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Grunwald L, Abbott DF, Mougel V. Gauging Iron-Sulfur Cubane Reactivity from Covalency: Trends with Oxidation State. JACS AU 2024; 4:1315-1322. [PMID: 38665672 PMCID: PMC11040707 DOI: 10.1021/jacsau.4c00213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 04/03/2024] [Accepted: 04/03/2024] [Indexed: 04/28/2024]
Abstract
We investigated room-temperature metal and ligand K-edge X-ray absorption (XAS) spectra of a complete redox series of cubane-type iron-sulfur clusters. The Fe K-edge position provides a qualitative but convenient alternative to the traditional spectroscopic descriptors used to identify oxidation states in these systems, which we demonstrate by providing a calibration curve based on two analytic methods. Furthermore, high energy resolution fluorescence detected XAS (HERFD-XAS) at the S K-edge was used to measure Fe-S bond covalencies and record their variation with the average valence of the Fe atoms. While the Fe-S(thiolate) covalency evolves linearly, gaining 11 ± 0.4% per bond and hole, the Fe-S(μ3) covalency evolves asystematically, reflecting changes in the magnetic exchange mechanism. A strong discontinuity manifested for superoxidation to the all-ferric state, distinguishing its electronic structure and its potential (bio)chemical role from those of its redox congeners. We highlight the functional implications of these trends for the reactivity of iron-sulfur cubanes.
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Affiliation(s)
- Liam Grunwald
- Department
of Chemistry and Applied Biosciences (D-CHAB), Swiss Federal Institute of Technology Zürich (ETHZ), Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Daniel F. Abbott
- Department
of Chemistry and Applied Biosciences (D-CHAB), Swiss Federal Institute of Technology Zürich (ETHZ), Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Victor Mougel
- Department
of Chemistry and Applied Biosciences (D-CHAB), Swiss Federal Institute of Technology Zürich (ETHZ), Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
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2
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Fasano A, Baffert C, Schumann C, Berggren G, Birrell JA, Fourmond V, Léger C. Kinetic Modeling of the Reversible or Irreversible Electrochemical Responses of FeFe-Hydrogenases. J Am Chem Soc 2024; 146:1455-1466. [PMID: 38166210 DOI: 10.1021/jacs.3c10693] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2024]
Abstract
The enzyme FeFe-hydrogenase catalyzes H2 evolution and oxidation at an active site that consists of a [4Fe-4S] cluster bridged to a [Fe2(CO)3(CN)2(azadithiolate)] subsite. Previous investigations of its mechanism were mostly conducted on a few "prototypical" FeFe-hydrogenases, such as that from Chlamydomonas reinhardtii(Cr HydA1), but atypical hydrogenases have recently been characterized in an effort to explore the diversity of this class of enzymes. We aim at understanding why prototypical hydrogenases are active in either direction of the reaction in response to a small deviation from equilibrium, whereas the homologous enzyme from Thermoanaerobacter mathranii (Tam HydS) shows activity only under conditions of very high driving force, a behavior that was referred to as "irreversible catalysis". We follow up on previous spectroscopic studies and recent developments in the kinetic modeling of bidirectional reactions to investigate and compare the catalytic cycles of Cr HydA1 and Tam HydS under conditions of direct electron transfer with an electrode. We compare the hypothetical catalytic cycles described in the literature, and we show that the observed changes in catalytic activity as a function of potential, pH, and H2 concentration can be explained with the assumption that the same catalytic mechanism applies. This helps us identify which variations in properties of the catalytic intermediates give rise to the distinct "reversible" or "irreversible" catalytic behaviors.
