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Hagen WR. Quantum Magnetism of the Iron Core in Ferritin Proteins-A Re-Evaluation of the Giant-Spin Model. Molecules 2024; 29:2254. [PMID: 38792115 PMCID: PMC11123763 DOI: 10.3390/molecules29102254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2024] [Revised: 05/04/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
The electron-electron, or zero-field interaction (ZFI) in the electron paramagnetic resonance (EPR) of high-spin transition ions in metalloproteins and coordination complexes, is commonly described by a simple spin Hamiltonian that is second-order in the spin S: H=D[Sz2-SS+1/3+E(Sx2-Sy2). Symmetry considerations, however, allow for fourth-order terms when S ≥ 2. In metalloprotein EPR studies, these terms have rarely been explored. Metal ions can cluster via non-metal bridges, as, for example, in iron-sulfur clusters, in which exchange interaction can result in higher system spin, and this would allow for sixth- and higher-order ZFI terms. For metalloproteins, these have thus far been completely ignored. Single-molecule magnets (SMMs) are multi-metal ion high spin complexes, in which the ZFI usually has a negative sign, thus affording a ground state level pair with maximal spin quantum number mS = ±S, giving rise to unusual magnetic properties at low temperatures. The description of EPR from SMMs is commonly cast in terms of the 'giant-spin model', which assumes a magnetically isolated system spin, and in which fourth-order, and recently, even sixth-order ZFI terms have been found to be required. A special version of the giant-spin model, adopted for scaling-up to system spins of order S ≈ 103-104, has been applied to the ubiquitous iron-storage protein ferritin, which has an internal core containing Fe3+ ions whose individual high spins couple in a way to create a superparamagnet at ambient temperature with very high system spin reminiscent to that of ferromagnetic nanoparticles. This scaled giant-spin model is critically evaluated; limitations and future possibilities are explicitly formulated.
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Affiliation(s)
- Wilfred R Hagen
- Department of Biotechnology, Delft University of Technology, Building 58, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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2
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Lemaire ON, Belhamri M, Wagner T. Structural and biochemical elucidation of class I hybrid cluster protein natively extracted from a marine methanogenic archaeon. Front Microbiol 2023; 14:1179204. [PMID: 37250035 PMCID: PMC10210160 DOI: 10.3389/fmicb.2023.1179204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 04/03/2023] [Indexed: 05/31/2023] Open
Abstract
Whilst widespread in the microbial world, the hybrid cluster protein (HCP) has been paradoxically a long-time riddle for microbiologists. During three decades, numerous studies on a few model organisms unravelled its structure and dissected its metal-containing catalyst, but the physiological function of the enzyme remained elusive. Recent studies on bacteria point towards a nitric oxide reductase activity involved in resistance during nitrate and nitrite reduction as well as host infection. In this study, we isolated and characterised a naturally highly produced HCP class I from a marine methanogenic archaeon grown on ammonia. The crystal structures of the enzyme in a reduced and partially oxidised state, obtained at a resolution of 1.45 and 1.36-Å, respectively, offered a precise picture of the archaeal enzyme intimacy. There are striking similarities with the well-studied enzymes from Desulfovibrio species regarding sequence, kinetic parameters, structure, catalyst conformations, and internal channelling systems. The close phylogenetic relationship between the enzymes from Methanococcales and many Bacteria corroborates this similarity. Indeed, Methanococcales HCPs are closer to these bacterial homologues than to any other archaeal enzymes. The relatively high constitutive production of HCP in M. thermolithotrophicus, in the absence of a notable nitric oxide source, questions the physiological function of the enzyme in these ancient anaerobes.
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3
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Jeoung JH, Fesseler J, Domnik L, Klemke F, Sinnreich M, Teutloff C, Dobbek H. A Morphing [4Fe-3S-nO]-Cluster within a Carbon Monoxide Dehydrogenase Scaffold. Angew Chem Int Ed Engl 2022; 61:e202117000. [PMID: 35133707 PMCID: PMC9311411 DOI: 10.1002/anie.202117000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Indexed: 11/12/2022]
Abstract
Ni,Fe‐containing carbon monoxide dehydrogenases (CODHs) catalyze the reversible reduction of CO2 to CO. Several anaerobic microorganisms encode multiple CODHs in their genome, of which some, despite being annotated as CODHs, lack a cysteine of the canonical binding motif for the active site Ni,Fe‐cluster. Here, we report on the structure and reactivity of such a deviant enzyme, termed CooS‐VCh. Its structure reveals the typical CODH scaffold, but contains an iron‐sulfur‐oxo hybrid‐cluster. Although closely related to true CODHs, CooS‐VCh catalyzes neither CO oxidation, nor CO2 reduction. The active site of CooS‐VCh undergoes a redox‐dependent restructuring between a reduced [4Fe‐3S]‐cluster and an oxidized [4Fe‐2S‐S*‐2O‐2(H2O)]‐cluster. Hydroxylamine, a slow‐turnover substrate of CooS‐VCh, oxidizes the hybrid‐cluster in two structurally distinct steps. Overall, minor changes in CODHs are sufficient to accommodate a Fe/S/O‐cluster in place of the Ni,Fe‐heterocubane‐cluster of CODHs.
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Affiliation(s)
- Jae-Hun Jeoung
- Humboldt-Universität zu Berlin, Institut für Biologie, Unter den Linden 6, 10099, Berlin, Germany
| | - Jochen Fesseler
- Humboldt-Universität zu Berlin, Institut für Biologie, Unter den Linden 6, 10099, Berlin, Germany
| | - Lilith Domnik
- Humboldt-Universität zu Berlin, Institut für Biologie, Unter den Linden 6, 10099, Berlin, Germany
| | - Friederike Klemke
- Humboldt-Universität zu Berlin, Institut für Biologie, Unter den Linden 6, 10099, Berlin, Germany
| | - Malte Sinnreich
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195, Berlin, Germany
| | - Christian Teutloff
- Freie Universität Berlin, Fachbereich Physik, Arnimallee 14, 14195, Berlin, Germany
| | - Holger Dobbek
- Humboldt-Universität zu Berlin, Institut für Biologie, Unter den Linden 6, 10099, Berlin, Germany
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Jeoung J, Fesseler J, Domnik L, Klemke F, Sinnreich M, Teutloff C, Dobbek H. Ein sich umstrukturierender [4Fe‐3S‐nO]‐Cluster in einem Kohlenmonoxid‐Dehydrogenase‐Gerüst. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202117000] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Jae‐Hun Jeoung
- Humboldt-Universität zu Berlin Institut für Biologie Unter den Linden 6 10099 Berlin Deutschland
| | - Jochen Fesseler
- Humboldt-Universität zu Berlin Institut für Biologie Unter den Linden 6 10099 Berlin Deutschland
| | - Lilith Domnik
- Humboldt-Universität zu Berlin Institut für Biologie Unter den Linden 6 10099 Berlin Deutschland
| | - Friederike Klemke
- Humboldt-Universität zu Berlin Institut für Biologie Unter den Linden 6 10099 Berlin Deutschland
| | - Malte Sinnreich
