 3, and 8). Strikingly, only seven of the eight conserved cysteines coordinating the Fe-S clusters are essential for cell viability. Mutagenesis of the cysteine at position 6 yielded a functional ABCE1 with the ferredoxin-like Fe-S cluster in a paramagnetic [3Fe-4S](+) state. Notably, a lethal mutation of the cysteine at position 4 can be rescued by ligand swapping with an adjacent, extra cysteine conserved among all eukaryotes.
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Affiliation(s)
- Dominik Barthelme
- Institute of Biochemistry, Biocenter, Johann Wolfgang Goethe University, Max-von-Laue-Strasse 9, D-60439 Frankfurt am Main, Germany
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21
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Rodrigues PM, Macedo AL, Goodfellow BJ, Moura I, Moura JJG. Desulfovibrio gigas ferredoxin II: redox structural modulation of the [3Fe-4S] cluster. J Biol Inorg Chem 2006; 11:307-15. [PMID: 16453120 DOI: 10.1007/s00775-005-0077-2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Accepted: 12/22/2005] [Indexed: 11/25/2022]
Abstract
Desulfovibrio gigas ferredoxin II (DgFdII) is a small protein with a polypeptide chain composed of 58 amino acids, containing one Fe3S4 cluster per monomer. Upon studying the redox cycle of this protein, we detected a stable intermediate (FdIIint) with four 1H resonances at 24.1, 20.5, 20.8 and 13.7 ppm. The differences between FdIIox and FdIIint were attributed to conformational changes resulting from the breaking/formation of an internal disulfide bridge. The same 1H NMR methodology used to fully assign the three cysteinyl ligands of the [3Fe-4S] core in the oxidized state (DgFdIIox) was used here for the assignment of the same three ligands in the intermediate state (DgFdIIint). The spin-coupling model used for the oxidized form of DgFdII where magnetic exchange coupling constants of around 300 cm-1 and hyperfine coupling constants equal to 1 MHz for all the three iron centres were found, does not explain the isotropic shift temperature dependence for the three cysteinyl cluster ligands in DgFdIIint. This study, together with the spin delocalization mechanism proposed here for DgFdIIint, allows the detection of structural modifications at the [3Fe-4S] cluster in DgFdIIox and DgFdIIint.
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Affiliation(s)
- Pedro M Rodrigues
- FCMA, CCMAR, Universidade do Algarve, Campus de Gambelas, 8005-139, Faro, Portugal
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23
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Tchong SI, Xu H, White RH. L-cysteine desulfidase: an [4Fe-4S] enzyme isolated from Methanocaldococcus jannaschii that catalyzes the breakdown of L-cysteine into pyruvate, ammonia, and sulfide. Biochemistry 2005; 44:1659-70. [PMID: 15683250 DOI: 10.1021/bi0484769] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A [4Fe-4S] enzyme that decomposes L-cysteine to hydrogen sulfide, ammonia, and pyruvate has been isolated and characterized from Methanocaldococcus jannaschii. The sequence of the isolated enzyme demonstrated that the protein was the product of the M. jannaschii MJ1025 gene. The protein product of this gene was recombinantly produced in Escherichia coli and purified to homogeneity. Both the isolated and recombinant enzymes are devoid of pyridoxal phosphate (PLP) and are rapidly inactivated upon exposure to air. The air-inactivated enzyme is activated by reaction with Fe2+ and dithiothreitol in the absence of air. The air-inactivated enzyme contains 3 mol of iron per subunit (43 kDa, SDS gel electrophoresis), and the native enzyme has a measured molecular mass of 135 kDa (gel filtration), indicating it is a trimer. The enzyme is very specific for L-cysteine, with no activity being detected with D-cysteine, L-homocysteine, 3-mercaptopropionic acid (cysteine without the amino group), cysteamine (cysteine without the carboxylic acid), or mercaptolactate (the hydroxyl analogue of cysteine). The activity of the enzyme was stimulated by 40% when the enzyme was assayed in the presence of methyl viologen (4 mM) and inhibited by 70% when the enzyme was assayed in the presence of EDTA (7.1 mM). Preincubation of the enzyme with iodoacetamide (17 mM) completely abolishes activity. The enzymatic activity has a half-life of 8 or 12 min when the enzyme is treated at room temperature with 0.42 mM N-ethylmaleimide (NEM) or 0.42 mM iodoacetamide, respectively. MALDI analysis of the NEM-inactivated enzyme showed Cys25 as the site of alkylation. Site-directed mutagenesis of each of four of the cysteines conserved in the orthologues of the enzyme reduced the catalytic efficiency and thermal stability of the enzyme. The enzyme was found to catalyze exchange of the C-2 hydrogen of the L-cysteine with solvent. These results are consistent with three of the conserved cysteines being involved in the formation of the [4Fe-4S] center and the thiolate of Cys25 serving as a base to abstract the alpha-hydrogen in the first step of the elimination. Although the enzyme has no sequence homology to any known enzymes, including the non-PLP-dependent serine/threonine dehydratases or aconitases, the mechanisms of action of all of these enzymes are similar, in that each catalyzes an alpha,beta-elimination reaction adjacent to a carboxylate group. It is proposed that the enzyme may be responsible for the production of sulfide required for the biosynthesis of iron-sulfur centers in this archaea. A mechanism of action of the enzyme is proposed.