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Affiliation(s)
- Andrea Fasano
- Laboratoire de Bioénergétique et Ingénierie des Protéines. CNRS, Aix Marseille Université, UMR, 7281 Marseille, France
| | - Carole Baffert
- Laboratoire de Bioénergétique et Ingénierie des Protéines. CNRS, Aix Marseille Université, UMR, 7281 Marseille, France
| | - Conrad Schumann
- Molecular Biomimetics, Department of Chemistry, Ångström Laboratory, Uppsala University, 75120 Uppsala, Sweden
| | - Gustav Berggren
- Molecular Biomimetics, Department of Chemistry, Ångström Laboratory, Uppsala University, 75120 Uppsala, Sweden
| | - James A Birrell
- School of Life Sciences, University of Essex, Wivenhoe Park, Colchester CO4 3SQ, U.K
| | - Vincent Fourmond
- Laboratoire de Bioénergétique et Ingénierie des Protéines. CNRS, Aix Marseille Université, UMR, 7281 Marseille, France
| | - Christophe Léger
- Laboratoire de Bioénergétique et Ingénierie des Protéines. CNRS, Aix Marseille Université, UMR, 7281 Marseille, France
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3
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Corrigan PS, Majer SH, Silakov A. Evidence of Atypical Structural Flexibility of the Active Site Surrounding of an [FeFe] Hydrogenase from Clostridium beijerinkii. J Am Chem Soc 2023; 145:11033-11044. [PMID: 37163727 DOI: 10.1021/jacs.2c13458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
[FeFe] hydrogenase from Clostridium beijerinkii (CbHydA1) is an unusual hydrogenase in that it can withstand prolonged exposure to O2 by reversibly converting into an O2-protected, inactive state (Hinact). It has been indicated in the past that an atypical conformation of the "SC367CP" loop near the [2Fe]H portion of the six-iron active site (H-cluster) allows the Cys367 residue to adopt an "off-H+-pathway" orientation, promoting a facile transition of the cofactor to Hinact. Here, we investigated the electronic structure of the H-cluster in the oxidized state (Hox) that directly converts to Hinact under oxidizing conditions and the related CO-inhibited state (Hox-CO). We demonstrate that both states exhibit two distinct forms in electron paramagnetic resonance (EPR) spectroscopy. The ratio between the two forms is pH-dependent but also sensitive to the buffer choice. Our IR and EPR analyses illustrate that the spectral heterogeneity is due to a perturbation of the coordination environment of the H-cluster's [4Fe4S]H subcluster without affecting the [2Fe]H subcluster. Overall, we conclude that the observation of two spectral components per state is evidence of heterogeneity of the environment of the H-cluster likely associated with conformational mobility of the SCCP loop. Such flexibility may allow Cys367 to switch rapidly between off- and on-H+-pathway rotamers. Consequently, we believe such structural mobility may be the key to maintaining high enzymatic activity while allowing a facile transition to the O2-protected state.
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Affiliation(s)
- Patrick S Corrigan
- Pennsylvania State University, 104 Chemistry Building, University Park, Pennsylvania 16802, United States
| | - Sean H Majer
- Pennsylvania State University, 104 Chemistry Building, University Park, Pennsylvania 16802, United States
| | - Alexey Silakov
- Pennsylvania State University, 104 Chemistry Building, University Park, Pennsylvania 16802, United States
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4
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Katsyv A, Kumar A, Saura P, Pöverlein MC, Freibert SA, T Stripp S, Jain S, Gamiz-Hernandez AP, Kaila VRI, Müller V, Schuller JM. Molecular Basis of the Electron Bifurcation Mechanism in the [FeFe]-Hydrogenase Complex HydABC. J Am Chem Soc 2023; 145:5696-5709. [PMID: 36811855 PMCID: PMC10021017 DOI: 10.1021/jacs.2c11683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Electron bifurcation is a fundamental energy coupling mechanism widespread in microorganisms that thrive under anoxic conditions. These organisms employ hydrogen to reduce CO2, but the molecular mechanisms have remained enigmatic. The key enzyme responsible for powering these thermodynamically challenging reactions is the electron-bifurcating [FeFe]-hydrogenase HydABC that reduces low-potential ferredoxins (Fd) by oxidizing hydrogen gas (H2). By combining single-particle cryo-electron microscopy (cryoEM) under catalytic turnover conditions with site-directed mutagenesis experiments, functional studies, infrared spectroscopy, and molecular simulations, we show that HydABC from the acetogenic bacteria Acetobacterium woodii and Thermoanaerobacter kivui employ a single flavin mononucleotide (FMN) cofactor to establish electron transfer pathways to the NAD(P)+ and Fd reduction sites by a mechanism that is fundamentally different from classical flavin-based electron bifurcation enzymes. By modulation of the NAD(P)+ binding affinity via reduction of a nearby iron-sulfur cluster, HydABC switches between the exergonic NAD(P)+ reduction and endergonic Fd reduction modes. Our combined findings suggest that the conformational dynamics establish a redox-driven kinetic gate that prevents the backflow of the electrons from the Fd reduction branch toward the FMN site, providing a basis for understanding general mechanistic principles of electron-bifurcating hydrogenases.
