1
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Bostelaar TM, Brown AC, Sridharan A, Suess DLM. A general method for metallocluster site-differentiation. NATURE SYNTHESIS 2023; 2:740-748. [PMID: 39055685 PMCID: PMC11271975 DOI: 10.1038/s44160-023-00286-7] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Accepted: 03/02/2023] [Indexed: 07/27/2024]
Abstract
The deployment of metalloclusters in applications such as catalysis and materials synthesis requires robust methods for site-differentiation: the conversion of clusters with symmetric ligand spheres to those with unsymmetrical ligand spheres. However, imparting precise patterns of site-differentiation is challenging because, compared with mononuclear complexes, the ligands bound to clusters exert limited spatial and electronic influence on one another. Here, we report a method that employs sterically encumbering ligands to bind to only a subset of a cluster's coordination sites. Specifically, we show that homoleptic, phosphine-ligated Fe-S clusters undergo ligand substitution with N-heterocyclic carbenes (NHCs) to give heteroleptic clusters in which the resultant clusters' site-differentiation patterns are encoded by the steric profile of the incoming NHC. This method affords access to every site-differentiation pattern for cuboidal [Fe4S4] clusters and can be extended to other cluster types, particularly in the stereoselective synthesis of site-differentiated Chevrel-type [Fe6S8] clusters.
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Affiliation(s)
- Trever M Bostelaar
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Alexandra C Brown
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Arun Sridharan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA, USA
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2
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Rutledge HL, Field MJ, Rittle J, Green MT, Akif Tezcan F. Role of Serine Coordination in the Structural and Functional Protection of the Nitrogenase P-Cluster. J Am Chem Soc 2022; 144:22101-22112. [PMID: 36445204 PMCID: PMC9957664 DOI: 10.1021/jacs.2c09480] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Nitrogenase catalyzes the multielectron reduction of dinitrogen to ammonia. Electron transfer in the catalytic protein (MoFeP) proceeds through a unique [8Fe-7S] cluster (P-cluster) to the active site (FeMoco). In the reduced, all-ferrous (PN) state, the P-cluster is coordinated by six cysteine residues. Upon two-electron oxidation to the P2+ state, the P-cluster undergoes conformational changes in which a highly conserved oxygen-based residue (a Ser or a Tyr) and a backbone amide additionally ligate the cluster. Previous studies of Azotobacter vinelandii (Av) MoFeP revealed that when the oxygen-based residue, βSer188, was mutated to a noncoordinating residue, Ala, the P-cluster became redox-labile and reversibly lost two of its eight Fe centers. Surprisingly, the Av strain with a MoFeP variant that lacked the serine ligand (Av βSer188Ala MoFeP) displayed the same diazotrophic growth and in vitro enzyme turnover rates as wild-type Av MoFeP, calling into question the necessity of this conserved ligand for nitrogenase function. Based on these observations, we hypothesized that βSer188 plays a role in protecting the P-cluster under nonideal conditions. Here, we investigated the protective role of βSer188 both in vivo and in vitro by characterizing the ability of Av βSer188Ala cells to grow under suboptimal conditions (high oxidative stress or Fe limitation) and by determining the tendency of βSer188Ala MoFeP to be mismetallated in vitro. Our results demonstrate that βSer188 (1) increases Av cell survival upon exposure to oxidative stress in the form of hydrogen peroxide, (2) is necessary for efficient Av diazotrophic growth under Fe-limiting conditions, and (3) may protect the P-cluster from metal exchange in vitro. Taken together, our findings suggest a structural adaptation of nitrogenase to protect the P-cluster via Ser ligation, which is a previously unidentified functional role of the Ser residue in redox proteins and adds to the expanding functional roles of non-Cys ligands to FeS clusters.
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Affiliation(s)
- Hannah L. Rutledge
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
| | - Mackenzie J. Field
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States
| | - Jonathan Rittle
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
| | - Michael T. Green
- Department of Chemistry, University of California, Irvine, Irvine, California 92697, United States.,Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, California 92697, United States
| | - F. Akif Tezcan
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States.,Corresponding Author:
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3
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Hunter GA, Ferreira GC. Metal ion coordination sites in ferrochelatase. Coord Chem Rev 2022. [DOI: 10.1016/j.ccr.2022.214464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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4
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Crack JC, Balasiny BK, Bennett SP, Rolfe MD, Froes A, MacMillan F, Green J, Cole JA, Le Brun NE. The Di-Iron Protein YtfE Is a Nitric Oxide-Generating Nitrite Reductase Involved in the Management of Nitrosative Stress. J Am Chem Soc 2022; 144:7129-7145. [PMID: 35416044 PMCID: PMC9052748 DOI: 10.1021/jacs.1c12407] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
![]()
Previously characterized
nitrite reductases fall into three classes:
siroheme-containing enzymes (NirBD), cytochrome c hemoproteins (NrfA and NirS), and copper-containing enzymes (NirK).
We show here that the di-iron protein YtfE represents a physiologically
relevant new class of nitrite reductases. Several functions have been
previously proposed for YtfE, including donating iron for the repair
of iron–sulfur clusters that have been damaged by nitrosative
stress, releasing nitric oxide (NO) from nitrosylated iron, and reducing
NO to nitrous oxide (N2O). Here, in vivo reporter assays confirmed that Escherichia coli YtfE increased cytoplasmic NO production from nitrite. Spectroscopic
and mass spectrometric investigations revealed that the di-iron site
of YtfE exists in a mixture of forms, including nitrosylated and nitrite-bound,
when isolated from nitrite-supplemented, but not nitrate-supplemented,
cultures. Addition of nitrite to di-ferrous YtfE resulted in nitrosylated
YtfE and the release of NO. Kinetics of nitrite reduction were dependent
on the nature of the reductant; the lowest Km, measured for the di-ferrous form, was ∼90 μM,
well within the intracellular nitrite concentration range. The vicinal
di-cysteine motif, located in the N-terminal domain of YtfE, was shown
to function in the delivery of electrons to the di-iron center. Notably,
YtfE exhibited very low NO reductase activity and was only able to
act as an iron donor for reconstitution of apo-ferredoxin under conditions
that damaged its di-iron center. Thus, YtfE is a high-affinity, low-capacity
nitrite reductase that we propose functions to relieve nitrosative
stress by acting in combination with the co-regulated NO-consuming
enzymes Hmp and Hcp.
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Affiliation(s)
- Jason C Crack
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Basema K Balasiny
- Institute of Microbiology and Infection and School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Sophie P Bennett
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Matthew D Rolfe
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Afonso Froes
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Fraser MacMillan
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
| | - Jeffrey Green
- School of Biosciences, University of Sheffield, Sheffield S10 2TN, UK
| | - Jeffrey A Cole
- Institute of Microbiology and Infection and School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry, School of Chemistry, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, UK
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5
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D'Angelo F, Fernández-Fueyo E, Garcia PS, Shomar H, Pelosse M, Manuel RR, Büke F, Liu S, van den Broek N, Duraffourg N, de Ram C, Pabst M, Bouveret E, Gribaldo S, Py B, Ollagnier de Choudens S, Barras F, Bokinsky G. Cellular assays identify barriers impeding iron-sulfur enzyme activity in a non-native prokaryotic host. eLife 2022; 11:70936. [PMID: 35244541 PMCID: PMC8896826 DOI: 10.7554/elife.70936] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Accepted: 02/03/2022] [Indexed: 11/24/2022] Open
Abstract
Iron-sulfur (Fe-S) clusters are ancient and ubiquitous protein cofactors and play irreplaceable roles in many metabolic and regulatory processes. Fe-S clusters are built and distributed to Fe-S enzymes by dedicated protein networks. The core components of these networks are widely conserved and highly versatile. However, Fe-S proteins and enzymes are often inactive outside their native host species. We sought to systematically investigate the compatibility of Fe-S networks with non-native Fe-S enzymes. By using collections of Fe-S enzyme orthologs representative of the entire range of prokaryotic diversity, we uncovered a striking correlation between phylogenetic distance and probability of functional expression. Moreover, coexpression of a heterologous Fe-S biogenesis pathway increases the phylogenetic range of orthologs that can be supported by the foreign host. We also find that Fe-S enzymes that require specific electron carrier proteins are rarely functionally expressed unless their taxon-specific reducing partners are identified and co-expressed. We demonstrate how these principles can be applied to improve the activity of a radical S-adenosyl methionine(rSAM) enzyme from a Streptomyces antibiotic biosynthesis pathway in Escherichia coli. Our results clarify how oxygen sensitivity and incompatibilities with foreign Fe-S and electron transfer networks each impede heterologous activity. In particular, identifying compatible electron transfer proteins and heterologous Fe-S biogenesis pathways may prove essential for engineering functional Fe-S enzyme-dependent pathways.