- Freie Universität Berlin, Fachbereich Physik Arnimallee 14 14195 Berlin Deutschland
| | - Christian Teutloff
- Freie Universität Berlin, Fachbereich Physik Arnimallee 14 14195 Berlin Deutschland
| | - Holger Dobbek
- Humboldt-Universität zu Berlin Institut für Biologie Unter den Linden 6 10099 Berlin Deutschland
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6
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Van Stappen C, Jiménez-Vicente E, Pérez-González A, Yang ZY, Seefeldt LC, DeBeer S, Dean DR, Decamps L. A Conformational Role for NifW in the Maturation of Molybdenum Nitrogenase P-cluster. Chem Sci 2022; 13:3489-3500. [PMID: 35432878 PMCID: PMC8943848 DOI: 10.1039/d1sc06418e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 02/28/2022] [Indexed: 12/03/2022] Open
Abstract
Reduction of dinitrogen by molybdenum nitrogenase relies on complex metalloclusters: the [8Fe:7S] P-cluster and the [7Fe:9S:Mo:C:homocitrate] FeMo-cofactor. Although both clusters bear topological similarities and require the reductive fusion of [4Fe:4S] sub-clusters to achieve their respective assemblies, P-clusters are assembled directly on the NifD2K2 polypeptide prior to the insertion of FeMo-co, which is fully assembled separately from NifD2K2. P-cluster maturation involves the iron protein NifH2 as well as several accessory proteins, whose role has not been elucidated. In the present work, two NifD2K2 species bearing immature P-clusters were isolated from an Azotobacter vinelandii strain in which the genes encoding NifH and the accessory protein NifZ were deleted, and characterized by X-ray absorption spectroscopy and EPR. These analyses showed that both NifD2K2 complexes harbor clusters that are electronically and structurally similar, with each NifDK unit containing two [4Fe:4S]2+/+ clusters. Binding of the accessory protein NifW parallels a decrease in the distance between these clusters, as well as a subtle change in their coordination. These results support a conformational role for NifW in P-cluster biosynthesis, bringing the two [4Fe:4S] precursors closer prior to their fusion, which may be crucial in challenging cellular contexts. Upon binding of NifW, a subtle conformation change occurs in NifD2K2, decreasing the distance between the two [4Fe:4S] clusters precursors of the P-cluster in nitrogenase.![]()
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Affiliation(s)
- Casey Van Stappen
- Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 45470 Mülheim an der Ruhr Germany
| | - Emilio Jiménez-Vicente
- Department of Biochemistry, Virginia Polytechnic Institute and State University Blacksburg VA 24061 USA
| | - Ana Pérez-González
- Department of Biochemistry, Virginia Polytechnic Institute and State University Blacksburg VA 24061 USA
| | - Zhi-Yong Yang
- Department of Chemistry and Biochemistry, Utah State University Logan UT 84322 USA
| | - Lance C Seefeldt
- Department of Chemistry and Biochemistry, Utah State University Logan UT 84322 USA
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 45470 Mülheim an der Ruhr Germany
| | - Dennis R Dean
- Department of Biochemistry, Virginia Polytechnic Institute and State University Blacksburg VA 24061 USA
| | - Laure Decamps
- Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 45470 Mülheim an der Ruhr Germany
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7
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Fujishiro T, Ooi M, Takaoka K. Crystal structure of Escherichia coli class II hybrid cluster protein, HCP, reveals a [4Fe-4S] cluster at the N-terminal protrusion. FEBS J 2021; 288:6752-6768. [PMID: 34101368 DOI: 10.1111/febs.16062] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 05/06/2021] [Accepted: 06/07/2021] [Indexed: 01/26/2023]
Abstract
Hybrid cluster protein (HCP) is a unique Fe-S-O-type metallocluster-containing enzyme present in many anaerobic organisms and is categorized into three distinct classes (I, II, and III). The class II HCP uniquely utilizes hybrid cluster protein reductase (HCR), unlike the other classes of HCPs. To gain structural insights into the electron transfer system between the class II HCP and HCR, we elucidated the X-ray crystal structure of Escherichia coli HCP (Ec HCP), representing the first report of a class II HCP structure. Surprisingly, Ec HCP was found to harbor a [4Fe-4S] cluster rather than a [2Fe-2S] cluster at the N-terminal Cys-rich region, similar to class I HCPs. It was also found that the Cys-rich motif forms a unique protrusion and that the surrounding charge distributions on the surface of class II Ec HCP are distinct from those of class I HCPs. The functional significance of the Cys-rich region was investigated using an Ec HCP variant (chimeric HCP) containing a class I HCP Cys-rich motif from Desulfovibrio desulfuricans. The biochemical analyses showed that the chimeric HCP lacks the hybrid cluster and the electron-accepting function from HCR despite the formation of the chimeric HCP-HCR complex. Furthermore, HCP-HCR molecular docking analysis suggested that the protrusion area serves as an HCR-binding region. Therefore, the protrusion of the unique Cys-rich motif and the surrounding area of class II HCP are likely important for maturation of Ec HCP and orienting HCR onto the surface of HCP to facilitate electron transfer in the HCP-HCR complex.
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Affiliation(s)
- Takashi Fujishiro
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Miho Ooi
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Kyosei Takaoka
- Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
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8
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van Lis R, Brugière S, Baffert C, Couté Y, Nitschke W, Atteia A. Hybrid cluster proteins in a photosynthetic microalga. FEBS J 2019; 287:721-735. [PMID: 31361397 DOI: 10.1111/febs.15025] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 05/21/2019] [Accepted: 07/28/2019] [Indexed: 11/30/2022]
Abstract
Hybrid cluster proteins (HCPs) are metalloproteins characterized by the presence of an iron-sulfur-oxygen cluster. These proteins occur in all three domains of life. In eukaryotes, HCPs have so far been found only in a few anaerobic parasites and photosynthetic microalgae. With respect to all species harboring an HCP, the green microalga Chlamydomonas reinhardtii stands out by the presence of four HCP genes. The study of the gene and protein structures as well as the phylogenetic analyses strongly support a model in which the HCP family in the alga has emerged from a single gene of alpha proteobacterial origin and then expanded by several rounds of duplications. The spectra and redox properties of HCP1 and HCP3, produced heterologously in Escherichia coli, were analyzed by electron paramagnetic resonance spectroscopy on redox-titrated samples. Both proteins contain a [4Fe-4S]-cluster as well as a [4Fe-2O-2S]-hybrid cluster with paramagnetic properties related to those of HCPs from Desulfovibrio species. Immunoblotting experiments combined with mass spectrometry-based proteomics showed that both nitrate and darkness contribute to the strong upregulation of the HCP levels in C. reinhardtii growing under oxic conditions. The link to the nitrate metabolism is discussed in the light of recent data on the potential role of HCP in S-nitrosylation in bacteria.
