1
|
Singh D, Knight BJ, Catalano VJ, García-Serres R, Maurel V, Mouesca JM, Murray LJ. Partial Deoxygenative CO Homocoupling by a Diiron Complex. Angew Chem Int Ed Engl 2023; 62:e202308813. [PMID: 37594782 DOI: 10.1002/anie.202308813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 08/17/2023] [Accepted: 08/18/2023] [Indexed: 08/19/2023]
Abstract
One route to address climate change is converting carbon dioxide to synthetic carbon-neutral fuels. Whereas carbon dioxide to CO conversion has precedent in homo- and heterogeneous catalysis, deoxygenative coupling of CO to products with C-C bonds-as in liquid fuels-remains challenging. Here, we report coupling of two CO molecules by a diiron complex. Reduction of Fe2 (CO)2 L (2), where L2- is a bis(β-diketiminate) cyclophane, gives [K(THF)5 ][Fe2 (CO)2 L] (3), which undergoes silylation to Fe2 (CO)(COSiMe3 )L (4). Subsequent C-OSiMe3 bond cleavage and C=C bond formation occurs upon reduction of 4, yielding Fe2 (μ-CCO)L. CO derived ligands in this series mediate weak exchange interactions with the ketenylidene affording the smallest J value, with changes to local metal ion spin states and coupling schemes (ferro- vs. antiferromagnetism) based on DFT calculations, Mössbauer and EPR spectroscopy. Finally, reaction of 5 with KEt3 BH or methanol releases the C2 O2- ligand with retention of the diiron core.
Collapse
Affiliation(s)
- Devender Singh
- Center for Catalysis and Florida Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL, USA
| | - Brian J Knight
- Center for Catalysis and Florida Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL, USA
| | | | - Ricardo García-Serres
- Université Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, 17 rue des Martyrs, 38000, Grenoble, France
| | - Vincent Maurel
- Université Grenoble Alpes, CEA, CNRS, IRIG, SyMMES, 38000, Grenoble, France
| | - Jean-Marie Mouesca
- Université Grenoble Alpes, CEA, CNRS, IRIG, SyMMES, 38000, Grenoble, France
| | - Leslie J Murray
- Center for Catalysis and Florida Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL, USA
| |
Collapse
|
2
|
Heghmanns M, Günzel A, Brandis D, Kutin Y, Engelbrecht V, Winkler M, Happe T, Kasanmascheff M. Fine-tuning of FeS proteins monitored via pulsed EPR redox potentiometry at Q-band. BIOPHYSICAL REPORTS 2021; 1:100016. [PMID: 36425453 PMCID: PMC9680799 DOI: 10.1016/j.bpr.2021.100016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 08/30/2021] [Indexed: 06/16/2023]
Abstract
As essential electron translocating proteins in photosynthetic organisms, multiple plant-type ferredoxin (Fdx) isoforms are involved in a high number of reductive metabolic processes in the chloroplast. To allow quick cellular responses under changing environmental conditions, different plant-type Fdxs in Chlamydomonas reinhardtii were suggested to have adapted their midpoint potentials to a wide range of interaction partners. We performed pulsed electron paramagnetic resonance (EPR) monitored redox potentiometry at Q-band on three Fdx isoforms for a straightforward determination of their midpoint potentials. Additionally, site-directed mutagenesis was used to tune the midpoint potential of CrFdx1 in a range of approximately -338 to -511 mV, confirming the importance of single positions in the protein environment surrounding the [2Fe2S] cluster. Our results present a new target for future studies aiming to modify the catalytic activity of CrFdx1 that plays an essential role either as electron acceptor of photosystem I or as electron donor to hydrogenases under certain conditions. Additionally, the precisely determined redox potentials in this work using pulsed EPR demonstrate an alternative method that provides additional advantages compared with the well-established continuous wave EPR technique.
Collapse
Affiliation(s)
- Melanie Heghmanns
- TU Dortmund University, Department of Chemistry and Chemical Biology, Dortmund, Germany
| | - Alexander Günzel
- Ruhr University Bochum, Faculty of Biology and Biotechnology, Photobiotechnology, Bochum, Germany
| | - Dörte Brandis
- TU Dortmund University, Department of Chemistry and Chemical Biology, Dortmund, Germany
| | - Yury Kutin
- TU Dortmund University, Department of Chemistry and Chemical Biology, Dortmund, Germany
| | - Vera Engelbrecht
- Ruhr University Bochum, Faculty of Biology and Biotechnology, Photobiotechnology, Bochum, Germany
| | - Martin Winkler
- Ruhr University Bochum, Faculty of Biology and Biotechnology, Photobiotechnology, Bochum, Germany
| | - Thomas Happe
- Ruhr University Bochum, Faculty of Biology and Biotechnology, Photobiotechnology, Bochum, Germany
| | - Müge Kasanmascheff
- TU Dortmund University, Department of Chemistry and Chemical Biology, Dortmund, Germany
| |
Collapse
|
3
|
Rosenbach H, Walla E, Cutsail GE, Birrell JA, Pascual-Ortiz M, DeBeer S, Fleig U, Span I. The Asp1 pyrophosphatase from S. pombe hosts a [2Fe-2S] 2+ cluster in vivo. J Biol Inorg Chem 2021; 26:93-108. [PMID: 33544225 PMCID: PMC8038993 DOI: 10.1007/s00775-020-01840-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Accepted: 11/29/2020] [Indexed: 11/25/2022]
Abstract
The Schizosaccharomyces pombe Asp1 protein is a bifunctional kinase/pyrophosphatase that belongs to the highly conserved eukaryotic diphosphoinositol pentakisphosphate kinase PPIP5K/Vip1 family. The N-terminal Asp1 kinase domain generates specific high-energy inositol pyrophosphate (IPP) molecules, which are hydrolyzed by the C-terminal Asp1 pyrophosphatase domain (Asp1365-920). Thus, Asp1 activities regulate the intracellular level of a specific class of IPP molecules, which control a wide number of biological processes ranging from cell morphogenesis to chromosome transmission. Recently, it was shown that chemical reconstitution of Asp1371-920 leads to the formation of a [2Fe-2S] cluster; however, the biological relevance of the cofactor remained under debate. In this study, we provide evidence for the presence of the Fe-S cluster in Asp1365-920 inside the cell. However, we show that the Fe-S cluster does not influence Asp1 pyrophosphatase activity in vitro or in vivo. Characterization of the as-isolated protein by electronic absorption spectroscopy, mass spectrometry, and X-ray absorption spectroscopy is consistent with the presence of a [2Fe-2S]2+ cluster in the enzyme. Furthermore, we have identified the cysteine ligands of the cluster. Overall, our work reveals that Asp1 contains an Fe-S cluster in vivo that is not involved in its pyrophosphatase activity.