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Affiliation(s)
- Francesca D'Angelo
- Unit Stress Adaptation and Metabolism of Enterobacteria, Department of Microbiology, Université de Paris, UMR CNRS 2001, Institut Pasteur, Paris, France
| | - Elena Fernández-Fueyo
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, Netherlands
| | - Pierre Simon Garcia
- Unit Stress Adaptation and Metabolism of Enterobacteria, Department of Microbiology, Université de Paris, UMR CNRS 2001, Institut Pasteur, Paris, France.,Institut Pasteur, Université de Paris, CNRS UMR6047, Evolutionary Biology of the Microbial Cell, Department of Microbiology, Paris, France
| | - Helena Shomar
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, Netherlands
| | - Martin Pelosse
- Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, Grenoble, France
| | - Rita Rebelo Manuel
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, Netherlands
| | - Ferhat Büke
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, Netherlands
| | - Siyi Liu
- Aix-Marseille Université-CNRS, Laboratoire de Chimie Bactérienne UMR 7283, Institut de Microbiologie de la Méditerranée, Institut Microbiologie Bioénergies Biotechnologie, Marseille, France
| | - Niels van den Broek
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, Netherlands
| | - Nicolas Duraffourg
- Univ. Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire de Chimie et Biologie des Métaux, Grenoble, France
| | - Carol de Ram
- Department of Biotechnology, Delft University of Technology, Delft, Netherlands
| | - Martin Pabst
- Department of Biotechnology, Delft University of Technology, Delft, Netherlands
| | - Emmanuelle Bouveret
- Unit Stress Adaptation and Metabolism of Enterobacteria, Department of Microbiology, Université de Paris, UMR CNRS 2001, Institut Pasteur, Paris, France
| | - Simonetta Gribaldo
- Institut Pasteur, Université de Paris, CNRS UMR6047, Evolutionary Biology of the Microbial Cell, Department of Microbiology, Paris, France
| | - Béatrice Py
- Aix-Marseille Université-CNRS, Laboratoire de Chimie Bactérienne UMR 7283, Institut de Microbiologie de la Méditerranée, Institut Microbiologie Bioénergies Biotechnologie, Marseille, France
| | | | - Frédéric Barras
- Unit Stress Adaptation and Metabolism of Enterobacteria, Department of Microbiology, Université de Paris, UMR CNRS 2001, Institut Pasteur, Paris, France
| | - Gregory Bokinsky
- Department of Bionanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, Netherlands
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6
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Ali F, Shafaa MW, Amin M. Computational Approach for Probing Redox Potential for Iron-Sulfur Clusters in Photosystem I. BIOLOGY 2022; 11:biology11030362. [PMID: 35336736 PMCID: PMC8945787 DOI: 10.3390/biology11030362] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 02/15/2022] [Accepted: 02/21/2022] [Indexed: 11/16/2022]
Abstract
Photosystem I is a light-driven electron transfer device. Available X-ray crystal structure from Thermosynechococcus elongatus showed that electron transfer pathways consist of two nearly symmetric branches of cofactors converging at the first iron-sulfur cluster FX, which is followed by two terminal iron-sulfur clusters FA and FB. Experiments have shown that FX has lower oxidation potential than FA and FB, which facilitates the electron transfer reaction. Here, we use density functional theory and Multi-Conformer Continuum Electrostatics to explain the differences in the midpoint Em potentials of the FX, FA and FB clusters. Our calculations show that FX has the lowest oxidation potential compared to FA and FB due to strong pairwise electrostatic interactions with surrounding residues. These interactions are shown to be dominated by the bridging sulfurs and cysteine ligands, which may be attributed to the shorter average bond distances between the oxidized Fe ion and ligating sulfurs for FX compared to FA and FB. Moreover, the electrostatic repulsion between the 4Fe-4S clusters and the positive potential of the backbone atoms is lowest for FX compared to both FA and FB. These results agree with the experimental measurements from the redox titrations of low-temperature EPR signals and of room temperature recombination kinetics.
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Affiliation(s)
- Fedaa Ali
- Medical Biophysics Division, Department of Physics, Faculty of Science, Helwan University, Cairo 11795, Egypt; (F.A.); (M.W.S.)
- Genome Science and Technology, The University of Tennessee, Knoxville, TN 37996, USA
| | - Medhat W. Shafaa
- Medical Biophysics Division, Department of Physics, Faculty of Science, Helwan University, Cairo 11795, Egypt; (F.A.); (M.W.S.)
| | - Muhamed Amin
- Department of Sciences, University College Groningen, University of Groningen, Hoendiepskade 23/24, 9718 BG Groningen, The Netherlands
- Universiteit Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9718 BG Groningen, The Netherlands
- Department of Physics, City College of New York, City University of New York, New York, NY 10031, USA
- Correspondence:
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7
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Heghmanns M, Rutz A, Kutin Y, Engelbrecht V, Winkler M, Happe T, Kasanmascheff M. The oxygen-resistant [FeFe]-hydrogenase CbA5H harbors an unknown radical signal. Chem Sci 2022; 13:7289-7294. [PMID: 35799827 PMCID: PMC9214887 DOI: 10.1039/d2sc00385f] [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: 01/20/2022] [Accepted: 05/28/2022] [Indexed: 11/21/2022] Open
Abstract
[FeFe]-hydrogenases catalyze the reversible conversion of molecular hydrogen into protons and electrons with remarkable efficiency. However, their industrial applications are limited by their oxygen sensitivity. Recently, it was shown that the [FeFe]-hydrogenase from Clostridium beijerinckii (CbA5H) is oxygen-resistant and can be reactivated after oxygen exposure. In this work, we used multifrequency continuous wave and pulsed electron paramagnetic resonance (EPR) spectroscopy to characterize the active center of CbA5H, the H-cluster. Under oxidizing conditions, the spectra were dominated by an additional and unprecedented radical species. The generation of this radical signal depends on the presence of an intact H-cluster and a complete proton transfer pathway including the bridging azadithiolate ligand. Selective 57Fe enrichment combined with isotope-sensitive electron-nuclear double resonance (ENDOR) spectroscopy revealed a spin density distribution that resembles an H-cluster state. Overall, we uncovered a radical species in CbA5H that is potentially involved in the redox sensing of CbA5H. Electron paramagnetic resonance spectroscopy revealed an unprecedented radical species in the oxygen-resistant [FeFe]-hydrogenase CbA5H. Analysis of the isotope-sensitive data suggests that it is related to the active site, the H-cluster.![]()
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Affiliation(s)
- Melanie Heghmanns
- TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Straße 6, 44227 Dortmund, Germany
| | - Andreas Rutz
- Ruhr University Bochum, Faculty of Biology and Biotechnology, Photobiotechnology, Universitätsstr. 150, 44801 Bochum, Germany
| | - Yury Kutin
- TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Straße 6, 44227 Dortmund, Germany
| | - Vera Engelbrecht
- Ruhr University Bochum, Faculty of Biology and Biotechnology, Photobiotechnology, Universitätsstr. 150, 44801 Bochum, Germany
| | - Martin Winkler
- Technical University of Munich Campus Straubing for Biotechnology and Sustainability, Professorship for Electrobiotechnology, Uferstrasse 53, 94315 Straubing, Germany
| | - Thomas Happe
- Ruhr University Bochum, Faculty of Biology and Biotechnology, Photobiotechnology, Universitätsstr. 150, 44801 Bochum, Germany
| | - Müge Kasanmascheff
- TU Dortmund University, Department of Chemistry and Chemical Biology, Otto-Hahn-Straße 6, 44227 Dortmund, Germany
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8
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Tzeli D, Raugei S, Xantheas SS. Quantitative Account of the Bonding Properties of a Rubredoxin Model Complex [Fe(SCH 3) 4] q, q = -2, -1, +2, +3. J Chem Theory Comput 2021; 17:6080-6091. [PMID: 34546757 DOI: 10.1021/acs.jctc.1c00485] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Iron-sulfur clusters play important roles in biology as parts of electron-transfer chains and catalytic cofactors. Here, we report a detailed computational analysis of a structural model of the simplest natural iron-sulfur cluster of rubredoxin and its cationic counterparts. Specifically, we investigated adiabatic reduction energies, dissociation energies, and bonding properties of the low-lying electronic states of the complexes [Fe(SCH3)4]2-/1-/2+/3+ using multireference (CASSCF, MRCISD), and coupled cluster [CCSD(T)] methodologies. We show that the nature of the Fe-S chemical bond and the magnitude of the ionization potentials in the anionic and cationic [Fe(SCH3)4] complexes offer a physical rationale for the relative stabilization, structure, and speciation of these complexes. Anionic and cationic complexes present different types of chemical bonds: prevalently ionic in [Fe(SCH3)4]2-/1- complexes and covalent in [Fe(SCH3)4]2+/3+ complexes. The ionic bonds result in an energy gain for the transition [Fe(SCH3)4]2- → [Fe(SCH3)4]- (i.e., FeII → FeIII) of 1.5 eV, while the covalent bonds result in an energy loss for the transition [Fe(SCH3)4]2+ → [Fe(SCH3)4]3+ of 16.6 eV, almost half of the ionization potential of Fe2+. The ionic versus covalent bond character influences the Fe-S bond strength and length, that is, ionic Fe-S bonds are longer than covalent ones by about 0.2 Å (for FeII) and 0.04 Å (for FeII). Finally, the average Fe-S heterolytic bond strength is 6.7 eV (FeII) and 14.6 eV (FeIII) at the RCCSD(T) level of theory.