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Affiliation(s)
- Robert van Lis
- Aix Marseille Univ, CNRS, Unité de Bioénergétique et Ingénierie des Protéines, UMR 7281, Marseille, France.,LBE, Univ Montpellier, INRA, Narbonne, France
| | - Sabine Brugière
- Univ Grenoble Alpes, CEA and INSERM, BIG-BGE, Grenoble, France
| | - Carole Baffert
- Aix Marseille Univ, CNRS, Unité de Bioénergétique et Ingénierie des Protéines, UMR 7281, Marseille, France
| | - Yohann Couté
- Univ Grenoble Alpes, CEA and INSERM, BIG-BGE, Grenoble, France
| | - Wolfgang Nitschke
- Aix Marseille Univ, CNRS, Unité de Bioénergétique et Ingénierie des Protéines, UMR 7281, Marseille, France
| | - Ariane Atteia
- Aix Marseille Univ, CNRS, Unité de Bioénergétique et Ingénierie des Protéines, UMR 7281, Marseille, France.,MARBEC CNRS, IFREMER, IRD, Univ. Montpellier, UMR 9091, Sète, France
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9
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Hagen WR. EPR spectroscopy of putative enzyme intermediates in the NO reductase and the auto‐nitrosylation reaction ofDesulfovibrio vulgarishybrid cluster protein. FEBS Lett 2019; 593:3075-3083. [DOI: 10.1002/1873-3468.13539] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2019] [Revised: 07/10/2019] [Accepted: 07/10/2019] [Indexed: 11/11/2022]
Affiliation(s)
- Wilfred R. Hagen
- Department of Biotechnology Delft University of Technology Delft the Netherlands
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10
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Zanello P. Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part IV. Canonical, non-canonical and hybrid iron-sulfur proteins. J Struct Biol 2019; 205:103-120. [PMID: 30677521 DOI: 10.1016/j.jsb.2019.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 01/11/2019] [Accepted: 01/11/2019] [Indexed: 12/26/2022]
Abstract
A plethora of proteins are able to express iron-sulfur clusters, but have a clear picture of the different types of proteins and the different iron-sulfur clusters they harbor it is not easy. In the last five years we have reviewed structure/electrochemistry of metalloproteins expressing: (i) single types of iron-sulfur clusters (namely: {Fe(Cys)4}, {[Fe2S2](Cys)4}, {[Fe2S2](Cys)3(X)} (X = Asp, Arg, His), {[Fe2S2](Cys)2(His)2}, {[Fe3S4](Cys)3}, {[Fe4S4](Cys)4} and {[Fe4S4](Cys)3(nonthiolate ligand)} cores); (ii) metalloproteins harboring iron-sulfur centres of different nuclearities (namely: [4Fe-4S] and [2Fe-2S], [4Fe-4S] and [3Fe-4S], and [4Fe-4S], [3Fe-4S] and [2Fe-2S] clusters. Our target is now to review structure and electrochemistry of proteins harboring canonical, non-canonical and hybrid iron-sulfur proteins.
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Affiliation(s)
- Piero Zanello
- Dipartimento di Biotecnologie, Chimica e Farmacia dell'Università di Siena, Via A. De Gasperi 2, 53100 Siena, Italy
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Sánchez RH, Betley TA. Thermally Persistent High-Spin Ground States in Octahedral Iron Clusters. J Am Chem Soc 2018; 140:16792-16806. [PMID: 30403845 DOI: 10.1021/jacs.8b10181] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chemical oxidation and reduction of the all-ferrous (HL)2Fe6 in THF affords isostructural, coordinatively unsaturated clusters of the type [(HL)2Fe6] n: [(HL)2Fe6][BArF24] (1, n = +1; where [BArF24]- = tetrakis[(3,5-trifluoromethyl)phenyl]borate), [Bu4N][(HL)2Fe6] (2a, n = -1), [P][(HL)2Fe6] (2b, n = -1; where [P]+ = tributyl(1,3-dioxolan-2-ylmethyl)phosphonium), and [Bu4N]2[(HL)2Fe6] (3, n = -2). Each member of the redox-transfer series was characterized by zero-field 57Fe Mössbauer spectroscopy, near-infrared spectroscopy, single-crystal X-ray crystallography, and magnetometry. Redox-directed trends are observed when comparing the structural metrics within the [Fe6] core. The metal octahedron [Fe6] decreases marginally in volume as the molecular reduction state increases as gauged by the Fe-Feavg distance varying from 2.608(11) Å ( n = +1) to 2.573(3) ( n = -2). In contrast, the mean Fe-N distances and ∠Fe-N-Fe angles correlate linearly with the [Fe6] oxidation level, or alternatively, the changes observed within the local Fe-N4 coordination planes vary linearly with the aggregate spin ground state. In general, as the spin ground state ( S) increases, the Fe-N(H)avg distances also increase. The structural metric perturbations within the [Fe6] core and measured spin ground states were rationalized extending the previously proposed molecular orbital diagram derived for (HL)2Fe6. Chemical reduction of the (HL)2Fe6 cluster results in an abrupt increase in spin ground state from S = 6 for the all-ferrous cluster, to S = 19/2 in the monoanionic 2b and S = 11 for the dianionic 3. The observation of asymmetric intervalence charge transfer bands in 3 provides further evidence of the fully delocalized ground state observed by 57Fe Mössbauer spectroscopy for all species examined (1-3). For each of the clusters examined within the electron-transfer series, the observed spin ground states thermally persist to 300 K. In particular, the S = 11 in dianionic 3 and S = 19/2 in the monoanionic 2b represent the highest spin ground states isolated up to room temperature known to date. The increase in spin ground state results from population of the antibonding orbital band comprised of the Fe-N σ* interactions. As such, the thermally persistent ground states arise from population of the resultant single spin manifolds in accordance with Hund's rules. The large spin ground states, indicative of strong ferromagnetic electronic alignment of the valence electrons, result from strong direct exchange electronic coupling mediated by Fe-Fe orbital overlap within the [Fe6] cores, equivalent to a strong double exchange magnetic coupling B for 3 that was calculated to be 309 cm-1.
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Affiliation(s)
- Raúl Hernández Sánchez
- Department of Chemistry and Chemical Biology , Harvard University , 12 Oxford Street , Cambridge , Massachusetts 02138 , United States
| | - Theodore A Betley
- Department of Chemistry and Chemical Biology , Harvard University , 12 Oxford Street , Cambridge , Massachusetts 02138 , United States
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Zanello P. The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part V. {[Fe4S4](SCysγ)4} proteins. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2016.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Sánchez RH, Bartholomew AK, Powers TM, Ménard G, Betley TA. Maximizing Electron Exchange in a [Fe3] Cluster. J Am Chem Soc 2016; 138:2235-43. [PMID: 26799500 PMCID: PMC5567842 DOI: 10.1021/jacs.5b12181] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The one-electron reduction of ((tbs)L)Fe₃(thf)¹ furnishes [M][((tbs)L)Fe₃] ([M]⁺ = [(18-C-6)K(thf)₂]⁺ (1, 76%) or [(crypt-222)K]⁺ (2, 54%)). Upon reduction, the ligand (tbs)L⁶⁻ rearranges around the triiron core to adopt an almost ideal C₃-symmetry. Accompanying the ((tbs)L) ligand rearrangement, the THF bound to the neutral starting material is expelled, and the Fe-Fe distances within the trinuclear cluster contract by ∼0.13 Å in 1. Variable-temperature magnetic susceptibility data indicates a well-isolated S = 11/2 spin ground state that persists to room temperature. Slow magnetic relaxation is observed at low temperature as evidenced by the out-of-phase (χ(M)″) component of the alternating current (ac) magnetic susceptibility data and by the appearance of hyperfine splitting in the zero-field ⁵⁷Fe Mössbauer spectra at 4.2 K. Analysis of the ac magnetic susceptibility yields an effective spin reversal barrier (U(eff)) of 22.6(2) cm⁻¹, nearly matching the theoretical barrier of 38.7 cm⁻¹ calculated from the axial zero-field splitting parameter (D = -1.29 cm⁻¹) extracted from the reduced magnetization data. A polycrystalline sample of 1 displays three sextets in the Mössbauer spectrum at 4.2 K (H(ext) = 0) which converge to a single six-line pattern in a frozen 2-MeTHF glass sample, indicating a unique iron environment and thus strong electron delocalization. The spin ground state and ligand rearrangement are discussed within the framework of a fully delocalized cluster exhibiting strong double and direct exchange interactions.