Collapse
Affiliation(s)
- Hannah Rosenbach
- Institut Für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
| | - Eva Walla
- Lehrstuhl Für Funktionelle Genomforschung Der Mikroorganismen, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany
| | - George E Cutsail
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470, Mülheim an der Ruhr, Germany
| | - James A Birrell
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Marina Pascual-Ortiz
- Department of Biomedical Sciences, Faculty of Health Sciences, Universidad Cardenal Herrera, CEU Universities, 46113, Valencia, Spain
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion, Stiftstr. 34-36, 45470, Mülheim an der Ruhr, Germany
| | - Ursula Fleig
- Lehrstuhl Für Funktionelle Genomforschung Der Mikroorganismen, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany.
| | - Ingrid Span
- Institut Für Physikalische Biologie, Heinrich-Heine-Universität Düsseldorf, Universitätsstr. 1, 40225, Düsseldorf, Germany.
| |
Collapse
|
4
|
Arnett CH, Bogacz I, Chatterjee R, Yano J, Oyala PH, Agapie T. Mixed-Valent Diiron μ-Carbyne, μ-Hydride Complexes: Implications for Nitrogenase. J Am Chem Soc 2020; 142:18795-18813. [PMID: 32976708 DOI: 10.1021/jacs.0c05920] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Binding of N2 by the FeMo-cofactor of nitrogenase is believed to occur after transfer of 4 e- and 4 H+ equivalents to the active site. Although pulse EPR studies indicate the presence of two Fe-(μ-H)-Fe moieties, the structural and electronic features of this mixed valent intermediate remain poorly understood. Toward an improved understanding of this bioorganometallic cluster, we report herein that diiron μ-carbyne complex (P6ArC)Fe2(μ-H) can be oxidized and reduced, allowing for the first time spectral characterization of two EPR-active Fe(μ-C)(μ-H)Fe model complexes linked by a 2 e- transfer which bear some resemblance to a pair of En and En+2 states of nitrogenase. Both species populate S = 1/2 states at low temperatures, and the influence of valence (de)localization on the spectroscopic signature of the μ-hydride ligand was evaluated by pulse EPR studies. Compared to analogous data for the {Fe2(μ-H)}2 state of FeMoco (E4(4H)), the data and analysis presented herein suggest that the hydride ligands in E4(4H) bridge isovalent (most probably FeIII) metal centers. Although electron transfer involves metal-localized orbitals, investigations of [(P6ArC)Fe2(μ-H)]+1 and [(P6ArC)Fe2(μ-H)]-1 by pulse EPR revealed that redox chemistry induces significant changes in Fe-C covalency (-50% upon 2 e- reduction), a conclusion further supported by X-ray absorption spectroscopy, 57Fe Mössbauer studies, and DFT calculations. Combined, our studies demonstrate that changes in covalency buffer against the accumulation of excess charge density on the metals by partially redistributing it to the bridging carbon, thereby facilitating multielectron transformations.
Collapse
Affiliation(s)
- Charles H Arnett
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Isabel Bogacz
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Ruchira Chatterjee
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Junko Yano
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States
| | - Paul H Oyala
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Theodor Agapie
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| |
Collapse
|
5
|
Banci L, Camponeschi F, Ciofi-Baffoni S, Piccioli M. The NMR contribution to protein-protein networking in Fe-S protein maturation. J Biol Inorg Chem 2018; 23:665-685. [PMID: 29569085 PMCID: PMC6006191 DOI: 10.1007/s00775-018-1552-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 03/12/2018] [Indexed: 12/12/2022]
Abstract
Iron–sulfur proteins were among the first class of metalloproteins that were actively studied using NMR spectroscopy tailored to paramagnetic systems. The hyperfine shifts, their temperature dependencies and the relaxation rates of nuclei of cluster-bound residues are an efficient fingerprint of the nature and the oxidation state of the Fe–S cluster. NMR significantly contributed to the analysis of the magnetic coupling patterns and to the understanding of the electronic structure occurring in [2Fe–2S], [3Fe–4S] and [4Fe–4S] clusters bound to proteins. After the first NMR structure of a paramagnetic protein was obtained for the reduced E. halophila HiPIP I, many NMR structures were determined for several Fe–S proteins in different oxidation states. It was found that differences in chemical shifts, in patterns of unobserved residues, in internal mobility and in thermodynamic stability are suitable data to map subtle changes between the two different oxidation states of the protein. Recently, the interaction networks responsible for maturing human mitochondrial and cytosolic Fe–S proteins have been largely characterized by combining solution NMR standard experiments with those tailored to paramagnetic systems. We show here the contribution of solution NMR in providing a detailed molecular view of “Fe–S interactomics”. This contribution was particularly effective when protein–protein interactions are weak and transient, and thus difficult to be characterized at high resolution with other methodologies.
Collapse
Affiliation(s)
- Lucia Banci
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Florence, Italy. .,Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, 50019, Florence, Italy.
| | - Francesca Camponeschi
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Florence, Italy.,Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, 50019, Florence, Italy
| | - Simone Ciofi-Baffoni
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Florence, Italy.,Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, 50019, Florence, Italy
| | - Mario Piccioli
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, Sesto Fiorentino, 50019, Florence, Italy. .,Department of Chemistry, University of Florence, Via della Lastruccia 3, Sesto Fiorentino, 50019, Florence, Italy.