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Affiliation(s)
- Demeter Tzeli
- Laboratory of Physical Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis Zografou, Athens 157 84, Greece.,Theoretical and Physical Chemistry Institute, National Hellenic Research Foundation, 48 Vassileos Constantinou Avenue, Athens 116 35, Greece
| | - Simone Raugei
- Physical Sciences Division, Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MS K1-83, Richland, Washington 99352, United States
| | - Sotiris S Xantheas
- Advanced Computing, Mathematics and Data Division, Pacific Northwest National Laboratory, 902 Battelle Boulevard, P.O. Box 999, MS K1-83, Richland, Washington 99352, United States.,Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
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9
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Abstract
The double-cubane cluster (DCC) refers to an [Fe8S9] iron-sulfur complex that is otherwise only known to exist in nitrogenases. Containing a bridging µ2-S ligand, the DCC in the DCC-containing protein (DCCP) is covalently linked to the protein scaffold via six coordinating cysteine residues. In this study, the nature of spin coupling and the effect of spin states on the cluster’s geometry are investigated computationally. Using density functional theory (DFT) and a broken symmetry (BS) approach to study the electronic ground state of the system, we computed the exchange interaction between the spin-coupled spins of the four FeFe dimers contained in the DCC. This treatment yields results that are in excellent agreement with both computed and experimentally determined exchange parameters for analogously coupled di-iron complexes. Hybrid quantum mechanical (QM)/molecular mechanical (MM) geometry optimizations show that cubane cluster A closest to charged amino acid side chains (Arg312, Glu140, Lys146) is less compact than cluster B, indicating that electrons of the same spin in a charged environment seek maximum separation. Overall, this study provides the community with a fundamental reference for subsequent studies of DCCP, as well as for investigations of other [Fe8S9]-containing enzymes.
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10
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McSkimming A, Sridharan A, Thompson NB, Müller P, Suess DLM. An [Fe 4S 4] 3+-Alkyl Cluster Stabilized by an Expanded Scorpionate Ligand. J Am Chem Soc 2020; 142:14314-14323. [PMID: 32692919 DOI: 10.1021/jacs.0c06334] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Alkyl-ligated iron-sulfur clusters in the [Fe4S4]3+ charge state have been proposed as short-lived intermediates in a number of enzymatic reactions. To better understand the properties of these intermediates, we have prepared and characterized the first synthetic [Fe4S4]3+-alkyl cluster. Isolation of this highly reactive species was made possible by the development of an expanded scorpionate ligand suited to the encapsulation of cuboidal clusters. Like the proposed enzymatic intermediates, this synthetic [Fe4S4]3+-alkyl cluster adopts an S = 1/2 ground state with giso > 2. Mössbauer spectroscopic studies reveal that the alkylated Fe has an unusually low isomer shift, which reflects the highly covalent Fe-C bond and the localization of Fe3+ at the alkylated site in the solid state. Paramagnetic 1H NMR studies establish that this valence localization persists in solution at physiologically relevant temperatures, an effect that has not been observed for [Fe4S4]3+ clusters outside of a protein. These findings establish the unusual electronic-structure effects imparted by the strong-field alkyl ligand and lay the foundation for understanding the electronic structures of [Fe4S4]3+-alkyl intermediates in biology.
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Affiliation(s)
- Alex McSkimming
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Arun Sridharan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Niklas B Thompson
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Peter Müller
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
| | - Daniel L M Suess
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States
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11
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Redox Partners: Function Modulators of Bacterial P450 Enzymes. Trends Microbiol 2020; 28:445-454. [DOI: 10.1016/j.tim.2020.02.012] [Citation(s) in RCA: 48] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 02/24/2020] [Indexed: 01/25/2023]
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12
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Smith AT, Linkous RO, Max NJ, Sestok AE, Szalai VA, Chacón KN. The FeoC [4Fe-4S] Cluster Is Redox-Active and Rapidly Oxygen-Sensitive. Biochemistry 2019; 58:4935-4949. [PMID: 31713418 DOI: 10.1021/acs.biochem.9b00745] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The acquisition of iron is essential to establishing virulence among most pathogens. Under acidic and/or anaerobic conditions, most bacteria utilize the widely distributed ferrous iron (Fe2+) uptake (Feo) system to import metabolically-required iron. The Feo system is inadequately understood at the atomic, molecular, and mechanistic levels, but we do know it is composed of a main membrane component (FeoB) essential for iron translocation, as well as two small, cytosolic proteins (FeoA and FeoC) hypothesized to function as accessories to this process. FeoC has many hypothetical functions, including that of an iron-responsive transcriptional regulator. Here, we demonstrate for the first time that Escherichia coli FeoC (EcFeoC) binds an [Fe-S] cluster. Using electronic absorption, X-ray absorption, and electron paramagnetic resonance spectroscopies, we extensively characterize the nature of this cluster. Under strictly anaerobic conditions after chemical reconstitution, we demonstrate that EcFeoC binds a redox-active [4Fe-4S]2+/+ cluster that is rapidly oxygen-sensitive and decays to a [2Fe-2S]2+ cluster (t1/2 ≈ 20 s), similar to the [Fe-S] cluster in the fumarate and nitrate reductase (FNR) transcriptional regulator. We further show that this behavior is nearly identical to the homologous K. pneumoniae FeoC, suggesting a redox-active, oxygen-sensitive [4Fe-4S]2+ cofactor is a general phenomenon of cluster-binding FeoCs. Finally, in contrast to FNR, we show that the [4Fe-4S]2+ cluster binding to FeoC is associated with modest conformational changes of the polypeptide, but not protein dimerization. We thus posit a working hypothesis in which the cluster-binding FeoCs may function as oxygen-sensitive iron sensors that fine-tune pathogenic ferrous iron acquisition.
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Affiliation(s)
- Aaron T Smith
- Department of Chemistry and Biochemistry , University of Maryland, Baltimore County , Baltimore , Maryland 21250 United States
| | - Richard O Linkous
- Department of Chemistry and Biochemistry , University of Maryland, Baltimore County , Baltimore , Maryland 21250 United States
| | - Nathan J Max
- Department of Chemistry and Biochemistry , University of Maryland, Baltimore County , Baltimore , Maryland 21250 United States
| | - Alexandrea E Sestok
- Department of Chemistry and Biochemistry , University of Maryland, Baltimore County , Baltimore , Maryland 21250 United States
| | - Veronika A Szalai
- Physical Measurement Laboratory , National Institute of Standards and Technology , Gaithersburg , Maryland 20899 , United States
| | - Kelly N Chacón
- Department of Chemistry , Reed College , Portland , Oregon 97202 , United States
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13
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Pellicer Martinez MT, Crack JC, Stewart MYY, Bradley JM, Svistunenko DA, Johnston AWB, Cheesman MR, Todd JD, Le Brun NE. Mechanisms of iron- and O 2-sensing by the [4Fe-4S] cluster of the global iron regulator RirA. eLife 2019; 8:e47804. [PMID: 31526471 PMCID: PMC6748827 DOI: 10.7554/elife.47804] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 07/29/2019] [Indexed: 01/05/2023] Open
Abstract
RirA is a global regulator of iron homeostasis in Rhizobium and related α-proteobacteria. In its [4Fe-4S] cluster-bound form it represses iron uptake by binding to IRO Box sequences upstream of RirA-regulated genes. Under low iron and/or aerobic conditions, [4Fe-4S] RirA undergoes cluster conversion/degradation to apo-RirA, which can no longer bind IRO Box sequences. Here, we apply time-resolved mass spectrometry and electron paramagnetic resonance spectroscopy to determine how the RirA cluster senses iron and O2. The data indicate that the key iron-sensing step is the O2-independent, reversible dissociation of Fe2+ from [4Fe-4S]2+ to form [3Fe-4S]0. The dissociation constant for this process was determined as Kd = ~3 µM, which is consistent with the sensing of 'free' iron in the cytoplasm. O2-sensing occurs through enhanced cluster degradation under aerobic conditions, via O2-mediated oxidation of the [3Fe-4S]0 intermediate to form [3Fe-4S]1+. This work provides a detailed mechanistic/functional view of an iron-responsive regulator.
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Affiliation(s)
- Ma Teresa Pellicer Martinez
- Centre for Molecular and Structural Biochemistry, School of ChemistryUniversity of East AngliaNorwichUnited Kingdom
| | - Jason C Crack
- Centre for Molecular and Structural Biochemistry, School of ChemistryUniversity of East AngliaNorwichUnited Kingdom
| | - Melissa YY Stewart
- Centre for Molecular and Structural Biochemistry, School of ChemistryUniversity of East AngliaNorwichUnited Kingdom
| | - Justin M Bradley
- Centre for Molecular and Structural Biochemistry, School of ChemistryUniversity of East AngliaNorwichUnited Kingdom
| | | | - Andrew WB Johnston
- School of Biological SciencesUniversity of East AngliaNorwichUnited Kingdom
| | - Myles R Cheesman
- Centre for Molecular and Structural Biochemistry, School of ChemistryUniversity of East AngliaNorwichUnited Kingdom
| | - Jonathan D Todd
- School of Biological SciencesUniversity of East AngliaNorwichUnited Kingdom
| | - Nick E Le Brun
- Centre for Molecular and Structural Biochemistry, School of ChemistryUniversity of East AngliaNorwichUnited Kingdom
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14
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Ye M, Thompson NB, Brown AC, Suess DLM. A Synthetic Model of Enzymatic [Fe 4S 4]-Alkyl Intermediates. J Am Chem Soc 2019; 141:13330-13335. [PMID: 31373801 PMCID: PMC6748666 DOI: 10.1021/jacs.9b06975] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Although
alkyl complexes of [Fe4S4] clusters
have been invoked as intermediates in a number of enzymatic reactions,
obtaining a detailed understanding of their reactivity patterns and
electronic structures has been difficult owing to their transient
nature. To address this challenge, we herein report the synthesis
and characterization of a 3:1 site-differentiated [Fe4S4]2+–alkyl cluster. Whereas [Fe4S4]2+ clusters typically exhibit pairwise delocalized
electronic structures in which each Fe has a formal valence of 2.5+,
Mössbauer spectroscopic and computational studies suggest that
the highly electron-releasing alkyl group partially localizes the
charge distribution within the cubane, an effect that has not been
previously observed in tetrahedrally coordinated [Fe4S4] clusters.
