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Grunwald L, Abbott DF, Mougel V. Gauging Iron-Sulfur Cubane Reactivity from Covalency: Trends with Oxidation State. JACS AU 2024; 4:1315-1322. [PMID: 38665672 PMCID: PMC11040707 DOI: 10.1021/jacsau.4c00213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 04/03/2024] [Accepted: 04/03/2024] [Indexed: 04/28/2024]
Abstract
We investigated room-temperature metal and ligand K-edge X-ray absorption (XAS) spectra of a complete redox series of cubane-type iron-sulfur clusters. The Fe K-edge position provides a qualitative but convenient alternative to the traditional spectroscopic descriptors used to identify oxidation states in these systems, which we demonstrate by providing a calibration curve based on two analytic methods. Furthermore, high energy resolution fluorescence detected XAS (HERFD-XAS) at the S K-edge was used to measure Fe-S bond covalencies and record their variation with the average valence of the Fe atoms. While the Fe-S(thiolate) covalency evolves linearly, gaining 11 ± 0.4% per bond and hole, the Fe-S(μ3) covalency evolves asystematically, reflecting changes in the magnetic exchange mechanism. A strong discontinuity manifested for superoxidation to the all-ferric state, distinguishing its electronic structure and its potential (bio)chemical role from those of its redox congeners. We highlight the functional implications of these trends for the reactivity of iron-sulfur cubanes.
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Affiliation(s)
- Liam Grunwald
- Department
of Chemistry and Applied Biosciences (D-CHAB), Swiss Federal Institute of Technology Zürich (ETHZ), Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Daniel F. Abbott
- Department
of Chemistry and Applied Biosciences (D-CHAB), Swiss Federal Institute of Technology Zürich (ETHZ), Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Victor Mougel
- Department
of Chemistry and Applied Biosciences (D-CHAB), Swiss Federal Institute of Technology Zürich (ETHZ), Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
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2
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Warmack RA, Rees DC. Nitrogenase beyond the Resting State: A Structural Perspective. Molecules 2023; 28:7952. [PMID: 38138444 PMCID: PMC10745740 DOI: 10.3390/molecules28247952] [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: 11/06/2023] [Revised: 11/30/2023] [Accepted: 12/01/2023] [Indexed: 12/24/2023] Open
Abstract
Nitrogenases have the remarkable ability to catalyze the reduction of dinitrogen to ammonia under physiological conditions. How does this happen? The current view of the nitrogenase mechanism focuses on the role of hydrides, the binding of dinitrogen in a reductive elimination process coupled to loss of dihydrogen, and the binding of substrates to a binuclear site on the active site cofactor. This review focuses on recent experimental characterizations of turnover relevant forms of the enzyme determined by cryo-electron microscopy and other approaches, and comparison of these forms to the resting state enzyme and the broader family of iron sulfur clusters. Emerging themes include the following: (i) The obligatory coupling of protein and electron transfers does not occur in synthetic and small-molecule iron-sulfur clusters. The coupling of these processes in nitrogenase suggests that they may involve unique features of the cofactor, such as hydride formation on the trigonal prismatic arrangement of irons, protonation of belt sulfurs, and/or protonation of the interstitial carbon. (ii) Both the active site cofactor and protein are dynamic under turnover conditions; the changes are such that more highly reduced forms may differ in key ways from the resting-state structure. Homocitrate appears to play a key role in coupling cofactor and protein dynamics. (iii) Structural asymmetries are observed in nitrogenase under turnover-relevant conditions by cryo-electron microscopy, although the mechanistic relevance of these states (such as half-of-sites reactivity) remains to be established.