| |
Collapse
|
6
|
Gao H, Azam T, Randeniya S, Couturier J, Rouhier N, Johnson MK. Function and maturation of the Fe-S center in dihydroxyacid dehydratase from Arabidopsis. J Biol Chem 2018; 293:4422-4433. [PMID: 29425096 DOI: 10.1074/jbc.ra117.001592] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 02/02/2018] [Indexed: 12/26/2022] Open
Abstract
Dihydroxyacid dehydratase (DHAD) is the third enzyme required for branched-chain amino acid biosynthesis in bacteria, fungi, and plants. DHAD enzymes contain two distinct types of active-site Fe-S clusters. The best characterized examples are Escherichia coli DHAD, which contains an oxygen-labile [Fe4S4] cluster, and spinach DHAD, which contains an oxygen-resistant [Fe2S2] cluster. Although the Fe-S cluster is crucial for DHAD function, little is known about the cluster-coordination environment or the mechanism of catalysis and cluster biogenesis. Here, using the combination of UV-visible absorption and circular dichroism and resonance Raman and electron paramagnetic resonance, we spectroscopically characterized the Fe-S center in DHAD from Arabidopsis thaliana (At). Our results indicated that AtDHAD can accommodate [Fe2S2] and [Fe4S4] clusters. However, only the [Fe2S2] cluster-bound form is catalytically active. We found that the [Fe2S2] cluster is coordinated by at least one non-cysteinyl ligand, which can be replaced by the thiol group(s) of dithiothreitol. In vitro cluster transfer and reconstitution reactions revealed that [Fe2S2] cluster-containing NFU2 protein is likely the physiological cluster donor for in vivo maturation of AtDHAD. In summary, AtDHAD binds either one [Fe4S4] or one [Fe2S2] cluster, with only the latter being catalytically competent and capable of substrate and product binding, and NFU2 appears to be the physiological [Fe2S2] cluster donor for DHAD maturation. This work represents the first in vitro characterization of recombinant AtDHAD, providing new insights into the properties, biogenesis, and catalytic role of the active-site Fe-S center in a plant DHAD.
Collapse
Affiliation(s)
- Huanyao Gao
- From the Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602 and
| | - Tamanna Azam
- From the Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602 and
| | - Sajini Randeniya
- From the Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602 and
| | - Jérémy Couturier
- the UMR1136 Interactions Arbres-Microorganismes, Université de Lorraine/INRA, Faculté des Sciences et Technologies, 54500 Vandoeuvre-lès-Nancy, France
| | - Nicolas Rouhier
- the UMR1136 Interactions Arbres-Microorganismes, Université de Lorraine/INRA, Faculté des Sciences et Technologies, 54500 Vandoeuvre-lès-Nancy, France
| | - Michael K Johnson
- From the Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602 and
| |
Collapse
|
7
|
Nasta V, Giachetti A, Ciofi-Baffoni S, Banci L. Structural insights into the molecular function of human [2Fe-2S] BOLA1-GRX5 and [2Fe-2S] BOLA3-GRX5 complexes. Biochim Biophys Acta Gen Subj 2017; 1861:2119-2131. [PMID: 28483642 DOI: 10.1016/j.bbagen.2017.05.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2016] [Revised: 04/03/2017] [Accepted: 05/04/2017] [Indexed: 01/12/2023]
Abstract
Members of the monothiol glutaredoxin family and members of the BolA-like protein family have recently emerged as specific interacting partners involved in iron-sulfur protein maturation and redox regulation pathways. It is known that human mitochondrial BOLA1 and BOLA3 form [2Fe-2S] cluster-bridged dimeric heterocomplexes with the monothiol glutaredoxin GRX5. The structure and cluster coordination of the two [2Fe-2S] heterocomplexes as well as their molecular function are, however, not defined yet. Experimentally-driven structural models of the two [2Fe-2S] cluster-bridged dimeric heterocomplexes, the relative stability of the two complexes and the redox properties of the [2Fe-2S] cluster bound to these complexes are here presented on the basis of UV/vis, CD, EPR and NMR spectroscopies and computational protein-protein docking. While the BOLA1-GRX5 complex coordinates a reduced, Rieske-type [2Fe-2S]1+ cluster, an oxidized, ferredoxin-like [2Fe-2S]2+ cluster is present in the BOLA3-GRX5 complex. The [2Fe-2S] BOLA1-GRX5 complex is preferentially formed over the [2Fe-2S] BOLA3-GRX5 complex, as a result of a higher cluster binding affinity. All these observed differences provide the first indications discriminating the molecular function of the two [2Fe-2S] heterocomplexes.
Collapse
Affiliation(s)
- Veronica Nasta
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy; Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy
| | - Andrea Giachetti
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy
| | - Simone Ciofi-Baffoni
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy; Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy
| | - Lucia Banci
- Magnetic Resonance Center CERM, University of Florence, Via Luigi Sacconi 6, 50019, Sesto Fiorentino, Florence, Italy; Department of Chemistry, University of Florence, Via della Lastruccia 3, 50019 Sesto Fiorentino, Florence, Italy.
| |
Collapse
|
8
|
Bergner M, Dechert S, Demeshko S, Kupper C, Mayer JM, Meyer F. Model of the MitoNEET [2Fe-2S] Cluster Shows Proton Coupled Electron Transfer. J Am Chem Soc 2017; 139:701-707. [PMID: 28055193 PMCID: PMC5812485 DOI: 10.1021/jacs.6b09180] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
MitoNEET is an outer membrane protein whose exact function remains unclear, though a role of this protein in redox and iron sensing as well as in controlling maximum mitochondrial respiratory rates has been discussed. It was shown to contain a redox active and acid labile [2Fe-2S] cluster which is ligated by one histidine and three cysteine residues. Herein we present the first synthetic analogue with biomimetic {SN/S2} ligation which could be structurally characterized in its diferric form, 52-. In addition to being a high fidelity structural model for the biological cofactor, the complex is shown to mediate proton coupled electron transfer (PCET) at the {SN} ligated site, pointing at a potential functional role of the enzyme's unique His ligand. Full PCET thermodynamic square schemes for the mitoNEET model 52- and a related homoleptic {SN/SN} capped [2Fe-2S] cluster 42- are established, and kinetics of PCET reactivity are investigated by double-mixing stopped-flow experiments for both complexes. While the N-H bond dissociation free energy (BDFE) of 5H2- (230 ± 4 kJ mol-1) and the free energy ΔG°PCET for the reaction with TEMPO (-48.4 kJ mol-1) are very similar to values for the homoleptic cluster 4H2- (232 ± 4 kJ mol-1, -46.3 kJ mol-1) the latter is found to react significantly faster than the mitoNEET model (data for 5H2-: k = 135 ± 27 M-1 s-1, ΔH‡ = 17.6 ± 3.0 kJ mol-1, ΔS‡ = -143 ± 11 J mol-1 K-1, and ΔG‡ = 59.8 kJ mol-1 at 293 K). Comparison of the PCET efficiency of these clusters emphasizes the relevance of reorganization energy in this process.