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Affiliation(s)
- Shih-I Tchong
- Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061-0308, USA
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24
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Cicchillo RM, Baker MA, Schnitzer EJ, Newman EB, Krebs C, Booker SJ. Escherichia coli L-Serine Deaminase Requires a [4Fe-4S] Cluster in Catalysis. J Biol Chem 2004; 279:32418-25. [PMID: 15155761 DOI: 10.1074/jbc.m404381200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
L-Serine deaminases catalyze the deamination of L-serine, producing pyruvate and ammonia. Two families of these proteins have been described and are delineated by the cofactor that each employs in catalysis. These are the pyridoxal 5'-phosphate-dependent deaminases and the deaminases that are activated in vitro by iron and dithiothreitol. In contrast to the enzymes that employ pyridoxal 5'-phosphate, detailed physical and mechanistic characterization of the iron-dependent deaminases is limited, primarily because of their extreme instability. We report here the characterization of L-serine deaminase from Escherichia coli, which is the product of the sdaA gene. When purified anaerobically, the isolated protein contains 1.86 +/- 0.46 eq of iron and 0.670 +/- 0.019 eq of sulfide per polypeptide and displays a UV-visible spectrum that is consistent with a [4Fe-4S] cluster. Reconstitution of the protein with iron and sulfide generates considerably more of the cluster, and treatment of the reconstituted protein with dithionite gives rise to an axial EPR spectrum, displaying g axially = 2.03 and g radially = 1.93. Mössbauer spectra of the (57)Fe-reconstituted protein reveal that the majority of the iron is in the form of [4Fe-4S](2+) clusters, as evidenced by the typical Mössbauer parameters-isomer shift, delta = 0.47 mm/s, quadrupole splitting of Delta E(Q) = 1.14 mm/s, and a diamagnetic (S = 0) ground state. Treatment of the dithionite-reduced protein with L-serine results in a slight broadening of the feature at g = 2.03 in the EPR spectrum of the protein, and a dramatic loss in signal intensity, suggesting that the amino acid interacts directly with the cluster.
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Affiliation(s)
- Robert M Cicchillo
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, 16802, USA
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25
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Tong WH, Jameson GNL, Huynh BH, Rouault TA. Subcellular compartmentalization of human Nfu, an iron-sulfur cluster scaffold protein, and its ability to assemble a [4Fe-4S] cluster. Proc Natl Acad Sci U S A 2003; 100:9762-7. [PMID: 12886008 PMCID: PMC187839 DOI: 10.1073/pnas.1732541100] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2003] [Indexed: 11/18/2022] Open
Abstract
Iron-sulfur (Fe-S) clusters serve as cofactors in many proteins that have important redox, catalytic, and regulatory functions. In bacteria, biogenesis of Fe-S clusters is mediated by multiple gene products encoded by the isc and nif operons. In particular, genetic and biochemical studies suggest that IscU, Nfu, and IscA function as scaffold proteins for assembly and delivery of rudimentary Fe-S clusters to target proteins. Here we report the characterization of human Nfu. A combination of biochemical and spectroscopic techniques, including UV-visible absorption and 57Fe Mössbauer spectroscopies, have been used to investigate the ability of purified human Nfu to assemble Fe-S clusters. The results suggest that Nfu can assemble approximately one labile [4Fe-4S] cluster per two Nfu monomers, and support the proposal that Nfu is an alternative scaffold protein for assembly of clusters that are subsequently used for maturation of targeted Fe-S proteins. Analyses of genomic DNA, transcripts, and translation products indicate that alternative splicing of a common pre-mRNA results in synthesis of two Nfu isoforms with distinct subcellular localizations. Isoform I is localized in the mitochondria, whereas isoform II is present in the cytosol and the nucleus. These results, together with previous reports of subcellular distributions of isoforms of human IscS and IscU in mitochondria, cytosol, and nucleus suggest that the Fe-S cluster assembly machineries are compartmentalized in higher eukaryotes.
