1
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Hagen WR. Quantum Magnetism of the Iron Core in Ferritin Proteins-A Re-Evaluation of the Giant-Spin Model. Molecules 2024; 29:2254. [PMID: 38792115 PMCID: PMC11123763 DOI: 10.3390/molecules29102254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2024] [Revised: 05/04/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
The electron-electron, or zero-field interaction (ZFI) in the electron paramagnetic resonance (EPR) of high-spin transition ions in metalloproteins and coordination complexes, is commonly described by a simple spin Hamiltonian that is second-order in the spin S: H=D[Sz2-SS+1/3+E(Sx2-Sy2). Symmetry considerations, however, allow for fourth-order terms when S ≥ 2. In metalloprotein EPR studies, these terms have rarely been explored. Metal ions can cluster via non-metal bridges, as, for example, in iron-sulfur clusters, in which exchange interaction can result in higher system spin, and this would allow for sixth- and higher-order ZFI terms. For metalloproteins, these have thus far been completely ignored. Single-molecule magnets (SMMs) are multi-metal ion high spin complexes, in which the ZFI usually has a negative sign, thus affording a ground state level pair with maximal spin quantum number mS = ±S, giving rise to unusual magnetic properties at low temperatures. The description of EPR from SMMs is commonly cast in terms of the 'giant-spin model', which assumes a magnetically isolated system spin, and in which fourth-order, and recently, even sixth-order ZFI terms have been found to be required. A special version of the giant-spin model, adopted for scaling-up to system spins of order S ≈ 103-104, has been applied to the ubiquitous iron-storage protein ferritin, which has an internal core containing Fe3+ ions whose individual high spins couple in a way to create a superparamagnet at ambient temperature with very high system spin reminiscent to that of ferromagnetic nanoparticles. This scaled giant-spin model is critically evaluated; limitations and future possibilities are explicitly formulated.
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Affiliation(s)
- Wilfred R Hagen
- Department of Biotechnology, Delft University of Technology, Building 58, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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2
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Quechol R, Solomon JB, Liu YA, Lee CC, Jasniewski AJ, Górecki K, Oyala P, Hedman B, Hodgson KO, Ribbe MW, Hu Y. Heterologous synthesis of the complex homometallic cores of nitrogenase P- and M-clusters in Escherichia coli. Proc Natl Acad Sci U S A 2023; 120:e2314788120. [PMID: 37871225 PMCID: PMC10622910 DOI: 10.1073/pnas.2314788120] [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: 08/26/2023] [Accepted: 09/28/2023] [Indexed: 10/25/2023] Open
Abstract
Nitrogenase is an active target of heterologous expression because of its importance for areas related to agronomy, energy, and environment. One major hurdle for expressing an active Mo-nitrogenase in Escherichia coli is to generate the complex metalloclusters (P- and M-clusters) within this enzyme, which involves some highly unique bioinorganic chemistry/metalloenzyme biochemistry that is not generally dealt with in the heterologous expression of proteins via synthetic biology; in particular, the heterologous synthesis of the homometallic P-cluster ([Fe8S7]) and M-cluster core (or L-cluster; [Fe8S9C]) on their respective protein scaffolds, which represents two crucial checkpoints along the biosynthetic pathway of a complete nitrogenase, has yet to be demonstrated by biochemical and spectroscopic analyses of purified metalloproteins. Here, we report the heterologous formation of a P-cluster-containing NifDK protein upon coexpression of Azotobacter vinelandii nifD, nifK, nifH, nifM, and nifZ genes, and that of an L-cluster-containing NifB protein upon coexpression of Methanosarcina acetivorans nifB, nifS, and nifU genes alongside the A. vinelandii fdxN gene, in E. coli. Our metal content, activity, EPR, and XAS/EXAFS data provide conclusive evidence for the successful synthesis of P- and L-clusters in a nondiazotrophic host, thereby highlighting the effectiveness of our metallocentric, divide-and-conquer approach that individually tackles the key events of nitrogenase biosynthesis prior to piecing them together into a complete pathway for the heterologous expression of nitrogenase. As such, this work paves the way for the transgenic expression of an active nitrogenase while providing an effective tool for further tackling the biosynthetic mechanism of this important metalloenzyme.
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Affiliation(s)
- Robert Quechol
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Joseph B. Solomon
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
- Department of Chemistry, University of California, Irvine, CA92697-2025
| | - Yiling A. Liu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Chi Chung Lee
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Andrew J. Jasniewski
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Kamil Górecki
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
| | - Paul Oyala
- Department of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA91125
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center National Accelerator Laboratory, Stanford University, Menlo Park, CA94025
| | - Keith O. Hodgson
- Stanford Synchrotron Radiation Lightsource, Stanford Linear Accelerator Center National Accelerator Laboratory, Stanford University, Menlo Park, CA94025
- Department of Chemistry, Stanford University, Stanford, CA94305
| | - Markus W. Ribbe
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
- Department of Chemistry, University of California, Irvine, CA92697-2025
| | - Yilin Hu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697-3900
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3
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Hagen WR. The Development of Tungsten Biochemistry-A Personal Recollection. Molecules 2023; 28:molecules28104017. [PMID: 37241758 DOI: 10.3390/molecules28104017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 04/27/2023] [Accepted: 05/08/2023] [Indexed: 05/28/2023] Open
Abstract
The development of tungsten biochemistry is sketched from the viewpoint of personal participation. Following its identification as a bio-element, a catalogue of genes, enzymes, and reactions was built up. EPR spectroscopic monitoring of redox states was, and remains, a prominent tool in attempts to understand tungstopterin-based catalysis. A paucity of pre-steady-state data remains a hindrance to overcome to this day. Tungstate transport systems have been characterized and found to be very specific for W over Mo. Additional selectivity is presented by the biosynthetic machinery for tungstopterin enzymes. Metallomics analysis of hyperthermophilic archaeon Pyrococcus furiosus indicates a comprehensive inventory of tungsten proteins.
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Affiliation(s)
- Wilfred R Hagen
- Department of Biotechnology, Delft University of Technology, Building 58, Van der Maasweg 9, 2629 HZ Delft, The Netherlands
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4
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Abstract
The Fischer-Tropsch (FT) process converts a mixture of CO and H2 into liquid hydrocarbons as a major component of the gas-to-liquid technology for the production of synthetic fuels. Contrary to the energy-demanding chemical FT process, the enzymatic FT-type reactions catalyzed by nitrogenase enzymes, their metalloclusters, and synthetic mimics utilize H+ and e- as the reducing equivalents to reduce CO, CO2, and CN- into hydrocarbons under ambient conditions. The C1 chemistry exemplified by these FT-type reactions is underscored by the structural and electronic properties of the nitrogenase-associated metallocenters, and recent studies have pointed to the potential relevance of this reactivity to nitrogenase mechanism, prebiotic chemistry, and biotechnological applications. This review will provide an overview of the features of nitrogenase enzymes and associated metalloclusters, followed by a detailed discussion of the activities of various nitrogenase-derived FT systems and plausible mechanisms of the enzymatic FT reactions, highlighting the versatility of this unique reactivity while providing perspectives onto its mechanistic, evolutionary, and biotechnological implications.