Collapse
Affiliation(s)
- Marie Bergner
- Institute of Inorganic Chemistry, Georg-August-University Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| | - Sebastian Dechert
- Institute of Inorganic Chemistry, Georg-August-University Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| | - Serhiy Demeshko
- Institute of Inorganic Chemistry, Georg-August-University Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| | - Claudia Kupper
- Institute of Inorganic Chemistry, Georg-August-University Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| | - James M. Mayer
- Yale University, 225 Prospect Street, New Haven, Connecticut 06511, USA
| | - Franc Meyer
- Institute of Inorganic Chemistry, Georg-August-University Göttingen, Tammannstr. 4, D-37077 Göttingen, Germany
| |
Collapse
|
9
|
Birrell JA, Laurich C, Reijerse EJ, Ogata H, Lubitz W. Importance of Hydrogen Bonding in Fine Tuning the [2Fe-2S] Cluster Redox Potential of HydC from Thermotoga maritima. Biochemistry 2016; 55:4344-55. [PMID: 27396836 DOI: 10.1021/acs.biochem.6b00341] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Iron-sulfur clusters form one of the largest and most diverse classes of enzyme cofactors in nature. They may serve as structural factors, form electron transfer chains between active sites and external redox partners, or form components of enzyme active sites. Their specific role is a consequence of the cluster type and the surrounding protein environment. The relative effects of these factors are not completely understood, and it is not yet possible to predict the properties of iron-sulfur clusters based on amino acid sequences or rationally tune their properties to generate proteins with new desirable functions. Here, we generate mutations in a [2Fe-2S] cluster protein, the TmHydC subunit of the trimeric [FeFe]-hydrogenase from Thermotoga maritima, to study the factors that affect its redox potential. Saturation mutagenesis of Val131 was used to tune the redox potential over a 135 mV range and revealed that cluster redox potential and electronic properties correlate with amino acid hydrophobicity and the ability to form hydrogen bonds to the cluster. Proline scanning mutagenesis between pairs of ligating cysteines was used to remove backbone amide hydrogen bonds to the cluster and decrease the redox potential by up to 132 mV, without large structural changes in most cases. However, substitution of Gly83 with proline caused a change of HydC to a [4Fe-4S] cluster protein with a redox potential of -526 mV. Together, these results confirm the importance of hydrogen bonding in tuning cluster redox potentials and demonstrate the versatility of iron-sulfur cluster protein folds at binding different types of clusters.
Collapse
Affiliation(s)
- James A Birrell
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Christoph Laurich
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Edward J Reijerse
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Hideaki Ogata
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, D-45470 Mülheim an der Ruhr, Germany
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion , Stiftstraße 34-36, D-45470 Mülheim an der Ruhr, Germany
| |
Collapse
|
10
|
Sarewicz M, Dutka M, Pietras R, Borek A, Osyczka A. Effect of H bond removal and changes in the position of the iron-sulphur head domain on the spin-lattice relaxation properties of the [2Fe-2S](2+) Rieske cluster in cytochrome bc(1). Phys Chem Chem Phys 2016; 17:25297-308. [PMID: 26355649 PMCID: PMC5716461 DOI: 10.1039/c5cp02815a] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Here, comparative electron spin–lattice relaxation studies of the 2Fe–2S iron–sulphur (Fe–S) cluster embedded in a large membrane protein complex – cytochrome bc1 – are reported.
Here, comparative electron spin–lattice relaxation studies of the 2Fe–2S iron–sulphur (Fe–S) cluster embedded in a large membrane protein complex – cytochrome bc1 – are reported. Structural modifications of the local environment alone (mutations S158A and Y160W removing specific H bonds between Fe–S and amino acid side chains) or in combination with changes in global protein conformation (mutations/inhibitors changing the position of the Fe–S binding domain within the protein complex) resulted in different redox potentials as well as g-, g-strain and the relaxation rates (T1–1) for the Fe–S cluster. The relaxation rates for T < 25 K were measured directly by inversion recovery, while for T > 60 K they were deduced from simulation of continuous wave EPR spectra of the cluster using a model that included anisotropy of Lorentzian broadening. In all cases, the relaxation rate involved contributions from direct, second-order Raman and Orbach processes, each dominating over different temperature ranges. The analysis of T1–1 (T) over the range 5–120 K yielded the values of the Orbach energy (EOrb), Debye temperature θD and Raman process efficiency CRam for each variant of the protein. As the Orbach energy was generally higher for mutants S158A and Y160W, compared to wild-type protein (WT), it is suggested that H bond removal influences the geometry leading to increased strength of antiferromagnetic coupling between two Fe ions of the cluster. While θD was similar for all variants (∼107 K), the efficiency of the Raman process generally depends on the spin–orbit coupling that is lower for S158A and Y160W mutants, when compared to the WT. However, in several cases CRam did not only correlate with spin–orbit coupling but was also influenced by other factors – possibly the modification of protein rigidity and therefore the vibrational modes around the Fe–S cluster that change upon the movement of the iron–sulphur head domain.
Collapse
Affiliation(s)
- Marcin Sarewicz
- Department of Molecular Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland.