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Affiliation(s)
- Raúl Hernández Sánchez
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Amymarie K. Bartholomew
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | | | | | - Theodore A. Betley
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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Sánchez RH, Zheng SL, Betley TA. Ligand Field Strength Mediates Electron Delocalization in Octahedral [((H)L)2Fe6(L')m](n+) Clusters. J Am Chem Soc 2015; 137:11126-43. [PMID: 26231520 PMCID: PMC5572642 DOI: 10.1021/jacs.5b06453] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
To assess the impact of terminal ligand binding on a variety of cluster properties (redox delocalization, ground-state stabilization, and breadth of redox state accessibility), we prepared three electron-transfer series based on the hexanuclear iron cluster [((H)L)2Fe6(L')m](n+) in which the terminal ligand field strength was modulated from weak to strong (L' = DMF, MeCN, CN). The extent of intracore M-M interactions is gauged by M-M distances, spin ground state persistence, and preference for mixed-valence states as determined by electrochemical comproportionation constants. Coordination of DMF to the [((H)L)2Fe6] core leads to weaker Fe-Fe interactions, as manifested by the observation of ground states populated only at lower temperatures (<100 K) and by the greater evidence of valence trapping within the mixed-valence states. Comproportionation constants determined electrochemically (Kc = 10(4)-10(8)) indicate that the redox series exhibits electronic delocalization (class II-III), yet no intervalence charge transfer (IVCT) bands are observable in the near-IR spectra. Ligation of the stronger σ donor acetonitrile results in stabilization of spin ground states to higher temperatures (∼300 K) and a high degree of valence delocalization (Kc = 10(2)-10(8)) with observable IVCT bands. Finally, the anionic cyanide-bound series reveals the highest degree of valence delocalization with the most intense IVCT bands (Kc = 10(12)-10(20)) and spin ground state population beyond room temperature. Across the series, at a given formal oxidation level, the capping ligand on the hexairon cluster dictates the overall properties of the aggregate, modulating the redox delocalization and the persistence of the intracore coupling of the metal sites.
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Affiliation(s)
- Raúl Hernández Sánchez
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Shao-Liang Zheng
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Theodore A. Betley
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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Antimicrobial Study of Newly Synthesized Lanthanide(III) Complexes of 2-[2-hydroxy-3-methoxyphenyl]-3-[2-hydroxy-3-methoxybenzylamino]-1,2-dihydroquinazolin-4(3H)-one. Met Based Drugs 2011; 2007:37348. [PMID: 18309372 PMCID: PMC2248225 DOI: 10.1155/2007/37348] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2007] [Accepted: 07/30/2007] [Indexed: 12/02/2022] Open
Abstract
New lanthanide(III) complexes with 2-[2-hydroxy-3-methoxyphenyl]-3-[hydroxyl-3-methoxybenzylamino]-1,2-dihydroquin-
azoline-4(3H)-one (Hmpbaq) have been synthesized and characterized by elemental analysis, conductance measurements, magnetic susceptibilities, spectroscopic (IR, NMR, UV, EPR), and thermal studies. Molar conductance studies indicate 1 : 1 electrolytic behavior for these complexes. IR spectra indicate that Hmpbaq acts as a tridentate ligand coordinating through carbonyl oxygen, benzyl amine nitrogen, and deprotonated phenolic oxygen. TG and DTA studies of La(III) and Pr(III) complexes indicate the presence of two coordinated water molecules. Based on these studies, the complexes have been formulated as [La(mpbaq)2(H2O)2]·NO3, where Ln = La(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Th(III), Dy(III), and Y(III). The ligand, lanthanide(III) salts, and the corresponding complexes have been simultaneously screened for their antibacterial and antifungal activities and compared with the drugs in use.
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Benmelouka M, Vanâ
Tol J, Borel A, Nellutla S, Port M, Helm L, Brunel LC, Merbach A. Multiple-Frequency and Variable-Temperature EPR Study of Gadolinium(III) Complexes with Polyaminocarboxylates: Analysis and Comparison of the Magnetically Dilute Powder and the Frozen-Solution Spectra. Helv Chim Acta 2009. [DOI: 10.1002/hlca.200900117] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Czerwiñski M, Matusiewicz M. Informatics and magnetic behavior of [Fe6S6]3+ superclusters. Theor Chem Acc 2009. [DOI: 10.1007/s00214-009-0572-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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20
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Crystal structure of chlorite dismutase, a detoxifying enzyme producing molecular oxygen. J Mol Biol 2009; 387:192-206. [PMID: 19361444 DOI: 10.1016/j.jmb.2009.01.036] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Revised: 01/16/2009] [Accepted: 01/20/2009] [Indexed: 11/22/2022]
Abstract
Chlorite dismutase (Cld) is a key enzyme of perchlorate and chlorate respiration. This heme-based protein reduces the toxic compound chlorite into the innocuous chloride anion in a very efficient way while producing molecular oxygen. A sequence comparison between Cld homologues shows a highly conserved family. The crystal structure of Azospira oryzae strain GR-1 Cld is reported to 2.1 A resolution. The structure reveals a hexameric organization of the Cld, while each monomer exhibits a ferredoxin-like fold. The six subunits are organized in a ring structure with a maximal diameter of 9 nm and an inner diameter of 2 nm. The heme active-site pocket is solvent accessible both from the inside and the outside of the ring. Moreover, a second anion binding site that could accommodate the assumed reaction intermediate ClO(-) for further transformation has been identified near the active site. The environment of the heme cofactor was investigated with electron paramagnetic resonance spectroscopy. Apart from the high-spin ferric signal of the five-coordinate resting-state enzyme, two low-spin signals were found corresponding to six-coordinate species. The current crystal structure confirms and complements a recently proposed catalytic mechanism that proceeds via a ferryl species and a ClO(-) anion. Our structural data exclude cooperativity between the iron centers.
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Silakov A, Wenk B, Reijerse E, Albracht SPJ, Lubitz W. Spin distribution of the H-cluster in the Hox–CO state of the [FeFe] hydrogenase from Desulfovibrio desulfuricans: HYSCORE and ENDOR study of 14N and 13C nuclear interactions. J Biol Inorg Chem 2008; 14:301-13. [DOI: 10.1007/s00775-008-0449-5] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2008] [Accepted: 11/02/2008] [Indexed: 10/21/2022]
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Lubitz W, Reijerse E, van Gastel M. [NiFe] and [FeFe] Hydrogenases Studied by Advanced Magnetic Resonance Techniques. Chem Rev 2007; 107:4331-65. [PMID: 17845059 DOI: 10.1021/cr050186q] [Citation(s) in RCA: 376] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wolfgang Lubitz
- Max-Planck-Institut für Bioanorganische Chemie, Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany
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Borel A, Clarkson RB, Belford RL. Stochastic Liouville equation treatment of the electron paramagnetic resonance line shape of an S-state ion in solution. J Chem Phys 2007; 126:054510. [PMID: 17302488 DOI: 10.1063/1.2433947] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The current approaches used for the analysis of electron paramagnetic resonance spectra of Gd3+ complexes suffer from a number of drawbacks. Even the elaborate model of [Rast et al., J. Chem. Phys. 113, 8724 (2000)] where the electron spin relaxation is explained by the modulation of the zero-field splitting (ZFS), by molecular tumbling (the so called static contribution), and deformations (transient contribution), is only readily applicable within the validity range of the Redfield theory [Advances in Magnetic Resonance, edited by J.-S. Waugh (Academic, New York, 1965), Vol. 1, p. 1], that is, when the ZFS is small compared to the Zeeman energy and the rotational and vibrational modulations are fast compared to the relaxation time. Spin labels (nitroxides and transition metal complexes) have been studied for years in systems that violate these conditions. The theoretical framework commonly used in such studies is the stochastic Liouville equation (SLE). The authors shall show how the physical model of Rast et al. can be cast into the SLE formalism, paying special attention to the specific problems introduced by the [Uhlenbeck and Ornstein, Phys. Rev. 36, 823 (1930)] process used to model the transient ZFS. The resulting equations are very general and valid for arbitrary correlation times, magnetic field strength, electron spin S, or symmetry. The authors demonstrate the equivalence of the SLE approach with the Redfield approximation for two well-known Gd3+ complexes.