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Affiliation(s)
- Mengshan Ye
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Niklas B Thompson
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Alexandra C Brown
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Daniel L M Suess
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
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15
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López Rivero AS, Rossi MA, Ceccarelli EA, Catalano-Dupuy DL. A bacterial 2[4Fe4S] ferredoxin as redox partner of the plastidic-type ferredoxin-NADP + reductase from Leptospira interrogans. Biochim Biophys Acta Gen Subj 2019; 1863:651-660. [PMID: 30639162 DOI: 10.1016/j.bbagen.2019.01.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2018] [Revised: 01/07/2019] [Accepted: 01/08/2019] [Indexed: 11/29/2022]
Abstract
BACKGROUND Ferredoxins are small iron-sulfur proteins that participate as electron donors in various metabolic pathways. They are recognized substrates of ferredoxin-NADP+ reductases (FNR) in redox metabolisms in mitochondria, plastids, and bacteria. We previously found a plastidic-type FNR in Leptospira interrogans (LepFNR), a parasitic bacterium of animals and humans. Nevertheless, we did not identify plant-type ferredoxins or flavodoxins, the common partners of this kind of FNR. METHODS Sequence alignment, phylogenetical analyses and structural modeling were performed for the identification of a 2[4Fe4S] ferredoxin (LepFd2) as a putative redox partner of LepFNR in L. interrogans. The gene encoding LepFd2 was cloned and the protein overexpressed and purified. The functional properties of LepFd2 and LepFNR-LepFd2 complex were analyzed by kinetic and mutagenesis studies. RESULTS We succeeded in expressing and purifying LepFd2 with its FeS cluster properly bound. We found that LepFd2 exchanges electrons with LepFNR. Moreover, a unique structural subdomain of LepFNR (loop P75-Y91), was shown to be involved in the recognition and binding of LepFd2. This structural subdomain is not found in other FNR homologs. CONCLUSIONS We report for the first time a redox pair in L. interrogans in which a plastidic FNR exchanges electron with a bacterial 2[4Fe4S] ferredoxin. We characterized this reaction and proposed a model for the productive LepFNR-LepFd2 complex. GENERAL SIGNIFICANCE Our findings suggest that the interaction of LepFNR with the iron-sulfur protein would be different from the one previously described for the homolog enzymes. This knowledge would be useful for the design of specific LepFNR inhibitors.
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Affiliation(s)
- Arleth S López Rivero
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, 2000 Rosario, Argentina
| | - Ma Agustina Rossi
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, 2000 Rosario, Argentina
| | - Eduardo A Ceccarelli
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, 2000 Rosario, Argentina
| | - Daniela L Catalano-Dupuy
- Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, 2000 Rosario, Argentina.
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16
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Reductive Mobilization of Iron from Intact Ferritin: Mechanisms and Physiological Implication. Pharmaceuticals (Basel) 2018; 11:ph11040120. [PMID: 30400623 PMCID: PMC6315955 DOI: 10.3390/ph11040120] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2018] [Revised: 10/31/2018] [Accepted: 11/01/2018] [Indexed: 01/18/2023] Open
Abstract
Ferritins are highly conserved supramolecular protein nanostructures composed of two different subunit types, H (heavy) and L (light). The two subunits co-assemble into a 24-subunit heteropolymer, with tissue specific distributions, to form shell-like protein structures within which thousands of iron atoms are stored as a soluble inorganic ferric iron core. In-vitro (or in cell free systems), the mechanisms of iron(II) oxidation and formation of the mineral core have been extensively investigated, although it is still unclear how iron is loaded into the protein in-vivo. In contrast, there is a wide spread belief that the major pathway of iron mobilization from ferritin involves a lysosomal proteolytic degradation of ferritin, and the dissolution of the iron mineral core. However, it is still unclear whether other auxiliary iron mobilization mechanisms, involving physiological reducing agents and/or cellular reductases, contribute to the release of iron from ferritin. In vitro iron mobilization from ferritin can be achieved using different reducing agents, capable of easily reducing the ferritin iron core, to produce soluble ferrous ions that are subsequently chelated by strong iron(II)-chelating agents. Here, we review our current understanding of iron mobilization from ferritin by various reducing agents, and report on recent results from our laboratory, in support of a mechanism that involves a one-electron transfer through the protein shell to the iron mineral core. The physiological significance of the iron reductive mobilization from ferritin by the non-enzymatic FMN/NAD(P)H system is also discussed.
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17
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Zhang W, Du L, Li F, Zhang X, Qu Z, Han L, Li Z, Sun J, Qi F, Yao Q, Sun Y, Geng C, Li S. Mechanistic Insights into Interactions between Bacterial Class I P450 Enzymes and Redox Partners. ACS Catal 2018. [DOI: 10.1021/acscatal.8b02913] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Wei Zhang
- State Key Laboratory of Microbial Technology, Shandong University, Qingdao, Shandong 266237, China
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
| | - Lei Du
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
| | - Fengwei Li
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
| | - Xingwang Zhang
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
| | - Zepeng Qu
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
- University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Beijing 100049, China
| | - Lei Han
- College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao, Shandong 266109, China
| | - Zhong Li
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
- University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Beijing 100049, China
| | - Jingran Sun
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
| | - Fengxia Qi
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
| | - Qiuping Yao
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
| | - Yue Sun
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
| | - Ce Geng
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
| | - Shengying Li
- Shandong Provincial Key Laboratory of Synthetic Biology, CAS Key Laboratory of Biofuels, Qingdao Institute of Bioenergy and Bioprocess Technology, Chinese Academy of Sciences, No. 189 Songling Road, Qingdao, Shandong 266101, China
- University of Chinese Academy of Sciences, No. 19(A) Yuquan Road, Beijing 100049, China
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18
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Das B, Patra S. Multisubstrate specific flavin containing monooxygenase from Chlorella pyrenoidosa with potential application for phenolic wastewater remediation and biosensor application. ENVIRONMENTAL TECHNOLOGY 2018; 39:2073-2089. [PMID: 28662620 DOI: 10.1080/09593330.2017.1349838] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Microbial degradation of phenolic pollutants in industrial wastewater is dependent on enzymatic pathway comprising a cascade of phenol metabolizing enzymes. Phenol hydroxylase is the first enzyme of the pathway catalysing the initial attack on phenol in green algae Chlorella pyrenoidosa. The present work reports cost-effective production of partially purified microalgal phenol hydroylase by single-step purification and characterization of its kinetic properties with the view of application for enzyme-based remediation of phenolic wastewater or in phenolic biosensor. The enzyme with a molecular weight of 25 kDa shows all characteristics of phenol hydroxylases, that is, hydroxylation of phenol to catechol (confirmed by HPLC), substrate-dependent NADPH oxidation, absorption spectrum typical of flavoproteins and peptide mass fingerprint corresponding to flavoprotein hydroxylase. The enzyme utilizes phenol with apparent Michealis constant (Km) of 1.71 µM, maximal velocity (Vmax) of 0.4 µM/min with optimal activity at pH 7 and 35°C. Fe2+chelators (Phenanthroline and sodium arsenate), heavy metals, denaturants and oxidizing agents showed inhibitory effect on phenol hydroxylation activity of the enzyme. The enzyme has broad substrate specificity against isomeric diphenols, isomeric methylphenols, halogen-substituted phenols, amino-substituted phenols, nitrophenols, hydroxybenzaldehyde and hydroxylbenzoic acid. The enzyme shows remarkable storage stability at room temperature and at 4°C. The multisubstrate specificity coupled to remarkable storage stability of the microalgal phenol hydroxylase opens up avenues for its application in remediation of a wide range of phenolics released in industrial wastewater or phenolic biosensor application.
