1
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Greening C, Kropp A, Vincent K, Grinter R. Developing high-affinity, oxygen-insensitive [NiFe]-hydrogenases as biocatalysts for energy conversion. Biochem Soc Trans 2023; 51:1921-1933. [PMID: 37743798 PMCID: PMC10657181 DOI: 10.1042/bst20230120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 09/13/2023] [Accepted: 09/14/2023] [Indexed: 09/26/2023]
Abstract
The splitting of hydrogen (H2) is an energy-yielding process, which is important for both biological systems and as a means of providing green energy. In biology, this reaction is mediated by enzymes called hydrogenases, which utilise complex nickel and iron cofactors to split H2 and transfer the resulting electrons to an electron-acceptor. These [NiFe]-hydrogenases have received considerable attention as catalysts in fuel cells, which utilise H2 to produce electrical current. [NiFe]-hydrogenases are a promising alternative to the platinum-based catalysts that currently predominate in fuel cells due to the abundance of nickel and iron, and the resistance of some family members to inhibition by gases, including carbon monoxide, which rapidly poison platinum-based catalysts. However, the majority of characterised [NiFe]-hydrogenases are inhibited by oxygen (O2), limiting their activity and stability. We recently reported the isolation and characterisation of the [NiFe]-hydrogenase Huc from Mycobacterium smegmatis, which is insensitive to inhibition by O2 and has an extremely high affinity, making it capable of oxidising H2 in air to below atmospheric concentrations. These properties make Huc a promising candidate for the development of enzyme-based fuel cells (EBFCs), which utilise H2 at low concentrations and in impure gas mixtures. In this review, we aim to provide context for the use of Huc for this purpose by discussing the advantages of [NiFe]-hydrogenases as catalysts and their deployment in fuel cells. We also address the challenges associated with using [NiFe]-hydrogenases for this purpose, and how these might be overcome to develop EBFCs that can be deployed at scale.
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Affiliation(s)
- Chris Greening
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
- Securing Antarctica's Environmental Future, Monash University, Clayton, VIC 3800, Australia
- Centre to Impact AMR, Monash University, Clayton, VIC 3800, Australia
- ARC Research Hub for Carbon Utilisation and Recycling, Monash University, Clayton, VIC 3800, Australia
| | - Ashleigh Kropp
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
| | - Kylie Vincent
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, Oxford OX1 3QR, U.K
| | - Rhys Grinter
- Department of Microbiology, Biomedicine Discovery Institute, Monash University, Clayton, VIC 3800, Australia
- Centre for Electron Microscopy of Membrane Proteins, Monash Institute of Pharmaceutical Sciences, Parkville, Victoria 3052, Australia
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2
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Fasano A, Guendon C, Jacq-Bailly A, Kpebe A, Wozniak J, Baffert C, Barrio MD, Fourmond V, Brugna M, Léger C. A Chimeric NiFe Hydrogenase Heterodimer to Assess the Role of the Electron Transfer Chain in Tuning the Enzyme's Catalytic Bias and Oxygen Tolerance. J Am Chem Soc 2023; 145:20021-20030. [PMID: 37657413 DOI: 10.1021/jacs.3c06895] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/03/2023]
Abstract
The observation that some homologous enzymes have the same active site but very different catalytic properties demonstrates the importance of long-range effects in enzyme catalysis, but these effects are often difficult to rationalize. The NiFe hydrogenases 1 and 2 (Hyd 1 and Hyd 2) from E. coli both consist of a large catalytic subunit that embeds the same dinuclear active site and a small electron-transfer subunit with a chain of three FeS clusters. Hyd 1 is mostly active in H2 oxidation and resistant to inhibitors, whereas Hyd 2 also catalyzes H2 production and is strongly inhibited by O2 and CO. Based on structural and site-directed mutagenesis data, it is currently believed that the catalytic bias and tolerance to O2 of Hyd 1 are defined by the distal and proximal FeS clusters, respectively. To test these hypotheses, we produced and characterized a hybrid enzyme made of the catalytic subunit of Hyd 1 and the electron transfer subunit of Hyd 2. We conclude that catalytic bias and sensitivity to CO are set by the catalytic subunit rather than by the electron transfer chain. We confirm the importance of the proximal cluster in making the enzyme Hyd 1 resist long-term exposure to O2, but we show that other structural determinants, in both subunits, contribute to O2 tolerance. A similar strategy based on the design of chimeric heterodimers could be used in the future to elucidate various structure-function relationships in hydrogenases and other multimeric metalloenzymes and to engineer useful hydrogenases that combine the desirable properties of distinct, homologous enzymes.
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Affiliation(s)
- Andrea Fasano
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, Aix Marseille Université, UMR 7281, Marseille, France
| | - Chloé Guendon
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, Aix Marseille Université, UMR 7281, Marseille, France
| | - Aurore Jacq-Bailly
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, Aix Marseille Université, UMR 7281, Marseille, France
| | - Arlette Kpebe
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, Aix Marseille Université, UMR 7281, Marseille, France
| | - Jérémy Wozniak
- 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
| | - Melisa Del Barrio
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, Aix Marseille Université, UMR 7281, Marseille, France
- Department of Analytical Chemistry, Faculty of Chemistry, Complutense University of Madrid, 28040 Madrid, Spain
| | - Vincent Fourmond
- Laboratoire de Bioénergétique et Ingénierie des Protéines, CNRS, Aix Marseille Université, UMR 7281, Marseille, France
| | - Myriam Brugna
- 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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Evans RM, Beaton SE, Rodriguez Macia P, Pang Y, Wong KL, Kertess L, Myers WK, Bjornsson R, Ash PA, Vincent KA, Carr SB, Armstrong FA. Comprehensive structural, infrared spectroscopic and kinetic investigations of the roles of the active-site arginine in bidirectional hydrogen activation by the [NiFe]-hydrogenase 'Hyd-2' from Escherichia coli. Chem Sci 2023; 14:8531-8551. [PMID: 37592998 PMCID: PMC10430524 DOI: 10.1039/d2sc05641k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2022] [Accepted: 07/01/2023] [Indexed: 08/19/2023] Open
Abstract
The active site of [NiFe]-hydrogenases contains a strictly-conserved pendant arginine, the guanidine head group of which is suspended immediately above the Ni and Fe atoms. Replacement of this arginine (R479) in hydrogenase-2 from E. coli results in an enzyme that is isolated with a very tightly-bound diatomic ligand attached end-on to the Ni and stabilised by hydrogen bonding to the Nζ atom of the pendant lysine and one of the three additional water molecules located in the active site of the variant. The diatomic ligand is bound under oxidising conditions and is removed only after a prolonged period of reduction with H2 and reduced methyl viologen. Once freed of the diatomic ligand, the R479K variant catalyses both H2 oxidation and evolution but with greatly decreased rates compared to the native enzyme. Key kinetic characteristics are revealed by protein film electrochemistry: most importantly, a very low activation energy for H2 oxidation that is not linked to an increased H/D isotope effect. Native electrocatalytic reversibility is retained. The results show that the sluggish kinetics observed for the lysine variant arise most obviously because the advantage of a more favourable low-energy pathway is massively offset by an extremely unfavourable activation entropy. Extensive efforts to establish the identity of the diatomic ligand, the tight binding of which is an unexpected further consequence of replacing the pendant arginine, prove inconclusive.
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Affiliation(s)
- Rhiannon M Evans
- University of Oxford, Department of Chemistry South Parks Road Oxford UK
| | - Stephen E Beaton
- University of Oxford, Department of Chemistry South Parks Road Oxford UK
| | | | - Yunjie Pang
- College of Chemistry, Beijing Normal University 100875 Beijing China
- Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion Stiftstraße 34-36 45470 Mülheim an der Ruhr Germany
| | - Kin Long Wong
- University of Oxford, Department of Chemistry South Parks Road Oxford UK
- Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus Didcot UK
| | - Leonie Kertess
- University of Oxford, Department of Chemistry South Parks Road Oxford UK
| | - William K Myers
- University of Oxford, Department of Chemistry South Parks Road Oxford UK
| | - Ragnar Bjornsson
- Department of Inorganic Spectroscopy, Max Planck Institute for Chemical Energy Conversion Stiftstraße 34-36 45470 Mülheim an der Ruhr Germany
- Univ Grenoble Alpes, CNRS, CEA, IRIG, Laboratoire Chimie et Biologie des Métaux 17 Rue Des Martyrs F-38054 Grenoble Cedex France
| | - Philip A Ash
- School of Chemistry, The University of Leicester University Road Leicester LE1 7RH UK
| | - Kylie A Vincent
- University of Oxford, Department of Chemistry South Parks Road Oxford UK
| | - Stephen B Carr
- University of Oxford, Department of Chemistry South Parks Road Oxford UK
- Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus Didcot UK
| | - Fraser A Armstrong
- University of Oxford, Department of Chemistry South Parks Road Oxford UK
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4
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Huang W, Zulkifli MYB, Chai M, Lin R, Wang J, Chen Y, Chen V, Hou J. Recent advances in enzymatic biofuel cells enabled by innovative materials and techniques. EXPLORATION (BEIJING, CHINA) 2023; 3:20220145. [PMID: 37933234 PMCID: PMC10624391 DOI: 10.1002/exp.20220145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Accepted: 03/21/2023] [Indexed: 11/08/2023]
Abstract
The past few decades have seen increasingly rapid advances in the field of sustainable energy technologies. As a new bio- and eco-friendly energy source, enzymatic biofuel cells (EBFCs) have garnered significant research interest due to their capacity to power implantable bioelectronics, portable devices, and biosensors by utilizing biomass as fuel under mild circumstances. Nonetheless, numerous obstacles impeded the commercialization of EBFCs, including their relatively modest power output and poor long-term stability of enzymes. To depict the current progress of EBFC and address the challenges it faces, this review traces back the evolution of EBFC and focuses on contemporary advances such as newly emerged multi or single enzyme systems, various porous framework-enzyme composites techniques, and innovative applications. Besides emphasizing current achievements in this field, from our perspective part we also introduced novel electrode and cell design for highly effective EBFC fabrication. We believe this review will assist readers in comprehending the basic research and applications of EBFCs as well as potentially spark interdisciplinary collaboration for addressing the pressing issues in this field.