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Affiliation(s)
- Wing-Hang Tong
- Cell Biology and Metabolism Branch, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
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26
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Jung YS, Bonagura CA, Tilley GJ, Gao-Sheridan HS, Armstrong FA, Stout CD, Burgess BK. Structure of C42D Azotobacter vinelandii FdI. A Cys-X-X-Asp-X-X-Cys motif ligates an air-stable [4Fe-4S]2+/+ cluster. J Biol Chem 2000; 275:36974-83. [PMID: 10961993 DOI: 10.1074/jbc.m004947200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
All naturally occurring ferredoxins that have Cys-X-X-Asp-X-X-Cys motifs contain [4Fe-4S](2+/+) clusters that can be easily and reversibly converted to [3Fe-4S](+/0) clusters. In contrast, ferredoxins with unmodified Cys-X-X-Cys-X-X-Cys motifs assemble [4Fe-4S](2+/+) clusters that cannot be easily interconverted with [3Fe-4S](+/0) clusters. In this study we changed the central cysteine of the Cys(39)-X-X-Cys(42)-X-X-Cys(45) of Azotobacter vinelandii FdI, which coordinates its [4Fe-4S](2+/+) cluster, into an aspartate. UV-visible, EPR, and CD spectroscopies, metal analysis, and x-ray crystallography show that, like native FdI, aerobically purified C42D FdI is a seven-iron protein retaining its [4Fe-4S](2+/+) cluster with monodentate aspartate ligation to one iron. Unlike known clusters of this type the reduced [4Fe-4S](+) cluster of C42D FdI exhibits only an S = 1/2 EPR with no higher spin signals detected. The cluster shows only a minor change in reduction potential relative to the native protein. All attempts to convert the cluster to a 3Fe cluster using conventional methods of oxygen or ferricyanide oxidation or thiol exchange were not successful. The cluster conversion was ultimately accomplished using a new electrochemical method. Hydrophobic and electrostatic interaction and the lack of Gly residues adjacent to the Asp ligand explain the remarkable stability of this cluster.
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Affiliation(s)
- Y S Jung
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA
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27
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Iwasaki T, Watanabe E, Ohmori D, Imai T, Urushiyama A, Akiyama M, Hayashi-Iwasaki Y, Cosper NJ, Scott RA. Spectroscopic investigation of selective cluster conversion of archaeal zinc-containing ferredoxin from Sulfolobus sp. strain 7. J Biol Chem 2000; 275:25391-401. [PMID: 10827091 DOI: 10.1074/jbc.m909243199] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Archaeal zinc-containing ferredoxin from Sulfolobus sp. strain 7 contains one [3Fe-4S] cluster (cluster I), one [4Fe-4S] cluster (cluster II), and one isolated zinc center. Oxidative degradation of this ferredoxin led to the formation of a stable intermediate with 1 zinc and approximately 6 iron atoms. The metal centers of this intermediate were analyzed by electron paramagnetic resonance (EPR), low temperature resonance Raman, x-ray absorption, and (1)H NMR spectroscopies. The spectroscopic data suggest that (i) cluster II was selectively converted to a cubane [3Fe-4S](1+) cluster in the intermediate, without forming a stable radical species, and that (ii) the local metric environments of cluster I and the isolated zinc site did not change significantly in the intermediate. It is concluded that the initial step of oxidative degradation of the archaeal zinc-containing ferredoxin is selective conversion of cluster II, generating a novel intermediate containing two [3Fe-4S] clusters and an isolated zinc center. At this stage, significant structural rearrangement of the protein does not occur. We propose a new scheme for oxidative degradation of dicluster ferredoxins in which each cluster converts in a stepwise manner, prior to apoprotein formation, and discuss its structural and evolutionary implications.
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Affiliation(s)
- T Iwasaki
- Department of Biochemistry and Molecular Biology, Nippon Medical School, Sendagi, Tokyo, Japan. iwasaki/
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28
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Liu A, Gräslund A. Electron paramagnetic resonance evidence for a novel interconversion of [3Fe-4S](+) and [4Fe-4S](+) clusters with endogenous iron and sulfide in anaerobic ribonucleotide reductase activase in vitro. J Biol Chem 2000; 275:12367-73. [PMID: 10777518 DOI: 10.1074/jbc.275.17.12367] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report an EPR study of the iron-sulfur enzyme, anaerobic ribonucleotide reductase activase from Lactococcus lactis. The activase (nrdG gene) together with S-adenosyl-L-methionine (AdoMet) give rise to a glycyl radical in the NrdD component. A semi-reduced [4Fe-4S](+) cluster with an axially symmetric EPR signal was produced upon photochemical reduction of the activase. Air exposure of the reduced enzyme gave a [3Fe-4S](+) cluster. The Fe(3)S(4) cluster was convertible to the EPR-active [4Fe-4S](+) cluster by renewed treatment with reducing agents, demonstrating a reversible [3Fe-4S](+)- to-[4Fe-4S](+) cluster conversion without exogenous addition of iron or sulfide. Anaerobic reduction of the activase by a moderate concentration of dithionite also resulted in a semi-reduced [4Fe-4S](+) cluster. Prolonged reduction gave an EPR-silent fully reduced state, which was enzymatically inactive. Both reduced states gave the [3Fe-4S](+) EPR signal after air exposure. The iron-sulfur cluster interconversion was also studied in the presence of AdoMet. The EPR signal of semi-reduced activase-AdoMet had rhombic symmetry and was independent of which reductant was applied, whereas the EPR signal of the [3Fe-4S](+) cluster after air exposure was unchanged. The results indicate that an AdoMet-mediated [4Fe-4S](+) center is the native active species that induces the formation of a glycyl radical in the NrdD component.