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Affiliation(s)
- Bhaskar Das
- a Centre for the Environment , Indian Institute of Technology Guwahati , Guwahati , India
| | - Sanjukta Patra
- b Department of Biosciences and Bioengineering , Indian Institute of Technology Guwahati , Guwahati , India
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19
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Miyazaki R, Yamazaki T, Yoshimatsu K, Kojima K, Asano R, Sode K, Tsugawa W. Elucidation of the intra- and inter-molecular electron transfer pathways of glucoside 3-dehydrogenase. Bioelectrochemistry 2018; 122:115-122. [DOI: 10.1016/j.bioelechem.2018.03.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2017] [Revised: 02/28/2018] [Accepted: 03/01/2018] [Indexed: 11/24/2022]
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20
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Kobayashi K. Sensing Mechanisms in the Redox-Regulated, [2Fe-2S] Cluster-Containing, Bacterial Transcriptional Factor SoxR. Acc Chem Res 2017. [PMID: 28636310 DOI: 10.1021/acs.accounts.7b00137] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Bacteria possess molecular biosensors that enable responses to a variety of stressful conditions, including oxidative stress, toxic compounds, and interactions with other organisms, through elaborately coordinated regulation of gene expression. In Escherichia coli and related bacteria, the transcription factor SoxR functions as a sensor of oxidative stress and nitric oxide (NO). SoxR protein contains a [2Fe-2S] cluster essential for its transcription-enhancing activity, which is regulated by redox changes in the [2Fe-2S] cluster. We have explored the mechanistic and structural basis of SoxR proteins function and determined how the chemistry at the [2Fe-2S] cluster causes the subsequent regulatory response. In this Account, I describe our recent achievements in three different areas using physicochemical techniques, primarily pulse radiolysis. First, redox-dependent conformational changes in SoxR-bound DNA were studied by site-specifically replacing selected bases with the fluorescent probes 2-aminopurine and pyrrolocytosine. X-ray analyses of the DNA-SoxR complex in the oxidized state revealed that the DNA structure is distorted in the center regions, resulting in local untwisting of base pairs. However, the inactive, reduced state had remained uncharacterized. We found that reduction of the [2Fe-2S] cluster in the SoxR-DNA complex weakens the fluorescence intensity within a region confined to the central base pairs in the promoter region. Second, the reactions of NO with [2Fe-2S] clusters of E. coli SoxR were analyzed using pulse radiolysis. The transcriptional activation of SoxR in E. coli occurs through direct modification of [2Fe-2S] by NO to form a dinitrosyl iron complex (DNIC). The reaction of NO with [2Fe-2S] cluster of SoxR proceeded nearly quantitatively with concomitant reductive elimination of two equivalents S0 atoms. Intermediate nitrosylation products, however, were too unstable to observe. We found that the conversion proceeds through at least two steps, with the faster phase being the first reaction of the NO molecule with the [2Fe-2S] cluster. The slower reaction with the second equivalent NO molecule, however, was important for the formation of DNIC. Third, to elucidate the differences between the distinct responses of SoxR proteins from two different species, we studied the interaction of E. coli and Pseudomonas aeruginosa SoxR with superoxide anion using a mutagenic approach. Despite the homology between E. coli SoxR and P. aeruginosa SoxR, the function of P. aeruginosa SoxR differs from that of E. coli. The substitution of E. coli SoxR lysine residues, located close to [2Fe-2S] clusters, into P. aeruginosa SoxR dramatically affected the reaction with superoxide anion.
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Affiliation(s)
- Kazuo Kobayashi
- The Institute of Scientific
and Industrial Research, Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
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21
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Ohta S, Ohki Y. Impact of ligands and media on the structure and properties of biological and biomimetic iron-sulfur clusters. Coord Chem Rev 2017. [DOI: 10.1016/j.ccr.2017.02.018] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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22
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An Fe-S cluster in the conserved Cys-rich region in the catalytic subunit of FAD-dependent dehydrogenase complexes. Bioelectrochemistry 2016; 112:178-83. [PMID: 26951961 DOI: 10.1016/j.bioelechem.2016.01.010] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2015] [Revised: 01/31/2016] [Accepted: 01/31/2016] [Indexed: 11/21/2022]
Abstract
Several bacterial flavin adenine dinucleotide (FAD)-harboring dehydrogenase complexes comprise three distinct subunits: a catalytic subunit with FAD, a cytochrome c subunit containing three hemes, and a small subunit. Owing to the cytochrome c subunit, these dehydrogenase complexes have the potential to transfer electrons directly to an electrode. Despite various electrochemical applications and engineering studies of FAD-dependent dehydrogenase complexes, the intra/inter-molecular electron transfer pathway has not yet been revealed. In this study, we focused on the conserved Cys-rich region in the catalytic subunits using the catalytic subunit of FAD dependent glucose dehydrogenase complex (FADGDH) as a model, and site-directed mutagenesis and electron paramagnetic resonance (EPR) were performed. By co-expressing a hitch-hiker protein (γ-subunit) and a catalytic subunit (α-subunit), FADGDH γα complexes were prepared, and the properties of the catalytic subunit of both wild type and mutant FADGDHs were investigated. Substitution of the conserved Cys residues with Ser resulted in the loss of dye-mediated glucose dehydrogenase activity. ICP-AEM and EPR analyses of the wild-type FADGDH catalytic subunit revealed the presence of a 3Fe-4S-type iron-sulfur cluster, whereas none of the Ser-substituted mutants showed the EPR spectrum characteristic for this cluster. The results suggested that three Cys residues in the Cys-rich region constitute an iron-sulfur cluster that may play an important role in the electron transfer from FAD (intra-molecular) to the multi-heme cytochrome c subunit (inter-molecular) electron transfer pathway. These features appear to be conserved in the other three-subunit dehydrogenases having an FAD cofactor.
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23
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Al-Rammahi TMM, Henderson RA. Binding small molecules and ions to [Fe4S4Cl4](2-) modulates rate of protonation of the cluster. Dalton Trans 2016; 45:1373-81. [PMID: 26661750 DOI: 10.1039/c5dt04523a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The mechanism of the acid-catalyzed substitution reaction of the terminal chloro-ligands in [Fe4S4Cl4](2-) by PhS(-) in the presence of NHBu(n)3(+) involves rate-limiting proton transfer from NHBu(n)3(+) to the cluster (k0 = 490 ± 20 dm(3) mol(-1) s(-1)). A variety of small molecules and ions (L = substrate = Cl(-), Br(-), I(-), RNHNH2 (R = Me or Ph), Me2NNH2, HCN, NCS(-), N3(-), Bu(t)NC or pyridine) bind to [Fe4S4Cl4](2-) and this affects the rate of subsequent protonation of [Fe4S4Cl4(L)](n-). Where the kinetics allow, the equilibrium constants for the substrates binding to [Fe4S4Cl4](2-) (K(L)) and the rates of proton transfer from NHBu(n)3(+) to [Fe4S4Cl4(L)](n-) (k) have been determined. The results indicate the following general features. (i) Bound substrates increase the rate of protonation of the cluster, but the rate increase is modest (k/k0 = 1.6 to ≥72). (ii) When K(L) is small, so is k/k0. (iii) Binding substrates which are good σ-donors or good π-acceptors lead to the largest k/k0. This behaviour is discussed in terms of the recent proposal that protonation of [Fe4S4Cl4](2-) at a μ3-S, is coupled to concomitant Fe-(μ3-SH) bond elongation/cleavage.
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Affiliation(s)
- Thaer M M Al-Rammahi
- School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK. and Department of Chemistry, College of Science, University of Kerbala, Kerbala, Iraq
| | - Richard A Henderson
- School of Chemistry, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK.
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24
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Kobayashi K, Fujikawa M, Kozawa T. Binding of promoter DNA to SoxR protein decreases the reduction potential of the [2Fe-2S] cluster. Biochemistry 2014; 54:334-9. [PMID: 25490746 DOI: 10.1021/bi500931w] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The [2Fe-2S] transcriptional factor SoxR, a member of the MerR family, functions as a sensor of oxidative stress in Escherichia coli. The transcriptional activity of SoxR is regulated by the reversible oxidation and reduction of [2Fe-2S] clusters. Electrochemistry measurements on DNA-modified electrodes have shown a dramatic shift in the reduction potential of SoxR from -290 to +200 mV with the promoter DNA-bound [ Gorodetsky , A. A. , Dietrich , L. E. P. , Lee , P. E. , Demple , B. , , Newman , D. K. , and Barton , J. K. ( 2008 ) DNA binding shifts the reduction potential of the transcription factor SoxR , Proc. Natl. Acad. Sci. U.S.A. 105 , 3684 - 3689 ]. To determine the change of the SoxR reduction potential using the new condition, the one-electron oxidation-reduction properties of [2Fe-2S] cluster in SoxR were investigated in the absence and presence of the DNA. The [2Fe-2S] cluster of SoxR was completely reduced by nicotinamide adenine dinucleotide phosphate (NADPH)-cytochrome P450 reductase (CRP) in the presence of a NADPH generating system (glucose 6-dehydrogenase and glucose-6 phosphate), indicating that CRP can serve as an NADPH-dependent electron carrier for SoxR. The reduction potential of SoxR was measured from equilibrium data coupled with NADPH and CRP in the presence of electron mediators. The reduction potentials of DNA-bound and DNA-free states of SoxR were -320 and -293 mV versus NHE (normal hydrogen electrode), respectively. These results indicate that DNA binding causes a moderate shift in the reduction potential of SoxR.