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Affiliation(s)
- Wengang Huang
- School of Chemical EngineeringThe University of QueenslandSaint LuciaQueenslandAustralia
| | - Muhammad Yazid Bin Zulkifli
- School of Chemical EngineeringThe University of QueenslandSaint LuciaQueenslandAustralia
- School of Chemical EngineeringThe University of New South WalesSydneyNew South WalesAustralia
| | - Milton Chai
- School of Chemical EngineeringThe University of QueenslandSaint LuciaQueenslandAustralia
| | - Rijia Lin
- School of Chemical EngineeringThe University of QueenslandSaint LuciaQueenslandAustralia
| | - Jingjing Wang
- Australian Institute for Bioengineering and NanotechnologyThe University of QueenslandSaint LuciaQueenslandAustralia
| | - Yuelei Chen
- School of Chemical EngineeringThe University of QueenslandSaint LuciaQueenslandAustralia
| | - Vicki Chen
- School of Chemical EngineeringThe University of QueenslandSaint LuciaQueenslandAustralia
| | - Jingwei Hou
- School of Chemical EngineeringThe University of QueenslandSaint LuciaQueenslandAustralia
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5
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Jiang Q, Li T, Yang J, Aitchison CM, Huang J, Chen Y, Huang F, Wang Q, Cooper AI, Liu LN. Synthetic engineering of a new biocatalyst encapsulating [NiFe]-hydrogenases for enhanced hydrogen production. J Mater Chem B 2023; 11:2684-2692. [PMID: 36883480 PMCID: PMC10032307 DOI: 10.1039/d2tb02781j] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Hydrogenases are microbial metalloenzymes capable of catalyzing the reversible interconversion between molecular hydrogen and protons with high efficiency, and have great potential in the development of new electrocatalysts for renewable fuel production. Here, we engineered the intact proteinaceous shell of the carboxysome, a self-assembling protein organelle for CO2 fixation in cyanobacteria and proteobacteria, and sequestered heterologously produced [NiFe]-hydrogenases into the carboxysome shell. The protein-based hybrid catalyst produced in E. coli shows substantially improved hydrogen production under both aerobic and anaerobic conditions and enhanced material and functional robustness, compared to unencapsulated [NiFe]-hydrogenases. The catalytically functional nanoreactor as well as the self-assembling and encapsulation strategies provide a framework for engineering new bioinspired electrocatalysts to improve the sustainable production of fuels and chemicals in biotechnological and chemical applications.
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Affiliation(s)
- Qiuyao Jiang
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
| | - Tianpei Li
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng 475004, China
| | - Jing Yang
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
- Materials Innovation Factory and Department of Chemistry, University of Liverpool, Liverpool L7 3NY, UK
| | - Catherine M Aitchison
- Materials Innovation Factory and Department of Chemistry, University of Liverpool, Liverpool L7 3NY, UK
| | - Jiafeng Huang
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
| | - Yu Chen
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
| | - Fang Huang
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
| | - Qiang Wang
- State Key Laboratory of Crop Stress Adaptation and Improvement, School of Life Sciences, Henan University, Kaifeng 475004, China
| | - Andrew I Cooper
- Materials Innovation Factory and Department of Chemistry, University of Liverpool, Liverpool L7 3NY, UK
| | - Lu-Ning Liu
- Institute of Systems, Molecular and Integrative Biology, University of Liverpool, Liverpool L69 7ZB, UK.
- College of Marine Life Sciences, and Frontiers Science Center for Deep Ocean Multispheres and Earth System, Ocean University of China, Qingdao 266003, China
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6
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McCool JD, Zhang S, Cheng I, Zhao X. Rational development of molecular earth-abundant metal complexes for electrocatalytic hydrogen production. CHINESE JOURNAL OF CATALYSIS 2022. [DOI: 10.1016/s1872-2067(22)64150-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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7
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Stripp ST, Duffus BR, Fourmond V, Léger C, Leimkühler S, Hirota S, Hu Y, Jasniewski A, Ogata H, Ribbe MW. Second and Outer Coordination Sphere Effects in Nitrogenase, Hydrogenase, Formate Dehydrogenase, and CO Dehydrogenase. Chem Rev 2022; 122:11900-11973. [PMID: 35849738 PMCID: PMC9549741 DOI: 10.1021/acs.chemrev.1c00914] [Citation(s) in RCA: 50] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Gases like H2, N2, CO2, and CO are increasingly recognized as critical feedstock in "green" energy conversion and as sources of nitrogen and carbon for the agricultural and chemical sectors. However, the industrial transformation of N2, CO2, and CO and the production of H2 require significant energy input, which renders processes like steam reforming and the Haber-Bosch reaction economically and environmentally unviable. Nature, on the other hand, performs similar tasks efficiently at ambient temperature and pressure, exploiting gas-processing metalloenzymes (GPMs) that bind low-valent metal cofactors based on iron, nickel, molybdenum, tungsten, and sulfur. Such systems are studied to understand the biocatalytic principles of gas conversion including N2 fixation by nitrogenase and H2 production by hydrogenase as well as CO2 and CO conversion by formate dehydrogenase, carbon monoxide dehydrogenase, and nitrogenase. In this review, we emphasize the importance of the cofactor/protein interface, discussing how second and outer coordination sphere effects determine, modulate, and optimize the catalytic activity of GPMs. These may comprise ionic interactions in the second coordination sphere that shape the electron density distribution across the cofactor, hydrogen bonding changes, and allosteric effects. In the outer coordination sphere, proton transfer and electron transfer are discussed, alongside the role of hydrophobic substrate channels and protein structural changes. Combining the information gained from structural biology, enzyme kinetics, and various spectroscopic techniques, we aim toward a comprehensive understanding of catalysis beyond the first coordination sphere.
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Affiliation(s)
- Sven T Stripp
- Freie Universität Berlin, Experimental Molecular Biophysics, Berlin 14195, Germany
| | | | - Vincent Fourmond
- Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Institut Microbiologie, Bioénergies et Biotechnologie, CNRS, Aix Marseille Université, Marseille 13402, France
| | - Christophe Léger
- Laboratoire de Bioénergétique et Ingénierie des Protéines, Institut de Microbiologie de la Méditerranée, Institut Microbiologie, Bioénergies et Biotechnologie, CNRS, Aix Marseille Université, Marseille 13402, France
| | - Silke Leimkühler
- University of Potsdam, Molecular Enzymology, Potsdam 14476, Germany
| | - Shun Hirota
- Nara Institute of Science and Technology, Division of Materials Science, Graduate School of Science and Technology, Nara 630-0192, Japan
| | - Yilin Hu
- Department of Molecular Biology & Biochemistry, University of California, Irvine, California 92697-3900, United States
| | - Andrew Jasniewski
- Department of Molecular Biology & Biochemistry, University of California, Irvine, California 92697-3900, United States
| | - Hideaki Ogata
- Nara Institute of Science and Technology, Division of Materials Science, Graduate School of Science and Technology, Nara 630-0192, Japan.,Hokkaido University, Institute of Low Temperature Science, Sapporo 060-0819, Japan.,Graduate School of Science, University of Hyogo, Hyogo 678-1297, Japan
| | - Markus W Ribbe
- Department of Molecular Biology & Biochemistry, University of California, Irvine, California 92697-3900, United States.,Department of Chemistry, University of California, Irvine, California 92697-2025, United States
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8
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Ash PA, Kendall-Price SET, Evans RM, Carr SB, Brasnett AR, Morra S, Rowbotham JS, Hidalgo R, Healy AJ, Cinque G, Frogley MD, Armstrong FA, Vincent KA. The crystalline state as a dynamic system: IR microspectroscopy under electrochemical control for a [NiFe] hydrogenase. Chem Sci 2021; 12:12959-12970. [PMID: 34745526 PMCID: PMC8514002 DOI: 10.1039/d1sc01734a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2021] [Accepted: 06/03/2021] [Indexed: 12/24/2022] Open
Abstract
Controlled formation of catalytically-relevant states within crystals of complex metalloenzymes represents a significant challenge to structure-function studies. Here we show how electrochemical control over single crystals of [NiFe] hydrogenase 1 (Hyd1) from Escherichia coli makes it possible to navigate through the full array of active site states previously observed in solution. Electrochemical control is combined with synchrotron infrared microspectroscopy, which enables us to measure high signal-to-noise IR spectra in situ from a small area of crystal. The output reports on active site speciation via the vibrational stretching band positions of the endogenous CO and CN- ligands at the hydrogenase active site. Variation of pH further demonstrates how equilibria between catalytically-relevant protonation states can be deliberately perturbed in the crystals, generating a map of electrochemical potential and pH conditions which lead to enrichment of specific states. Comparison of in crystallo redox titrations with measurements in solution or of electrode-immobilised Hyd1 confirms the integrity of the proton transfer and redox environment around the active site of the enzyme in crystals. Slowed proton-transfer equilibria in the hydrogenase in crystallo reveals transitions which are only usually observable by ultrafast methods in solution. This study therefore demonstrates the possibilities of electrochemical control over single metalloenzyme crystals in stabilising specific states for further study, and extends mechanistic understanding of proton transfer during the [NiFe] hydrogenase catalytic cycle.