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Affiliation(s)
- A Liu
- Department of Biophysics, Arrhenius Laboratories, Stockholm University, S-106 91 Stockholm, Sweden
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29
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Hannan JP, Busch JL, James R, Thomson AJ, Moore GR, Davy SL. Slow formation of [3Fe-4S](1+) clusters in mutant forms of Desulfovibrio africanus ferredoxin III. FEBS Lett 2000; 468:161-5. [PMID: 10692579 DOI: 10.1016/s0014-5793(00)01210-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Desulfovibrio africanus ferredoxin III (Da FdIII) readily interconverts between a 7Fe and an 8Fe form with Asp-14 believed to provide a cluster ligand in the latter form. To investigate the factors important for cluster interconversion in Fe/S cluster-containing proteins we have studied two variants of Da FdIII produced by site-directed mutagenesis, Asp14Glu and Asp14His, with cluster incorporation performed in vitro. Characterisation of these proteins by UV/visible, EPR and (1)H NMR spectroscopies revealed that the formation of the stable 7Fe form of these proteins takes some time to occur. Evidence is presented which indicates the [4Fe-4S](2+) cluster is incorporated prior to the [3Fe-4S](1+) cluster.
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Affiliation(s)
- J P Hannan
- School of Chemical Sciences, University of East Anglia, Norwich Research Park, Norwich, UK
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30
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The 3Fe containing ferredoxin from Desulfovibrio gigas: an NMR characterization of the oxidised and intermediate states. Coord Chem Rev 1999. [DOI: 10.1016/s0010-8545(99)00126-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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32
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Simple and Complex Iron-Sulfur Proteins in Sulfate Reducing Bacteria. ADVANCES IN INORGANIC CHEMISTRY 1999. [DOI: 10.1016/s0898-8838(08)60083-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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33
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Johnson MK, Duderstadt RE, Duin EC. Biological and Synthetic [Fe3S4] Clusters. ADVANCES IN INORGANIC CHEMISTRY 1999. [DOI: 10.1016/s0898-8838(08)60076-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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34
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Guigliarelli B, Bertrand P. Application of EPR Spectroscopy to the Structural and Functional Study of Iron-Sulfur Proteins. ADVANCES IN INORGANIC CHEMISTRY 1999. [DOI: 10.1016/s0898-8838(08)60084-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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35
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Gao-Sheridan HS, Kemper MA, Khayat R, Tilley GJ, Armstrong FA, Sridhar V, Prasad GS, Stout CD, Burgess BK. A T14C variant of Azotobacter vinelandii ferredoxin I undergoes facile [3Fe-4S]0 to [4Fe-4S]2+ conversion in vitro but not in vivo. J Biol Chem 1998; 273:33692-701. [PMID: 9837955 DOI: 10.1074/jbc.273.50.33692] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
[4Fe-4S]2+/+ clusters that are ligated by Cys-X-X-Cys-X-X-Cys sequence motifs share the general feature of being hard to convert to [3Fe-4S]+/0 clusters, whereas those that contain a Cys-X-X-Asp-X-X-Cys motif undergo facile and reversible cluster interconversion. Little is known about the factors that control the in vivo assembly and conversion of these clusters. In this study we have designed and constructed a 3Fe to 4Fe cluster conversion variant of Azotobacter vinelandii ferredoxin I (FdI) in which the sequence that ligates the [3Fe-4S] cluster in native FdI was altered by converting a nearby residue, Thr-14, to Cys. Spectroscopic and electrochemical characterization shows that when purified in the presence of dithionite, T14C FdI is an O2-sensitive 8Fe protein. Both the new and the indigenous clusters have reduction potentials that are significantly shifted compared with those in native FdI, strongly suggesting a significantly altered environment around the clusters. Interestingly, whole cell EPR have revealed that T14C FdI exists as a 7Fe protein in vivo. This 7Fe form of T14C FdI is extremely similar to native FdI in its spectroscopic, electrochemical, and structural features. However, unlike native FdI which does not undergo facile cluster conversion, the 7Fe form T14C FdI quickly converts to the 8Fe form with a high efficiency under reducing conditions.