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Affiliation(s)
- Rebeccah A. Warmack
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA
| | - Douglas C. Rees
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- Howard Hughes Medical Institute, California Institute of Technology, Pasadena, CA 91125, USA
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3
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Hiromoto T, Nishikawa K, Inoue S, Ogata H, Hori Y, Kusaka K, Hirano Y, Kurihara K, Shigeta Y, Tamada T, Higuchi Y. New insights into the oxidation process from neutron and X-ray crystal structures of an O 2-sensitive [NiFe]-hydrogenase. Chem Sci 2023; 14:9306-9315. [PMID: 37712026 PMCID: PMC10498676 DOI: 10.1039/d3sc02156d] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 08/11/2023] [Indexed: 09/16/2023] Open
Abstract
[NiFe]-hydrogenase from Desulfovibrio vulgaris Miyazaki F is an O2-sensitive enzyme that is inactivated in the presence of O2 but the oxidized enzyme can recover its catalytic activity by reacting with H2 under anaerobic conditions. Here, we report the first neutron structure of [NiFe]-hydrogenase in its oxidized state, determined at a resolution of 2.20 Å. This resolution allowed us to reinvestigate the structure of the oxidized active site and to observe the positions of protons in several short hydrogen bonds. X-ray anomalous scattering data revealed that a part of the Ni ion is dissociated from the active site Ni-Fe complex and forms a new square-planar Ni complex, accompanied by rearrangement of the coordinated thiolate ligands. One of the thiolate Sγ atoms is oxidized to a sulfenate anion but remains attached to the Ni ion, which was evaluated by quantum chemical calculations. These results suggest that the square-planar complex can be generated by the attack of reactive oxygen species derived from O2, as distinct from one-electron oxidation leading to a conventional oxidized form of the Ni-Fe complex. Another major finding of this neutron structure analysis is that the Cys17S thiolate Sγ atom coordinating to the proximal Fe-S cluster forms an unusual hydrogen bond with the main-chain amide N atom of Gly19S with a distance of 3.25 Å, where the amide proton appears to be delocalized between the donor and acceptor atoms. This observation provides insight into the contribution of the coordinated thiolate ligands to the redox reaction of the Fe-S cluster.
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Affiliation(s)
- Takeshi Hiromoto
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology 4-9-1 Anagawa, Inage Chiba 263-8555 Japan
- Graduate School of Science, University of Hyogo 3-2-1 Koto, Kamigori Hyogo 678-1297 Japan
| | - Koji Nishikawa
- Graduate School of Science, University of Hyogo 3-2-1 Koto, Kamigori Hyogo 678-1297 Japan
| | - Seiya Inoue
- Graduate School of Science, University of Hyogo 3-2-1 Koto, Kamigori Hyogo 678-1297 Japan
| | - Hideaki Ogata
- Graduate School of Science, University of Hyogo 3-2-1 Koto, Kamigori Hyogo 678-1297 Japan
| | - Yuta Hori
- Center for Computational Sciences, University of Tsukuba 1-1-1 Tennodai Tsukuba Ibaraki 305-8577 Japan
| | - Katsuhiro Kusaka
- Neutron Industrial Application Promotion Center, Comprehensive Research Organization for Science and Society 162-1 Shirakata, Tokai Ibaraki 319-1106 Japan
| | - Yu Hirano
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology 4-9-1 Anagawa, Inage Chiba 263-8555 Japan
- Department of Quantum Life Science, Graduate School of Science, Chiba University 1-33 Yayoi, Inage Chiba 263-8522 Japan
| | - Kazuo Kurihara
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology 4-9-1 Anagawa, Inage Chiba 263-8555 Japan
| | - Yasuteru Shigeta
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology 4-9-1 Anagawa, Inage Chiba 263-8555 Japan
- Center for Computational Sciences, University of Tsukuba 1-1-1 Tennodai Tsukuba Ibaraki 305-8577 Japan
| | - Taro Tamada
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology 4-9-1 Anagawa, Inage Chiba 263-8555 Japan
- Department of Quantum Life Science, Graduate School of Science, Chiba University 1-33 Yayoi, Inage Chiba 263-8522 Japan
| | - Yoshiki Higuchi
- Graduate School of Science, University of Hyogo 3-2-1 Koto, Kamigori Hyogo 678-1297 Japan
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4