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Affiliation(s)
- Philip A Ash
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
- School of Chemistry, University of Leicester Leicester LE1 7RH UK
- Leicester Institute of Structural and Chemical Biology, University of Leicester LE1 7RH UK
| | - Sophie E T Kendall-Price
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Rhiannon M Evans
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Stephen B Carr
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
- Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus Didcot UK
| | - Amelia R Brasnett
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Simone Morra
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Jack S Rowbotham
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Ricardo Hidalgo
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Adam J Healy
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Gianfelice Cinque
- Diamond Light Source, Harwell Science and Innovation Campus Didcot OX11 0QX UK
- Department of Engineering Sciences, University of Oxford Parks Road Oxford OX1 3PJ UK
| | - Mark D Frogley
- Diamond Light Source, Harwell Science and Innovation Campus Didcot OX11 0QX UK
| | - Fraser A Armstrong
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
| | - Kylie A Vincent
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory South Parks Road Oxford OX1 3QR UK
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9
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Evans RM, Krahn N, Murphy BJ, Lee H, Armstrong FA, Söll D. Selective cysteine-to-selenocysteine changes in a [NiFe]-hydrogenase confirm a special position for catalysis and oxygen tolerance. Proc Natl Acad Sci U S A 2021; 118:e2100921118. [PMID: 33753519 PMCID: PMC8020662 DOI: 10.1073/pnas.2100921118] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
In [NiFe]-hydrogenases, the active-site Ni is coordinated by four cysteine-S ligands (Cys; C), two of which are bridging to the Fe(CO)(CN)2 fragment. Substitution of a single Cys residue by selenocysteine (Sec; U) occurs occasionally in nature. Using a recent method for site-specific Sec incorporation into proteins, each of the four Ni-coordinating cysteine residues in the oxygen-tolerant Escherichia coli [NiFe]-hydrogenase-1 (Hyd-1) has been replaced by U to identify its importance for enzyme function. Steady-state solution activity of each Sec-substituted enzyme (on a per-milligram basis) is lowered, although this may reflect the unquantified presence of recalcitrant inactive/immature/misfolded forms. Protein film electrochemistry, however, reveals detailed kinetic data that are independent of absolute activities. Like native Hyd-1, the variants have low apparent KMH2 values, do not produce H2 at pH 6, and display the same onset overpotential for H2 oxidation. Mechanistically important differences were identified for the C576U variant bearing the equivalent replacement found in native [NiFeSe]-hydrogenases, its extreme O2 tolerance (apparent KMH2 and Vmax [solution] values relative to native Hyd-1 of 0.13 and 0.04, respectively) implying the importance of a selenium atom in the position cis to the site where exogenous ligands (H-, H2, O2) bind. Observation of the same unusual electrocatalytic signature seen earlier for the proton transfer-defective E28Q variant highlights the direct role of the chalcogen atom (S/Se) at position 576 close to E28, with the caveat that Se is less effective than S in facilitating proton transfer away from the Ni during H2 oxidation by this enzyme.
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Affiliation(s)
- Rhiannon M Evans
- Inorganic Chemistry Laboratory, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Natalie Krahn
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511
| | - Bonnie J Murphy
- Inorganic Chemistry Laboratory, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Harrison Lee
- Inorganic Chemistry Laboratory, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Fraser A Armstrong
- Inorganic Chemistry Laboratory, University of Oxford, Oxford OX1 3QR, United Kingdom;
| | - Dieter Söll
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511;
- Department of Chemistry, Yale University, New Haven, CT 06520
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10
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Zhang L, Morello G, Carr SB, Armstrong FA. Aerobic Photocatalytic H2 Production by a [NiFe] Hydrogenase Engineered to Place a Silver Nanocluster in the Electron Relay. J Am Chem Soc 2020; 142:12699-12707. [DOI: 10.1021/jacs.0c04302] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Liyun Zhang
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, Oxfordshire United Kingdom
| | - Giorgio Morello
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, Oxfordshire United Kingdom
| | - Stephen B. Carr
- Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
| | - Fraser A. Armstrong
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, Oxfordshire United Kingdom
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11
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Nishikawa K, Ogata H, Higuchi Y. Structural Basis of the Function of [NiFe]-hydrogenases. CHEM LETT 2020. [DOI: 10.1246/cl.190814] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Koji Nishikawa
- Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
| | - Hideaki Ogata
- Institute of Low Temperature Science, Hokkaido University, Kita19Nishi8, Kita-ku, Sapporo, Hokkaido 060-0819, Japan
| | - Yoshiki Higuchi
- Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
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12
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Selvan D, Shi Y, Prasad P, Crane S, Zhang Y, Chakraborty S. The oxygen reactivity of an artificial hydrogenase designed in a reengineered copper storage protein. Dalton Trans 2020; 49:1928-1934. [DOI: 10.1039/c9dt04913d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The O2 reactivity of an artificial biomolecular hydrogenase, the nickel binding protein (NBP) is investigated.
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Affiliation(s)
- Dhanashree Selvan
- Department of Chemistry and Biochemistry
- University of Mississippi
- University
- USA
| | - Yelu Shi
- Department of Chemistry and Chemical Biology
- Stevens Institute of Technology
- USA
| | - Pallavi Prasad
- Department of Chemistry and Biochemistry
- University of Mississippi
- University
- USA
| | - Skyler Crane
- Department of Chemistry and Biochemistry
- University of Mississippi
- University
- USA
| | - Yong Zhang
- Department of Chemistry and Chemical Biology
- Stevens Institute of Technology
- USA
| | - Saumen Chakraborty
- Department of Chemistry and Biochemistry
- University of Mississippi
- University
- USA
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13
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Zanello P. Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part IV. Canonical, non-canonical and hybrid iron-sulfur proteins. J Struct Biol 2019; 205:103-120. [PMID: 30677521 DOI: 10.1016/j.jsb.2019.01.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Revised: 01/11/2019] [Accepted: 01/11/2019] [Indexed: 12/26/2022]
Abstract
A plethora of proteins are able to express iron-sulfur clusters, but have a clear picture of the different types of proteins and the different iron-sulfur clusters they harbor it is not easy. In the last five years we have reviewed structure/electrochemistry of metalloproteins expressing: (i) single types of iron-sulfur clusters (namely: {Fe(Cys)4}, {[Fe2S2](Cys)4}, {[Fe2S2](Cys)3(X)} (X = Asp, Arg, His), {[Fe2S2](Cys)2(His)2}, {[Fe3S4](Cys)3}, {[Fe4S4](Cys)4} and {[Fe4S4](Cys)3(nonthiolate ligand)} cores); (ii) metalloproteins harboring iron-sulfur centres of different nuclearities (namely: [4Fe-4S] and [2Fe-2S], [4Fe-4S] and [3Fe-4S], and [4Fe-4S], [3Fe-4S] and [2Fe-2S] clusters. Our target is now to review structure and electrochemistry of proteins harboring canonical, non-canonical and hybrid iron-sulfur proteins.
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Affiliation(s)
- Piero Zanello
- Dipartimento di Biotecnologie, Chimica e Farmacia dell'Università di Siena, Via A. De Gasperi 2, 53100 Siena, Italy
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14
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Evans RM, Siritanaratkul B, Megarity CF, Pandey K, Esterle TF, Badiani S, Armstrong FA. The value of enzymes in solar fuels research – efficient electrocatalysts through evolution. Chem Soc Rev 2019; 48:2039-2052. [DOI: 10.1039/c8cs00546j] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Enzymes which evolved more than 2 billion years ago set exceptional standards for electrocatalysts being sought today.
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Affiliation(s)
- Rhiannon M. Evans
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | | | - Clare F. Megarity
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Kavita Pandey
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Thomas F. Esterle
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Selina Badiani
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
| | - Fraser A. Armstrong
- Department of Chemistry
- Inorganic Chemistry Laboratory
- University of Oxford
- Oxford
- UK
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15
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Noor NDM, Matsuura H, Nishikawa K, Tai H, Hirota S, Kim J, Kang J, Tateno M, Yoon KS, Ogo S, Kubota S, Shomura Y, Higuchi Y. Redox-dependent conformational changes of a proximal [4Fe-4S] cluster in Hyb-type [NiFe]-hydrogenase to protect the active site from O 2. Chem Commun (Camb) 2018; 54:12385-12388. [PMID: 30328414 DOI: 10.1039/c8cc06261g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Citrobacter sp. S-77 [NiFe]-hydrogenase harbors a standard [4Fe-4S] cluster proximal to the Ni-Fe active site. The presence of relocatable water molecules and a flexible aspartate enables the [4Fe-4S] to display redox-dependent conformational changes. These structural features are proposed to be the key aspects that protect the active site from O2 attack.
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Affiliation(s)
- Noor Dina Muhd Noor
- Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
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16
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Tai H, Higuchi Y, Hirota S. Comprehensive reaction mechanisms at and near the Ni-Fe active sites of [NiFe] hydrogenases. Dalton Trans 2018. [PMID: 29532823 DOI: 10.1039/c7dt04910b] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
[NiFe] hydrogenase (H2ase) catalyzes the oxidation of dihydrogen to two protons and two electrons and/or its reverse reaction. For this simple reaction, the enzyme has developed a sophisticated but intricate mechanism with heterolytic cleavage of dihydrogen (or a combination of a hydride and a proton), where its Ni-Fe active site exhibits various redox states. Recently, thermodynamic parameters of the acid-base equilibrium for activation-inactivation, a new intermediate in the catalytic reaction, and new crystal structures of [NiFe] H2ases have been reported, providing significant insights into the activation-inactivation and catalytic reaction mechanisms of [NiFe] H2ases. This Perspective provides an overview of the reaction mechanisms of [NiFe] H2ases based on these new findings.
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Affiliation(s)
- Hulin Tai
- Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama-cho, Ikoma-shi, Nara 630-0192, Japan.