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Affiliation(s)
- H S Gao-Sheridan
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, USA
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36
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Sticht H, Rösch P. The structure of iron-sulfur proteins. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1998; 70:95-136. [PMID: 9785959 DOI: 10.1016/s0079-6107(98)00027-3] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Ferredoxins are a group of iron-sulfur proteins for which a wealth of structural and mutational data have recently become available. Previously unknown structures of ferredoxins which are adapted to halophilic, acidophilic or hyperthermophilic environments and new cysteine patterns for cluster ligation and non-cysteine cluster ligation have been described. Site-directed mutagenesis experiments have given insight into factors that influence the geometry, stability, redox potential, electronic properties and electron-transfer reactivity of iron-sulfur clusters.
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Affiliation(s)
- H Sticht
- Lehrstuhl für Struktur und Chemie der Biopolymere, Universität Bayreuth, Germany.
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37
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Abstract
Iron-sulfur proteins are found in all life forms. Most frequently, they contain Fe2S2, Fe3S4, and Fe4S4 clusters. These modular clusters undergo oxidation-reduction reactions, may be inserted or removed from proteins, can influence protein structure by preferential side chain ligation, and can be interconverted. In addition to their electron transfer function, iron-sulfur clusters act as catalytic centers and sensors of iron and oxygen. Their most common oxidation states are paramagnetic and present significant challenges for understanding the magnetic properties of mixed valence systems. Iron-sulfur clusters now rank with such biological prosthetic groups as hemes and flavins in pervasive occurrence and multiplicity of function.
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Affiliation(s)
- H Beinert
- Institute for Enzyme Research and the Department of Biochemistry, University of Wisconsin, Madison, WI 53705, USA
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38
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Khoroshilova N, Popescu C, Münck E, Beinert H, Kiley PJ. Iron-sulfur cluster disassembly in the FNR protein of Escherichia coli by O2: [4Fe-4S] to [2Fe-2S] conversion with loss of biological activity. Proc Natl Acad Sci U S A 1997; 94:6087-92. [PMID: 9177174 PMCID: PMC21006 DOI: 10.1073/pnas.94.12.6087] [Citation(s) in RCA: 250] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The transcription factor FNR (fumarate nitrate reduction) requires the presence of an iron-sulfur (Fe-S) cluster for its function as a global transcription regulator in Escherichia coli when oxygen becomes scarce. To define the oxidation state and type of Fe-S cluster present in the active form of FNR, we have studied anaerobically purified FNR with Mössbauer spectroscopy. Our data showed that this form of FNR contained a [4Fe-4S]2+ cluster (delta = 0.45 mm/s; DeltaEQ = 1.22 mm/s) and that the [4Fe-4S]2+ cluster was rapidly destroyed on exposure of FNR to air. Under these conditions, the yellow-green active form of FNR turned deep red; analysis of sulfide indicated that 70% of the labile sulfide was still present, suggesting that the Fe-S cluster had been converted into a different form. Little [3Fe-4S] cluster was, however, detected by EPR. According to Mössbauer spectroscopy, the [4Fe-4S]2+ cluster was converted in about 60% yield to a [2Fe-2S]2+ cluster (delta = 0.28 mm/s; DeltaEQ = 0.58 mm/s) following 17 min of exposure to air. The [2Fe-2S]2+ cluster form of FNR was much more stable to oxygen, but was unable to sustain biological activity (e.g., DNA binding). However, DNA binding and the absorption spectrum characteristic of the [4Fe-4S]2+ cluster could be largely restored from the [2Fe-2S]2+ form when Cys, Fe, DTT, and the NifS protein were added. It has yet to be determined whether the form of FNR containing the [2Fe-2S]2+ cluster has any biological significance, e.g., as an in vivo intermediate that is more rapidly converted to the active form than the apoprotein.