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Affiliation(s)
- Yilin Hu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine 92697-3900, USA
| | - Chi Chung Lee
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine 92697-3900, USA
| | - Mario Grosch
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine 92697-3900, USA
| | - Joseph B. Solomon
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
| | - Wolfgang Weigand
- Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, 07743 Jena, Germany
| | - Markus W. Ribbe
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine 92697-3900, USA
- Department of Chemistry, University of California, Irvine, CA 92697-2025, USA
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5
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Quantum Mechanical Calculations of Redox Potentials of the Metal Clusters in Nitrogenase. MOLECULES (BASEL, SWITZERLAND) 2022; 28:molecules28010065. [PMID: 36615260 PMCID: PMC9822455 DOI: 10.3390/molecules28010065] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Revised: 12/14/2022] [Accepted: 12/19/2022] [Indexed: 12/24/2022]
Abstract
We have calculated redox potentials of the two metal clusters in Mo-nitrogenase with quantum mechanical (QM) calculations. We employ an approach calibrated for iron-sulfur clusters with 1-4 Fe ions, involving QM-cluster calculations in continuum solvent and large QM systems (400-500 atoms), based on structures from combined QM and molecular mechanics (QM/MM) geometry optimisations. Calculations on the P-cluster show that we can reproduce the experimental redox potentials within 0.33 V. This is similar to the accuracy obtained for the smaller clusters, although two of the redox reactions involve also proton transfer. The calculated P1+/PN redox potential is nearly the same independently of whether P1+ is protonated or deprotonated, explaining why redox titrations do not show any pH dependence. For the FeMo cluster, the calculations clearly show that the formal oxidation state of the cluster in the resting E0 state is MoIIIFe3IIFe4III , in agreement with previous experimental studies and QM calculations. Moreover, the redox potentials of the first five E0-E4 states are nearly constant, as is expected if the electrons are delivered by the same site (the P-cluster). However, the redox potentials are insensitive to the formal oxidation states of the Fe ion (i.e., whether the added protons bind to sulfide or Fe ions). Finally, we show that the later (E4-E8) states of the reaction mechanism have redox potential that are more positive (i.e., more exothermic) than that of the E0/E1 couple.
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6
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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: 55] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [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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7
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Van Stappen C, Jiménez-Vicente E, Pérez-González A, Yang ZY, Seefeldt LC, DeBeer S, Dean DR, Decamps L. A conformational role for NifW in the maturation of molybdenum nitrogenase P-cluster. Chem Sci 2022; 13:3489-3500. [PMID: 35432878 PMCID: PMC8943848 DOI: 10.1039/d1sc06418e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2021] [Accepted: 02/28/2022] [Indexed: 12/03/2022] Open
Abstract
Reduction of dinitrogen by molybdenum nitrogenase relies on complex metalloclusters: the [8Fe:7S] P-cluster and the [7Fe:9S:Mo:C:homocitrate] FeMo-cofactor. Although both clusters bear topological similarities and require the reductive fusion of [4Fe:4S] sub-clusters to achieve their respective assemblies, P-clusters are assembled directly on the NifD2K2 polypeptide prior to the insertion of FeMo-co, which is fully assembled separately from NifD2K2. P-cluster maturation involves the iron protein NifH2 as well as several accessory proteins, whose role has not been elucidated. In the present work, two NifD2K2 species bearing immature P-clusters were isolated from an Azotobacter vinelandii strain in which the genes encoding NifH and the accessory protein NifZ were deleted, and characterized by X-ray absorption spectroscopy and EPR. These analyses showed that both NifD2K2 complexes harbor clusters that are electronically and structurally similar, with each NifDK unit containing two [4Fe:4S]2+/+ clusters. Binding of the accessory protein NifW parallels a decrease in the distance between these clusters, as well as a subtle change in their coordination. These results support a conformational role for NifW in P-cluster biosynthesis, bringing the two [4Fe:4S] precursors closer prior to their fusion, which may be crucial in challenging cellular contexts.
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Affiliation(s)
- Casey Van Stappen
- Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 45470 Mülheim an der Ruhr Germany
| | - Emilio Jiménez-Vicente
- Department of Biochemistry, Virginia Polytechnic Institute and State University Blacksburg VA 24061 USA
| | - Ana Pérez-González
- Department of Biochemistry, Virginia Polytechnic Institute and State University Blacksburg VA 24061 USA
| | - Zhi-Yong Yang
- Department of Chemistry and Biochemistry, Utah State University Logan UT 84322 USA
| | - Lance C Seefeldt
- Department of Chemistry and Biochemistry, Utah State University Logan UT 84322 USA
| | - Serena DeBeer
- Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 45470 Mülheim an der Ruhr Germany
| | - Dennis R Dean
- Department of Biochemistry, Virginia Polytechnic Institute and State University Blacksburg VA 24061 USA
| | - Laure Decamps
- Max Planck Institute for Chemical Energy Conversion Stiftstrasse 34-36 45470 Mülheim an der Ruhr Germany
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8
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Chica B, Ruzicka J, Pellows LM, Kallas H, Kisgeropoulos E, Vansuch GE, Mulder DW, Brown KA, Svedruzic D, Peters JW, Dukovic G, Seefeldt LC, King PW. Dissecting Electronic-Structural Transitions in the Nitrogenase MoFe Protein P-Cluster during Reduction. J Am Chem Soc 2022; 144:5708-5712. [PMID: 35315658 PMCID: PMC8991001 DOI: 10.1021/jacs.1c13311] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The [8Fe-7S] P-cluster of nitrogenase MoFe protein mediates electron transfer from nitrogenase Fe protein during the catalytic production of ammonia. The P-cluster transitions between three oxidation states, PN, P+, P2+ of which PN↔P+ is critical to electron exchange in the nitrogenase complex during turnover. To dissect the steps in formation of P+ during electron transfer, photochemical reduction of MoFe protein at 231-263 K was used to trap formation of P+ intermediates for analysis by EPR. In complexes with CdS nanocrystals, illumination of MoFe protein led to reduction of the P-cluster P2+ that was coincident with formation of three distinct EPR signals: S = 1/2 axial and rhombic signals, and a high-spin S = 7/2 signal. Under dark annealing the axial and high-spin signal intensities declined, which coincided with an increase in the rhombic signal intensity. A fit of the time-dependent changes of the axial and high-spin signals to a reaction model demonstrates they are intermediates in the formation of the P-cluster P+ resting state and defines how spin-state transitions are coupled to changes in P-cluster oxidation state in MoFe protein during electron transfer.
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Affiliation(s)
- Bryant Chica
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Jesse Ruzicka
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Lauren M Pellows
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States
| | - Hayden Kallas
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Effie Kisgeropoulos
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Gregory E Vansuch
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - David W Mulder
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Katherine A Brown
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - Drazenka Svedruzic
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
| | - John W Peters
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99163, United States
| | - Gordana Dukovic
- Department of Chemistry, University of Colorado Boulder, Boulder, Colorado 80309, United States.,Renewable and Sustainable Energy Institute (RASEI), University of Colorado Boulder, Boulder, Colorado 80309, United States.,Materials Science and Engineering, University of Colorado Boulder, Boulder, Colorado 80303, United States
| | - Lance C Seefeldt
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Paul W King
- Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States.,Renewable and Sustainable Energy Institute (RASEI), University of Colorado Boulder, Boulder, Colorado 80309, United States
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9
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Yuan C, Jin WT, Zhou ZH. Statistical analysis of P N clusters in Mo/VFe protein crystals using a bond valence method toward their electronic structures. RSC Adv 2022; 12:5214-5224. [PMID: 35425536 PMCID: PMC8981338 DOI: 10.1039/d1ra08507g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2021] [Accepted: 01/26/2022] [Indexed: 11/21/2022] Open
Abstract
Nowadays, large numbers of MoFe proteins have been reported and their crystal data obtained by X-ray crystallography and uploaded to the Protein Data Bank (PDB). By big data analysis using a bond valence method, we make conclusions based on 79 selected PN in all 119 P-clusters of 53 MoFe proteins and 10 P-clusters of 5 VFe proteins from all deposited crystallographic data of the PDB. In the condition of MoFe protein crystals, the resting state PN clusters are proposed to have the formal oxidation state of 2Fe(iii)6Fe(ii), hiding two oxidized electron holes with high electron delocalization. The calculations show that Fe1, Fe2, Fe5, Fe6 and Fe7 perform unequivocally as Fe2+, and Fe3 is remarkably prone to Fe(iii), while Fe4 and Fe8 have different degrees of mixed valences. For PN clusters in VFe protein crystals, Fe1, Fe2, Fe4, Fe5 and Fe6 tend to be Fe2+, but the electron distributions rearrange with Fe7 and Fe8 being more oxidized mixed valences, and Fe3 presenting a little more reductive mixed valence than that in MoFe proteins. In terms of spatial location, Fe3 and Fe6 in P-clusters of MoFe proteins are calculated as the most oxidized and reduced irons, which have the shortest distances from homocitrate in the FeMo-cofactor and [Fe4S4] cluster, respectively, and thus could function as potential electron transport sites. This work shows different electron distributions of PN clusters in Mo/VFe protein crystals, from those obtained from previous data from solution with excess reducing agent from which it was concluded that PN clusters are all ferrous according to Mössbauer and electron paramagnetic resonance spectra.