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17
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Yates NDJ, Fascione MA, Parkin A. Methodologies for "Wiring" Redox Proteins/Enzymes to Electrode Surfaces. Chemistry 2018; 24:12164-12182. [PMID: 29637638 PMCID: PMC6120495 DOI: 10.1002/chem.201800750] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2018] [Indexed: 12/22/2022]
Abstract
The immobilization of redox proteins or enzymes onto conductive surfaces has application in the analysis of biological processes, the fabrication of biosensors, and in the development of green technologies and biochemical synthetic approaches. This review evaluates the methods through which redox proteins can be attached to electrode surfaces in a "wired" configuration, that is, one that facilitates direct electron transfer. The feasibility of simple electroactive adsorption onto a range of electrode surfaces is illustrated, with a highlight on the recent advances that have been achieved in biotechnological device construction using carbon materials and metal oxides. The covalent crosslinking strategies commonly used for the modification and biofunctionalization of electrode surfaces are also evaluated. Recent innovations in harnessing chemical biology methods for electrically wiring redox biology to surfaces are emphasized.
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Affiliation(s)
| | | | - Alison Parkin
- Department of ChemistryUniversity of YorkHeslington RoadYorkYO10 5DDUK
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18
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Evans RM, Ash PA, Beaton SE, Brooke EJ, Vincent KA, Carr SB, Armstrong FA. Mechanistic Exploitation of a Self-Repairing, Blocked Proton Transfer Pathway in an O2-Tolerant [NiFe]-Hydrogenase. J Am Chem Soc 2018; 140:10208-10220. [DOI: 10.1021/jacs.8b04798] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Rhiannon M. Evans
- Department of Chemistry, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Philip A. Ash
- Department of Chemistry, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Stephen E. Beaton
- Department of Chemistry, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Emily J. Brooke
- Department of Chemistry, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Kylie A. Vincent
- Department of Chemistry, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Stephen B. Carr
- Research Complex at Harwell, Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, United Kingdom
- Department of Biochemistry, University of Oxford, Oxford OX1 3QU, United Kingdom
| | - Fraser A. Armstrong
- Department of Chemistry, University of Oxford, Oxford OX1 3QR, United Kingdom
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19
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Volbeda A, Mouesca JM, Darnault C, Roessler MM, Parkin A, Armstrong FA, Fontecilla-Camps JC. X-ray structural, functional and computational studies of the O 2-sensitive E. coli hydrogenase-1 C19G variant reveal an unusual [4Fe-4S] cluster. Chem Commun (Camb) 2018; 54:7175-7178. [PMID: 29888350 DOI: 10.1039/c8cc02896f] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The crystal structure of the Escherichia coli O2-sensitive C19G [NiFe]-hydrogenase-1 variant shows that the mutation results in a novel FeS cluster, proximal to the Ni-Fe active site. While the proximal cluster of the native O2-tolerant enzyme can transfer two electrons to that site, EPR spectroscopy shows that the modified cluster can transfer only one electron, this shortfall coinciding with O2 sensitivity. Computational studies on electron transfer help to explain how the structural and redox properties of the novel FeS cluster modulate the observed phenotype.
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Affiliation(s)
- A Volbeda
- Univ. Grenoble Alpes, CEA, CNRS, IBS, F-38000 Grenoble, France.
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20
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Zanello P. Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part II. [4Fe-4S] and [3Fe-4S] iron-sulfur proteins. J Struct Biol 2018; 202:250-263. [DOI: 10.1016/j.jsb.2018.01.010] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 01/11/2018] [Accepted: 01/29/2018] [Indexed: 01/27/2023]
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21
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The structure of hydrogenase-2 from Escherichia coli: implications for H 2-driven proton pumping. Biochem J 2018; 475:1353-1370. [PMID: 29555844 PMCID: PMC5902676 DOI: 10.1042/bcj20180053] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2018] [Revised: 03/12/2018] [Accepted: 03/16/2018] [Indexed: 01/19/2023]
Abstract
Under anaerobic conditions, Escherichia coli is able to metabolize molecular hydrogen via the action of several [NiFe]-hydrogenase enzymes. Hydrogenase-2, which is typically present in cells at low levels during anaerobic respiration, is a periplasmic-facing membrane-bound complex that functions as a proton pump to convert energy from hydrogen (H2) oxidation into a proton gradient; consequently, its structure is of great interest. Empirically, the complex consists of a tightly bound core catalytic module, comprising large (HybC) and small (HybO) subunits, which is attached to an Fe–S protein (HybA) and an integral membrane protein (HybB). To date, efforts to gain a more detailed picture have been thwarted by low native expression levels of Hydrogenase-2 and the labile interaction between HybOC and HybA/HybB subunits. In the present paper, we describe a new overexpression system that has facilitated the determination of high-resolution crystal structures of HybOC and, hence, a prediction of the quaternary structure of the HybOCAB complex.
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22
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Ash PA, Carr SB, Reeve HA, Skorupskaitė A, Rowbotham JS, Shutt R, Frogley MD, Evans RM, Cinque G, Armstrong FA, Vincent KA. Generating single metalloprotein crystals in well-defined redox states: electrochemical control combined with infrared imaging of a NiFe hydrogenase crystal. Chem Commun (Camb) 2018; 53:5858-5861. [PMID: 28504793 PMCID: PMC5708527 DOI: 10.1039/c7cc02591b] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We describe an approach to generating and verifying well-defined redox states in metalloprotein single crystals by combining electrochemical control with synchrotron infrared microspectroscopic imaging. For NiFe hydrogenase 1 from Escherichia coli we demonstrate fully reversible and uniform electrochemical reduction from the oxidised inactive to the fully reduced state, and temporally resolve steps during this reduction.
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Affiliation(s)
- P A Ash
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
| | - S B Carr
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA, UK and Department of Biochemistry, University of Oxford, South Parks Road, Oxford, OX1 3QU, UK
| | - H A Reeve
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
| | - A Skorupskaitė
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
| | - J S Rowbotham
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
| | - R Shutt
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
| | - M D Frogley
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, UK
| | - R M Evans
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
| | - G Cinque
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0QX, UK
| | - F A Armstrong
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
| | - K A Vincent
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR, UK.
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23
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Abstract
Obtaining abundant pure hydrogen by reduction of water has an important implication in the development of clean and renewable energy. Hence research focused on the development of non-noble metal based facile and energy efficient catalysts for proton reduction is on the rise. However, for practical utilization, it is necessary that these complexes function unabated in the presence of atmospheric oxygen and other common contaminants in abundant water sources. There has been very little activity towards the development of oxygen-tolerant hydrogen producing catalysts. This article aims to draw attention to this issue of oxygen sensitivity in the HER and highlights the development of a few air-stable HER catalysts (enzymatic as well as artificial) elaborating the challenges involved and the techniques discovered to overcome this significant deterrent to large-scale hydrogen production by electrolysis from abundant water sources.
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Affiliation(s)
- Biswajit Mondal
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A&2B Raja S.C. Mullick Road, Jadavpur, Kolkata-700032, India.
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24
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Flanagan LA, Chidwick HS, Walton J, Moir JWB, Parkin A. Conserved Histidine Adjacent to the Proximal Cluster Tunes the Anaerobic Reductive Activation of Escherichia coli Membrane-Bound [NiFe] Hydrogenase-1. ChemElectroChem 2018; 5:855-860. [PMID: 29696103 PMCID: PMC5900901 DOI: 10.1002/celc.201800047] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Indexed: 12/13/2022]
Abstract
[NiFe] hydrogenases are electrocatalysts that oxidize H2 at a rapid rate without the need for precious metals. All membrane-bound [NiFe] hydrogenases (MBH) possess a histidine residue that points to the electron-transfer iron sulfur cluster closest ("proximal") to the [NiFe] H2-binding active site. Replacement of this amino acid with alanine induces O2 sensitivity, and this has been attributed to the role of the histidine in enabling the reversible O2-induced over-oxidation of the [Fe4S3Cys2] proximal cluster possessed by all O2-tolerant MBH. We have created an Escherichia coli Hyd-1 His-to-Ala variant and report O2-free electrochemical measurements at high potential that indicate the histidine-mediated [Fe4S3Cys2] cluster-opening/closing mechanism also underpins anaerobic reactivation. We validate these experiments by comparing them to the impact of an analogous His-to-Ala replacement in Escherichia coli Hyd-2, a [NiFe]-MBH that contains a [Fe4S4] center.
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Affiliation(s)
| | | | - Julia Walton
- Department of ChemistryUniversity of YorkHeslington, York
| | | | - Alison Parkin
- Department of ChemistryUniversity of YorkHeslington, York
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25
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Armstrong FA, Evans RM, Megarity CF. Protein Film Electrochemistry of Iron–Sulfur Enzymes. Methods Enzymol 2018; 599:387-407. [DOI: 10.1016/bs.mie.2017.11.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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26
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Breglia R, Greco C, Fantucci P, De Gioia L, Bruschi M. Theoretical investigation of aerobic and anaerobic oxidative inactivation of the [NiFe]-hydrogenase active site. Phys Chem Chem Phys 2018; 20:1693-1706. [DOI: 10.1039/c7cp06228a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The extraordinary capability of [NiFe]-hydrogenases to catalyse the reversible interconversion of protons and electrons into dihydrogen (H2) has stimulated numerous experimental and theoretical studies addressing the direct utilization of these enzymes in H2 production processes.