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Affiliation(s)
- Alain Borel
- Illinois EPR Research Center, Department of Chemistry, University of Illinois, Urbana, Illinois, USA.
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Benmelouka M, Van Tol J, Borel A, Port M, Helm L, Brunel LC, Merbach AE. A High-Frequency EPR Study of Frozen Solutions of GdIII Complexes: Straightforward Determination of the Zero-Field Splitting Parameters and Simulation of the NMRD Profiles. J Am Chem Soc 2006; 128:7807-16. [PMID: 16771494 DOI: 10.1021/ja0583261] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Gd(III) (S = 7/2) polyaminocarboxylates, used as contrast agents for Magnetic Resonance Imaging (MRI), were studied in frozen solutions by High-Frequency-High-Field Electron Paramagnetic Resonance (HF-EPR). EPR spectra recorded at 240 GHz and temperatures below 150 K allowed the direct and straightforward determination of parameters governing the strength of zero-field splitting (ZFS). For the first time, a correlation has been established between the sign of the axial ZFS parameter, D, and the nature of the chelating ligand in Gd(III) complexes: positive and negative signs have been observed for acyclic and macrocyclic complexes, respectively. Furthermore, it has been shown that complexes of the less symmetric acyclic DTPA derivatives possess a substantial rhombicity, E, in contrast to the more symmetric macrocyclic DOTA derivatives, where E is negligible. The results obtained are compatible with recent results of liquid-state EPR and allowed to simulate 1H Nuclear Magnetic Relaxation Dispersion (NMRD) profiles with more directly physically meaningful EPR and NMR parameters over the full frequency range from 0.01 to 50 MHz.
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Affiliation(s)
- Meriem Benmelouka
- Laboratoire de Chimie Inorganique et Bioinorganique, Ecole Polytechnique Fédérale de Lausanne, EPFL-BCH, CH-1015 Lausanne, Switzerland
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A Novel Architecture of a Heptadentate Macroacyclic 2,6-Bis [(3-methoxy salicylidene) Hydrazino carbonyl] Pyridine Towards Lanthanides: A Synthetic and Structural Studies of Dinuclear Lanthanide (III) Complexes. J INCL PHENOM MACRO 2006. [DOI: 10.1007/s10847-005-9023-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
Molecular paramagnetism pervades the bioinorganic chemistry of V, Mn, Fe, Co, Ni, Cu, Mo, W, and of a number of non-biological transition elements. To date we can look back at half a century of fruitful EPR studies on metalloproteins, and against this background evaluate the significance of modern EPR spectroscopy from the perspective of a biochemist, making a distinction between conventional continuous wave X-band spectroscopy as a reliable work horse with broad, established applicability even on crude preparations, vs. a diffuse set of "advanced EPR" technologies whose practical application typically calls for narrowly focused research hypotheses and very high quality samples. The type of knowledge on metalloproteins that is readily obtainable with EPR spectroscopy, is explained with illustrative examples, as is the relation between experimental complexity and the spin value of the system.
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Affiliation(s)
- Wilfred R Hagen
- Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628, BC Delft, The Netherlands.
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Cabello P, Pino C, Olmo-Mira MF, Castillo F, Roldán MD, Moreno-Vivián C. Hydroxylamine Assimilation by Rhodobacter capsulatus E1F1. J Biol Chem 2004; 279:45485-94. [PMID: 15322098 DOI: 10.1074/jbc.m404417200] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rhodobacter capsulatus E1F1 grows phototrophically with nitrate as nitrogen source. Using primers designed for conserved motifs in bacterial assimilatory nitrate reductases, a 450-bp DNA was amplified by PCR and used for the screening of a genomic library. A cosmid carrying an insert with four SalI fragments of 2.8, 4.1, 4.5, and 5.8 kb was isolated, and DNA sequencing revealed that it contains a nitrate assimilation (nas) gene region, including the hcp gene coding for a hybrid cluster protein (HCP). Expression of hcp is probably regulated by a nitrite-sensitive repressor encoded by the adjacent nsrR gene. A His(6)-HCP was overproduced in Escherichia coli and purified. HCP contained about 6 iron and 4 labile sulfide atoms per molecule, in agreement with the presence of both [2Fe-2S] and [4Fe-2S-2O] clusters, and showed hydroxylamine reductase activity, forming ammonia in vitro with methyl viologen as reductant. The apparent K(m) values for NH(2)OH and methyl viologen were 1 mM and 7 microM, respectively, at the pH and temperature optima (9.3 and 40 degrees C). The activity was oxygen-sensitive and was inhibited by sulfide and iron reagents. R. capsulatus E1F1 grew phototrophically, but not heterotrophically, with 1 mM NH(2)OH as nitrogen source, and up to 10 mM NH(2)OH was taken up by anaerobic resting cells. Ammonium was transiently accumulated in the media, and its assimilation was prevented by L-methionine-D,L-sulfoximine, a glutamine synthetase inhibitor. In addition, hydroxylamine- or nitrite-grown cells showed the higher hydroxylamine reductase activities. However, R. capsulatus B10S, a strain lacking the whole hcp-nas region, did not grow with 1 mM NH(2)OH. Also, E. coli cells overproducing HCP tolerate hydroxyl-amine better during anaerobic growth. These results suggest that HCP is involved in assimilation of NH(2)OH, a toxic product that could be formed during nitrate assimilation, probably in the nitrite reduction step.
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Affiliation(s)
- Purificación Cabello
- Departamento de Biología Vegetal, Area de Fisiología Vegetal, Edificio Celestino Mutis, 3 planta, Campus Universitario de Rabanales, Universidad de Córdoba, Córdoba, Spain
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van den Berg WA, Hagen WR, van Dongen WM. The hybrid-cluster protein ('prismane protein') from Escherichia coli. Characterization of the hybrid-cluster protein, redox properties of the [2Fe-2S] and [4Fe-2S-2O] clusters and identification of an associated NADH oxidoreductase containing FAD and [2Fe-2S]. EUROPEAN JOURNAL OF BIOCHEMISTRY 2000; 267:666-76. [PMID: 10651802 DOI: 10.1046/j.1432-1327.2000.01032.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hybrid-cluster proteins ('prismane proteins') have previously been isolated and characterized from strictly anaerobic sulfate-reducing bacteria. These proteins contain two types of Fe/S clusters unique in biological systems: a [4Fe-4S] cubane cluster with spin-admixed S = 3/2 ground-state paramagnetism and a novel type of hybrid [4Fe-2S-2O] cluster, which can attain four redox states. Genomic sequencing reveals that genes encoding putative hybrid-cluster proteins are present in a range of bacterial and archaeal species. In this paper we describe the isolation and spectroscopic characterization of the hybrid-cluster protein from Escherichia coli. EPR spectroscopy shows the presence of a hybrid cluster in the E. coli protein with characteristics similar to those in the proteins of anaerobic sulfate reducers. EPR spectra of the reduced E. coli hybrid-cluster protein, however, give evidence for the presence of a [2Fe-2S] cluster instead of a [4Fe-4S] cluster. The hcp gene encoding the hybrid-cluster protein in E. coli and other facultative anaerobes occurs, in contrast with hcp genes in obligate anaerobic bacteria and archaea, in a small operon with a gene encoding a putative NADH oxidoreductase. This NADH oxidoreductase was also isolated and shown to contain FAD and a [2Fe-2S] cluster as cofactors. It catalysed the reduction of the hybrid-cluster protein with NADH as an electron donor. Midpoint potentials (25 degrees C, pH 7.5) for the Fe/S clusters in both proteins indicate that electrons derived from the oxidation of NADH (Em NADH/NAD+ couple: -320 mV) are transferred along the [2Fe-2S] cluster of the NADH oxidoreductase (Em = -220 mV) and the [2Fe-2S] cluster of the hybrid-cluster protein (Em = -35 mV) to the hybrid cluster (Em = -50, +85 and +365 mV for the three redox transitions). The physiological function of the hybrid-cluster protein has not yet been elucidated. The protein is only detected in the facultative anaerobes E. coli and Morganella morganii after cultivation under anaerobic conditions in the presence of nitrate or nitrite, suggesting a role in nitrate-and/or nitrite respiration.