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Affiliation(s)
- N Khoroshilova
- Department of Biomolecular Chemistry, Medical School, University of Wisconsin, Madison, WI 53706, USA
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39
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Bian S, Hemann CF, Hille R, Cowan JA. Characterization of an autoreduction pathway for the [Fe4S4]3+ cluster of mutant Chromatium vinosum high-potential iron proteins. Site-directed mutagenesis studies to probe the role of phenylalanine 66 in defining the stability of the [Fe4S4] center provide evidence for oxidative degradation via a [Fe3S4] cluster. Biochemistry 1996; 35:14544-52. [PMID: 8931551 DOI: 10.1021/bi961658l] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A number of point mutations of the conserved aromatic residue phenylalanine 66 (Phe66Tyr, -Asn, -Cys, -Ser) in Chromatium vinosum high-potential iron sulfur protein have been examined with the aim of understanding the functional role of this residue. Nonconservative replacements with polar residues have a minimal effect on the midpoint potential of the [Fe4S4]3+/2+ cluster, typically < +25 mV, with a maximum change of +40 mV for Phe66Asn. With the exception of the Phe66Tyr mutant, the oxidized state was found to be unstable relative to the recombinant native, with regeneration of the reduced state. The pathway for this transformation involves degradation of the cluster in a fraction of the sample, which provides the reducing equivalents required to bring about reduction of the remainder of the sample. This degradative reaction proceeds through a transient [Fe3S4]+ intermediate that is characterized by typical g values and power saturation behavior and is prompted by the increased solvent accessibility of the cluster core in the nonconservative Phe66 mutants as evidenced by 1H-15N HMQC NMR experiments. These results are consistent with a model where the critical role of the aromatic residues in the high-potential iron proteins is to protect the cluster from hydrolytic degradation in the oxidized state.
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Affiliation(s)
- S Bian
- Evans Laboratory of Chemistry, Ohio State University, Columbus 43210, USA
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40
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Beinert H, Kennedy MC, Stout CD. Aconitase as Ironminus signSulfur Protein, Enzyme, and Iron-Regulatory Protein. Chem Rev 1996; 96:2335-2374. [PMID: 11848830 DOI: 10.1021/cr950040z] [Citation(s) in RCA: 422] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Helmut Beinert
- Institute for Enzyme Research, Graduate School, and Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin, Madison, Wisconsin 53705, Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, and Department of Molecular Biology, The Scripps Research Institute, La Jolla, California 92037
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41
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Caldeira J, Feicht R, White H, Teixeira M, Moura JJ, Simon H, Moura I. EPR and Mössbauer spectroscopic studies on enoate reductase. J Biol Chem 1996; 271:18743-8. [PMID: 8702530 DOI: 10.1074/jbc.271.31.18743] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Enoate reductase (EC 1.3.1.31) is a protein isolated from Clostridium tyrobutyricum that contains iron, labile sulfide, FAD, and FMN. The enzyme reduces the alpha,beta carbon-carbon double bond of nonactivated 2-enoates and in a reversible way that of 2-enals at the expense of NADH or reduced methyl viologen. UV-visible and EPR potentiometric titrations detect a semiquinone species in redox intermediate states characterized by an isotropic EPR signal at g = 2.0 without contribution at 580 nm. EPR redox titration shows two widely spread mid-point redox potentials (-190 and -350 mV at pH 7. 0), and a nearly stoichiometric amount of this species is detected. The data suggest the semiquinone radical has an anionic nature. In the reduced form, the [Fe-S] moiety is characterized by a single rhombic EPR spectrum, observed in a wide range of temperatures (4. 2-60 K) with g values at 2.013, 1.943, and 1.860 (-180 mV at pH 7.0). The gmax value is low when compared with what has been reported for other iron-sulfur clusters. Mössbauer studies reveal the presence of a [4Fe-4S]+2/+1 center. One of the subcomponents of the spectrum shows an unusually large value of quadrupole splitting (ferrous character) in both the oxidized and reduced states. Substrate binding to the reduced enzyme induces subtle changes in the spectroscopic Mössbauer parameters. The Mössbauer data together with known kinetic information suggest the involvement of this iron-sulfur center in the enzyme mechanism.