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Li L, Zhou L, Jiang C, Liu Z, Meng D, Luo F, He Q, Yin H. AI-driven pan-proteome analyses reveal insights into the biohydrometallurgical properties of Acidithiobacillia. Front Microbiol 2023; 14:1243987. [PMID: 37744906 PMCID: PMC10512742 DOI: 10.3389/fmicb.2023.1243987] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 08/21/2023] [Indexed: 09/26/2023] Open
Abstract
Microorganism-mediated biohydrometallurgy, a sustainable approach for metal recovery from ores, relies on the metabolic activity of acidophilic bacteria. Acidithiobacillia with sulfur/iron-oxidizing capacities are extensively studied and applied in biohydrometallurgy-related processes. However, only 14 distinct proteins from Acidithiobacillia have experimentally determined structures currently available. This significantly hampers in-depth investigations of Acidithiobacillia's structure-based biological mechanisms pertaining to its relevant biohydrometallurgical processes. To address this issue, we employed a state-of-the-art artificial intelligence (AI)-driven approach, with a median model confidence of 0.80, to perform high-quality full-chain structure predictions on the pan-proteome (10,458 proteins) of the type strain Acidithiobacillia. Additionally, we conducted various case studies on de novo protein structural prediction, including sulfate transporter and iron oxidase, to demonstrate how accurate structure predictions and gene co-occurrence networks can contribute to the development of mechanistic insights and hypotheses regarding sulfur and iron utilization proteins. Furthermore, for the unannotated proteins that constitute 35.8% of the Acidithiobacillia proteome, we employed the deep-learning algorithm DeepFRI to make structure-based functional predictions. As a result, we successfully obtained gene ontology (GO) terms for 93.6% of these previously unknown proteins. This study has a significant impact on improving protein structure and function predictions, as well as developing state-of-the-art techniques for high-throughput analysis of large proteomic data.
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Affiliation(s)
- Liangzhi Li
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| | - Lei Zhou
- Beijing Research Institute of Chemical Engineering and Metallurgy, Beijing, China
| | - Chengying Jiang
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Zhenghua Liu
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| | - Delong Meng
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
| | - Feng Luo
- School of Computing, Clemson University, Clemson, SC, United States
| | - Qiang He
- Department of Civil and Environmental Engineering, University of Tennessee, Knoxville, Knoxville, TN, United States
| | - Huaqun Yin
- School of Minerals Processing and Bioengineering, Central South University, Changsha, China
- Key Laboratory of Biometallurgy of Ministry of Education, Central South University, Changsha, China
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5
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Hanazono Y, Hirano Y, Tamada T, Miki K. Description of peptide bond planarity from high-resolution neutron crystallography. Biophys Physicobiol 2023; 20:e200035. [PMID: 38124796 PMCID: PMC10728621 DOI: 10.2142/biophysico.bppb-v20.0035] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 09/04/2023] [Indexed: 12/23/2023] Open
Abstract
Neutron crystallography is a highly effective method for visualizing hydrogen atoms in proteins. In our recent study, we successfully determined the high-resolution (1.2 Å) neutron structure of high-potential iron-sulfur protein, refining the coordinates of some amide protons without any geometric restraints. Interestingly, we observed that amide protons are deviated from the peptide plane due to electrostatic interactions. Moreover, the difference in the position of the amide proton of Cys75 between reduced and oxidized states is possibly attributed to the electron storage capacity of the iron-sulfur cluster. Additionally, we have discussed about the rigidity of the iron-sulfur cluster based on the results of the hydrogen-deuterium exchange. Our research underscores the significance of neutron crystallography in protein structure elucidation, enriching our understanding of protein functions at an atomic resolution.