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Affiliation(s)
- W A van den Berg
- Department of Biomolecular Sciences, Wageningen University, The Netherlands.
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Matusiewicz M, Czerwiński M, Kasperczyk J, Kityk IV. Description of spin interactions in model [Fe6S6]4+ supercluster. J Chem Phys 1999. [DOI: 10.1063/1.480024] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Pereira AS, Tavares P, Krebs C, Huynh BH, Rusnak F, Moura I, Moura JJ. Biochemical and spectroscopic characterization of overexpressed fuscoredoxin from Escherichia coli. Biochem Biophys Res Commun 1999; 260:209-15. [PMID: 10381368 DOI: 10.1006/bbrc.1999.0748] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Fuscoredoxin is a unique iron containing protein of yet unknown function originally discovered in the sulfate reducers of the genus Desulfovibrio. It contains two iron-sulfur clusters: a cubane [4Fe-4S] and a mixed oxo- and sulfido-bridged 4Fe cluster of unprecedented structure. The recent determination of the genomic sequence of Escherichia coli (E. coli) has revealed a homologue of fuscoredoxin in this facultative microbe. The presence of this gene in E. coli raises interesting questions regarding the function of fuscoredoxin and whether this gene represents a structural homologue of the better-characterized Desulfovibrio proteins. In order to explore the latter, an overexpression system for the E. coli fuscoredoxin gene was devised. The gene was cloned from genomic DNA by use of the polymerase chain reaction into the expression vector pT7-7 and overexpressed in E. coli BL21(DE3) cells. After two chromatographic steps a good yield of recombinant protein was obtained (approximately 4 mg of pure protein per liter of culture). The purified protein exhibits an optical spectrum characteristic of the homologue from D. desulfuricans, indicating that cofactor assembly was accomplished. Iron analysis indicated that the protein contains circa 8 iron atoms/molecule which were shown by EPR and Mössbauer spectroscopies to be present as two multinuclear clusters, albeit with slightly altered spectroscopic features. A comparison of the primary sequences of fuscoredoxins is presented and differences on cluster coordination modes are discussed on the light of the spectroscopic data.
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Affiliation(s)
- A S Pereira
- Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Monte de Caparica, 2825-114, Portugal
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31
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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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32
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Arendsen AF, Lindley PF. The Search for A “Prismane” Fe–S Protein. ADVANCES IN INORGANIC CHEMISTRY 1999. [DOI: 10.1016/s0898-8838(08)60079-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Dominy CN, Deane SM, Rawlings DE. A geographically widespread plasmid from Thiobacillus ferrooxidans has genes for ferredoxin-, FNR-, prismane- and NADH-oxidoreductase-like proteins which are also located on the chromosome. MICROBIOLOGY (READING, ENGLAND) 1997; 143 ( Pt 10):3123-3136. [PMID: 9353917 DOI: 10.1099/00221287-143-10-3123] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
During a search for genes encoding electron transport proteins from a Thiobacillus ferroxidans ATCC 33020 gene bank, a 19.8 kb plasmid, pTF5, which conferred increased sensitivity to the antimicrobial agent metronidazole upon an Escherichia coli mutant, was isolated and cloned in E. coli. The plasmid had an identical restriction enzyme map to a plasmid which has been found in T. ferrooxidans strains isolated from many different parts of the world. The plasmid was present at between two and four copies per genome and contained a region of approximately 5-6 kb which was also found on the chromosome. This region was sequenced and found to have four complete ORFs, which when translated had high percentage amino acid similarity to [3Fe-4S,4Fe-4S] ferredoxins, proteins of the FNR regulator family, prismane-like proteins and the NADH oxidoreductase subunit of a methane monooxygenase. In vitro protein analysis using an E. coli-derived transcription-translation system indicated that three of the four products (FdxA, PsmA and RedA) were expressed in the heterologous system. Ferredoxins, prismane-like proteins and NADH oxidoreductases are redox-active proteins and it is likely that the proteins on pTF5 represent an electron transport system of as yet unknown function. Surprisingly, although genes for redox-active proteins have been isolated from other bacteria by screening gene banks for increased sensitivity to metronidazole, the region of pTF5 containing the genes for these proteins was not responsible for the increase in metronidazole sensitivity conferred by the plasmid. The region of pTF5 which did confer increased metronidazole sensitivity to an E. coli metronidazole-resistant mutant was a 319 bp region of DNA close to the origin of plasmid replication. This region contained no ORFs and was identical to that previously reported for the replicon of a 9.8 kb T. ferrooxidans plasmid, pTF191.
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Affiliation(s)
- Clifford N Dominy
- Department of Microbiology, University of Cape Town, Private Bag Rondebosch, Cape Town 7700, South Africa
| | - Shelly M Deane
- Department of Microbiology, University of Cape Town, Private Bag Rondebosch, Cape Town 7700, South Africa
| | - Douglas E Rawlings
- Department of Microbiology, University of Cape Town, Private Bag Rondebosch, Cape Town 7700, South Africa
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Boll M, Albracht SS, Fuchs G. Benzoyl-CoA reductase (dearomatizing), a key enzyme of anaerobic aromatic metabolism. A study of adenosinetriphosphatase activity, ATP stoichiometry of the reaction and EPR properties of the enzyme. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 244:840-51. [PMID: 9108255 DOI: 10.1111/j.1432-1033.1997.00840.x] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
An enzyme was recently described, benzoyl-CoA reductase (dearomatizing), which catalyses the ATP-driven reduction of the aromatic ring of benzoyl-CoA yielding a non-aromatic CoA thioester, ADP and phosphate [Boll, M. & Fuchs, G. (1995) Eur. J. Biochem. 234, 921-933]. The 170-kDa enzyme consists of four different subunits and contains approximately 12 Fe and acid-labile sulfur/mol. Benzoyl-CoA reductase exhibits ATPase activity in the absence of substrate. It is shown that only the reduced form of this iron-sulfur protein has ATPase activity. ATPase activity is reversibly lost when the enzyme is oxidized by thionine; reduction of the enzyme fully restores ATPase and ring-reduction activity. 2 mol ATP are hydrolyzed/2 mol electrons transferred in the course of the reaction. The product ADP acts as competitive inhibitor (Ki = 1.1 mM) for ATP in benzoyl-CoA reduction; ADP inhibits ATPase activity to the same extent as ring-reduction activity. EPR investigation of the dithionite-reduced enzyme suggested the presence of two separate [2Fe-2S] clusters and two interacting [4Fe-4S] clusters. Addition of MgATP to the reduced enzyme resulted in a new isotropic signal at g = 5.15 and a weak signal at g = 12; in controls with MgADP only a minor signal at g = 5.15 was observed. The positions, shapes and temperature dependencies of these MgATP-induced signals are indicative for excited states of a S = 7/2 spin multiplet. The [2Fe-2S] signals were not affected by ATP, but one of the [4Fe-4S] clusters became slowly oxidized. Addition of both benzoyl-CoA and MgATP resulted in a major oxidation of the iron-sulfur clusters accompanied by the appearance of some minor signals of unknown origin in the g = 2.037-1.96 region. Neither the benzoyl-CoA plus MgATP-oxidized nor the thionine-oxidized enzyme showed the ATP-dependent formation of the high-spin signals of the reduced enzyme. At present we hypothesize that the S = 7/2 signal is due to an ATP-induced change of one of the [4Fe-4S] clusters. The data suggest that hydrolysis of MgATP is required to activate the enzyme; in the absence of substrate the energy involved in this activation dissipates. MgATP-driven formation of this excited state of the reduced enzyme rather than transfer of electrons from the reduced enzyme to the aromatic substrate appears to be the rate-limiting step in the catalytic cycle. We suggest that the excited state is required to overcome the high activation energy associated with the loss of the aromatic character and/or to render ring reduction irreversible.