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Affiliation(s)
- J Caldeira
- Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2825 Monte de Caparica, Portugal
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42
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Zhou J, Hu Z, Münck E, Holm RH. The Cuboidal Fe3S4 Cluster: Synthesis, Stability, and Geometric and Electronic Structures in a Non-Protein Environment. J Am Chem Soc 1996. [DOI: 10.1021/ja9537843] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Jian Zhou
- Contribution from the Departments of Chemistry, Harvard University, Cambridge, Massachusetts 02138, and Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213
| | - Zhengguo Hu
- Contribution from the Departments of Chemistry, Harvard University, Cambridge, Massachusetts 02138, and Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213
| | - Eckard Münck
- Contribution from the Departments of Chemistry, Harvard University, Cambridge, Massachusetts 02138, and Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213
| | - R. H. Holm
- Contribution from the Departments of Chemistry, Harvard University, Cambridge, Massachusetts 02138, and Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213
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43
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Armengaud J, Gaillard J, Forest E, Jouanneau Y. Characterization of a 2[4Fe-4S] ferredoxin obtained by chemical insertion of the Fe-S clusters into the apoferredoxin II from Rhodobacter capsulatus. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 231:396-404. [PMID: 7635151 DOI: 10.1111/j.1432-1033.1995.tb20712.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The Rhodobacter capsulatus ferredoxin II (FdII) belongs to a family of 7Fe ferredoxins containing one [3Fe-4S] cluster and one [4Fe-4S] cluster. This protein, encoded by the fdxA gene, has been overproduced in Escherichia coli as a soluble apoferredoxin. The purified recombinant protein was subjected to reconstitution experiments by chemical incorporation of the Fe-S clusters under anaerobic conditions. A brown protein was obtained, the formation of which was dependent upon the complete unfolding of the polypeptide prior to incorporation of iron and sulfur atoms. The yield of the reconstituted product was higher when the reaction was carried out at slightly basic pH. The reconstituted ferredoxin was purified and shown to be distinct from the native [7Fe-8S] ferredoxin, based on several biochemical and spectroscopic criteria. In the oxidized state, EPR revealed the quasi-absence of [3Fe-4S] cluster. 1H-NMR spectroscopic analyses provided evidence that the protein was reconstituted as a 2[4Fe-4S] ferredoxin. This conclusion was further supported by the determination by electrospray mass spectrometry of the molecular mass of the reconstituted protein, which matched within 2 Da to the mass of the FdII polypeptide incremented of eight atoms each of iron and sulfur. Exposure of the reconstituted protein to air resulted in a fast and irreversible oxidative denaturation of the Fe-S clusters, without formation of [7Fe-8S] form. Unlike the natural 7Fe ferredoxin, the reconstituted ferredoxin appeared incompetent in an electron-transfer assay coupled to nitrogenase activity. The fact that the apoFdII was reconstituted as a highly unstable 8Fe ferredoxin instead of the 7Fe naturally occurring FdII is discussed in relation to the results obtained with other types of ferredoxins.
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Affiliation(s)
- J Armengaud
- CEA, CNRS URA 1130 alliée à l'INSERM, Département de Biologie Moléculaire et Structurale, Centre d'Etudes Nucléaires de Grenoble, France
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44
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Imai T, Urushiyama A, Saito H, Sakamoto Y, Ota K, Ohmori D. A novel 6Fe (2 x [3Fe-4S]) ferredoxin from Mycobacterium smegmatis. FEBS Lett 1995; 368:23-6. [PMID: 7615081 DOI: 10.1016/0014-5793(95)00601-5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A novel ferredoxin was purified from Mycobacterium smegmatis by a series of hydrophobic chromatographies in the presence of high concentrations of ammonium sulfate and sodium chloride. The ferredoxin exhibited the same peptide map and N-terminal amino acid sequence as the known 7Fe ferredoxin from the same bacterium. On the other hand, this ferredoxin was found to contain approximately 6 Fe/mol ferredoxin and was also shown to contain only [3Fe-4S] clusters by resonance Raman spectroscopy, indicating that it is a novel 6Fe ferredoxin which contains two [3Fe-4S] clusters.
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Affiliation(s)
- T Imai
- Department of Chemistry, Rikkyo (St. Paul's) University, Tokyo, Japan
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45
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Teixeira M, Batista R, Campos AP, Gomes C, Mendes J, Pacheco I, Anemuller S, Hagen WR. A seven-iron ferredoxin from the thermoacidophilic archaeon Desulfurolobus ambivalens. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 227:322-7. [PMID: 7851403 DOI: 10.1111/j.1432-1033.1995.tb20392.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
A seven-iron ferredoxin was isolated from aerobically grown cells of the hyperthermoacidophilic archaeon Desulfurolobus ambivalens (DSM 3772). The protein is monomeric, with an apparent molecular mass of 15 kDa and contains 7 iron atoms/molecule. The N-terminal sequence shows a large similarity (70% identity) with that of the ferredoxin isolated from the archaeon Sulfolobus acidocaldarius. The EPR characteristics in both the native (oxidized) and dithionite-reduced states of this protein allowed an unequivocal identification of a [3Fe-4S]1+/0 center, with a reduction potential of -270 +/- 20 mV, at pH 7.5. The protein also contains a [4Fe-4S]2+/1+ center with a very low reduction potential (Eo = -540 mV, pH 7.0), which yields a rhombic EPR spectrum upon reduction with sodium dithionite at high pH. The reduction potentials of both centers are slightly pH dependent between pH 6 and 9. The [3Fe-4S] ferredoxin center is able to accept electrons from pyruvate oxidase and NADH oxidase isolated from D. ambivalens. This ferredoxin is present in large amounts (at least 130 mg/kg wet cells), which allowed the unequivocal observation of oxidized [3Fe-4S] clusters in intact D. ambivalens cells.