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Affiliation(s)
- Kazuo Kobayashi
- The Institute of Scientific and Industrial Research, Osaka University , Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan
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25
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Mössbauer spectroscopy of Fe/S proteins. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2014; 1853:1395-405. [PMID: 25498248 DOI: 10.1016/j.bbamcr.2014.12.005] [Citation(s) in RCA: 85] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2014] [Revised: 11/17/2014] [Accepted: 12/03/2014] [Indexed: 01/02/2023]
Abstract
Iron-sulfur (Fe/S) clusters are structurally and functionally diverse cofactors that are found in all domains of life. (57)Fe Mössbauer spectroscopy is a technique that provides information about the chemical nature of all chemically distinct Fe species contained in a sample, such as Fe oxidation and spin state, nuclearity of a cluster with more than one metal ion, electron spin ground state of the cluster, and delocalization properties in mixed-valent clusters. Moreover, the technique allows for quantitation of all Fe species, when it is used in conjunction with electron paramagnetic resonance (EPR) spectroscopy and analytical methods. (57)Fe-Mössbauer spectroscopy played a pivotal role in unraveling the electronic structures of the "well-established" [2Fe-2S](2+/+), [3Fe-4S](1+/0), and [4Fe-4S](3+/2+/1+/0) clusters and -more-recently- was used to characterize novel Fe/S clustsers, including the [4Fe-3S] cluster of the O2-tolerant hydrogenase from Aquifex aeolicus and the 3Fe-cluster intermediate observed during the reaction of lipoyl synthase, a member of the radical SAM enzyme superfamily.
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26
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Zanello P. The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part II. {[Fe2S2](SγCys)4} proteins. Coord Chem Rev 2014. [DOI: 10.1016/j.ccr.2014.08.003] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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27
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Valdez CE, Smith QA, Nechay MR, Alexandrova AN. Mysteries of metals in metalloenzymes. Acc Chem Res 2014; 47:3110-7. [PMID: 25207938 DOI: 10.1021/ar500227u] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Natural metalloenzymes are often the most proficient catalysts in terms of their activity, selectivity, and ability to operate at mild conditions. However, metalloenzymes are occasionally surprising in their selection of catalytic metals, and in their responses to metal substitution. Indeed, from the isolated standpoint of producing the best catalyst, a chemist designing from first-principles would likely choose a different metal. For example, some enzymes employ a redox active metal where a simple Lewis acid is needed. Such are several hydrolases. In other cases, substitution of a non-native metal leads to radical improvements in reactivity. For example, histone deacetylase 8 naturally operates with Zn(2+) in the active site but becomes much more active with Fe(2+). For β-lactamases, the replacement of the native Zn(2+) with Ni(2+) was suggested to lead to higher activity as predicted computationally. There are also intriguing cases, such as Fe(2+)- and Mn(2+)-dependent ribonucleotide reductases and W(4+)- and Mo(4+)-dependent DMSO reductases, where organisms manage to circumvent the scarcity of one metal (e.g., Fe(2+)) by creating protein structures that utilize another metal (e.g., Mn(2+)) for the catalysis of the same reaction. Naturally, even though both metal forms are active, one of the metals is preferred in every-day life, and the other metal variant remains dormant until an emergency strikes in the cell. These examples lead to certain questions. When are catalytic metals selected purely for electronic or structural reasons, implying that enzymatic catalysis is optimized to its maximum? When are metal selections a manifestation of competing evolutionary pressures, where choices are dictated not just by catalytic efficiency but also by other factors in the cell? In other words, how can enzymes be improved as catalysts merely through the use of common biological building blocks available to cells? Addressing these questions is highly relevant to the enzyme design community, where the goal is to prepare maximally efficient quasi-natural enzymes for the catalysis of reactions that interest humankind. Due to competing evolutionary pressures, many natural enzymes may not have evolved to be ideal catalysts and can be improved for the isolated purpose of catalysis in vitro when the competing factors are removed. The goal of this Account is not to cover all the possible stories but rather to highlight how variable enzymatic catalysis can be. We want to bring up possible factors affecting the evolution of enzyme structure, and the large- and intermediate-scale structural and electronic effects that metals can induce in the protein, and most importantly, the opportunities for optimization of these enzymes for catalysis in vitro.
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Affiliation(s)
- Crystal E. Valdez
- Department
of Chemistry and Biochemistry, and ‡California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Quentin A. Smith
- Department
of Chemistry and Biochemistry, and ‡California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Michael R. Nechay
- Department
of Chemistry and Biochemistry, and ‡California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
| | - Anastassia N. Alexandrova
- Department
of Chemistry and Biochemistry, and ‡California NanoSystems Institute, University of California, Los Angeles, California 90095, United States
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28
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One-pot synthesis of sulphur-bridged rhenium containing molecular cubanes: Spectroscopic and structural characterisation. J Organomet Chem 2014. [DOI: 10.1016/j.jorganchem.2014.07.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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29
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Cammack R, Balk J. Iron-sulfur Clusters. BINDING, TRANSPORT AND STORAGE OF METAL IONS IN BIOLOGICAL CELLS 2014. [DOI: 10.1039/9781849739979-00333] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Iron-sulfur clusters are universally distributed groups occurring in iron-sulfur proteins. They have a wide range of cellular functions which reflect the chemistry of the clusters. Some clusters are involved in electron transport and energy transduction in photosynthesis and respiration. Others can bind substrates and participate in enzyme catalysis. Regulatory functions have also been documented for clusters that respond to oxygen partial pressure and iron availability. Finally, there are some for which no function has been defined; they may act as stabilizing structures, for example, in enzymes involved in nucleic acid metabolism. The clusters are constructed intracellularly and inserted into proteins, which can then be transported to intracellular targets, in some cases, across membranes. Three different types of iron-sulfur cluster assembly machinery have evolved in prokaryotes: NIF, ISC and SUF. Each system involves a scaffold protein on which the cluster is constructed (encoded by genes nifU, iscU, sufU or sufB) and a cysteine desulfurase (encoded by nifS, iscS or sufS) which provides the sulfide sulfur. In eukaryotic cells, clusters are formed in the mitochondria for the many iron-sulfur proteins in this organelle. The mitochondrial biosynthesis pathway is linked to the cytoplasmic iron-sulfur assembly system (CIA) for the maturation of cytoplasmic and nuclear iron-sulfur proteins. In plant cells, a SUF-type system is used for cluster assembly in the plastids. Many accessory proteins are involved in cluster transfer before insertion into the appropriate sites in Fe-S proteins.
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Affiliation(s)
- Richard Cammack
- King's College London, Department of Biochemistry, 150 Stamford Street London SE1 9NH UK
| | - Janneke Balk
- John Innes Centre and University of East Anglia Norwich Research Park, Colney Lane Norwich NR4 7UH UK
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30
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Bergeler M, Stiebritz MT, Reiher M. Structure-Property Relationships of Fe4S4Clusters. Chempluschem 2013; 78:1082-1098. [DOI: 10.1002/cplu.201300186] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Indexed: 11/08/2022]
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31
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Zanello P. The competition between chemistry and biology in assembling iron–sulfur derivatives. Molecular structures and electrochemistry. Part I. {Fe(SγCys)4} proteins. Coord Chem Rev 2013. [DOI: 10.1016/j.ccr.2013.02.006] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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32
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Tam W, Pell LG, Bona D, Tsai A, Dai XX, Edwards AM, Hendrix RW, Maxwell KL, Davidson AR. Tail tip proteins related to bacteriophage λ gpL coordinate an iron-sulfur cluster. J Mol Biol 2013; 425:2450-62. [PMID: 23542343 DOI: 10.1016/j.jmb.2013.03.032] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2013] [Revised: 03/12/2013] [Accepted: 03/23/2013] [Indexed: 01/20/2023]
Abstract
The assembly of long non-contractile phage tails begins with the formation of the tail tip complex (TTC). TTCs are multi-functional protein structures that mediate host cell adsorption and genome injection. The TTC of phage λ is assembled from multiple copies of eight different proteins, including gpL. Purified preparations of gpL and several homologues all displayed a distinct reddish color, suggesting the binding of iron by these proteins. Further characterization of the gpL homologue from phage N15, which was most amenable to in vitro analyses, showed that it contains two domains. The C-terminal domain was demonstrated to coordinate an iron-sulfur cluster, providing the first example of a viral structural protein binding to this type of metal group. We characterized the iron-sulfur cluster using inductively coupled plasma-atomic emission spectroscopy, absorbance spectroscopy, and electron paramagnetic resonance spectroscopy and found that it is an oxygen-sensitive [4Fe-4S](2+) cluster. Four highly conserved cysteine residues were shown to be required for coordinating the iron-sulfur cluster, and substitution of any of these Cys residues with Ser or Ala within the context of λ gpL abolished biological activity. These data imply that the intact iron-sulfur cluster is required for function. The presence of four conserved Cys residues in the C-terminal regions of very diverse gpL homologues suggest that utilization of an iron-sulfur cluster is a widespread feature of non-contractile tailed phages that infect Gram-negative bacteria. In addition, this is the first example of a viral structural protein that binds an iron-sulfur cluster.