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Affiliation(s)
- M Boll
- Mikrobiologie, Institut Biologie II, Universität Freiburg, Germany
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Iron-sulfur clusters: fascinating magnetic structures at the heart of ubiquitous proteins. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s1251-8069(99)80015-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Marritt SJ, Hagen WF. Dissimilatory sulfite reductase revisited. The desulfoviridin molecule does contain 20 iron ions, extensively demetallated sirohaem, and an S = 9/2 iron-sulfur cluster. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 238:724-7. [PMID: 8706673 DOI: 10.1111/j.1432-1033.1996.0724w.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: 02/01/2023]
Abstract
Assimilatory sulfite reductase contains a sirohaem that is very weakly coupled to a [4Fe-4S] cubane, i.e. five iron atoms in total. Dissimilatory sulfite reductase is a complex system with 20 Fe atoms/alpha 2 beta 2 gamma 2 hexamer. A recent revision of the purification procedure for the Desulfovibrio vulgaris dissimilatory enzyme has afforded a preparation of only 10 Fe atoms hexamer, this has led to the convulsion that the topology of prosthetic groups parallels that of the assimilatory system [Wolfe, B. M., Lui, S. M. & Cowan, J. A. (1994) Eur. J. Biochem. 223, 79-89]. The new purification procedure has been reproduced but the claimed molecular properties are not reproducible. The highly purified, active desulfoviridin contains 20, not 10, Fe atoms/molecule: the sirohaem is extensively dematallated, not metallated; and the S = 9/2 iron-sulfur cluster is present, not absent.
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Affiliation(s)
- S J Marritt
- Department of Biochemistry, Wageningen Agricultural University, The Netherlands
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Eggen RI, van Kranenburg R, Vriesema AJ, Geerling AC, Verhagen MF, Hagen WR, de Vos WM. Carbon monoxide dehydrogenase from Methanosarcina frisia Gö1. Characterization of the enzyme and the regulated expression of two operon-like cdh gene clusters. J Biol Chem 1996; 271:14256-63. [PMID: 8662887 DOI: 10.1074/jbc.271.24.14256] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Carbon monoxide dehydrogenase (Cdh) has been anaerobically purified from Methanosarcina frisia Gö1. The enzyme is a Ni2+-, Fe2+-, and S2--containing alpha2beta2 heterotetramer of 214 kDa with a pI of 5.2 and subunits of 94 and 19 kDa. It has a Vmax of 0.3 mmol of CO min-1 mg-1 and Km values for CO and methyl viologen of approximately 0.9 mM and 0.12 mM, respectively. EPR spectroscopy on the reduced enzyme showed two overlapping signals: one indicative for 2 (4Fe-4S)+ clusters and a second signal that is atypical for standard Fe/S clusters. The latter was, together with high-spin EPR signals of the oxidized enzyme tentatively assigned to an Fe/S cluster of high nuclearity.
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Affiliation(s)
- R I Eggen
- Department of Microbiology, Wageningen Agricultural University, Wageningen 6703 CT, The Netherlands
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41
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de Vocht ML, Kooter IM, Bulsink YBM, Hagen WR, Johnson MK. Resonance Raman Evidence for Non-Heme Fe−O Species in the [6Fe−6S]-containing Iron−Sulfur Proteins from Sulfate-Reducing Bacteria. J Am Chem Soc 1996. [DOI: 10.1021/ja954099z] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Marcel L. de Vocht
- Department of Chemistry and Center for Metalloenzyme Studies University of Georgia, Athens, Georgia 30602 Department of Biochemistry Wageningen Agricultural University, Dreijenlaan 3 6703 HA Wageningen, The Netherlands
| | - Ingeborg M. Kooter
- Department of Chemistry and Center for Metalloenzyme Studies University of Georgia, Athens, Georgia 30602 Department of Biochemistry Wageningen Agricultural University, Dreijenlaan 3 6703 HA Wageningen, The Netherlands
| | - Yvonne B. M. Bulsink
- Department of Chemistry and Center for Metalloenzyme Studies University of Georgia, Athens, Georgia 30602 Department of Biochemistry Wageningen Agricultural University, Dreijenlaan 3 6703 HA Wageningen, The Netherlands
| | - Wilfred R. Hagen
- Department of Chemistry and Center for Metalloenzyme Studies University of Georgia, Athens, Georgia 30602 Department of Biochemistry Wageningen Agricultural University, Dreijenlaan 3 6703 HA Wageningen, The Netherlands
| | - Michael K. Johnson
- Department of Chemistry and Center for Metalloenzyme Studies University of Georgia, Athens, Georgia 30602 Department of Biochemistry Wageningen Agricultural University, Dreijenlaan 3 6703 HA Wageningen, The Netherlands
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42
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Heering HA, Bulsink YB, Hagen WR, Meyer TE. Reversible super-reduction of the cubane [4Fe-4S](3+;2+;1+) in the high-potential iron-sulfur protein under non-denaturing conditions. EPR spectroscopic and electrochemical studies. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 232:811-817. [PMID: 7588720 DOI: 10.1111/j.1432-1033.1995.0811a.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The reversible 2 x 1 e- reduction of the cubane cluster from oxidized to reduced to super-reduced states ([4Fe-4S]3+<-->[4Fe-4S]2+<-->[4Fe-4S]1+) was studied in high-potential iron-sulfur proteins (HiPIPs). Super-reduction to the 1+ state was not observed in any of the seven HiPIPs tested during cyclic voltammetry (down to -0.95 V). However, equilibration at low potential (pH 7.5) of Rhodopila globiformis HiPIP yields a transient peak around -0.47 V due to the oxidation of super-reduced HiPIP adsorbed at the electrode. The peak area depends on the equilibration potential according to a one-electron Nernst curve with a half-wave potential at -0.91 V. Reduction of R. globiformis HiPIP with titanium (III)citrate at pH 9.5 is very slow [pseudo-first-order half-life of 23 min with a 100-fold excess Ti(III)] but is reversible, and the EPR spectrum with g values of 2.04 and 1.92 is similar to that of reduced [4Fe-4S]1+ ferredoxins. Chemical or electrochemical reoxidation of the super-reduced form resulted in an EPR spectrum with g parallel = 2.12 and g perpendicular = 2.03, i.e. identical to that of oxidized HiPIP. From the equilibrium concentration of super-reduced HiPIP at a low concentration of Ti(III), a reduction potential of -0.64 V can be estimated. Super-reduction of the large HiPIP (iso-2) from Rhodospirillum salinarum is also possible with Ti(III)(gz = 2.05) but the super-reduced state is unstable. No super-reduction with Ti(III) was observed for the other HiPIPs. The difference between the electrochemically observed reduction potential and oxidation potential is explained by a fast and reversible conformational change upon super-reduction. The rate of super-reduction with Ti(III) is limited by the small amount (0.1%) of HiPIP in the 2+ state with the super-reduced conformation.