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Affiliation(s)
- M Teixeira
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
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46
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The electronic structure of FeS centers in proteins and models a contribution to the understanding of their electron transfer properties. STRUCTURE AND BONDING 1995. [DOI: 10.1007/3-540-59105-2_1] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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47
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Chen B, Menon NK, Dervertarnian L, Moura JJ, Przybyla AE. Cloning, sequencing and overexpression of the Desulfovibrio gigas ferredoxin gene in E. coli. FEBS Lett 1994; 351:401-4. [PMID: 8082803 DOI: 10.1016/0014-5793(94)00891-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
We have cloned the gene encoding Desulfovibrio gigas ferredoxin using a photodigoxigenin-labelled probe synthesized with the polymerase chain reaction. The DNA sequence of the gene predicts a polypeptide of 58 residues after removal of the initial formyl methionine (polypeptide M(r) = 6,276). The ferredoxin gene was expressed in aerobically grown E. coli behind the lac promoter of pUC18 resulting in a high level of ferredoxin expression which comprises about 10% of the total cell protein. EPR analysis of recombinant ferredoxin revealed the presence of a [3Fe-4S] cluster which is characteristic of native D. gigas ferredoxin II.
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Affiliation(s)
- B Chen
- Department of Biochemistry, University of Georgia, Athens 30602
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48
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Macedo A, Moura I, Surerus K, Papaefthymiou V, Liu M, LeGall J, Münck E, Moura J. Thiol/disulfide formation associated with the redox activity of the [Fe3S4] cluster of Desulfovibrio gigas ferredoxin II. 1H NMR and Mössbauer spectroscopic study. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(17)37158-2] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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49
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Moreno C, Macedo AL, Moura I, LeGall J, Moura JJ. Redox properties of Desulfovibrio gigas [Fe3S4] and [Fe4S4] ferredoxins and heterometal cubane-type clusters formed within the [Fe3S4] core. Square wave voltammetric studies. J Inorg Biochem 1994; 53:219-34. [PMID: 8133257 DOI: 10.1016/0162-0134(94)80006-5] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The same polypeptide chain (58 amino acids, 6 cysteines) is used to build up two ferredoxins in Desulfovibrio gigas a sulfate reducing organism. Ferredoxin II (FdII) contains a single [Fe3S4] core and ferredoxin I (FdI) mainly a [Fe4S4] core. The [Fe3S4] core can readily be interconverted into a [Fe4S4] complex (J.J.G. Moura, I. Moura, T.A. Kent, J.D. Lipscomb, B.H. Huynh, J. LeGall, A.V. Xavier, and E. Munck, J. Biol. Chem. 257, 6259 (1982)). This interconversion process suggested that the [Fe3S4] core could be used as a synthetic precursor for the formation of heterometal clusters. Co, Zn, Cd, and Ni derivatives were produced (I. Moura, J.J.G. Moura, E. Munck, V. Papaephthymiou, and J. LeGall, J. Am. Chem. Soc. 108, 349 (1986), K. Sureurs, E. Munck, I. Moura, J.J.G. Moura, and J. LeGall, J. Am. Chem. Soc. 109, 3805 (1986), and A.L. Macedo, I. Moura, J.J.G. Moura, K. Surerus, and E. Munck, unpublished results). The redox properties of a series of heterometal clusters (MFe3S4] are assessed using direct electrochemistry (square wave voltammetry--SWV) promoted by Mg(II) at a glassy carbon electrode (derivatives: Cd (-495 mV), Fe (-420 mV), Ni (-360 mV), and Co (-245 mV) vs normal hydrogen electrode (NHE)). In parallel, the electrochemical behavior (cyclic voltammetry--CV, differential pulse voltammetry--DPV and SWV) of FdI and FdII were investigated as well as the cluster interconversion process. In addition to the +1/0 (3Fe cluster) and +2/+1 (4Fe cluster) redox transitions, a very negative redox step, at -690 mV, was detected for the 3Fe core, reminiscent of a postulated further 2e- reduction step, as proposed for D. africanus ferredoxin III by F.A. Armstrong, S.J. George, R. Cammack, E.C. Hatchikian, and A.J. Thomson, Biochem. J. 264, 265 (1989). The electrochemical redox potential values are compared with those determined by independent methods (namely by electron paramagnetic resonance (EPR) and visible spectroscopy).
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Affiliation(s)
- C Moreno
- Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova Lisboa, Portugal
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50
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Affiliation(s)
- J J Moura
- Departamento de Quimica, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Portugal
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