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Affiliation(s)
- William Tam
- Department of Biochemistry, University of Toronto, Medical Sciences Building, Toronto, ON, Canada M5S 1A8
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33
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Span I, Wang K, Wang W, Zhang Y, Bacher A, Eisenreich W, Li K, Schulz C, Oldfield E, Groll M. Discovery of acetylene hydratase activity of the iron-sulphur protein IspH. Nat Commun 2013; 3:1042. [PMID: 22948824 DOI: 10.1038/ncomms2052] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Accepted: 08/03/2012] [Indexed: 11/09/2022] Open
Abstract
The final step of the methylerythritol phosphate isoprenoid biosynthesis pathway is catalysed by the iron-sulphur enzyme IspH, producing the universal precursors of terpenes: isopentenyl diphosphate and dimethylallyl diphosphate. Here we report an unforeseen reaction discovered during the investigation of the interaction of IspH with acetylene inhibitors by X-ray crystallography, Mößbauer, and nuclear magnetic resonance spectroscopy. In addition to its role as a 2H(+)/2e(-) reductase, IspH can hydrate acetylenes to aldehydes and ketones via anti-Markovnikov/Markovnikov addition. The reactions only occur with the oxidised protein and proceed via η(1)-O-enolate intermediates. One of these is characterized crystallographically and contains a C4 ligand oxygen bound to the unique, fourth iron in the 4Fe-4S cluster: this intermediate subsequently hydrolyzes to produce an aldehyde product. This unexpected side to IspH reactivity is of interest in the context of the mechanism of action of other acetylene hydratases, as well as in the design of antiinfectives targeting IspH.
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Affiliation(s)
- Ingrid Span
- Department of Chemistry, Center for Integrated Protein Science, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Ke Wang
- Department of Chemistry, 600 South Mathews Avenue, University of Illinois, Urbana, Illinois 61801, USA
| | - Weixue Wang
- Center for Biophysics and Computational Biology, 607 South Mathews Avenue, University of Illinois, Urbana, Illinois 61801, USA
| | - Yonghui Zhang
- Department of Chemistry, 600 South Mathews Avenue, University of Illinois, Urbana, Illinois 61801, USA
| | - Adelbert Bacher
- Department of Chemistry, Center for Integrated Protein Science, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Wolfgang Eisenreich
- Department of Chemistry, Center for Integrated Protein Science, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Kai Li
- Department of Chemistry, 600 South Mathews Avenue, University of Illinois, Urbana, Illinois 61801, USA
| | - Charles Schulz
- Department of Physics, Knox College, 2 East South Street, Galesburg, Illinois 61401, USA
| | - Eric Oldfield
- Department of Chemistry, 600 South Mathews Avenue, University of Illinois, Urbana, Illinois 61801, USA.,Center for Biophysics and Computational Biology, 607 South Mathews Avenue, University of Illinois, Urbana, Illinois 61801, USA
| | - Michael Groll
- Department of Chemistry, Center for Integrated Protein Science, Technische Universität München, Lichtenbergstrasse 4, 85747 Garching, Germany
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34
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Sparta M, Shirvanyants D, Ding F, Dokholyan NV, Alexandrova AN. Hybrid dynamics simulation engine for metalloproteins. Biophys J 2013; 103:767-76. [PMID: 22947938 DOI: 10.1016/j.bpj.2012.06.024] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2012] [Revised: 06/08/2012] [Accepted: 06/18/2012] [Indexed: 11/15/2022] Open
Abstract
Quality computational description of metalloproteins is a great challenge due to the vast span of time- and lengthscales characteristic of their existence. We present an efficient new method that allows for robust characterization of metalloproteins. It combines quantum mechanical (QM) description of the metal-containing active site, and extensive dynamics of the protein captured by discrete molecular dynamics (DMD) (QM/DMD). DMD samples the entire protein, including the backbone, and most of the active site, except for the immediate coordination region of the metal. QM operates on the part of the protein of electronic and chemical significance, which may include tens to hundreds of atoms. The breathing quantum-classical boundary provides a continuous mutual feedback between the two machineries. We test QM/DMD using the Fe-containing electron transporter protein, rubredoxin, and its three mutants as a model. QM/DMD can provide a reliable balanced description of metalloproteins' structure, dynamics, and electronic structure in a reasonable amount of time. As an illustration of QM/DMD capabilities, we then predict the structure of the Ca(2+) form of the enzyme catechol O-methyl transferase, which, unlike the native Mg(2+) form, is catalytically inactive. The Mg(2+) site is ochtahedral, but the Ca(2+) is 7-coordinate and features the misalignment of the reacting parts of the system. The change is facilitated by the backbone adjustment. QM/DMD is ideal and fast for providing this level of structural insight.
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Affiliation(s)
- Manuel Sparta
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California, USA
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35
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Luo Y, Niu S, Ichiye T. Understanding rubredoxin redox sites by density functional theory studies of analogues. J Phys Chem A 2012; 116:8918-24. [PMID: 22881577 DOI: 10.1021/jp3057509] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Determining the redox energetics of redox site analogues of metalloproteins is essential in unraveling the various contributions to electron transfer properties of these proteins. Since studies of the [4Fe-4S] analogues show that the energies are dependent on the ligand dihedral angles, broken symmetry density functional theory (BS-DFT) with the B3LYP functional and double-ζ basis sets calculations of optimized geometries and electron detachment energies of [1Fe] rubredoxin analogues are compared to crystal structures and gas-phase photoelectron spectroscopy data, respectively, for [Fe(SCH(3))(4)](0/1-/2-), [Fe(S(2)-o-xyl)(2)](0/1-/2-), and Na(+)[Fe(S(2)-o-xyl)(2)](1-/2-) in different conformations. In particular, the study of Na(+)[Fe(S(2)-o-xyl)(2)](1-/2-) is the only direct comparison of calculated and experimental gas phase detachment energies for the 1-/2- couple found in the rubredoxins. These results show that variations in the inner sphere energetics by up to ∼0.4 eV can be caused by differences in the ligand dihedral angles in either or both redox states. Moreover, these results indicate that the protein stabilizes the conformation that favors reduction. In addition, the free energies and reorganization energies of oxidation and reduction as well as electrostatic potential charges are calculated, which can be used as estimates in continuum electrostatic calculations of electron transfer properties of [1Fe] proteins.
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Affiliation(s)
- Yan Luo
- Department of Chemistry, Georgetown University, Washington, DC 20057, USA
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36
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37
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Niu S, Ichiye T. Density functional theory calculations of redox properties of iron–sulphur protein analogues. MOLECULAR SIMULATION 2011. [DOI: 10.1080/08927022.2011.582111] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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38
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Majumdar A, Sarkar S. Bioinorganic chemistry of molybdenum and tungsten enzymes: A structural–functional modeling approach. Coord Chem Rev 2011. [DOI: 10.1016/j.ccr.2010.11.027] [Citation(s) in RCA: 122] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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39
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Takano Y, Yonezawa Y, Fujita Y, Kurisu G, Nakamura H. Electronic structures of a [4Fe–4S] cluster, [Fe4S4(SCH3)3(CH3COO)], in dark-operative protochlorophyllide oxidoreductase (DPOR). Chem Phys Lett 2011. [DOI: 10.1016/j.cplett.2011.01.026] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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40
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41
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Sharma AK, Kim N, Cameron CS, Lyndon M, Gorman CB. Dendritically encapsulated, water-soluble fe(4)s(4): synthesis and electrochemical properties. Inorg Chem 2010; 49:5072-8. [PMID: 20450203 DOI: 10.1021/ic1002447] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amphiphilic, Fe(4)S(4) cluster core dendrimers can be prepared via ligand exchange with dendrons containing carboxylic acid peripheral groups and a thiol focal group. These amphiphilic dendrons are more susceptible to oxidative disulfide formation than their non-amphiphilic analogues reported previously. Thus, an in situ deprotection of an aromatic thioacetate was necessary to prepare the dendrimers. These molecules showed the expected decrease in rate with increasing generation. A slower rate of heterogeneous electron transfer was found when these molecules were compared with non-amphiphilic analogues. This behavior correlated with their larger size and thus a larger effective distance of electron transfer. Voltammetry in DMSO with added water makes the dendrimers easier to reduce, but the change in redox potential is much smaller for all dendrimers when compared to a non-dendritic analogue. This behavior is consistent with the idea that the dendrimers encapsulate the cluster to some degree, creating a hydrophobic microenvironment around the cluster.