| | | | | | | | | |
Collapse
|
11
|
Harris TV, Szilagyi RK. Protein environmental effects on iron-sulfur clusters: A set of rules for constructing computational models for inner and outer coordination spheres. J Comput Chem 2016; 37:1681-96. [DOI: 10.1002/jcc.24384] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Revised: 03/09/2016] [Accepted: 03/10/2016] [Indexed: 01/08/2023]
Affiliation(s)
- Travis V. Harris
- NAI Astrobiology Biogeocatalysis Research Center, Department of Chemistry and Biochemistry, Montana State University; Bozeman Montana 59717
| | - Robert K. Szilagyi
- NAI Astrobiology Biogeocatalysis Research Center, Department of Chemistry and Biochemistry, Montana State University; Bozeman Montana 59717
| |
Collapse
|
12
|
Wang H, Nair VS, Holland AA, Capolicchio S, Jessen HJ, Johnson MK, Shears SB. Asp1 from Schizosaccharomyces pombe binds a [2Fe-2S](2+) cluster which inhibits inositol pyrophosphate 1-phosphatase activity. Biochemistry 2015; 54:6462-74. [PMID: 26422458 DOI: 10.1021/acs.biochem.5b00532] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron-sulfur (Fe-S) clusters are widely distributed protein cofactors that are vital to cellular biochemistry and the maintenance of bioenergetic homeostasis, but to our knowledge, they have never been identified in any phosphatase. Here, we describe an iron-sulfur cluster in Asp1, a dual-function kinase/phosphatase that regulates cell morphogenesis in Schizosaccharomyces pombe. Full-length Asp1, and its phosphatase domain (Asp1(371-920)), were each heterologously expressed in Escherichia coli. The phosphatase activity is exquisitely specific: it hydrolyzes the 1-diphosphate from just two members of the inositol pyrophosphate (PP-InsP) signaling family, namely, 1-InsP7 and 1,5-InsP8. We demonstrate that Asp1 does not hydrolyze either InsP6, 2-InsP7, 3-InsP7, 4-InsP7, 5-InsP7, 6-InsP7, or 3,5-InsP8. We also recorded 1-phosphatase activity in a human homologue of Asp1, hPPIP5K1, which was heterologously expressed in Drosophila S3 cells with a biotinylated N-terminal tag, and then isolated from cell lysates with avidin beads. Purified, recombinant Asp1(371-920) contained iron and acid-labile sulfide, but the stoichiometry (0.8 atoms of each per protein molecule) indicates incomplete iron-sulfur cluster assembly. We reconstituted the Fe-S cluster in vitro under anaerobic conditions, which increased the stoichiometry to approximately 2 atoms of iron and acid-labile sulfide per Asp1 molecule. The presence of a [2Fe-2S](2+) cluster in Asp1(371-920) was demonstrated by UV-visible absorption, resonance Raman spectroscopy, and electron paramagnetic resonance spectroscopy. We determined that this [2Fe-2S](2+) cluster is unlikely to participate in redox chemistry, since it rapidly degraded upon reduction by dithionite. Biochemical and mutagenic studies demonstrated that the [2Fe-2S](2+) cluster substantially inhibits the phosphatase activity of Asp1, thereby increasing its net kinase activity.
Collapse
Affiliation(s)
- Huanchen Wang
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health , 101 T. W. Alexander Drive, Research Triangle Park, North Carolina 27709, United States
| | - Vasudha S Nair
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health , 101 T. W. Alexander Drive, Research Triangle Park, North Carolina 27709, United States
| | - Ashley A Holland
- Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia 30602, United States
| | - Samanta Capolicchio
- Department of Chemistry, University of Zurich (UZH) , Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Henning J Jessen
- Department of Chemistry, University of Zurich (UZH) , Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Michael K Johnson
- Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia , Athens, Georgia 30602, United States
| | - Stephen B Shears
- Laboratory of Signal Transduction, National Institute of Environmental Health Sciences, National Institutes of Health , 101 T. W. Alexander Drive, Research Triangle Park, North Carolina 27709, United States
| |
Collapse
|
13
|
Yao S, Meier F, Lindenmaier N, Rudolph R, Blom B, Adelhardt M, Sutter J, Mebs S, Haumann M, Meyer K, Kaupp M, Driess M. Biomimetische [2Fe-2S]-Cluster mit stark delokalisierten gemischtvalenten Eisenzentren. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201506788] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
14
|
Yao S, Meier F, Lindenmaier N, Rudolph R, Blom B, Adelhardt M, Sutter J, Mebs S, Haumann M, Meyer K, Kaupp M, Driess M. Biomimetic [2Fe-2S] Clusters with Extensively Delocalized Mixed-Valence Iron Centers. Angew Chem Int Ed Engl 2015; 54:12506-10. [DOI: 10.1002/anie.201506788] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Indexed: 11/09/2022]
|
15
|
Subramanian S, Duin EC, Fawcett SEJ, Armstrong FA, Meyer J, Johnson MK. Spectroscopic and redox studies of valence-delocalized [Fe2S2](+) centers in thioredoxin-like ferredoxins. J Am Chem Soc 2015; 137:4567-80. [PMID: 25790339 PMCID: PMC4436695 DOI: 10.1021/jacs.5b01869] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Reduced forms of the C56S and C60S variants of the thioredoxin-like Clostridium pasteurianum [Fe2S2] ferredoxin (CpFd) provide the only known examples of valence-delocalized [Fe2S2](+) clusters, which constitute a fundamental building block of all higher nuclearity Fe-S clusters. In this work, we have revisited earlier work on the CpFd variants and carried out redox and spectroscopic studies on the [Fe2S2](2+,+) centers in wild-type and equivalent variants of the highly homologous and structurally characterized Aquifex aeolicus ferredoxin 4 (AaeFd4) using EPR, UV-visible-NIR absorption, CD and variable-temperature MCD, and protein-film electrochemistry. The results indicate that the [Fe2S2](+) centers in the equivalent AaeFd4 and CpFd variants reversibly interconvert between similar valence-localized S = 1/2 and valence-delocalized S = 9/2 forms as a function of pH, with pKa values in the range 8.3-9.0, because of protonation of the coordinated serinate residue. However, freezing high-pH samples results in partial or full conversion from valence-delocalized S = 9/2 to valence-localized S = 1/2 [Fe2S2](+) clusters. MCD saturation magnetization data for valence-delocalized S = 9/2 [Fe2S2](+) centers facilitated determination of transition polarizations and thereby assignments of low-energy MCD bands associated with the Fe-Fe interaction. The assignments provide experimental assessment of the double exchange parameter, B, for valence-delocalized [Fe2S2](+) centers and demonstrate that variable-temperature MCD spectroscopy provides a means of detecting and investigating the properties of valence-delocalized S = 9/2 [Fe2S2](+) fragments in higher nuclearity Fe-S clusters. The origin of valence delocalization in thioredoxin-like ferredoxin Cys-to-Ser variants and Fe-S clusters in general is discussed in light of these results.
Collapse
Affiliation(s)
- Sowmya Subramanian
- Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602, USA
| | - Evert C. Duin
- Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602, USA
| | - Sarah E. J. Fawcett
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom
| | - Fraser A. Armstrong
- Department of Chemistry, University of Oxford, South Parks Road, Oxford, OX1 3QR, United Kingdom
| | | | - Michael K. Johnson
- Department of Chemistry and Center for Metalloenzyme Studies, University of Georgia, Athens, Georgia 30602, USA
| |
Collapse
|
16
|
Study of metalloproteins using continuous wave electron paramagnetic resonance (EPR). METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2015; 1122:139-51. [PMID: 24639258 DOI: 10.1007/978-1-62703-794-5_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Electron paramagnetic resonance (EPR) is an invaluable tool when studying systems with paramagnetic centers. It is a sensitive spectroscopic method, which can be used with dilute samples in aqueous buffer solutions. Here, we describe the basic procedure for recording an X-band EPR spectrum of a metalloprotein sample at low temperature. We also discuss basic optimization techniques to provide spectra with a high signal to noise ratio and minimum distortion.
Collapse
|
17
|
Cutsail GE, Telser J, Hoffman BM. Advanced paramagnetic resonance spectroscopies of iron-sulfur proteins: Electron nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM). BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1370-94. [PMID: 25686535 DOI: 10.1016/j.bbamcr.2015.01.025] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Revised: 01/29/2015] [Accepted: 01/29/2015] [Indexed: 12/20/2022]
Abstract
The advanced electron paramagnetic resonance (EPR) techniques, electron nuclear double resonance (ENDOR) and electron spin echo envelope modulation (ESEEM) spectroscopies, provide unique insights into the structure, coordination chemistry, and biochemical mechanism of nature's widely distributed iron-sulfur cluster (FeS) proteins. This review describes the ENDOR and ESEEM techniques and then provides a series of case studies on their application to a wide variety of FeS proteins including ferredoxins, nitrogenase, and radical SAM enzymes. This article is part of a Special Issue entitled: Fe/S proteins: Analysis, structure, function, biogenesis and diseases.
Collapse
Affiliation(s)
- George E Cutsail
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | - Joshua Telser
- Department of Biological, Chemical and Physical Sciences, Roosevelt University, Chicago, IL 60605, USA
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA.
| |
Collapse
|
18
|
Karagas NE, Jones CN, Osborn DJ, Dzierlenga AL, Oyala P, Konkle ME, Whitney EM, David Britt R, Hunsicker-Wang LM. The reduction rates of DEPC-modified mutant Thermus thermophilus Rieske proteins differ when there is a negative charge proximal to the cluster. J Biol Inorg Chem 2014; 19:1121-35. [PMID: 24916128 DOI: 10.1007/s00775-014-1167-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2013] [Accepted: 05/31/2014] [Indexed: 10/25/2022]
Abstract
Rieske and Rieske-type proteins are electron transport proteins involved in key biological processes such as respiration, photosynthesis, and detoxification. They have a [2Fe-2S] cluster ligated by two cysteines and two histidines. A series of mutations, L135E, L135R, L135A, and Y158F, of the Rieske protein from Thermus thermophilus has been produced which probe the effects of the neighboring residues, in the second sphere, on the dynamics of cluster reduction and the reactivity of the ligating histidines. These properties were probed using titrations and modifications with diethyl pyrocarbonate (DEPC) at various pH values monitored using UV-Visible and circular dichroism spectrophotometry. These results, along with results from EPR studies, provide information on ligating histidine modification and rate of reduction of each of the mutant proteins. L135R, L135A, and Y158F react with DEPC similarly to wild type, resulting in modified protein with a reduced [2Fe-2S] cluster in <90 min, whereas L135E requires >15 h under the same conditions. Thus, the negative charge slows down the rate of reduction and provides an explanation as to why negatively charged residues are rarely, if ever, found in the equivalent position of other Rieske and Rieske-type proteins.
Collapse
Affiliation(s)
- Nicholas E Karagas
- Department of Chemistry, Trinity University, One Trinity Place, San Antonio, TX, 78212, USA
| | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Albers A, Demeshko S, Dechert S, Saouma CT, Mayer JM, Meyer F. Fast proton-coupled electron transfer observed for a high-fidelity structural and functional [2Fe-2S] Rieske model. J Am Chem Soc 2014; 136:3946-54. [PMID: 24506804 PMCID: PMC3985845 DOI: 10.1021/ja412449v] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
![]()
Rieske cofactors
have a [2Fe–2S] cluster with unique {His2Cys2} ligation and distinct Fe subsites. The histidine
ligands are functionally relevant, since they allow for coupling of
electron and proton transfer (PCET) during quinol oxidation in respiratory
and photosynthetic ET chains. Here we present the highest fidelity
synthetic analogue for the Rieske [2Fe–2S] cluster reported
so far. This synthetic analogue 5x– emulates the heteroleptic {His2Cys2} ligation of the [2Fe–2S] core, and it also serves
as a functional model that undergoes fast concerted proton and electron
transfer (CPET) upon reaction of the mixed-valent (ferrous/ferric)
protonated 5H2– with TEMPO. The thermodynamics
of the PCET square scheme for 5x– have been determined, and three species (diferric 52–, protonated diferric 5H–, and mixed-valent 53–) have been characterized by X-ray diffraction. pKa values for 5H– and 5H2– differ by about 4 units, and the reduction
potential of 5H– is shifted anodically
by about +230 mV compared to that of 52–. While the N–H bond dissociation free energy of 5H2– (60.2 ± 0.5 kcal mol–1) and the free energy, ΔG°CPET, of its reaction with TEMPO (−6.3 kcal mol–1) are similar to values recently reported for a homoleptic {N2/N2}-coordinated [2Fe–2S] cluster, CPET
is significantly faster for 5H2– with
biomimetic {N2/S2} ligation (k = (9.5 ± 1.2) × 104 M–1 s–1, ΔH‡ = 8.7
± 1.0 kJ mol–1, ΔS‡ = −120 ± 40 J mol–1 K–1, and ΔG‡ = 43.8 ± 0.3 kJ mol–1 at 293 K). These parameters,
and the comparison with homoleptic analogues, provide important information
and new perspectives for the mechanistic understanding of the biological
Rieske cofactor.