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Affiliation(s)
- Chang Yuan
- State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 P. R. China
| | - Wan-Ting Jin
- State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 P. R. China
| | - Zhao-Hui Zhou
- State Key Laboratory for Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University Xiamen 361005 P. R. China
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10
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Large anions induce H2-production from the nitrogenase MoFe proteins of Clostridium Pasteurianum and Azotobacter vinelandii. J Inorg Biochem 2020; 208:111075. [DOI: 10.1016/j.jinorgbio.2020.111075] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 03/13/2020] [Accepted: 03/19/2020] [Indexed: 11/20/2022]
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11
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Abstract
Nitrogenase is the only enzyme capable of reducing N2 to NH3. This challenging reaction requires the coordinated transfer of multiple electrons from the reductase, Fe-protein, to the catalytic component, MoFe-protein, in an ATP-dependent fashion. In the last two decades, there have been significant advances in our understanding of how nitrogenase orchestrates electron transfer (ET) from the Fe-protein to the catalytic site of MoFe-protein and how energy from ATP hydrolysis transduces the ET processes. In this review, we summarize these advances, with focus on the structural and thermodynamic redox properties of nitrogenase component proteins and their complexes, as well as on new insights regarding the mechanism of ET reactions during catalysis and how they are coupled to ATP hydrolysis. We also discuss recently developed chemical, photochemical, and electrochemical methods for uncoupling substrate reduction from ATP hydrolysis, which may provide new avenues for studying the catalytic mechanism of nitrogenase.
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Affiliation(s)
- Hannah L Rutledge
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
| | - F Akif Tezcan
- Department of Chemistry and Biochemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0340, United States
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12
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Jasniewski AJ, Lee CC, Ribbe MW, Hu Y. Reactivity, Mechanism, and Assembly of the Alternative Nitrogenases. Chem Rev 2020; 120:5107-5157. [PMID: 32129988 PMCID: PMC7491575 DOI: 10.1021/acs.chemrev.9b00704] [Citation(s) in RCA: 110] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Biological nitrogen fixation is catalyzed by the enzyme nitrogenase, which facilitates the cleavage of the relatively inert triple bond of N2. Nitrogenase is most commonly associated with the molybdenum-iron cofactor called FeMoco or the M-cluster, and it has been the subject of extensive structural and spectroscopic characterization over the past 60 years. In the late 1980s and early 1990s, two "alternative nitrogenase" systems were discovered, isolated, and found to incorporate V or Fe in place of Mo. These systems are regulated by separate gene clusters; however, there is a high degree of structural and functional similarity between each nitrogenase. Limited studies with the V- and Fe-nitrogenases initially demonstrated that these enzymes were analogously active as the Mo-nitrogenase, but more recent investigations have found capabilities that are unique to the alternative systems. In this review, we will discuss the reactivity, biosynthetic, and mechanistic proposals for the alternative nitrogenases as well as their electronic and structural properties in comparison to the well-characterized Mo-dependent system. Studies over the past 10 years have been particularly fruitful, though key aspects about V- and Fe-nitrogenases remain unexplored.
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Affiliation(s)
- Andrew J Jasniewski
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
| | - Chi Chung Lee
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
| | - Markus W Ribbe
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
- Department of Chemistry, University of California, Irvine, California 92697-2025, United States
| | - Yilin Hu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, United States
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13
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Van Stappen C, Decamps L, Cutsail GE, Bjornsson R, Henthorn JT, Birrell JA, DeBeer S. The Spectroscopy of Nitrogenases. Chem Rev 2020; 120:5005-5081. [PMID: 32237739 PMCID: PMC7318057 DOI: 10.1021/acs.chemrev.9b00650] [Citation(s) in RCA: 115] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Indexed: 01/08/2023]
Abstract
Nitrogenases are responsible for biological nitrogen fixation, a crucial step in the biogeochemical nitrogen cycle. These enzymes utilize a two-component protein system and a series of iron-sulfur clusters to perform this reaction, culminating at the FeMco active site (M = Mo, V, Fe), which is capable of binding and reducing N2 to 2NH3. In this review, we summarize how different spectroscopic approaches have shed light on various aspects of these enzymes, including their structure, mechanism, alternative reactivity, and maturation. Synthetic model chemistry and theory have also played significant roles in developing our present understanding of these systems and are discussed in the context of their contributions to interpreting the nature of nitrogenases. Despite years of significant progress, there is still much to be learned from these enzymes through spectroscopic means, and we highlight where further spectroscopic investigations are needed.
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Affiliation(s)
- Casey Van Stappen
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Laure Decamps
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - George E. Cutsail
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Ragnar Bjornsson
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Justin T. Henthorn
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - James A. Birrell
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Serena DeBeer
- Max Planck Institute for
Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
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14
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Kang W, Lee CC, Jasniewski AJ, Ribbe MW, Hu Y. Structural evidence for a dynamic metallocofactor during N 2 reduction by Mo-nitrogenase. Science 2020; 368:1381-1385. [PMID: 32554596 PMCID: PMC8410457 DOI: 10.1126/science.aaz6748] [Citation(s) in RCA: 93] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Revised: 03/11/2020] [Accepted: 04/20/2020] [Indexed: 01/06/2023]
Abstract
The enzyme nitrogenase uses a suite of complex metallocofactors to reduce dinitrogen (N2) to ammonia. Mechanistic details of this reaction remain sparse. We report a 1.83-angstrom crystal structure of the nitrogenase molybdenum-iron (MoFe) protein captured under physiological N2 turnover conditions. This structure reveals asymmetric displacements of the cofactor belt sulfurs (S2B or S3A and S5A) with distinct dinitrogen species in the two αβ dimers of the protein. The sulfur-displaced sites are distinct in the ability of protein ligands to donate protons to the bound dinitrogen species, as well as the elongation of either the Mo-O5 (carboxyl) or Mo-O7 (hydroxyl) distance that switches the Mo-homocitrate ligation from bidentate to monodentate. These results highlight the dynamic nature of the cofactor during catalysis and provide evidence for participation of all belt-sulfur sites in this process.
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Affiliation(s)
- Wonchull Kang
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA
| | - Chi Chung Lee
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA
| | - Andrew J Jasniewski
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA
| | - Markus W Ribbe
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA.
- Department of Chemistry, University of California, Irvine, Irvine, CA 92697-2025, USA
| | - Yilin Hu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697-3900, USA.