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Affiliation(s)
- Yuya Hanazono
- Medical Research Institute, Tokyo Medical and Dental University, Bunkyo-ku, Tokyo 113-8510, Japan
| | - Yu Hirano
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology, Inage-ku, Chiba 263-8555, Japan
- Department of Quantum Life Science, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan
| | - Taro Tamada
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology, Inage-ku, Chiba 263-8555, Japan
- Department of Quantum Life Science, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan
| | - Kunio Miki
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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6
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Hanazono Y, Hirano Y, Takeda K, Kusaka K, Tamada T, Miki K. Revisiting the concept of peptide bond planarity in an iron-sulfur protein by neutron structure analysis. SCIENCE ADVANCES 2022; 8:eabn2276. [PMID: 35594350 PMCID: PMC9122329 DOI: 10.1126/sciadv.abn2276] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/12/2021] [Accepted: 04/05/2022] [Indexed: 06/15/2023]
Abstract
The planarity of the peptide bond is important for the stability and structure formation of proteins. However, substantial distortion of peptide bonds has been reported in several high-resolution structures and computational analyses. To investigate the peptide bond planarity, including hydrogen atoms, we report a 1.2-Å resolution neutron structure of the oxidized form of high-potential iron-sulfur protein. This high-resolution neutron structure shows that the nucleus positions of the amide protons deviate from the peptide plane and shift toward the acceptors. The planarity of the H─N─C═O plane depends strongly on the pyramidalization of the nitrogen atom. Moreover, the orientation of the amide proton of Cys75 is different in the reduced and oxidized states, possibly because of the electron storage capacity of the iron-sulfur cluster.
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Affiliation(s)
- Yuya Hanazono
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology, Tokai, Ibaraki 319-1106, Japan
| | - Yu Hirano
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology, Tokai, Ibaraki 319-1106, Japan
- JST, PRESTO, Kawaguchi, Saitama 332-0012, Japan
| | - Kazuki Takeda
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
| | - Katsuhiro Kusaka
- Frontier Research Center for Applied Atomic Sciences, Ibaraki University, Tokai, Ibaraki 319-1106 Japan
| | - Taro Tamada
- Institute for Quantum Life Science, National Institutes for Quantum Science and Technology, Tokai, Ibaraki 319-1106, Japan
| | - Kunio Miki
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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7
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Expression, purification, characterization and direct electrochemistry of two HiPIPs from Acidithiobacillus caldus SM-1. Anal Biochem 2022; 650:114724. [DOI: 10.1016/j.ab.2022.114724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Revised: 04/15/2022] [Accepted: 05/05/2022] [Indexed: 11/18/2022]
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8
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Di Rocco G, Battistuzzi G, Borsari M, Bortolotti CA, Ranieri A, Sola M. The enthalpic and entropic terms of the reduction potential of metalloproteins: Determinants and interplay. Coord Chem Rev 2021. [DOI: 10.1016/j.ccr.2021.214071] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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9
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Radon C, Mittelstädt G, Duffus BR, Bürger J, Hartmann T, Mielke T, Teutloff C, Leimkühler S, Wendler P. Cryo-EM structures reveal intricate Fe-S cluster arrangement and charging in Rhodobacter capsulatus formate dehydrogenase. Nat Commun 2020; 11:1912. [PMID: 32313256 PMCID: PMC7171172 DOI: 10.1038/s41467-020-15614-0] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2019] [Accepted: 03/19/2020] [Indexed: 11/09/2022] Open
Abstract
Metal-containing formate dehydrogenases (FDH) catalyse the reversible oxidation of formate to carbon dioxide at their molybdenum or tungsten active site. They display a diverse subunit and cofactor composition, but structural information on these enzymes is limited. Here we report the cryo-electron microscopic structures of the soluble Rhodobacter capsulatus FDH (RcFDH) as isolated and in the presence of reduced nicotinamide adenine dinucleotide (NADH). RcFDH assembles into a 360 kDa dimer of heterotetramers revealing a putative interconnection of electron pathway chains. In the presence of NADH, the RcFDH structure shows charging of cofactors, indicative of an increased electron load. