1
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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.
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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
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2
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Tao L, Stich TA, Fugate CJ, Jarrett JT, Britt RD. EPR-Derived Structure of a Paramagnetic Intermediate Generated by Biotin Synthase BioB. J Am Chem Soc 2018; 140:12947-12963. [PMID: 30222930 PMCID: PMC6363123 DOI: 10.1021/jacs.8b07613] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Biotin (vitamin B7) is an enzyme cofactor required by organisms from all branches of life but synthesized only in microbes and plants. In the final step of biotin biosynthesis, a radical S-adenosyl-l-methionine (SAM) enzyme, biotin synthase (BioB), converts the substrate dethiobiotin to biotin through the stepwise formation of two C-S bonds. Previous electron paramagnetic resonance (EPR) spectroscopic studies identified a semistable intermediate in the formation of the first C-S bond as 9-mercaptodethiobiotin linked to a paramagnetic [2Fe-2S] cluster through one of its bridging sulfides. Herein, we report orientation-selected pulse EPR spectroscopic results that reveal hyperfine interactions between the [2Fe-2S] cluster and a number of magnetic nuclei (e.g., 57Fe, 15N, 13C, and 2H) introduced in a site-specific manner via biosynthetic methods. Combining these results with quantum chemical modeling gives a structural model of the intermediate showing that C6, the target of the second hydrogen-atom abstraction, is now in close proximity to the nascent thioether sulfur and is ideally positioned for the second C-S bond forming event.
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Affiliation(s)
- Lizhi Tao
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Troy A. Stich
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Corey J. Fugate
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - Joseph T. Jarrett
- Department of Chemistry, University of Hawaii at Manoa, Honolulu, Hawaii 96822, United States
| | - R. David Britt
- Department of Chemistry, University of California, Davis, California 95616, United States
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3
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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.
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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
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4
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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.
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5
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Colin F, Martelli A, Clémancey M, Latour JM, Gambarelli S, Zeppieri L, Birck C, Page A, Puccio H, Ollagnier de Choudens S. Mammalian frataxin controls sulfur production and iron entry during de novo Fe4S4 cluster assembly. J Am Chem Soc 2013; 135:733-40. [PMID: 23265191 DOI: 10.1021/ja308736e] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Iron-sulfur (Fe-S) cluster-containing proteins are essential components of cells. In eukaryotes, Fe-S clusters are synthesized by the mitochondrial iron-sulfur cluster (ISC) machinery and the cytosolic iron-sulfur assembly (CIA) system. In the mammalian ISC machinery, preassembly of the Fe-S cluster on the scaffold protein (ISCU) involves a cysteine desulfurase complex (NFS1/ISD11) and frataxin (FXN), the protein deficient in Friedreich's ataxia. Here, by comparing the biochemical and spectroscopic properties of quaternary (ISCU/NFS1/ISD11/FXN) and ternary (ISCU/NFS1/ISD11) complexes, we show that FXN stabilizes the quaternary complex and controls iron entry to the complex through activation of cysteine desulfurization. Furthermore, we show for the first time that in the presence of iron and L-cysteine, an [Fe(4)S(4)] cluster is formed within the quaternary complex that can be transferred to mammalian aconitase (mACO2) to generate an active enzyme. In the absence of FXN, although the ternary complex can assemble an Fe-S cluster, the cluster is inefficiently transferred to ACO2. Taken together, these data help to unravel further the Fe-S cluster assembly process and the molecular basis of Friedreich's ataxia.
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Affiliation(s)
- Florent Colin
- Translational Medicine and Neurogenetics, Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France
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6
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Atypical features of Thermus thermophilus succinate:quinone reductase. PLoS One 2013; 8:e53559. [PMID: 23308253 PMCID: PMC3538594 DOI: 10.1371/journal.pone.0053559] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2012] [Accepted: 11/29/2012] [Indexed: 11/26/2022] Open
Abstract
The Thermus thermophilus succinate:quinone reductase (SQR), serving as the respiratory complex II, has been homologously produced under the control of a constitutive promoter and subsequently purified. The detailed biochemical characterization of the resulting wild type (wt-rcII) and His-tagged (rcII-His8-SdhB and rcII-SdhB-His6) complex II variants showed the same properties as the native enzyme with respect to the subunit composition, redox cofactor content and sensitivity to the inhibitors malonate, oxaloacetate, 3-nitropropionic acid and nonyl-4-hydroxyquinoline-N-oxide (NQNO). The position of the His-tag determined whether the enzyme retained its native trimeric conformation or whether it was present in a monomeric form. Only the trimer exhibited positive cooperativity at high temperatures. The EPR signal of the [2Fe-2S] cluster was sensitive to the presence of substrate and showed an increased rhombicity in the presence of succinate in the native and in all recombinant forms of the enzyme. The detailed analysis of the shape of this signal as a function of pH, substrate concentration and in the presence of various inhibitors and quinones is presented, leading to a model for the molecular mechanism that underlies the influence of succinate on the rhombicity of the EPR signal of the proximal iron-sulfur cluster.
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7
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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.
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Affiliation(s)
- George E Cutsail
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA
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8
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Türker L. A Model Study on the Possible Effects of an External Electrical Field on Enzymes Having Dinuclear Iron Cluster [2Fe-2S]. ScientificWorldJournal 2012; 2012:985958. [PMID: 22629229 PMCID: PMC3353660 DOI: 10.1100/2012/985958] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 12/01/2011] [Indexed: 11/17/2022] Open
Abstract
Hydrogenases which catalyze the H2↔ 2H+ + 2e− reaction are metalloenzymes that can be divided into two classes, the NiFe and Fe enzymes, on the basis of their metal content. Iron-sulfur clusters [2Fe-2S] and [4Fe-4S] are common in ironhydrogenases. In the present model study, [2Fe-2S] cluster has been considered to visualize the effect of external electric field on various quantum chemical properties of it. In the model, all the cysteinyl residues are in the amide form. The PM3 type semiempirical calculations have been performed for the geometry optimization of the model structure in the absence and presence of the external field. Then, single point DFT calculations (B3LYP/6-31+G(d)) have been carried out. Depending on the direction of the field, the chemical reactivity of the model enzyme varies which suggests that an external electric field could, under proper conditions, improve the enzymatic hydrogen production.
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Affiliation(s)
- Lemi Türker
- Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey
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9
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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]
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10
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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.
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Affiliation(s)
- Michelle M Dicus
- Department of Chemistry, University of California, Davis, California 95616, USA
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11
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Dikanov SA, Samoilova RI, Kappl R, Crofts AR, Hüttermann J. The reduced [2Fe-2S] clusters in adrenodoxin and Arthrospira platensis ferredoxin share spin density with protein nitrogens, probed using 2D ESEEM. Phys Chem Chem Phys 2009; 11:6807-19. [PMID: 19639155 PMCID: PMC2773023 DOI: 10.1039/b904597j] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
We have used X-band ESEEM to study the reduced [2Fe-2S] cluster in adrenodoxin and Arthrospira platensis ferredoxin. By use of a 2D approach (HYSCORE), we have shown that the cluster is involved in weak magnetic interactions with several nitrogens in each protein. Despite substantial differences in the shape and orientational dependence of individual cross-peaks, the major spectral features in both proteins are attributable to two peptide nitrogens (N1 and N2) with similar hyperfine couplings approximately 1.1 and approximately 0.70 MHz. The couplings determined represent a small fraction (0.0003-0.0005) of the unpaired spin density of the reduced cluster transferred to these nitrogens over H-bond bridges or the covalent bonds of cysteine ligands. Simulation of the HYSCORE spectra has allowed us to estimate the orientation of the nuclear quadrupole tensors of N1 and N2 in the g-tensor coordinate system. The most likely candidates for the role of N1 and N2 have been identified in the protein environment by comparing magnetic-resonance data with crystallographic structures of the oxidized proteins. A possible influence of redox-linked structural changes on ESEEM data is analyzed using available structures for related proteins in two redox states.
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Affiliation(s)
- Sergei A Dikanov
- Department of Veterinary Clinical Medicine, University of Illinois, Urbana, IL 61801, USA.
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12
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Orio M, Mouesca JM. Variation of average g values and effective exchange coupling constants among [2Fe-2S] clusters: a density functional theory study of the impact of localization (trapping forces) versus delocalization (double-exchange) as competing factors. Inorg Chem 2008; 47:5394-416. [PMID: 18491857 DOI: 10.1021/ic701730h] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A phenomenological model aimed at rationalizing variations in both average g-tensor values (gav identical with 1/3Sigmaigi ) and effective exchange coupling constants Jeff (defined as two-thirds of the energy difference between the S = 3/2 and S = 1/2 spin states) has been derived in order to describe the great variety of magnetic properties exhibited by reduced [2Fe-2S] clusters in proteins. The key quantity in the present analysis is the ratio Delta E/B computed from two competing terms. Delta Ecomprises various effects that result in trapping-site asymmetries: vibronic coupling and the chemical nature (S/N/O) and conformations of the ligands on the one hand and solvation terms, the hydrogen bonding network, etc., on the other. All of these additive terms (in a "bottom-up" approach) favor valence localization of the reducing electron onto one of the two iron sites. In contrast, the B term is the double-exchange term, which favors electronic delocalization. Both gav and Jeff can be expressed as functions of Delta E/ B. We have also shown that electronic localization generally favors small gav and large Jeff values (while the opposite is true for electronic delocalization) in a comparative study of the spectroscopic features of plant-type ferredoxins (Fd's) and Rieske centers (and related mutants). Two other types of problems were particularly challenging. The first of these involved deprotonated Rieske centers and the xanthine oxidase clusters II, which are characterized by very small Jeff values (40-45 cm (-1) with a J S A. S B model) correlated with unusually large gav values (in the range 1.97-2.01) as a result of an antisymmetric exchange coupling mechanism. The second concerned the analogous Fd's from Clostridium pasteurianum (Cp) and Aquifex aeolicus (Aa). Detailed Mössbauer studies of the C56S mutant of the Cp system revealed a mixture of clusters with valence-localized S = 1/2 and valence-delocalized S = 9/2 ground states. We relied on crystallographic structures of wild-type and mutant Aa Fd's in order to explain such a distribution of spin states.
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Affiliation(s)
- Maylis Orio
- Laboratory of Inorganic and Biological Chemistry, Grenoble cedex, France
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Spin–orbit coupling in the double exchange model 1. Antisymmetric double exchange in a valence-delocalized [Fe2.5+Fe2.5+] cluster. Chem Phys 2006. [DOI: 10.1016/j.chemphys.2005.12.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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14
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More C, Asso M, Roger G, Guigliarelli B, Caldeira J, Moura J, Bertrand P. Study of the spin-spin interactions between the metal centers of Desulfovibrio gigas aldehyde oxidoreductase: identification of the reducible sites of the [2Fe-2S]1+,2+ clusters. Biochemistry 2005; 44:11628-35. [PMID: 16114900 DOI: 10.1021/bi0510025] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The aldehyde oxidoreductase from Desulfovibrio gigas belongs to the family of molybdenum hydroxylases. Besides a molybdenum cofactor which constitutes their active site, these enzymes contain two [2Fe-2S](2+,1+) clusters which are believed to transfer the electrons provided by the substrate to an acceptor which is either a FAD group or an electron-transferring protein. When the three metal centers of D. gigas AOR are simultaneously paramagnetic, splittings due to intercenter spin-spin interactions are visible when the EPR spectra are recorded at low temperatures. By studying quantitatively these interactions with a model based on the X-ray crystal structure, which takes into consideration the interactions between the magnetic moments carried by all the metal sites of the system, it is possible to determine the location of the reducible sites of the [2Fe-2S] clusters. When combined with the electron-transfer pathways proposed on the basis of the X-ray crystal structure, the results provide a detailed description of the electron-transfer system of D. gigas AOR.
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Affiliation(s)
- Claude More
- Laboratoire de Bioénergétique et Ingénierie des Protéines, UPR 9036 CNRS and Université de Provence, 31 Chemin Joseph Aiguier, 13402 Marseille, France
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15
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Fritscher J. Influence of hydrogen bond geometry on quadrupole coupling parameters: A theoretical study of imidazole–water and imidazole–semiquinone complexes. Phys Chem Chem Phys 2004. [DOI: 10.1039/b408764j] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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