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15
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Abstract
The fixation of atmospheric dinitrogen to ammonia by industrial technologies (such as the Haber Bosch process) has revolutionized humankind. In contrast to industrial technologies, a single enzyme is known for its ability to reduce or "fix" dinitrogen: nitrogenase. Nitrogenase is a complex oxidoreductase enzymatic system that includes a catalytic protein (where dinitrogen is reduced) and an electron-transferring reductase protein (termed the Fe protein) that delivers the electrons necessary for dinitrogen fixation. The catalytic protein most commonly contains a FeMo cofactor (called the MoFe protein), but it can also contain a VFe or FeFe cofactor. Besides their ability to fix dinitrogen to ammonia, these nitrogenases can also reduce substrates such as carbon dioxide to formate. Interestingly, the VFE nitrogenase can also form carbon-carbon bonds. The vast majority of research surrounding nitrogenase employs the Fe protein to transfer electrons, which is also associated with the rate-limiting step of nitrogenase catalysis and also requires the hydrolysis of adenosine triphosphate. Thus, there is significant interest in artificially transferring electrons to the catalytic nitrogenase proteins. In this Account, we review nitrogenase electrocatalysis whereby electrons are delivered to nitrogenase from electrodes. We first describe the use of an electron mediator (cobaltocene) to transfer electrons from electrodes to the MoFe protein. The reduction of protons to molecular hydrogen was realized, in addition to azide and nitrite reduction to ammonia. Bypassing the rate-limiting step within the Fe protein, we also describe how this approach was used to interrogate the rate-limiting step of the MoFe protein: metal-hydride protonolysis at the FeMo-co. This Account next reviews the use of cobaltocene to mediate electron transfer to the VFe protein, where the reduction of carbon dioxide and the formation of carbon-carbon bonds (yielding the formation of ethene and propene) was realized. This approach also found success in mediating electron transfer to the FeFe catalytic protein, which exhibited improved carbon dioxide reduction in comparison to the MoFe protein. In the final example of mediated electron transfer to the catalytic protein, this Account also reviews recent work where the coupling of infrared spectroscopy with electrochemistry enabled the potential-dependent binding of carbon monoxide to the FeMo-co to be studied. As an alternative to mediated electron transfer, recent work that has sought to transfer electrons to the catalytic proteins in the absence of electron mediators (by direct electron transfer) is also reviewed. This approach has subsequently enabled a thermodynamic landscape to be proposed for the cofactors of the catalytic proteins. Finally, this Account also describes nitrogenase electrocatalysis whereby electrons are first transferred from an electrode to the Fe protein, before being transferred to the MoFe protein alongside the hydrolysis of adenosine triphosphate. In this way, increased quantities of ammonia can be electrocatalytically produced from dinitrogen fixation. We discuss how this has led to the further upgrade of electrocatalytically produced ammonia, in combination with additional enzymes (diaphorase, alanine dehydrogenase, and transaminase), to selective production of chiral amine intermediates for pharmaceuticals. This Account concludes by discussing current and future research challenges in the field of electrocatalytic nitrogen fixation by nitrogenase.
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Affiliation(s)
- Ross D. Milton
- Department of Inorganic and Analytical Chemistry, University of Geneva, Sciences II, Quai Ernest-Ansermet 30, 1211 Geneva 4, Switzerland
| | - Shelley D. Minteer
- NSF Center for Synthetic Organic Electrochemistry, Department of Chemistry, University of Utah, 315 S 1400 E, Salt Lake City, Utah 84112, United States
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16
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Progress in Synthesizing Analogues of Nitrogenase Metalloclusters for Catalytic Reduction of Nitrogen to Ammonia. Catalysts 2019. [DOI: 10.3390/catal9110939] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Ammonia (NH3) has played an essential role in meeting the increasing demand for food and the worldwide need for nitrogen (N2) fertilizer since 1913. Unfortunately, the traditional Haber–Bosch process for producing NH3 from N2 is a high energy-consumption process with approximately 1.9 metric tons of fossil CO2 being released per metric ton of NH3 produced. As a very challenging target, any ideal NH3 production process reducing fossil energy consumption and environmental pollution would be welcomed. Catalytic NH3 synthesis is an attractive and promising alternative approach. Therefore, developing efficient catalysts for synthesizing NH3 from N2 under ambient conditions would create a significant opportunity to directly provide nitrogenous fertilizers in agricultural fields as needed in a distributed manner. In this paper, the literature on alternative, available, and sustainable NH3 production processes in terms of the scientific aspects of the spatial structures of nitrogenase metalloclusters, the mechanism of reducing N2 to NH3 catalyzed by nitrogenase, the synthetic analogues of nitrogenase metalloclusters, and the opportunities for continued research are reviewed.
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17
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Zanello P. Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part V. Nitrogenases. Coord Chem Rev 2019. [DOI: 10.1016/j.ccr.2019.07.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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18
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Lydon BR, Lee CC, Tanifuji K, Sickerman NS, Newcomb MP, Hu Y, Ribbe MW, Yang JY. Electrochemical Characterization of Isolated Nitrogenase Cofactors from Azotobacter vinelandii. Chembiochem 2019; 21:1773-1778. [PMID: 31392810 DOI: 10.1002/cbic.201900425] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2019] [Indexed: 11/09/2022]
Abstract
The nitrogenase cofactors are structurally and functionally unique in biological chemistry. Despite a substantial amount of spectroscopic characterization of protein-bound and isolated nitrogenase cofactors, electrochemical characterization of these cofactors and their related species is far from complete. Herein we present voltammetric studies of three isolated nitrogenase cofactor species: the iron-molybdenum cofactor (M-cluster), iron-vanadium cofactor (V-cluster), and a homologue to the iron-iron cofactor (L-cluster). We observe two reductive events in the redox profiles of all three cofactors. Of the three, the V-cluster is the most reducing. The reduction potentials of the isolated cofactors are significantly more negative than previously measured values within the molybdenum-iron and vanadium-iron proteins. The outcome of this study provides insight into the importance of the heterometal identity, the overall ligation of the cluster, and the impact of the protein scaffolds on the overall electronic structures of the cofactors.
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Affiliation(s)
- Brian R Lydon
- Department of Chemistry, University of California, 1102 Natural Sciences II, Irvine, CA, 92697, USA
| | - Chi Chung Lee
- Department of Molecular Biology and Biochemistry, University of California, 3205 McGaugh Hall, Irvine, CA, 92697, USA
| | - Kazuki Tanifuji
- Department of Molecular Biology and Biochemistry, University of California, 3205 McGaugh Hall, Irvine, CA, 92697, USA
| | - Nathaniel S Sickerman
- Department of Molecular Biology and Biochemistry, University of California, 3205 McGaugh Hall, Irvine, CA, 92697, USA
| | - Megan P Newcomb
- Department of Chemistry, University of California, 1102 Natural Sciences II, Irvine, CA, 92697, USA
| | - Yilin Hu
- Department of Molecular Biology and Biochemistry, University of California, 3205 McGaugh Hall, Irvine, CA, 92697, USA
| | - Markus W Ribbe
- Department of Chemistry, University of California, 1102 Natural Sciences II, Irvine, CA, 92697, USA.,Department of Molecular Biology and Biochemistry, University of California, 3205 McGaugh Hall, Irvine, CA, 92697, USA
| | - Jenny Y Yang
- Department of Chemistry, University of California, 1102 Natural Sciences II, Irvine, CA, 92697, USA
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19
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Hickey DP, Cai R, Yang ZY, Grunau K, Einsle O, Seefeldt LC, Minteer SD. Establishing a Thermodynamic Landscape for the Active Site of Mo-Dependent Nitrogenase. J Am Chem Soc 2019; 141:17150-17157. [DOI: 10.1021/jacs.9b06546] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Affiliation(s)
- David P. Hickey
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Rong Cai
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
| | - Zhi-Yong Yang
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Katharina Grunau
- Institut für Biochemie and BIOSS Centre for Biological Signaling Studies, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
| | - Oliver Einsle
- Institut für Biochemie and BIOSS Centre for Biological Signaling Studies, Albert-Ludwigs-Universität Freiburg, 79104 Freiburg, Germany
| | - Lance C. Seefeldt
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah 84322, United States
| | - Shelley D. Minteer
- Department of Chemistry, University of Utah, Salt Lake City, Utah 84112, United States
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20
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Cao L, Börner MC, Bergmann J, Caldararu O, Ryde U. Geometry and Electronic Structure of the P-Cluster in Nitrogenase Studied by Combined Quantum Mechanical and Molecular Mechanical Calculations and Quantum Refinement. Inorg Chem 2019; 58:9672-9690. [DOI: 10.1021/acs.inorgchem.9b00400] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Lili Cao
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Melanie C. Börner
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00 Lund, Sweden
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
| | - Justin Bergmann
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Octav Caldararu
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00 Lund, Sweden
| | - Ulf Ryde
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-221 00 Lund, Sweden
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21
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Abstract
Biological nitrogen fixation, the conversion of dinitrogen (N2) into ammonia (NH3), stands as a particularly challenging chemical process. As the entry point into a bioavailable form of nitrogen, biological nitrogen fixation is a critical step in the global nitrogen cycle. In Nature, only one enzyme, nitrogenase, is competent in performing this reaction. Study of this complex metalloenzyme has revealed a potent substrate reduction system that utilizes some of the most sophisticated metalloclusters known. This chapter discusses the structure and function of nitrogenase, covers methods that have proven useful in the elucidation of enzyme properties, and provides an overview of the three known nitrogenase variants.
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22
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Stegmaier K, Blinn CM, Bechtel DF, Greth C, Auerbach H, Müller CS, Jakob V, Reijerse EJ, Netz DJA, Schünemann V, Pierik AJ. Apd1 and Aim32 Are Prototypes of Bishistidinyl-Coordinated Non-Rieske [2Fe–2S] Proteins. J Am Chem Soc 2019; 141:5753-5765. [DOI: 10.1021/jacs.8b13274] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
| | | | | | | | | | | | | | - Edward J. Reijerse
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, D45470 Mülheim an der Ruhr, Germany
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23
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Sánchez RH, Betley TA. Thermally Persistent High-Spin Ground States in Octahedral Iron Clusters. J Am Chem Soc 2018; 140:16792-16806. [PMID: 30403845 DOI: 10.1021/jacs.8b10181] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chemical oxidation and reduction of the all-ferrous (HL)2Fe6 in THF affords isostructural, coordinatively unsaturated clusters of the type [(HL)2Fe6] n: [(HL)2Fe6][BArF24] (1, n = +1; where [BArF24]- = tetrakis[(3,5-trifluoromethyl)phenyl]borate), [Bu4N][(HL)2Fe6] (2a, n = -1), [P][(HL)2Fe6] (2b, n = -1; where [P]+ = tributyl(1,3-dioxolan-2-ylmethyl)phosphonium), and [Bu4N]2[(HL)2Fe6] (3, n = -2). Each member of the redox-transfer series was characterized by zero-field 57Fe Mössbauer spectroscopy, near-infrared spectroscopy, single-crystal X-ray crystallography, and magnetometry. Redox-directed trends are observed when comparing the structural metrics within the [Fe6] core. The metal octahedron [Fe6] decreases marginally in volume as the molecular reduction state increases as gauged by the Fe-Feavg distance varying from 2.608(11) Å ( n = +1) to 2.573(3) ( n = -2). In contrast, the mean Fe-N distances and ∠Fe-N-Fe angles correlate linearly with the [Fe6] oxidation level, or alternatively, the changes observed within the local Fe-N4 coordination planes vary linearly with the aggregate spin ground state. In general, as the spin ground state ( S) increases, the Fe-N(H)avg distances also increase. The structural metric perturbations within the [Fe6] core and measured spin ground states were rationalized extending the previously proposed molecular orbital diagram derived for (HL)2Fe6. Chemical reduction of the (HL)2Fe6 cluster results in an abrupt increase in spin ground state from S = 6 for the all-ferrous cluster, to S = 19/2 in the monoanionic 2b and S = 11 for the dianionic 3. The observation of asymmetric intervalence charge transfer bands in 3 provides further evidence of the fully delocalized ground state observed by 57Fe Mössbauer spectroscopy for all species examined (1-3). For each of the clusters examined within the electron-transfer series, the observed spin ground states thermally persist to 300 K. In particular, the S = 11 in dianionic 3 and S = 19/2 in the monoanionic 2b represent the highest spin ground states isolated up to room temperature known to date. The increase in spin ground state results from population of the antibonding orbital band comprised of the Fe-N σ* interactions. As such, the thermally persistent ground states arise from population of the resultant single spin manifolds in accordance with Hund's rules. The large spin ground states, indicative of strong ferromagnetic electronic alignment of the valence electrons, result from strong direct exchange electronic coupling mediated by Fe-Fe orbital overlap within the [Fe6] cores, equivalent to a strong double exchange magnetic coupling B for 3 that was calculated to be 309 cm-1.
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Affiliation(s)
- Raúl Hernández Sánchez
- Department of Chemistry and Chemical Biology , Harvard University , 12 Oxford Street , Cambridge , Massachusetts 02138 , United States
| | - Theodore A Betley
- Department of Chemistry and Chemical Biology , Harvard University , 12 Oxford Street , Cambridge , Massachusetts 02138 , United States
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24
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Hagen WR, Hagedoorn PL, Honarmand Ebrahimi K. The workings of ferritin: a crossroad of opinions. Metallomics 2018; 9:595-605. [PMID: 28573266 DOI: 10.1039/c7mt00124j] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Biochemistry of the essential element iron is complicated by radical chemistry associated with Fe(ii) ions and by the extremely low solubility of the Fe(iii) ion in near-neutral water. To mitigate these problems cells from all domains of life synthesize the protein ferritin to take up and oxidize Fe(ii) and to form a soluble storage of Fe(iii) from which iron can be made available for physiology. A long history of studies on ferritin has not yet resulted in a generally accepted mechanism of action of this enzyme. In fact strong disagreement exists between extant ideas on several key steps in the workings of ferritin. The scope of this review is to explain the experimental background of these controversies and to indicate directions towards their possible resolution.
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Affiliation(s)
- Wilfred R Hagen
- Delft University of Technology, Department of Biotechnology, van der Maasweg 9, 2629 HZ Delft, The Netherlands.
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25
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Abstract
From the very first discovery of biological iron-sulfur clusters with EPR, the spectroscopy has been used to study not only purified proteins but also complex systems such as respiratory complexes, membrane particles and, later, whole cells. In recent times, the emphasis of iron-sulfur biochemistry has moved from characterization of individual proteins to the systems biology of iron-sulfur biosynthesis, regulation, degradation, and implications for human health. Although this move would suggest a blossoming of System-EPR as a specific, non-invasive monitor of Fe/S (dys)homeostasis in whole cells, a review of the literature reveals limited success possibly due to technical difficulties in adherence to EPR spectroscopic and biochemical standards. In an attempt to boost application of System-EPR the required boundary conditions and their practical applications are explicitly and comprehensively formulated.
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Affiliation(s)
- Wilfred R Hagen
- Department of Biotechnology, Delft University of Technology, Van der Maasweg 9, 2629HZ, Delft, The Netherlands.
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26
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Montgomery JM, Mazziotti DA. Strong Electron Correlation in Nitrogenase Cofactor, FeMoco. J Phys Chem A 2018; 122:4988-4996. [DOI: 10.1021/acs.jpca.8b00941] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Affiliation(s)
- Jason M. Montgomery
- Department of Chemistry, Biochemistry, and Physics, Florida Southern College, Lakeland, Florida 33801, United States
| | - David A. Mazziotti
- Department of Chemistry and The James Franck Institute, University of Chicago, Chicago, Illinois 60637, United States
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27
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Morrison CN, Spatzal T, Rees DC. Reversible Protonated Resting State of the Nitrogenase Active Site. J Am Chem Soc 2017; 139:10856-10862. [PMID: 28692802 PMCID: PMC5553094 DOI: 10.1021/jacs.7b05695] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
![]()
Protonated states of the nitrogenase
active site are mechanistically
significant since substrate reduction is invariably accompanied by
proton uptake. We report the low pH characterization by X-ray crystallography
and EPR spectroscopy of the nitrogenase molybdenum iron (MoFe) proteins
from two phylogenetically distinct nitrogenases (Azotobacter
vinelandii, Av, and Clostridium pasteurianum, Cp) at pHs between 4.5 and 8. X-ray data at pHs of 4.5–6
reveal the repositioning of side chains along one side of the FeMo-cofactor,
and the corresponding EPR data shows a new S = 3/2
spin system with spectral features similar to a state previously observed
during catalytic turnover. The structural changes suggest that FeMo-cofactor
belt sulfurs S3A or S5A are potential protonation sites. Notably,
the observed structural and electronic low pH changes are correlated
and reversible. The detailed structural rearrangements differ between
the two MoFe proteins, which may reflect differences in potential
protonation sites at the active site among nitrogenase species. These
observations emphasize the benefits of investigating multiple nitrogenase
species. Our experimental data suggest that reversible protonation
of the resting state is likely occurring, and we term this state “E0H+”, following the Lowe–Thorneley
naming scheme.
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Affiliation(s)
- Christine N Morrison
- Division of Chemistry and Chemical Engineering and ‡Howard Hughes Medical Institute, California Institute of Technology , Pasadena, California 91125, United States
| | - Thomas Spatzal
- Division of Chemistry and Chemical Engineering and ‡Howard Hughes Medical Institute, California Institute of Technology , Pasadena, California 91125, United States
| | - Douglas C Rees
- Division of Chemistry and Chemical Engineering and ‡Howard Hughes Medical Institute, California Institute of Technology , Pasadena, California 91125, United States
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28
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Affiliation(s)
- Yilin Hu
- Department of Molecular Biology and Biochemistry and
| | - Markus W. Ribbe
- Department of Molecular Biology and Biochemistry and
- Department of Chemistry, University of California, Irvine, California 92697-2025; ,
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29
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Nitrogenase FeMoco investigated by spatially resolved anomalous dispersion refinement. Nat Commun 2016; 7:10902. [PMID: 26973151 PMCID: PMC4793075 DOI: 10.1038/ncomms10902] [Citation(s) in RCA: 114] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 01/31/2016] [Indexed: 02/06/2023] Open
Abstract
The [Mo:7Fe:9S:C] iron-molybdenum cofactor (FeMoco) of nitrogenase is the largest known metal cluster and catalyses the 6-electron reduction of dinitrogen to ammonium in biological nitrogen fixation. Only recently its atomic structure was clarified, while its reactivity and electronic structure remain under debate. Here we show that for its resting S=3/2 state the common iron oxidation state assignments must be reconsidered. By a spatially resolved refinement of the anomalous scattering contributions of the 7 Fe atoms of FeMoco, we conclude that three irons (Fe1/3/7) are more reduced than the other four (Fe2/4/5/6). Our data are in agreement with the recently revised oxidation state assignment for the molybdenum ion, providing the first spatially resolved picture of the resting-state electron distribution within FeMoco. This might provide the long-sought experimental basis for a generally accepted theoretical description of the cluster that is in line with available spectroscopic and functional data. The [Mo:7Fe:9S:C] iron-molybdenum cofactor (FeMoco) of nitrogenase is a large metal cluster with an important role in biological nitrogen fixation. Here, the authors use spatially resolved refinement of the anomalous scattering contributions of the iron atoms to determine the resting-state electron distribution of FeMoco.
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30
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Sánchez RH, Zheng SL, Betley TA. Ligand Field Strength Mediates Electron Delocalization in Octahedral [((H)L)2Fe6(L')m](n+) Clusters. J Am Chem Soc 2015; 137:11126-43. [PMID: 26231520 PMCID: PMC5572642 DOI: 10.1021/jacs.5b06453] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
To assess the impact of terminal ligand binding on a variety of cluster properties (redox delocalization, ground-state stabilization, and breadth of redox state accessibility), we prepared three electron-transfer series based on the hexanuclear iron cluster [((H)L)2Fe6(L')m](n+) in which the terminal ligand field strength was modulated from weak to strong (L' = DMF, MeCN, CN). The extent of intracore M-M interactions is gauged by M-M distances, spin ground state persistence, and preference for mixed-valence states as determined by electrochemical comproportionation constants. Coordination of DMF to the [((H)L)2Fe6] core leads to weaker Fe-Fe interactions, as manifested by the observation of ground states populated only at lower temperatures (<100 K) and by the greater evidence of valence trapping within the mixed-valence states. Comproportionation constants determined electrochemically (Kc = 10(4)-10(8)) indicate that the redox series exhibits electronic delocalization (class II-III), yet no intervalence charge transfer (IVCT) bands are observable in the near-IR spectra. Ligation of the stronger σ donor acetonitrile results in stabilization of spin ground states to higher temperatures (∼300 K) and a high degree of valence delocalization (Kc = 10(2)-10(8)) with observable IVCT bands. Finally, the anionic cyanide-bound series reveals the highest degree of valence delocalization with the most intense IVCT bands (Kc = 10(12)-10(20)) and spin ground state population beyond room temperature. Across the series, at a given formal oxidation level, the capping ligand on the hexairon cluster dictates the overall properties of the aggregate, modulating the redox delocalization and the persistence of the intracore coupling of the metal sites.
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Affiliation(s)
- Raúl Hernández Sánchez
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Shao-Liang Zheng
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Theodore A. Betley
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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31
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32
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 560] [Impact Index Per Article: 56.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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33
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Rupnik K, Lee CC, Wiig JA, Hu Y, Ribbe MW, Hales BJ. Nonenzymatic synthesis of the P-cluster in the nitrogenase MoFe protein: evidence of the involvement of all-ferrous [Fe4S4](0) intermediates. Biochemistry 2014; 53:1108-16. [PMID: 24520862 PMCID: PMC3970913 DOI: 10.1021/bi401699u] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
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The
P-cluster in the nitrogenase MoFe protein is a [Fe8S7] cluster and represents the most complex FeS cluster
found in Nature. To date, the exact mechanism of the in vivo synthesis of the P-cluster remains unclear. What is known is that
the precursor to the P-cluster is a pair of neighboring [Fe4S4]-like clusters found on the ΔnifH MoFe protein, a protein expressed in the absence of the nitrogenase
Fe protein (NifH). Moreover, incubation of the ΔnifH MoFe protein with NifH and MgATP results in the synthesis of the
MoFe protein P-clusters. To improve our understanding of the mechanism
of this reaction, we conducted a magnetic circular dichroism (MCD)
spectroscopic study of the [Fe4S4]-like clusters
on the ΔnifH MoFe protein. Reducing the ΔnifH MoFe protein with Ti(III) citrate results in the quenching
of the S = 1/2 electron paramagnetic
resonance signal
associated with the [Fe4S4]+ state
of the clusters. MCD spectroscopy reveals this reduction results in
all four 4Fe clusters being converted into the unusual, all-ferrous
[Fe4S4]0 state. Subsequent increases
of the redox potential generate new clusters. Most significantly,
one of these newly formed clusters is the P-cluster, which represents
approximately 20–25% of the converted Fe concentration. The
other two clusters are an
X cluster, of unknown structure, and a classic [Fe4S4] cluster, which represents approximately 30–35% of
the Fe concentration. Diamagnetic FeS clusters may also have
been generated but, because of their low spectral intensity, would
not have been identified. These results demonstrate that the nitrogenase
P-cluster can be generated in the absence of NifH and MgATP.
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Affiliation(s)
- Kresimir Rupnik
- Department of Chemistry, Louisiana State University , Baton Rouge, Louisiana 70808, United States
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34
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Ohki Y. Synthetic Analogues of the Active Sites of Nitrogenase and [NiFe] Hydrogenase. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2014. [DOI: 10.1246/bcsj.20130207] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Yasuhiro Ohki
- Department of Chemistry, Graduate School of Science, Nagoya University
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35
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Cleaving the n,n triple bond: the transformation of dinitrogen to ammonia by nitrogenases. Met Ions Life Sci 2014; 14:147-76. [PMID: 25416394 DOI: 10.1007/978-94-017-9269-1_7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Biological nitrogen fixation is a natural process that converts atmospheric nitrogen (N2) to bioavailable ammonia (NH3). This reaction not only plays a key role in supplying bio-accessible nitrogen to all life forms on Earth, but also embodies the powerful chemistry of cleaving the inert N,N triple bond under ambient conditions. The group of enzymes that carry out this reaction are called nitrogenases and typically consist of two redox active protein components, each containing metal cluster(s) that are crucial for catalysis. In the past decade, a number of crystal structures, including several at high resolutions, have been solved. However, the catalytic mechanism of nitrogenase, namely, how the N,N triple bond is cleaved by this enzyme under ambient conditions, has remained elusive. Nevertheless, recent biochemical and spectroscopic studies have led to a better understanding of the potential intermediates of N2 reduction by the molybdenum (Mo)-nitrogenase. In addition, it has been demonstrated that carbon monoxide (CO), which was thought to be an inhibitor of N2 reduction, could also be reduced by the vanadium (V)-nitrogenase to small alkanes and alkenes. This chapter will begin with an introduction to biological nitrogen fixation and Mo-nitrogenase, continue with a discussion of the catalytic mechanism of N2 reduction by Mo-nitrogenase, and conclude with a survey of the current knowledge of N2- and CO-reduction by V-nitrogenase and how V-nitrogenase compares to its Mo-counterpart in these catalytic activities.
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36
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Ribbe MW, Hu Y, Hodgson KO, Hedman B. Biosynthesis of nitrogenase metalloclusters. Chem Rev 2013; 114:4063-80. [PMID: 24328215 DOI: 10.1021/cr400463x] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Markus W Ribbe
- Department of Molecular Biology and Biochemistry, University of California , Irvine, California 92697-3900, United States
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37
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Spatzal T, Einsle O, Andrade SLA. Analysis of the Magnetic Properties of Nitrogenase FeMo Cofactor by Single-Crystal EPR Spectroscopy. Angew Chem Int Ed Engl 2013; 52:10116-9. [DOI: 10.1002/anie.201303000] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2013] [Revised: 06/11/2013] [Indexed: 11/09/2022]
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38
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Spatzal T, Einsle O, Andrade SLA. Analyse der magnetischen Eigenschaften des FeMo-Cofaktors der Nitrogenase mittels Einkristall-EPR-Spektroskopie. Angew Chem Int Ed Engl 2013. [DOI: 10.1002/ange.201303000] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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39
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Jacobs D, Watt GD. Nucleotide-assisted [Fe4S4] redox state interconversions of the Azotobacter vinelandii Fe protein and their relevance to nitrogenase catalysis. Biochemistry 2013; 52:4791-9. [PMID: 23815521 DOI: 10.1021/bi301547b] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The [Fe4S4] cluster of the nitrogenase Fe protein from Azotobacter vinelandii can exist in three redox states: oxidized [Fe4S4](2+), dithionite reduced [Fe4S4](1+), and two forms of the all ferrous [Fe4S4](0), S = 4 and 0. Operation of the [Fe4S4](2+)/ [Fe4S4](1+) redox couple transfers one electron to the MoFe protein during catalysis with hydrolysis of two MgATPs. In contrast, the [Fe4S4](2+)/[Fe4S4](0) couple transfers two electrons per binding event, accompanied by hydrolysis of only two MgATPs. Both reactions occur at nearly identical rates even though the number of electrons transferred differs by a factor of 2. MgATP and MgADP facilitate interconversion of the three redox states: 2[Fe4S4](1+) + 4 MgATP = [Fe4S4](2+)(MgATP)2 + [Fe4S4](0)(MgATP)2, as demonstrated by the MgATP reaction. This reaction was investigated as a possible precursor reaction to provide two electrons in the form of [Fe4S4](0)(MgATP)2 for delivery to the MoFe protein to then conduct a two-electron substrate reduction. However, experiments showed that this disproportionation reaction, which readily occurs, was not viable during nitrogenase catalysis utilizing the [Fe4S4](1+) cluster state. The known cooperative behavior of the Fe protein in the [Fe4S4](1+) state taken together with a measured turnover potential of -460 mV with an n = 2 value, suggest a gating process on the MoFe protein involving a two electron step.
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Affiliation(s)
- Deloria Jacobs
- Department of Chemistry and Biochemistry, Brigham Young University , Provo, Utah 84602, United States
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40
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New Synthetic Routes to Metal-Sulfur Clusters Relevant to the Nitrogenase Metallo-Clusters. Z Anorg Allg Chem 2013. [DOI: 10.1002/zaac.201300081] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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41
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Hu Y, Ribbe MW. Nitrogenase assembly. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1827:1112-22. [PMID: 23232096 DOI: 10.1016/j.bbabio.2012.12.001] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 12/02/2012] [Accepted: 12/03/2012] [Indexed: 11/18/2022]
Abstract
Nitrogenase contains two unique metalloclusters: the P-cluster and the M-cluster. The assembly processes of P- and M-clusters are arguably the most complicated processes in bioinorganic chemistry. There is considerable interest in decoding the biosynthetic mechanisms of the P- and M-clusters, because these clusters are not only biologically important, but also chemically unprecedented. Understanding the assembly mechanisms of these unique metalloclusters is crucial for understanding the structure-function relationship of nitrogenase. Here, we review the recent advances in this research area, with an emphasis on our work that provide important insights into the biosynthetic pathways of these high-nuclearity metal centers. This article is part of a Special Issue entitled: Metals in Bioenergetics and Biomimetics Systems.
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Affiliation(s)
- Yilin Hu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92687-3900, USA.
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42
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Rupnik K, Hu Y, Lee CC, Wiig JA, Ribbe MW, Hales BJ. P+ state of nitrogenase p-cluster exhibits electronic structure of a [Fe4S4]+ cluster. J Am Chem Soc 2012; 134:13749-54. [PMID: 22839751 DOI: 10.1021/ja304077h] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Mo nitrogenase consists of two component proteins: the Fe protein, which contains a [Fe(4)S(4)] cluster, and the MoFe protein, which contains two different classes of metal cluster: P-cluster ([Fe(8)S(7)]) and FeMoco ([MoFe(7)S(9)C·homocitrate]). The P-cluster is believed to mediate the electron transfer between the Fe protein and the MoFe protein via interconversions between its various oxidation states, such as the all-ferrous state (P(N)) and the one- (P(+)) and two-electron (P(2+)) oxidized states. While the structural and electronic properties of P(N) and P(2+) states have been well characterized, little is known about the electronic structure of the P(+) state. Here, a mutant strain of Azotobacter vinelandii (DJ1193) was used to facilitate the characterization of the P(+) state of P-cluster. This strain expresses a MoFe protein variant (designated ΔnifB β-188(Cys) MoFe protein) that accumulates the P(+) form of P-cluster in the resting state. Magnetic circular dichroism (MCD) spectrum of the P-cluster in the oxidized ΔnifB β-188(Cys) MoFe protein closely resembles that of the P(2+) state in the oxidized wild-type MoFe protein, except for the absence of a major charge-transfer band centered at 823 nm. Moreover, magnetization curves of ΔnifB β-188(Cys) and wild-type MoFe proteins suggest that the P(2+) species in both proteins have the same spin state. MCD spectrum of the P(+) state in the ΔnifB β-188(Cys) MoFe protein, on the other hand, is associated with a classic [Fe(4)S(4)](+) cluster, suggesting that the P-cluster could be viewed as two coupled 4Fe clusters and that it could donate either one or two electrons to FeMoco by using one or both of its 4Fe halves. Such a mode of action of P-cluster could provide energetic and kinetic advantages to nitrogenase in the complex mechanism of N(2) reduction.