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Affiliation(s)
- Raffaella Breglia
- Department of Earth and Environmental Science
- University of Milano Bicocca
- 20126 Milan
- Italy
| | - Claudio Greco
- Department of Earth and Environmental Science
- University of Milano Bicocca
- 20126 Milan
- Italy
| | - Piercarlo Fantucci
- Department of Biotechnology and Biosciences
- University of Milano Bicocca
- 20126 Milan
- Italy
| | - Luca De Gioia
- Department of Biotechnology and Biosciences
- University of Milano Bicocca
- 20126 Milan
- Italy
| | - Maurizio Bruschi
- Department of Earth and Environmental Science
- University of Milano Bicocca
- 20126 Milan
- Italy
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27
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Adamson H, Robinson M, Wright JJ, Flanagan LA, Walton J, Elton D, Gavaghan DJ, Bond AM, Roessler MM, Parkin A. Retuning the Catalytic Bias and Overpotential of a [NiFe]-Hydrogenase via a Single Amino Acid Exchange at the Electron Entry/Exit Site. J Am Chem Soc 2017; 139:10677-10686. [PMID: 28697596 PMCID: PMC5562392 DOI: 10.1021/jacs.7b03611] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The redox chemistry of the electron entry/exit site in Escherichia coli hydrogenase-1 is shown to play a vital role in tuning biocatalysis. Inspired by nature, we generate a HyaA-R193L variant to disrupt a proposed Arg-His cation-π interaction in the secondary coordination sphere of the outermost, "distal", iron-sulfur cluster. This rewires the enzyme, enhancing the relative rate of H2 production and the thermodynamic efficiency of H2 oxidation catalysis. On the basis of Fourier transformed alternating current voltammetry measurements, we relate these changes in catalysis to a shift in the distal [Fe4S4]2+/1+ redox potential, a previously experimentally inaccessible parameter. Thus, metalloenzyme chemistry is shown to be tuned by the second coordination sphere of an electron transfer site distant from the catalytic center.
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Affiliation(s)
- Hope Adamson
- Department of Chemistry, University of York , Heslington, York YO10 5DD, U.K
| | - Martin Robinson
- Department of Computer Science, University of Oxford , Oxford, OX1 3QD, U.K
| | - John J Wright
- School of Biological and Chemical Sciences, Queen Mary University of London , Mile End Road, London, E1 4NS, U.K
| | - Lindsey A Flanagan
- Department of Chemistry, University of York , Heslington, York YO10 5DD, U.K
| | - Julia Walton
- Department of Chemistry, University of York , Heslington, York YO10 5DD, U.K
| | - Darrell Elton
- Department of Engineering, School of Engineering and Mathematical Sciences, La Trobe University , Melbourne, Victoria 3086, Australia
| | - David J Gavaghan
- Department of Computer Science, University of Oxford , Oxford, OX1 3QD, U.K
| | - Alan M Bond
- School of Chemistry, Monash University , Clayton, Victoria 3800, Australia
| | - Maxie M Roessler
- School of Biological and Chemical Sciences, Queen Mary University of London , Mile End Road, London, E1 4NS, U.K
| | - Alison Parkin
- Department of Chemistry, University of York , Heslington, York YO10 5DD, U.K
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28
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Abstract
Hydrogenase-1 (Hyd-1) from Escherichia coli is a membrane-bound enzyme that catalyses the reversible oxidation of molecular H2 The active site contains one Fe and one Ni atom and several conserved amino acids including an arginine (Arg(509)), which interacts with two conserved aspartate residues (Asp(118) and Asp(574)) forming an outer shell canopy over the metals. There is also a highly conserved glutamate (Glu(28)) positioned on the opposite side of the active site to the canopy. The mechanism of hydrogen activation has been dissected by site-directed mutagenesis to identify the catalytic base responsible for splitting molecular hydrogen and possible proton transfer pathways to/from the active site. Previous reported attempts to mutate residues in the canopy were unsuccessful, leading to an assumption of a purely structural role. Recent discoveries, however, suggest a catalytic requirement, for example replacing the arginine with lysine (R509K) leaves the structure virtually unchanged, but catalytic activity falls by more than 100-fold. Variants containing amino acid substitutions at either or both, aspartates retain significant activity. We now propose a new mechanism: heterolytic H2 cleavage is via a mechanism akin to that of a frustrated Lewis pair (FLP), where H2 is polarized by simultaneous binding to the metal(s) (the acid) and a nitrogen from Arg(509) (the base).
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29
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Puggioni V, Tempel S, Latifi A. Distribution of Hydrogenases in Cyanobacteria: A Phylum-Wide Genomic Survey. Front Genet 2016; 7:223. [PMID: 28083017 PMCID: PMC5186783 DOI: 10.3389/fgene.2016.00223] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2016] [Accepted: 12/13/2016] [Indexed: 01/02/2023] Open
Abstract
Microbial Molecular hydrogen (H2) cycling plays an important role in several ecological niches. Hydrogenases (H2ases), enzymes involved in H2 metabolism, are of great interest for investigating microbial communities, and producing BioH2. To obtain an overall picture of the genetic ability of Cyanobacteria to produce H2ases, we conducted a phylum wide analysis of the distribution of the genes encoding these enzymes in 130 cyanobacterial genomes. The concomitant presence of the H2ase and genes involved in the maturation process, and that of well-conserved catalytic sites in the enzymes were the three minimal criteria used to classify a strain as being able to produce a functional H2ase. The [NiFe] H2ases were found to be the only enzymes present in this phylum. Fifty-five strains were found to be potentially able produce the bidirectional Hox enzyme and 33 to produce the uptake (Hup) enzyme. H2 metabolism in Cyanobacteria has a broad ecological distribution, since only the genomes of strains collected from the open ocean do not possess hox genes. In addition, the presence of H2ase was found to increase in the late branching clades of the phylogenetic tree of the species. Surprisingly, five cyanobacterial genomes were found to possess homologs of oxygen tolerant H2ases belonging to groups 1, 3b, and 3d. Overall, these data show that H2ases are widely distributed, and are therefore probably of great functional importance in Cyanobacteria. The present finding that homologs to oxygen-tolerant H2ases are present in this phylum opens new perspectives for applying the process of photosynthesis in the field of H2 production.
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Affiliation(s)
- Vincenzo Puggioni
- Laboratoire de Chimie Bactérienne UMR 7283, Centre National de la Recherche Scientifique (CNRS), Aix-Marseille University Marseille, France
| | - Sébastien Tempel
- Laboratoire de Chimie Bactérienne UMR 7283, Centre National de la Recherche Scientifique (CNRS), Aix-Marseille University Marseille, France
| | - Amel Latifi
- Laboratoire de Chimie Bactérienne UMR 7283, Centre National de la Recherche Scientifique (CNRS), Aix-Marseille University Marseille, France
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30
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Brooke EJ, Evans RM, Islam STA, Roberts GM, Wehlin SAM, Carr SB, Phillips SEV, Armstrong FA. Importance of the Active Site “Canopy” Residues in an O2-Tolerant [NiFe]-Hydrogenase. Biochemistry 2016; 56:132-142. [DOI: 10.1021/acs.biochem.6b00868] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
| | | | | | - Gerri M. Roberts
- Division
of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | | | - Stephen B. Carr
- Research
Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, U.K
- Department
of Biochemistry, University of Oxford, Oxford, U.K
| | - Simon E. V. Phillips
- Research
Complex at Harwell, Rutherford Appleton Laboratory, Harwell Campus, Didcot, U.K
- Department
of Biochemistry, University of Oxford, Oxford, U.K
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31
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Abstract
Hydrogenases are enzymes of great biotechnological relevance because they catalyse the interconversion of H2, water (protons) and electricity using non-precious metal catalytic active sites. Electrochemical studies into the reactivity of NiFe membrane-bound hydrogenases (MBH) have provided a particularly detailed insight into the reactivity and mechanism of this group of enzymes. Significantly, the control centre for enabling O2 tolerance has been revealed as the electron-transfer relay of FeS clusters, rather than the NiFe bimetallic active site. The present review paper will discuss how electrochemistry results have complemented those obtained from structural and spectroscopic studies, to present a complete picture of our current understanding of NiFe MBH.
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32
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Ogata H, Lubitz W, Higuchi Y. Structure and function of [NiFe] hydrogenases. J Biochem 2016; 160:251-258. [PMID: 27493211 DOI: 10.1093/jb/mvw048] [Citation(s) in RCA: 68] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 07/06/2016] [Indexed: 12/22/2022] Open
Abstract
Hydrogenases catalyze the reversible conversion of molecular hydrogen to protons and electrons via a heterolytic splitting mechanism. The active sites of [NiFe] hydrogenases comprise a dinuclear Ni-Fe center carrying CO and CN- ligands. The catalytic activity of the standard (O2-sensitive) [NiFe] hydrogenases vanishes under aerobic conditions. The O2-tolerant [NiFe] hydrogenases can sustain H2 oxidation activity under atmospheric conditions. These hydrogenases have very similar active site structures that change the ligand sphere during the activation/catalytic process. An important structural difference between these hydrogenases has been found for the proximal iron-sulphur cluster located in the vicinity of the active site. This unprecedented [4Fe-3S]-6Cys cluster can supply two electrons, which lead to rapid recovery of the O2 inactivation, to the [NiFe] active site.
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Affiliation(s)
- Hideaki Ogata
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, Mülheim an der Ruhr 45470, Germany
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, Mülheim an der Ruhr 45470, Germany
| | - Yoshiki Higuchi
- Department of Life Science, Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan .,RIKEN SPring-8 Center, 1-1-1 Koto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.,CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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Flanagan LA, Wright JJ, Roessler MM, Moir JW, Parkin A. Re-engineering a NiFe hydrogenase to increase the H2 production bias while maintaining native levels of O2 tolerance. Chem Commun (Camb) 2016; 52:9133-6. [PMID: 27055899 PMCID: PMC5040170 DOI: 10.1039/c6cc00515b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Accepted: 03/31/2016] [Indexed: 11/30/2022]
Abstract
Naturally occurring oxygen tolerant NiFe membrane bound hydrogenases have a conserved catalytic bias towards hydrogen oxidation which limits their technological value. We present an Escherichia coli Hyd-1 amino acid exchange that apparently causes the catalytic rate of H2 production to double but does not impact the O2 tolerance.