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Affiliation(s)
- H A Heering
- Department of Biochemistry, Wageningen Agricultural University, The Netherlands
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43
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Marritt SJ, Farrar JA, Breton JL, Hagen WR, Thomson AJ. Characterization of the prismane protein from Desulfovibrio vulgaris (Hildenborough) by low-temperature magnetic circular dichroic spectroscopy. EUROPEAN JOURNAL OF BIOCHEMISTRY 1995; 232:501-5. [PMID: 7556199 DOI: 10.1111/j.1432-1033.1995.501zz.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The prismane protein of Desulfovibrio vulgaris (Hildenborough) contains a putative [6Fe-6S] cluster. This novel iron-sulfur cluster has been characterized here by magnetic circular dichroism (MCD) spectroscopy. Three paramagnetic redox states of the cluster, [6Fe-6S]5+, [6Fe-6S]4+ and [6Fe-6S]3+, each show a distinctive low-temperature MCD spectrum which is unlike that observed for any other iron-sulfur clusters. Magnetization data for the prismane protein in these three redox states indicate ground state spins that are in accordance with previous EPR assignments. For the protein as isolated, with the [6Fe-6S]5+ form of the cluster, magnetizations show an exceptionally steep initial slope that can be fit to a ground state of spin S = 9/2. For the semi-reduced protein, the cluster in the [6Fe-6S]4+ form, magnetizations show an initial slope characteristic for a ground state of spin S = 4. For the dithionite-reduced protein, with the [6Fe-6S]3+ form of the cluster, magnetizations are typical for a ground state of spin S = 1/2.
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Affiliation(s)
- S J Marritt
- Department of Biochemistry, Wageningen Agricultural University, The Netherlands
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44
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Heering HA, Bulsink YBM, Hagen WR, Meyer TE. Reversible Super-Reduction of the Cubane [4Fe-4S](3+;2+;1+) in the High-Potential Iron-Sulfur Protein Under Non-Denaturing Conditions. EPR Spectroscopic and Electrochemical Studies. ACTA ACUST UNITED AC 1995. [DOI: 10.1111/j.1432-1033.1995.tb20877.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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45
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Arendsen AF, Veenhuizen PT, Hagen WR. Redox properties of the sulfhydrogenase from Pyrococcus furiosus. FEBS Lett 1995; 368:117-21. [PMID: 7615063 DOI: 10.1016/0014-5793(95)00622-g] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The sulfhydrogenase from the extreme thermophile Pyrococcus furiosus has been re-investigated. The alpha beta gamma delta heterotetrameric enzyme of 153.3 kDa was found to contain 17 Fe, 17 S2-, and 0.74 Ni. The specific activity of the purified protein was 80 U/mg. Three EPR signals were found. A rhombic S = 1/2 signal (g = 2.07, 1.93, 1.89) was observed reminiscent in its shape and temperature dependence of spectra from [4Fe-4S](2+; 1+) clusters. However, in reductive titrations the spectrum appeared at the unusually high potential Em,7.5 = -90 mV. Moreover, the signal disappeared again at Em7.5 = -328 mV. Also, two other signals appear upon reduction: a near-axial (g = 2.02, 1.95, 1.92) S = 1/2 spectrum (Em,7.5 = -303 mV) indicative for the presence of a [2Fe-2S](2+; 1+) cluster, and a broad spectrum of unknown origin with effective g-values 2.25, 1.89 (Em,7.5 = -310 mV). We hypothesize that the latter signal is caused by magnetic interaction of the rhombic signal and a third cluster.
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Affiliation(s)
- A F Arendsen
- Department of Biochemistry, Wageningen Agricultural University, The Netherlands
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46
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Müller A, Krahn E. On the Synthesis of the FeMo Cofactor of Nitrogenase: Gene-Controlled in Nature versus Laboratory-Produced by Man. ACTA ACUST UNITED AC 1995. [DOI: 10.1002/anie.199510711] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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47
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Müller A, Krahn E. Zur Bildung des FeMo-Cofaktors der Nitrogenase in der Natur und im Reagensglas – ein Zusammenspiel von Genetik und Chemie. Angew Chem Int Ed Engl 1995. [DOI: 10.1002/ange.19951071005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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48
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Verhagen MF, Link TA, Hagen WR. Electrochemical study of the redox properties of [2Fe-2S] ferredoxins. Evidence for superreduction of the Rieske [2Fe-2S] cluster. FEBS Lett 1995; 361:75-8. [PMID: 7890043 DOI: 10.1016/0014-5793(95)00152-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Direct, unmediated electrochemistry has been used to compare the redox properties of [2Fe-2S] clusters in spinach ferredoxin, Spirulina platensis ferredoxin and the water soluble fragment of the Rieske protein. The use of electrochemistry enabled, for the first time, the observation of the second reduction step, [Fe(III), Fe(II)] to [Fe(II), Fe(II)], in a biological [2Fe-2S] system. A water-soluble fragment of the Rieske protein from bovine heart bc1 complex exhibits two subsequent quasi-reversible responses in cyclic voltammetry on activated glassy carbon. In contrast the ferredoxins from spinach and Spirulina platensis only show one single reduction potential. These results support a seniority scheme for biological iron-sulfur clusters related cluster size to electron transfer versatility. Electrochemical reduction of spinach ferredoxin in the presence of NADP+ and ferredoxin: NADP+ oxidoreductase results in the generation of NADPH. The second order rate constant for the reaction between the ferredoxin and the reductase was estimated from cyclic voltammetry experiments to be > 3.10(5) M-1.s-1.
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Affiliation(s)
- M F Verhagen
- Department of Biochemistry, Wageningen Agricultural University, The Netherlands
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49
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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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50
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van den Berg WA, Stevens AA, Verhagen MF, van Dongen WM, Hagen WR. Overproduction of the prismane protein from Desulfovibrio desulfuricans ATCC 27774 in Desulfovibrio vulgaris (Hildenborough) and EPR spectroscopy of the [6Fe-6S] cluster in different redox states. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1206:240-6. [PMID: 8003528 DOI: 10.1016/0167-4838(94)90214-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The Desulfovibrio desulfuricans ATCC 27774 prismane protein was isolated from a Desulfovibrio vulgaris (Hildenborough) strain that contained the gene for this protein in expression vector pSUP104. A redox titration demonstrated that the [Fe-S] cluster in this protein may attain four different redox states, indicated as +3, +4, +5 and +6, with midpoint potentials for the transitions of approx. -220, +50/-25 and +370 mV, respectively. EPR spectra of the protein in the various redox states are reminiscent of those of the D. vulgaris prismane protein (Pierik et al. (1992) Eur. J. Biochem. 206, 705-719), but differ in details. In the +5-state, virtually all the iron is in a S = 9/2 spin state, indicative for a cluster that is more complex than common [4Fe-4S] or [2Fe-2S] clusters. Similarity of the EPR spectrum of the protein in the +3-state with those of inorganic [6Fe-6S] model compounds suggests that the cluster in the protein is also [6Fe-6S]. In the +4-state of the protein a broad signal due to an integer-spin system can be detected with normal-mode EPR. A dramatic sharpening-up and increase of intensity of this band (g = 14.7) is observed with parallel-mode EPR. In accordance with the chemically determined iron content of the protein (6.0 +/- 0.45 moles of iron/mole of protein), the spectroscopic data indicate one [6Fe-6S] cluster in this protein. We did not find evidence for a previous claim (Moura et al. (1992) J. Biol. Chem. 267, 4489-4496) that the D. desulfuricans protein contains two [6Fe-6S] clusters.
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Affiliation(s)
- W A van den Berg
- Department of Biochemistry, Wageningen Agricultural University, The Netherlands
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