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Affiliation(s)
- Anil K Sharma
- Department of Chemistry, North Carolina State University, Box 8204, Raleigh, North Carolina 28795-8204, USA
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42
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43
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Garrett B, Henderson RA. Protonation and substitution reactions of [{WFe₃S₄Cl₃}₂(μ-L)₃]³⁻ (L = SEt or OMe): quantifying how metal content and spectator ligands individually affect reactivity. Dalton Trans 2010; 39:4586-92. [PMID: 20386803 DOI: 10.1039/b925835c] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Kinetic studies on the substitution reactions of the terminal chloro-ligands of [{WFe₃S₄Cl₃}₂(μ-L)₃]³⁻ (L = SEt or MeO) by PhS⁻ in the presence of [NHEt₃](+) or [pyrH](+) allow determination of the proton affinities and rates of PhS⁻ and proton binding to the clusters. The behaviours of both clusters are similar and follow the same general kinetic characteristics established in earlier work for other synthetic Fe-S-based clusters. Comparison of the results obtained with [{WFe₃S₄Cl₃}₂(μ-SEt)₃]³⁻ with those of the isostructural [{MoFe₃S₄Cl₃}₂(μ-SEt)₃]³⁻ shows that changing a Mo for W in the cuboidal cluster framework has a large effect on the rates of binding of PhS⁻ or a proton. In contrast, comparison of the results of [{WFe₃S₄Cl₃}₂(μ-SEt)₃]³⁻ with those of [{WFe₃S₄Cl₃}₂(μ-OMe)₃]³⁻ shows that changing the bridging ligands has only a small effect on the rates of binding of PhS⁻ or a proton. The reactivities of [{MFe₃S₄Cl₃}₂(μ-L)₃]³⁻ are inconsistent with the major influence of the metal or bridging ligands being electronic, and are more consistent with their modulating the ability of the cluster to undergo bond length reorganisation during binding of the nucleophile or proton.
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Affiliation(s)
- Brendan Garrett
- School of Chemistry, Newcastle University, Newcastle upon Tyne, UK
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44
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Luo Y, Ergenekan CE, Fischer JT, Tan ML, Ichiye T. The molecular determinants of the increased reduction potential of the rubredoxin domain of rubrerythrin relative to rubredoxin. Biophys J 2010; 98:560-8. [PMID: 20159152 DOI: 10.1016/j.bpj.2009.11.006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 11/03/2009] [Accepted: 11/04/2009] [Indexed: 11/28/2022] Open
Abstract
Based on the crystal structures, three possible sequence determinants have been suggested as the cause of a 285 mV increase in reduction potential of the rubredoxin domain of rubrerythrin over rubredoxin by modulating the polar environment around the redox site. Here, electrostatic calculations of crystal structures of rubredoxin and rubrerythrin and molecular dynamics simulations of rubredoxin wild-type and mutants are used to elucidate the contributions to the increased reduction potential. Asn(160) and His(179) in rubrerythrin versus valines in rubredoxins are predicted to be the major contributors, as the polar side chains contribute significantly to the electrostatic potential in the redox site region. The mutant simulations show both side chains rotating on a nanosecond timescale between two conformations with different electrostatic contributions. Reduction also causes a change in the reduction energy that is consistent with a linear response due to the interesting mechanism of shifting the relative populations of the two conformations. In addition to this, a simulation of a triple mutant indicates the side-chain rotations are approximately anticorrelated so whereas one is in the high potential conformation, the other is in the low potential conformation. However, Ala(176) in rubrerythrin versus a leucine in rubredoxin is not predicted to be a large contributor, because the solvent accessibility increases only slightly in mutant simulations and because it is buried in the interface of the rubrerythrin homodimer.
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Affiliation(s)
- Yan Luo
- Department of Chemistry, Georgetown University, Washington, District of Columbia, USA
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45
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Cammack R, MacMillan F. Electron Magnetic Resonance of Iron–Sulfur Proteins in Electron-Transfer Chains: Resolving Complexity. METALS IN BIOLOGY 2010. [DOI: 10.1007/978-1-4419-1139-1_2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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46
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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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47
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Niu S, Ichiye T. Insight into environmental effects on bonding and redox properties of [4Fe-4S] clusters in proteins. J Am Chem Soc 2009; 131:5724-5. [PMID: 19341280 DOI: 10.1021/ja900406j] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The large differences in redox potentials between the HiPIPs and ferredoxins are generally attributed to hydrogen bonds and electrostatic effects from the protein and solvent. Recent ligand K-edge X-ray absorption studies by Solomon and co-workers show that the Fe-S covalencies of [4Fe-4S] clusters in the two proteins differ considerably apparently because of hydrogen bonds from water, indicating electronic effects may be important. However, combined density function theory (DFT) and photoelectron spectroscopy studies by our group and Wang and co-workers indicate that hydrogen bonds tune the potential of [4Fe-4S] clusters by mainly electrostatics. The DFT studies here rationalize both results, namely that the observed change in the Fe-S covalency is due to differences in ligand conformation between the two proteins rather than hydrogen bonds. Moreover, the ligand conformation affects the calculated potentials by approximately 100 mV and, thus, is a heretofore unconsidered means of tuning the potential.
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Affiliation(s)
- Shuqiang Niu
- Department of Chemistry, Georgetown University, Washington, DC 20057-1227, USA
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48
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Kersting B, Lehmann U. Chemistry of metalated container molecules. ADVANCES IN INORGANIC CHEMISTRY 2009. [DOI: 10.1016/s0898-8838(09)00207-4] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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49
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Cerrada E, Laguna M, Lardíes N. Bis(1,2,3‐thiadiazole)s as Precursors in the Synthesis of Bis(alkynethiolate)gold(I) Derivatives. Eur J Inorg Chem 2008. [DOI: 10.1002/ejic.200800861] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Elena Cerrada
- Departamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza – C. S. I. C., 50009 Zaragoza, Spain
| | - Mariano Laguna
- Departamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza – C. S. I. C., 50009 Zaragoza, Spain
| | - Nora Lardíes
- Departamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza – C. S. I. C., 50009 Zaragoza, Spain
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50
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Dridge E, Watts C, Jepson B, Line K, Santini J, Richardson D, Butler C. Investigation of the redox centres of periplasmic selenate reductase from Thauera selenatis by EPR spectroscopy. Biochem J 2007; 408:19-28. [PMID: 17688424 PMCID: PMC2049085 DOI: 10.1042/bj20070669] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Periplasmic SER (selenate reductase) from Thauera selenatis is classified as a member of the Tat (twin-arginine translocase)-translocated (Type II) molybdoenzymes and comprises three subunits each containing redox cofactors. Variable-temperature X-band EPR spectra of the purified SER complex showed features attributable to centres [3Fe-4S]1+, [4Fe-4S]1+, Mo(V) and haem-b. EPR-monitored redox-potentiometric titration of the SerABC complex (SerA-SerB-SerC, a hetero-trimetric complex of alphabetagamma subunits) revealed that the [3Fe-4S] cluster (FS4, iron-sulfur cluster 4) titrated as n=1 Nernstian component with a midpoint redox potential (E(m)) of +118+/-10 mV for the [3Fe-4S]1+/0 couple. A [4Fe-4S]1+ cluster EPR signal developed over a range of potentials between 300 and -200 mV and was best fitted to two sequential Nernstian n=1 curves with midpoint redox potentials of +183+/-10 mV (FS1) and -51+/-10 mV (FS3) for the two [4Fe-4S]1+/2+ cluster couples. Upon further reduction, the observed signal intensity of the [4Fe-4S]1+ cluster decreases. This change in intensity can again be fitted to an n=1 Nernstian component with a midpoint potential (E(m)) of about -356 mV (FS2). It is considered likely that, at low redox potential (E(m) less than -300 mV), the remaining oxidized cluster is reduced (spin S=1/2) and strongly spin-couples to a neighbouring [4Fe-4S]1+ cluster rendering both centres EPR-silent. The involvement of both [3Fe-4S] and [4Fe-4S] clusters in electron transfer to the active site of the periplasmic SER was demonstrated by the re-oxidation of the clusters under anaerobic selenate turnover conditions. Attempts to detect a high-spin [4Fe-4S] cluster (FS0) in SerA at low temperature (5 K) and high power (100 mW) were unsuccessful. The Mo(V) EPR recorded at 60 K, in samples poised at pH 6.0, displays principal g values of g3 approximately 1.999, g2 approximately 1.996 and g1 approximately 1.965 (g(av) 1.9867). The dominant features at g2 and g3 are not split, but hyperfine splitting is observed in the g1 region of the spectrum and can be best simulated as arising from a single proton with a coupling constant of A1 (1H)=1.014 mT. The presence of the haem-b moiety in SerC was demonstrated by the detection of a signal at g approximately 3.33 and is consistent with haem co-ordinated by methionine and lysine axial ligands. The combined evidence from EPR analysis and sequence alignments supports the assignment of the periplasmic SER as a member of the Type II molybdoenzymes and provides the first spectro-potentiometric insight into an enzyme that catalyses a key reductive reaction in the biogeochemical selenium cycle.
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Affiliation(s)
- Elizabeth J. Dridge
- *School of Biosciences, Centre for Biocatalysis, University of Exeter, Stocker Road, Exeter EX4 4QD, U.K
- †Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, U.K
| | - Carys A. Watts
- †Institute for Cell and Molecular Biosciences, University of Newcastle, Newcastle upon Tyne NE2 4HH, U.K
| | - Brian J. N. Jepson
- ‡School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Kirsty Line
- *School of Biosciences, Centre for Biocatalysis, University of Exeter, Stocker Road, Exeter EX4 4QD, U.K
| | - Joanne M. Santini
- §Department of Biology, University College London, Gower Street, London WC1E 6BT, U.K
| | - David J. Richardson
- ‡School of Biological Sciences, University of East Anglia, Norwich NR4 7TJ, U.K
| | - Clive S. Butler
- *School of Biosciences, Centre for Biocatalysis, University of Exeter, Stocker Road, Exeter EX4 4QD, U.K
- To whom correspondence should be addressed (email )
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