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Affiliation(s)
- Lindsey A Flanagan
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
| | - John J Wright
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - Maxie M Roessler
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, UK
| | - James W Moir
- Department of Biology, University of York, York YO10 5DD, UK
| | - Alison Parkin
- Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK.
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Armstrong FA, Evans RM, Hexter SV, Murphy BJ, Roessler MM, Wulff P. Guiding Principles of Hydrogenase Catalysis Instigated and Clarified by Protein Film Electrochemistry. Acc Chem Res 2016; 49:884-92. [PMID: 27104487 DOI: 10.1021/acs.accounts.6b00027] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Protein film electrochemistry (PFE) is providing cutting-edge insight into the chemical principles underpinning biological hydrogen. Attached to an electrode, many enzymes exhibit "reversible" electrocatalytic behavior, meaning that a catalyzed redox reaction appears reversible or quasi-reversible when viewed by cyclic voltammetry. This efficiency is most relevant for enzymes that are inspiring advances in renewable energy, such as hydrogen-activating and CO2-reducing enzymes. Exploiting the rich repertoire of available instrumental methods, PFE experiments yield both a general snapshot and fine detail, all from tiny samples of enzyme. The dynamic electrochemical investigations blaze new trails and add exquisite detail to the information gained from structural and spectroscopic studies. This Account describes recent investigations of hydrogenases carried out in Oxford, including ideas initiated with PFE and followed through with complementary techniques, all contributing to an eventual complete picture of fast and efficient H2 activation without Pt. By immobilization of an enzyme on an electrode, catalytic electron flow and the chemistry controlling it can be addressed at the touch of a button. The buried nature of the active site means that structures that have been determined by crystallography or spectroscopy are likely to be protected, retained, and fully relevant in a PFE experiment. An electrocatalysis model formulated for the PFE of immobilized enzymes predicts interesting behavior and gives insight into why some hydrogenases are H2 producers and others are H2 oxidizers. Immobilization also allows for easy addition and removal of inhibitors along with precise potential control, one interesting outcome being that formaldehyde forms a reversible complex with reduced [FeFe]-hydrogenases, thereby providing insight into the order of electron and proton transfers. Experiments on O2-tolerant [NiFe]-hydrogenases show that O2 behaves like a reversible inhibitor: it is also a substrate, and implicit in the description of some hydrogenases as "H2/O2 oxidoreductases" is the hypothesis that fast and efficient multielectron transfer is a key to O2 tolerance because it promotes complete reduction of O2 to harmless water. Not only is a novel [4Fe-3S] cluster (able to transfer two electrons consecutively) an important component, but connections to additional electron sources (other Fe-S clusters, an electrode, another quaternary structure unit, or the physiological membrane itself) ensure that H2 oxidation can be sustained in the presence of O2, as demonstrated with enzyme fuel cells able to operate on a H2/air mixture. Manipulating the H-H bond in the active site is the simplest proton-coupled electron-transfer reaction to be catalyzed by an enzyme. Unlike small molecular catalysts or the surfaces of materials, metalloenzymes are far better suited to engineering the all-important outer-coordination shell. Hence, recent successful site-directed mutagenesis of the conserved outer-shell "canopy" residues in a [NiFe]-hydrogenase opens up new opportunities for understanding the mechanism of H2 activation beyond the role of the inner coordination shell.
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Affiliation(s)
- Fraser A. Armstrong
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - Rhiannon M. Evans
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - Suzannah V. Hexter
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - Bonnie J. Murphy
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - Maxie M. Roessler
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - Philip Wulff
- Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
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Lauterbach L, Gee LB, Pelmenschikov V, Jenney FE, Kamali S, Yoda Y, Adams MWW, Cramer SP. Characterization of the [3Fe-4S](0/1+) cluster from the D14C variant of Pyrococcus furiosus ferredoxin via combined NRVS and DFT analyses. Dalton Trans 2016; 45:7215-9. [PMID: 27063792 PMCID: PMC4940129 DOI: 10.1039/c5dt04760a] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The D14C variant of Pyrococcus furiosus ferredoxin provides an extraordinary framework to investigate a [3Fe-4S] cluster at two oxidation levels and compare the results to its physiologic [4Fe-4S] counterpart in the very same protein. Our spectroscopic and computational study reveals vibrational property changes related to the electronic and structural aspects of both Fe-S clusters.
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Affiliation(s)
- Lars Lauterbach
- Department of Chemistry, University of California, Davis, CA 95616, USA and Institut für Chemie, Technische Universität Berlin, 10623 Berlin, Germany.
| | - Leland B Gee
- Department of Chemistry, University of California, Davis, CA 95616, USA
| | | | - Francis E Jenney
- Georgia Campus, Philadelphia College of Osteopathic Medicine, Suwanee, GA 30024, USA
| | - Saeed Kamali
- Department of Chemistry, University of California, Davis, CA 95616, USA and Department of Mechanical, Aerospace and Biomedical Engineering, University of Tennessee Space Institute, Tullahoma, TN 37388, USA
| | | | - Michael W W Adams
- Department of Biochemistry & Molecular Biology, Life Sciences Building, University of Georgia, Athens, GA 30602, USA
| | - Stephen P Cramer
- Department of Chemistry, University of California, Davis, CA 95616, USA and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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Wulff P, Thomas C, Sargent F, Armstrong FA. How the oxygen tolerance of a [NiFe]-hydrogenase depends on quaternary structure. J Biol Inorg Chem 2016; 21:121-34. [PMID: 26861789 PMCID: PMC4771823 DOI: 10.1007/s00775-015-1327-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2015] [Accepted: 12/23/2015] [Indexed: 11/28/2022]
Abstract
‘Oxygen-tolerant’ [NiFe]-hydrogenases can catalyze H2 oxidation under aerobic conditions, avoiding oxygenation and destruction of the active site. In one mechanism accounting for this special property, membrane-bound [NiFe]-hydrogenases accommodate a pool of electrons that allows an O2 molecule attacking the active site to be converted rapidly to harmless water. An important advantage may stem from having a dimeric or higher-order quaternary structure in which the electron-transfer relay chain of one partner is electronically coupled to that in the other. Hydrogenase-1 from E. coli has a dimeric structure in which the distal [4Fe-4S] clusters in each monomer are located approximately 12 Å apart, a distance conducive to fast electron tunneling. Such an arrangement can ensure that electrons from H2 oxidation released at the active site of one partner are immediately transferred to its counterpart when an O2 molecule attacks. This paper addresses the role of long-range, inter-domain electron transfer in the mechanism of O2-tolerance by comparing the properties of monomeric and dimeric forms of Hydrogenase-1. The results reveal a further interesting advantage that quaternary structure affords to proteins.
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Affiliation(s)
- Philip Wulff
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Claudia Thomas
- Department of Chemistry, University of Oxford, Oxford, UK
| | - Frank Sargent
- Division of Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
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Structure of an Actinobacterial-Type [NiFe]-Hydrogenase Reveals Insight into O 2 -Tolerant H 2 Oxidation. Structure 2016; 24:285-92. [DOI: 10.1016/j.str.2015.11.010] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Revised: 11/19/2015] [Accepted: 11/20/2015] [Indexed: 11/18/2022]
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38
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Volbeda A, Martin L, Liebgott PP, De Lacey AL, Fontecilla-Camps JC. [NiFe]-hydrogenases revisited: nickel-carboxamido bond formation in a variant with accrued O2-tolerance and a tentative re-interpretation of Ni-SI states. Metallomics 2016; 7:710-8. [PMID: 25780984 DOI: 10.1039/c4mt00309h] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
[NiFe]-hydrogenases are well-studied enzymes capable of oxidizing molecular hydrogen and reducing protons. EPR and FTIR spectroscopic studies have shown that these enzymes can be isolated in several redox states that include paramagnetic oxidized inactive Ni-A and Ni-B species and a reduced Ni-C form. The latter and the diamagnetic respectively more oxidized Ni-SI and more reduced Ni-R forms are generally thought to be involved in the catalytic cycle of [NiFe]-hydrogenases. With the exception of Ni-SI, these different stable states have been well characterized. Here, based on the crystal structure of a partially reduced Desulfovibrio fructosovorans (Df) enzyme and data from the literature we propose that at least one of the Ni-SI sub-states contains an unexpected combination of hydride and sulfenic acid moieties. We have also determined the structure of the less oxygen-sensitive Df [NiFe]-hydrogenase V74C mutant and found that more than half of the active site nickel occupies a novel position, called Ni'. In this new position, the metal ion is coordinated by two cysteine thiolates, a bridging species modeled as SH(-) and a main chain carboxamido N atom. The Ni' coordination is similar to the one found in Ni superoxide dismutase, an enzyme that operates at significantly more positive potentials than [NiFe]-hydrogenases. We propose that the oxygen-tolerance of the V74C variant results from a high potential stabilization of a Ni'(iii) species induced by the change in the metal ion coordination sphere. We also propose that transient Ni'(iii) species can rapidly attract successive electrons from the Fe4S4 proximal cluster accelerating the reduction of oxygen to water and hydroxide. The naturally occurring oxygen-tolerant [NiFe]-hydrogenases have an unusual proximal cluster that has been shown to be exceptionally plastic and capable of undergoing two successive one-electron oxidations. This double oxidation is modulated by the migration of one of the iron atoms in the cluster to the main chain where, as Fe(iii), it forms a bond with a carboxamido N ligand. Like in the Df V74C variant the electrons from the proximal cluster help reducing O2 to H2O and OH(-). In conclusion, in both cases a metal-carboxamido bond may explain, at least partially, the observed oxygen tolerance.