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Affiliation(s)
- Alexander Katsyv
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main 60438, Germany
| | - Anuj Kumar
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main 60438, Germany.,SYNMIKRO Research Center and Department of Chemistry, Philipps-University of Marburg, Marburg 35032, Germany
| | - Patricia Saura
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Maximilian C Pöverlein
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Sven A Freibert
- Institut für Zytobiologie im Zentrum SYNMIKRO, Philipps-University of Marburg, Marburg 35032, Germany.,Core Facility "Protein Biochemistry and Spectroscopy", Marburg 35032, Germany
| | - Sven T Stripp
- Department of Physics, Experimental Molecular Biophysics, Freie Universität Berlin, Berlin 14195, Germany
| | - Surbhi Jain
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main 60438, Germany
| | - Ana P Gamiz-Hernandez
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Ville R I Kaila
- Department of Biochemistry and Biophysics, Stockholm University, Stockholm 10691, Sweden
| | - Volker Müller
- Department of Molecular Microbiology & Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt am Main 60438, Germany
| | - Jan M Schuller
- SYNMIKRO Research Center and Department of Chemistry, Philipps-University of Marburg, Marburg 35032, Germany
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5
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Sidabras JW, Stripp ST. A personal account on 25 years of scientific literature on [FeFe]-hydrogenase. J Biol Inorg Chem 2023; 28:355-378. [PMID: 36856864 DOI: 10.1007/s00775-023-01992-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Accepted: 01/25/2023] [Indexed: 03/02/2023]
Abstract
[FeFe]-hydrogenases are gas-processing metalloenzymes that catalyze H2 oxidation and proton reduction (H2 release) in microorganisms. Their high turnover frequencies and lack of electrical overpotential in the hydrogen conversion reaction has inspired generations of biologists, chemists, and physicists to explore the inner workings of [FeFe]-hydrogenase. Here, we revisit 25 years of scientific literature on [FeFe]-hydrogenase and propose a personal account on 'must-read' research papers and review article that will allow interested scientists to follow the recent discussions on catalytic mechanism, O2 sensitivity, and the in vivo synthesis of the active site cofactor with its biologically uncommon ligands carbon monoxide and cyanide. Focused on-but not restricted to-structural biology and molecular biophysics, we highlight future directions that may inspire young investigators to pursue a career in the exciting and competitive field of [FeFe]-hydrogenase research.
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Affiliation(s)
- Jason W Sidabras
- Department of Biophysics, Medical College of Wisconsin, 8701 Watertown Plank Rd, Milwaukee, WI, USA, 53226.
| | - Sven T Stripp
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany.
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6
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Bedendi G, Kulkarni A, Maroni P, Milton RD. Alternative Electron Donors for the Nitrogenase‐like Dark‐Operative Protochlorophyllide Oxidoreductase (DPOR). ChemElectroChem 2022. [DOI: 10.1002/celc.202200774] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Giada Bedendi
- University of Geneva Faculty of Science: Universite de Geneve Faculte des Sciences Inorganic and Analytical Chemistry SWITZERLAND
| | - Amogh Kulkarni
- University of Geneva Faculty of Science: Universite de Geneve Faculte des Sciences Inorganic and Analytical Chemistry SWITZERLAND
| | - Plinio Maroni
- University of Geneva Faculty of Science: Universite de Geneve Faculte des Sciences Inorganic and Analytical Chemistry SWITZERLAND
| | - Ross D Milton
- Universite de Geneve Faculte de Medecine Department of Inorganic and Analytical Chemistry Sciences IIQuai Ernest-Ansermet 30 1211 Geneva 4 SWITZERLAND
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