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Affiliation(s)
- Kresimir Rupnik
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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43
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Abstract
Nitrogenase catalyzes a key step in the global nitrogen cycle, the nucleotide-dependent reduction of atmospheric dinitrogen to bioavailable ammonia. There is a substantial amount of interest in elucidating the biosynthetic mechanisms of the FeMoco and the P-cluster of nitrogenase, because these clusters are not only biologically important but also chemically unprecedented. In this review, we summarize the recent advances in this research area, with an emphasis on our work that aims at providing structural and spectroscopic insights into the assembly of these complex metalloclusters.
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44
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Danyal K, Yang ZY, Seefeldt LC. Electron paramagnetic resonance spectroscopy. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2011; 766:191-205. [PMID: 21833869 DOI: 10.1007/978-1-61779-194-9_13] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
EPR spectroscopy has been an important tool in nitrogenase research for the last 50 years. The three metalloclusters in nitrogenase, the Fe protein [4Fe-4S] cluster, and the MoFe protein P-cluster, and FeMo-cofactor, all have EPR spectra when poised in the appropriate paramagnetic states. EPR spectroscopy can probe changes in the electronic properties of each metal cluster, such as when substrates bind, and can provide a definitive method for observing changes in the redox states of the clusters. In this chapter, the methods for analysis of the three metal clusters of nitrogenase by EPR spectroscopy are described, along with methods for trapping substrate-derived intermediates on the active site that are amenable to characterization by EPR and other magnetic resonance spectroscopy techniques.
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Affiliation(s)
- Karamatullah Danyal
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322, USA.
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45
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Abstract
Biosynthesis of MoFe protein and, particularly, that of its associated P-cluster and FeMoco has raised a significant amount of interest because of the biological importance and chemical exclusiveness of these unique clusters. Following a brief introduction to the properties of Azotobacter vinelandii MoFe protein, this chapter will focus on the recent progress toward understanding the assembly mechanism of MoFe protein, with an emphasis on studies that provide important structural or spectroscopic insights into this process.
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Affiliation(s)
- Chi-Chung Lee
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA.
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46
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Abstract
Nitrogenase is the enzyme responsible for biological reduction of dinitrogen (N(2)) to ammonia, a form usable for life. Playing a central role in the global biogeochemical nitrogen cycle, this enzyme has been the focus of intensive research for over 60 years. This chapter provides an overview of the features of nitrogenase as a background to the subsequent chapters of this volume that detail the many methods that have been applied in an attempt to gain a deeper understanding of this complex enzyme.
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Affiliation(s)
- Zhi-Yong Yang
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322, USA.
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47
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Ohki Y, Imada M, Murata A, Sunada Y, Ohta S, Honda M, Sasamori T, Tokitoh N, Katada M, Tatsumi K. Synthesis, Structures, and Electronic Properties of [8Fe-7S] Cluster Complexes Modeling the Nitrogenase P-Cluster. J Am Chem Soc 2009; 131:13168-78. [DOI: 10.1021/ja9055036] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yasuhiro Ohki
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Motosuke Imada
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Ayuro Murata
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Yusuke Sunada
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Shun Ohta
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Masaru Honda
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Takahiro Sasamori
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Norihiro Tokitoh
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Motomi Katada
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
| | - Kazuyuki Tatsumi
- Department of Chemistry, Graduate School of Science and Research Center for Materials Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan, Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto 611-0011, Japan, and Graduate School of Science and Engineering, Tokyo Metropolitan University, Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan
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48
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Abstract
Nitrogen-fixing bacteria catalyze the reduction of dinitrogen (N(2)) to two ammonia molecules (NH(3)), the major contribution of fixed nitrogen to the biogeochemical nitrogen cycle. The most widely studied nitrogenase is the molybdenum (Mo)-dependent enzyme. The reduction of N(2) by this enzyme involves the transient interaction of two component proteins, designated the iron (Fe) protein and the MoFe protein, and minimally requires 16 magnesium ATP (MgATP), eight protons, and eight electrons. The current state of knowledge on how these proteins and small molecules together effect the reduction of N(2) to ammonia is reviewed. Included is a summary of the roles of the Fe protein and MgATP hydrolysis, information on the roles of the two metal clusters contained in the MoFe protein in catalysis, insights gained from recent success in trapping substrates and inhibitors at the active-site metal cluster FeMo cofactor, and finally, considerations of the mechanism of N(2) reduction catalyzed by nitrogenase.
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Affiliation(s)
- Lance C Seefeldt
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322, USA.
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49
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Unique features of the nitrogenase VFe protein from Azotobacter vinelandii. Proc Natl Acad Sci U S A 2009; 106:9209-14. [PMID: 19478062 DOI: 10.1073/pnas.0904408106] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nitrogenase is an essential metalloenzyme that catalyzes the biological conversion of dinitrogen (N(2)) to ammonia (NH(3)). The vanadium (V)-nitrogenase is very similar to the "conventional" molybdenum (Mo)-nitrogenase, yet it holds unique properties of its own that may provide useful insights into the general mechanism of nitrogenase catalysis. So far, characterization of the vanadium iron (VFe) protein of Azotobacter vinelandii V-nitrogenase has been focused on 2 incomplete forms of this protein: alphabeta(2) and alpha(2)beta(2), both of which contain the small delta-subunit in minor amounts. Although these studies provided important information about the V-dependent nitrogenase system, they were hampered by the heterogeneity of the protein samples. Here, we report the isolation and characterization of a homogeneous, His-tagged form of VFe protein from A. vinelandii. This VFe protein has a previously-unsuspected, alpha(2)beta(2)delta(4)-heterooctameric composition. Further, it contains a P-cluster that is electronically and, perhaps, structurally different from the P-cluster of molybdenum iron (MoFe) protein. More importantly, it is catalytically distinct from the MoFe protein, particularly with regard to the mechanism of H(2) evolution. A detailed EPR investigation of the origins and interplays of FeV cofactor- and P-cluster-associated signals is presented herein, which lays the foundation for future kinetic and structural analysis of the VFe protein.
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50
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Hu Y, Fay AW, Lee CC, Yoshizawa J, Ribbe MW. Assembly of nitrogenase MoFe protein. Biochemistry 2008; 47:3973-81. [PMID: 18314963 DOI: 10.1021/bi7025003] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Assembly of nitrogenase MoFe protein is arguably one of the most complex processes in the field of bioinorganic chemistry, requiring, at least, the participation of nifS, nifU, nifB, nifE, nifN, nifV, nifQ, nifZ, nifH, nifD, and nifK gene products. Previous genetic studies have identified factors involved in MoFe protein assembly; however, the exact functions of these factors and the precise sequence of events during the process have remained unclear until the recent characterization of a number of assembly-related intermediates that provided significant insights into this biosynthetic "black box". This review summarizes the recent advances in elucidation of the mechanism of FeMoco biosynthesis in four aspects: (1) the ex situ assembly of FeMoco on NifEN, (2) the incorporation of FeMoco into MoFe protein, (3) the in situ assembly of P-cluster on MoFe protein, and (4) the stepwise assembly of MoFe protein.
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Affiliation(s)
- Yilin Hu
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697-3900, USA.
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