Collapse
Affiliation(s)
- Antonia Albers
- Institute of Inorganic Chemistry, Georg-August-University Göttingen , Tammannstrasse 4, D-37077 Göttingen, Germany
| | | | | | | | | | | |
Collapse
|
20
|
Albers A, Bayer T, Demeshko S, Dechert S, Meyer F. A Functional Model for the Rieske Center: Full Characterization of a Biomimetic N-Ligated [2Fe-2S] Cluster in Different Protonation States. Chemistry 2013; 19:10101-6. [DOI: 10.1002/chem.201301760] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Indexed: 11/08/2022]
|
21
|
Mouesca JM, Fontecilla-Camps JC, Amara P. The Structural Plasticity of the Proximal [4Fe3S] Cluster is Responsible for the O2Tolerance of Membrane-Bound [NiFe] Hydrogenases. Angew Chem Int Ed Engl 2013; 52:2002-6. [DOI: 10.1002/anie.201209063] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Indexed: 11/08/2022]
|
22
|
Mouesca JM, Fontecilla-Camps JC, Amara P. The Structural Plasticity of the Proximal [4Fe3S] Cluster is Responsible for the O2
Tolerance of Membrane-Bound [NiFe] Hydrogenases. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201209063] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
23
|
Cutsail GE, Doan PE, Hoffman BM, Meyer J, Telser J. EPR and (57)Fe ENDOR investigation of 2Fe ferredoxins from Aquifex aeolicus. J Biol Inorg Chem 2012; 17:1137-50. [PMID: 22872138 DOI: 10.1007/s00775-012-0927-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Accepted: 07/12/2012] [Indexed: 01/09/2023]
Abstract
We have employed EPR and a set of recently developed electron nuclear double resonance (ENDOR) spectroscopies to characterize a suite of [2Fe-2S] ferredoxin clusters from Aquifex aeolicus (Aae Fd1, Fd4, and Fd5). Antiferromagnetic coupling between the Fe(II), S = 2, and Fe(III), S = 5/2, sites of the [2Fe-2S](+) cluster in these proteins creates an S = 1/2 ground state. A complete discussion of the spin-Hamiltonian contributions to g includes new symmetry arguments along with references to related FeS model compounds and their symmetry and EPR properties. Complete (57)Fe hyperfine coupling (hfc) tensors for each iron, with respective orientations relative to g, have been determined by the use of "stochastic" continuous wave and/or "random hopped" pulsed ENDOR, with the relative utility of the two approaches being emphasized. The reported hyperfine tensors include absolute signs determined by a modified pulsed ENDOR saturation and recovery (PESTRE) technique, RD-PESTRE-a post-processing protocol of the "raw data" that comprises an ENDOR spectrum. The (57)Fe hyperfine tensor components found by ENDOR are nicely consistent with those previously found by Mössbauer spectroscopy, while accurate tensor orientations are unique to the ENDOR approach. These measurements demonstrate the capabilities of the newly developed methods. The high-precision hfc tensors serve as a benchmark for this class of FeS proteins, while the variation in the (57)Fe hfc tensors as a function of symmetry in these small FeS clusters provides a reference for higher-nuclearity FeS clusters, such as those found in nitrogenase.
Collapse
Affiliation(s)
- George E Cutsail
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
| | | | | | | | | |
Collapse
|
24
|
Fleischhacker AS, Stubna A, Hsueh KL, Guo Y, Teter SJ, Rose JC, Brunold TC, Markley JL, Münck E, Kiley PJ. Characterization of the [2Fe-2S] cluster of Escherichia coli transcription factor IscR. Biochemistry 2012; 51:4453-62. [PMID: 22583201 DOI: 10.1021/bi3003204] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
IscR is an Fe-S cluster-containing transcription factor involved in a homeostatic mechanism that controls Fe-S cluster biogenesis in Escherichia coli. Although IscR has been proposed to act as a sensor of the cellular demands for Fe-S cluster biogenesis, the mechanism by which IscR performs this function is not known. In this study, we investigated the biochemical properties of the Fe-S cluster of IscR to gain insight into the proposed sensing activity. Mössbauer studies revealed that IscR contains predominantly a reduced [2Fe-2S](+) cluster in vivo. However, upon anaerobic isolation of IscR, some clusters became oxidized to the [2Fe-2S](2+) form. Cluster oxidation did not, however, alter the affinity of IscR for its binding site within the iscR promoter in vitro, indicating that the cluster oxidation state is not important for regulation of DNA binding. Furthermore, characterization of anaerobically isolated IscR using resonance Raman, Mössbauer, and nuclear magnetic resonance spectroscopies leads to the proposal that the [2Fe-2S] cluster does not have full cysteinyl ligation. Mutagenesis studies indicate that, in addition to the three previously identified cysteine residues (Cys92, Cys98, and Cys104), the highly conserved His107 residue is essential for cluster ligation. Thus, these data suggest that IscR binds the cluster with an atypical ligation scheme of three cysteines and one histidine, a feature that may be relevant to the proposed function of IscR as a sensor of cellular Fe-S cluster status.