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Wang Y, Esterle TF, Armstrong FA. Electrocatalysis by H2–O2 membrane-free fuel cell enzymes in aqueous microenvironments confined by an ionic liquid. RSC Adv 2016. [DOI: 10.1039/c6ra06548a] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A synaptic enzyme fuel cell comprising wet hydrogenase and bilirubin oxidase electrodes surrounded by ionic liquid shell.
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Affiliation(s)
- Yiduo Wang
- Department of Chemistry
- Inorganic Chemistry Laboratory
- Oxford OX1 3QR
- UK
| | - Thomas F. Esterle
- Department of Chemistry
- Inorganic Chemistry Laboratory
- Oxford OX1 3QR
- UK
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40
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Abstract
In Escherichia coli, hydrogen metabolism plays a prominent role in anaerobic physiology. The genome contains the capability to produce and assemble up to four [NiFe]-hydrogenases, each of which are known, or predicted, to contribute to different aspects of cellular metabolism. In recent years, there have been major advances in the understanding of the structure, function, and roles of the E. coli [NiFe]-hydrogenases. The membrane-bound, periplasmically oriented, respiratory Hyd-1 isoenzyme has become one of the most important paradigm systems for understanding an important class of oxygen-tolerant enzymes, as well as providing key information on the mechanism of hydrogen activation per se. The membrane-bound, periplasmically oriented, Hyd-2 isoenzyme has emerged as an unusual, bidirectional redox valve able to link hydrogen oxidation to quinone reduction during anaerobic respiration, or to allow disposal of excess reducing equivalents as hydrogen gas. The membrane-bound, cytoplasmically oriented, Hyd-3 isoenzyme is part of the formate hydrogenlyase complex, which acts to detoxify excess formic acid under anaerobic fermentative conditions and is geared towards hydrogen production under those conditions. Sequence identity between some Hyd-3 subunits and those of the respiratory NADH dehydrogenases has led to hypotheses that the activity of this isoenzyme may be tightly coupled to the formation of transmembrane ion gradients. Finally, the E. coli genome encodes a homologue of Hyd-3, termed Hyd-4, however strong evidence for a physiological role for E. coli Hyd-4 remains elusive. In this review, the versatile hydrogen metabolism of E. coli will be discussed and the roles and potential applications of the spectrum of different types of [NiFe]-hydrogenases available will be explored.
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41
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Radu V, Frielingsdorf S, Lenz O, Jeuken LJC. Reactivation from the Ni–B state in [NiFe] hydrogenase of Ralstonia eutropha is controlled by reduction of the superoxidised proximal cluster. Chem Commun (Camb) 2016; 52:2632-5. [DOI: 10.1039/c5cc10382g] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The tolerance towards oxic conditions of O2-tolerant [NiFe] hydrogenases has been attributed to an unusual [4Fe–3S] cluster that lies proximal to the [NiFe] active site.
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Affiliation(s)
- Valentin Radu
- School of Biomedical Sciences
- The Astbury Centre for Structural Molecular Biology
- University of Leeds
- Leeds LS2 9JT
- UK
| | - Stefan Frielingsdorf
- Institut für Chemie
- Sekretariat PC14
- Technische Universität Berlin
- 10623 Berlin
- Germany
| | - Oliver Lenz
- Institut für Chemie
- Sekretariat PC14
- Technische Universität Berlin
- 10623 Berlin
- Germany
| | - Lars J. C. Jeuken
- School of Biomedical Sciences
- The Astbury Centre for Structural Molecular Biology
- University of Leeds
- Leeds LS2 9JT
- UK
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42
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Hirst J, Roessler MM. Energy conversion, redox catalysis and generation of reactive oxygen species by respiratory complex I. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2015; 1857:872-83. [PMID: 26721206 PMCID: PMC4893023 DOI: 10.1016/j.bbabio.2015.12.009] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Figures] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 12/15/2015] [Accepted: 12/16/2015] [Indexed: 12/30/2022]
Abstract
Complex I (NADH:ubiquinone oxidoreductase) is critical for respiration in mammalian mitochondria. It oxidizes NADH produced by the Krebs' tricarboxylic acid cycle and β-oxidation of fatty acids, reduces ubiquinone, and transports protons to contribute to the proton-motive force across the inner membrane. Complex I is also a significant contributor to cellular oxidative stress. In complex I, NADH oxidation by a flavin mononucleotide, followed by intramolecular electron transfer along a chain of iron–sulfur clusters, delivers electrons and energy to bound ubiquinone. Either at cluster N2 (the terminal cluster in the chain) or upon the binding/reduction/dissociation of ubiquinone/ubiquinol, energy from the redox process is captured to initiate long-range energy transfer through the complex and drive proton translocation. This review focuses on current knowledge of how the redox reaction and proton transfer are coupled, with particular emphasis on the formation and role of semiquinone intermediates in both energy transduction and reactive oxygen species production. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt. Current knowledge of the redox reactions catalyzed by complex I is reviewed. Possible quinone reduction pathways are presented. The presence and number of semiquinone intermediates are deliberated. The involvement of cluster N2/semiquinones in coupled proton transfer is discussed. Evidence for reactive oxygen species production by semiquinones is examined.
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Affiliation(s)
- Judy Hirst
- Medical Research Council Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Cambridge Biomedical Campus, Hills Road, Cambridge, CB2 0XY, United Kingdom.
| | - Maxie M Roessler
- School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS, United Kingdom.
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43
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Mechanism of hydrogen activation by [NiFe] hydrogenases. Nat Chem Biol 2015; 12:46-50. [DOI: 10.1038/nchembio.1976] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 10/26/2015] [Indexed: 11/08/2022]
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44
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Wang H, Yoda Y, Ogata H, Tanaka Y, Lubitz W. A strenuous experimental journey searching for spectroscopic evidence of a bridging nickel-iron-hydride in [NiFe] hydrogenase. JOURNAL OF SYNCHROTRON RADIATION 2015; 22:1334-44. [PMID: 26524296 PMCID: PMC4629863 DOI: 10.1107/s1600577515017816] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/24/2015] [Accepted: 09/23/2015] [Indexed: 05/24/2023]
Abstract
Direct spectroscopic evidence for a hydride bridge in the Ni-R form of [NiFe] hydrogenase has been obtained using iron-specific nuclear resonance vibrational spectroscopy (NRVS). The Ni-H-Fe wag mode at 675 cm(-1) is the first spectroscopic evidence for a bridging hydride in Ni-R as well as the first iron-hydride-related NRVS feature observed for a biological system. Although density function theory (DFT) calculation assisted the determination of the Ni-R structure, it did not predict the Ni-H-Fe wag mode at ∼ 675 cm(-1) before NRVS. Instead, the observed Ni-H-Fe mode provided a critical reference for the DFT calculations. While the overall science about Ni-R is presented and discussed elsewhere, this article focuses on the long and strenuous experimental journey to search for and experimentally identify the Ni-H-Fe wag mode in a Ni-R sample. As a methodology, the results presented here will go beyond Ni-R and hydrogenase research and will also be of interest to other scientists who use synchrotron radiation for measuring dilute samples or weak spectroscopic features.
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Affiliation(s)
- Hongxin Wang
- Department of Chemistry, University of California, 1 Cyclotron Road, Davis, CA 95616, USA
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Yoshitaka Yoda
- Research and Utilization Division, SPring-8/JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
| | - Hideaki Ogata
- Max Planck Institute for Chemical Energy Conversion, D-45470 Mülheim an der Ruhr, Germany
| | - Yoshihito Tanaka
- Research and Utilization Division, SPring-8/JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan
- Graduate School of Material Science, University of Hyogo, 3-2-1 Kouto, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion, D-45470 Mülheim an der Ruhr, Germany
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45
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Kwan P, McIntosh CL, Jennings DP, Hopkins RC, Chandrayan SK, Wu CH, Adams MWW, Jones AK. The [NiFe]-Hydrogenase of Pyrococcus furiosus Exhibits a New Type of Oxygen Tolerance. J Am Chem Soc 2015; 137:13556-65. [PMID: 26436715 DOI: 10.1021/jacs.5b07680] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
We report the first direct electrochemical characterization of the impact of oxygen on the hydrogen oxidation activity of an oxygen-tolerant, group 3, soluble [NiFe]-hydrogenase: hydrogenase I from Pyrococcus furiosus (PfSHI), which grows optimally near 100 °C. Chronoamperometric experiments were used to probe the sensitivity of PfSHI hydrogen oxidation activity to both brief and prolonged exposure to oxygen. For experiments between 15 and 80 °C, following short (<200 s) exposure to 14 μM O2 under oxidizing conditions, PfSHI always maintains some fraction of its initial hydrogen oxidation activity; i.e., it is oxygen-tolerant. Reactivation experiments show that two inactive states are formed by interaction with oxygen and both can be quickly (<150 s) reactivated. Analogous experiments, in which the interval of oxygen exposure is extended to 900 s, reveal that the response is highly temperature-dependent. At 25 °C, under sustained 1% O2/ 99% H2 exposure, the H2oxidation activity drops nearly to zero. However, at 80 °C, up to 32% of the enzyme's oxidation activity is retained. Reactivation of PfSHI following sustained exposure to oxygen occurs on a much longer time scale (tens of minutes), suggesting that a third inactive species predominates under these conditions. These results stand in contrast to the properties of oxygen-tolerant, group 1 [NiFe]-hydrogenases, which form a single state upon reaction with oxygen, and we propose that this new type of hydrogenase should be referred to as oxygen-resilient. Furthermore, PfSHI, like other group 3 [NiFe]-hydrogenases, does not possess the proximal [4Fe3S] cluster associated with the oxygen tolerance of some group 1 enzymes. Thus, a new mechanism is necessary to explain the observed oxygen tolerance in soluble, group 3 [NiFe]-hydrogenases, and we present a model integrating both electrochemical and spectroscopic results to define the relationships of these inactive states.
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Affiliation(s)
- Patrick Kwan
- Department of Chemistry and Biochemistry, Arizona State University , Tempe, Arizona 85287, United States
| | - Chelsea L McIntosh
- Department of Chemistry and Biochemistry, Arizona State University , Tempe, Arizona 85287, United States
| | - David P Jennings
- Department of Chemistry and Biochemistry, Arizona State University , Tempe, Arizona 85287, United States
| | - R Chris Hopkins
- Department of Biochemistry and Molecular Biology, The University of Georgia , Athens, Georgia 30602, United States
| | - Sanjeev K Chandrayan
- Department of Biochemistry and Molecular Biology, The University of Georgia , Athens, Georgia 30602, United States
| | - Chang-Hao Wu
- Department of Biochemistry and Molecular Biology, The University of Georgia , Athens, Georgia 30602, United States
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, The University of Georgia , Athens, Georgia 30602, United States
| | - Anne K Jones
- Department of Chemistry and Biochemistry, Arizona State University , Tempe, Arizona 85287, United States
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46
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McDowall JS, Hjersing MC, Palmer T, Sargent F. Dissection and engineering of the Escherichia coli formate hydrogenlyase complex. FEBS Lett 2015; 589:3141-7. [PMID: 26358294 DOI: 10.1016/j.febslet.2015.08.043] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 08/26/2015] [Accepted: 08/28/2015] [Indexed: 11/25/2022]
Abstract
The Escherichia coli formate hydrogenlyase (FHL) complex is produced under fermentative conditions and couples formate oxidation to hydrogen production. In this work, the architecture of FHL has been probed by analysing affinity-tagged complexes from various genetic backgrounds. In a successful attempt to stabilize the complex, a strain encoding a fusion between FdhF and HycB has been engineered and characterised. Finally, site-directed mutagenesis of the hycG gene was performed, which is predicted to encode a hydrogenase subunit important for regulating sensitivity to oxygen. This work helps to define the core components of FHL and provides solutions to improving the stability of the enzyme.
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Affiliation(s)
| | | | - Tracy Palmer
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK
| | - Frank Sargent
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, UK.
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47
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Hydride bridge in [NiFe]-hydrogenase observed by nuclear resonance vibrational spectroscopy. Nat Commun 2015; 6:7890. [PMID: 26259066 PMCID: PMC4531378 DOI: 10.1038/ncomms8890] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 06/18/2015] [Indexed: 11/28/2022] Open
Abstract
The metabolism of many anaerobes relies on [NiFe]-hydrogenases, whose characterization when bound to substrates has proven non-trivial. Presented here is direct evidence for a hydride bridge in the active site of the 57Fe-labelled fully reduced Ni-R form of Desulfovibrio vulgaris Miyazaki F [NiFe]-hydrogenase. A unique ‘wagging' mode involving H− motion perpendicular to the Ni(μ-H)57Fe plane was studied using 57Fe-specific nuclear resonance vibrational spectroscopy and density functional theory (DFT) calculations. On Ni(μ-D)57Fe deuteride substitution, this wagging causes a characteristic perturbation of Fe–CO/CN bands. Spectra have been interpreted by comparison with Ni(μ-H/D)57Fe enzyme mimics [(dppe)Ni(μ-pdt)(μ-H/D)57Fe(CO)3]+ and DFT calculations, which collectively indicate a low-spin Ni(II)(μ-H)Fe(II) core for Ni-R, with H− binding Ni more tightly than Fe. The present methodology is also relevant to characterizing Fe–H moieties in other important natural and synthetic catalysts. Understanding the catalytic mechanism of redox-active hydrogenases is a key to efficient hydrogen production and consumption. Here, the authors use nuclear resonance vibrational spectroscopy to study [NiFe]-hydrogenase, and observe a bridging hydride structure in an EPR silent intermediate.
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48
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Wang VCC, Islam STA, Can M, Ragsdale SW, Armstrong FA. Investigations by Protein Film Electrochemistry of Alternative Reactions of Nickel-Containing Carbon Monoxide Dehydrogenase. J Phys Chem B 2015; 119:13690-7. [PMID: 26176986 DOI: 10.1021/acs.jpcb.5b03098] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein film electrochemistry has been used to investigate reactions of highly active nickel-containing carbon monoxide dehydrogenases (CODHs). When attached to a pyrolytic graphite electrode, these enzymes behave as reversible electrocatalysts, displaying CO2 reduction or CO oxidation at minimal overpotential. The O2 sensitivity of CODH is suppressed by adding cyanide, a reversible inhibitor of CO oxidation, or by raising the electrode potential. Reduction of N2O, isoelectronic with CO2, is catalyzed by CODH, but the reaction is sluggish, despite a large overpotential, and results in inactivation. Production of H2 and formate under highly reducing conditions is consistent with calculations predicting that a nickel-hydrido species might be formed, but the very low rates suggest that such a species is not on the main catalytic pathway.
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Affiliation(s)
- Vincent C-C Wang
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K
| | - Shams T A Islam
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K
| | - Mehmet Can
- Department of Biological Chemistry, University of Michigan , Ann Arbor, Michigan 48109-0606, United States
| | - Stephen W Ragsdale
- Department of Biological Chemistry, University of Michigan , Ann Arbor, Michigan 48109-0606, United States
| | - Fraser A Armstrong
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford , South Parks Road, Oxford, OX1 3QR, U.K
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Murphy BJ, Hidalgo R, Roessler MM, Evans RM, Ash PA, Myers WK, Vincent KA, Armstrong FA. Discovery of Dark pH-Dependent H(+) Migration in a [NiFe]-Hydrogenase and Its Mechanistic Relevance: Mobilizing the Hydrido Ligand of the Ni-C Intermediate. J Am Chem Soc 2015; 137:8484-9. [PMID: 26103582 PMCID: PMC4500644 DOI: 10.1021/jacs.5b03182] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Despite extensive studies on [NiFe]-hydrogenases,
the mechanism
by which these enzymes produce and activate H2 so efficiently
remains unclear. A well-known EPR-active state produced under H2 and known as Ni-C is assigned as a NiIII–FeII species with a hydrido ligand in the bridging position between
the two metals. It has long been known that low-temperature photolysis
of Ni-C yields distinctive EPR-active states, collectively termed
Ni-L, that are attributed to migration of the bridging-H species as
a proton; however, Ni-L has mainly been regarded as an artifact with
no mechanistic relevance. It is now demonstrated, based on EPR and
infrared spectroscopic studies, that the Ni-C to Ni-L interconversion
in Hydrogenase-1 (Hyd-1) from Escherichia coli is a pH-dependent process that proceeds readily in the dark—proton
migration from Ni-C being favored as the pH is increased. The persistence
of Ni-L in Hyd-1 must relate to unassigned differences in proton affinities
of metal and adjacent amino acid sites, although the unusually high
reduction potentials of the adjacent Fe–S centers in this O2-tolerant hydrogenase might also be a contributory factor,
impeding elementary electron transfer off the [NiFe] site after proton
departure. The results provide compelling evidence that Ni-L is a
true, albeit elusive, catalytic intermediate of [NiFe]-hydrogenases.
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Affiliation(s)
- Bonnie J Murphy
- †Department of Chemistry and ‡Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Ricardo Hidalgo
- †Department of Chemistry and ‡Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Maxie M Roessler
- †Department of Chemistry and ‡Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Rhiannon M Evans
- †Department of Chemistry and ‡Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Philip A Ash
- †Department of Chemistry and ‡Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - William K Myers
- †Department of Chemistry and ‡Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Kylie A Vincent
- †Department of Chemistry and ‡Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford OX1 3QR, United Kingdom
| | - Fraser A Armstrong
- †Department of Chemistry and ‡Centre for Advanced Electron Spin Resonance, University of Oxford, Oxford OX1 3QR, United Kingdom
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50
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Hidalgo R, Ash PA, Healy AJ, Vincent KA. Infrared Spectroscopy During Electrocatalytic Turnover Reveals the Ni-L Active Site State During H2 Oxidation by a NiFe Hydrogenase. Angew Chem Int Ed Engl 2015; 54:7110-3. [PMID: 25925315 PMCID: PMC4531817 DOI: 10.1002/anie.201502338] [Citation(s) in RCA: 93] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2015] [Revised: 04/01/2015] [Indexed: 01/25/2023]
Abstract
A novel in situ IR spectroscopic approach is demonstrated for the characterization of hydrogenase during catalytic turnover. E. coli hydrogenase 1 (Hyd-1) is adsorbed on a high surface-area carbon electrode and subjected to the same electrochemical control and efficient supply of substrate as in protein film electrochemistry during spectral acquisition. The spectra reveal that the active site state known as Ni-L, observed in other NiFe hydrogenases only under illumination or at cryogenic temperatures, can be generated reversibly in the dark at ambient temperature under both turnover and non-turnover conditions. The observation that Ni-L is present at all potentials during turnover under H2 suggests that the final steps in the catalytic cycle of H2 oxidation by Hyd-1 involve sequential proton and electron transfer via Ni-L. A broadly applicable IR spectroscopic technique is presented for addressing electrode-adsorbed redox enzymes under fast catalytic turnover.
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Affiliation(s)
- Ricardo Hidalgo
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (UK)
| | - Philip A Ash
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (UK)
| | - Adam J Healy
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (UK)
| | - Kylie A Vincent
- Department of Chemistry, University of Oxford, Inorganic Chemistry Laboratory, South Parks Road, Oxford, OX1 3QR (UK).
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