Collapse
Affiliation(s)
- Angela S Fleischhacker
- Department of Biomolecular Chemistry, University of Wisconsin, Madison, Wisconsin 53706, United States
| | | | | | | | | | | | | | | | | | | |
Collapse
|
25
|
Abdalla JAB, Bowen AM, Bell SG, Wong LL, Timmel CR, Harmer J. Characterisation of the paramagnetic [2Fe–2S]+ centre in palustrisredoxin-B (PuxB) from Rhodopseudomonas palustris CGA009: g-matrix determination and spin coupling analysis. Phys Chem Chem Phys 2012; 14:6526-37. [DOI: 10.1039/c2cp24112a] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
26
|
|
27
|
Grigoropoulos A, Szilagyi RK. In silico evaluation of proposed biosynthetic pathways for the unique dithiolate ligand of the H-cluster of [FeFe]-hydrogenase. J Comput Chem 2011; 32:3194-206. [DOI: 10.1002/jcc.21901] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 07/02/2011] [Accepted: 07/03/2011] [Indexed: 12/30/2022]
|
28
|
Albers A, Demeshko S, Dechert S, Bill E, Bothe E, Meyer F. Die vollständige Charakterisierung eines reduzierten biomimetischen [2 Fe-2 S]-Clusters. Angew Chem Int Ed Engl 2011. [DOI: 10.1002/ange.201100727] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
29
|
Albers A, Demeshko S, Dechert S, Bill E, Bothe E, Meyer F. The Complete Characterization of a Reduced Biomimetic [2 Fe-2 S] Cluster. Angew Chem Int Ed Engl 2011; 50:9191-4. [DOI: 10.1002/anie.201100727] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 05/24/2011] [Indexed: 11/08/2022]
|
30
|
Harris TV, Szilagyi RK. Comparative assessment of the composition and charge state of nitrogenase FeMo-cofactor. Inorg Chem 2011; 50:4811-24. [PMID: 21545160 DOI: 10.1021/ic102446n] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A significant limitation in our understanding of the molecular mechanism of biological nitrogen fixation is the uncertain composition of the FeMo-cofactor (FeMo-co) of nitrogenase. In this study we present a systematic, density functional theory-based evaluation of spin-coupling schemes, iron oxidation states, ligand protonation states, and interstitial ligand composition using a wide range of experimental criteria. The employed functionals and basis sets were validated with molecular orbital information from X-ray absorption spectroscopic data of relevant iron-sulfur clusters. Independently from the employed level of theory, the electronic structure with the greatest number of antiferromagnetic interactions corresponds to the lowest energy state for a given charge and oxidation state distribution of the iron ions. The relative spin state energies of resting and oxidized FeMo-co already allowed exclusion of certain iron oxidation state distributions and interstitial ligand compositions. Geometry-optimized FeMo-co structures of several models further eliminated additional states and compositions, while reduction potentials indicated a strong preference for the most likely charge state of FeMo-co. Mössbauer and ENDOR parameter calculations were found to be remarkably dependent on the employed training set, density functional, and basis set. Overall, we found that a more oxidized [Mo(IV)-2Fe(II)-5Fe(III)-9S(2-)-C(4-)] composition with a hydroxyl-protonated homocitrate ligand satisfies all of the available experimental criteria and is thus favored over the currently preferred composition of [Mo(IV)-4Fe(II)-3Fe(III)-9S(2-)-N(3-)] from the literature.
Collapse
Affiliation(s)
- Travis V Harris
- NAI Astrobiology Biogeocatalysis Research Center, Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, USA
| | | |
Collapse
|
31
|
Dicus MM, Conlan A, Nechushtai R, Jennings PA, Paddock ML, Britt RD, Stoll S. Binding of histidine in the (Cys)3(His)1-coordinated [2Fe-2S] cluster of human mitoNEET. J Am Chem Soc 2010; 132:2037-49. [PMID: 20099820 PMCID: PMC2820139 DOI: 10.1021/ja909359g] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Human mitoNEET is a homodimeric iron-sulfur protein located in the outer mitochondrial membrane with unknown function, but which is known to interact with thiazolidinedione diabetes drugs. Each monomer houses a [2Fe-2S] cluster with an unusual (Cys)(3)(His)(1) ligation. The His ligand is important for enabling cluster release and for tuning the redox potential. We use multifrequency (X-, Ka-, and Q-band) and multitechnique (continuous-wave, electron spin-echo envelope modulation (ESEEM), pulsed electron-nuclear double resonance (ENDOR), and hyperfine sublevel correlation (HYSCORE)) electron paramagnetic resonance spectroscopy to investigate the cluster in its paramagnetic reduced [Fe(2+)Fe(3+)] (S = 1/2) state. It has a rhombic g tensor (2.007, 1.937, 1.897) with an average g value of 1.947 that falls between those of Rieske-type and ferredoxin-type [2Fe-2S] clusters. Simulation and least-squares fitting of orientation-selective Ka- and Q-band ENDOR, 1D ESEEM, and HYSCORE spectra of (14)N and (15)N-labeled mitoNEET yield the principal values and orientations of both the hyperfine tensor ((14)N, A(iso) = -6.25 MHz, T = -0.94 MHz) and the quadrupolar tensor (e(2)Qq/h = -2.47 MHz, eta = 0.38) of the ligating histidine nitrogen N(delta). From these, we can infer the absolute g tensor orientation with respect to the cluster: The g(2) axis is close to perpendicular to the [2Fe-2S] plane, and g(1) and g(3) are in-plane, but skewed from the Fe-Fe and S-S axes. In X-band ENDOR and ESEEM spectra, a weakly coupled nitrogen is visible, most likely the N(epsilon) of the histidine in the protonated state. We find that the cluster is in a valence-localized state, where Fe(2+) is His-bound. The field-sweep spectra show evidence of intercluster dipolar coupling that can be simulated using an uncoupled spin model for each cluster (S(Fe(2+)) = 2, S(Fe(3+)) = 5/2). The parameters determined in this work can function as reporters on how the cluster structure is altered upon pH changes and drug binding.
Collapse
Affiliation(s)
- Michelle M Dicus
- Department of Chemistry, University of California, Davis, California 95616, USA
| | | | | | | | | | | | | |
Collapse
|
32
|
Unexpected electron transfer mechanism upon AdoMet cleavage in radical SAM proteins. Proc Natl Acad Sci U S A 2009; 106:14867-71. [PMID: 19706452 DOI: 10.1073/pnas.0904385106] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Radical S-adenosine-L-methionine (SAM or AdoMet) proteins are involved in chemically difficult reactions including the synthesis of cofactors, the generation of protein radicals, and the maturation of complex organometallic catalytic sites. In the first and common step of the reaction, a conserved [Fe4S4] cluster donates an electron to perform the reductive cleavage of AdoMet into methionine and a reactive radical 5'-dA. species. The latter extracts a hydrogen atom from substrate eliciting one of the about 40 reactions so far characterized for this family of proteins. It has been suggested that the radical-generating mechanism differs depending on whether AdoMet is a cofactor or a substrate. It has also been speculated that electron transfer from the [Fe4S4] cluster to AdoMet is sulfur-based. Here we have used protein crystallography and theoretical calculations to show that regardless whether AdoMet serves as a cofactor or a substrate, the 5'-dA. generating mechanism should be common to the radical SAM proteins studied so far, and that electron transfer is mediated by a unique Fe from the conserved [Fe4S4] cluster. This unusual electron transfer is determined by the sulfonium ion in AdoMet.
Collapse
|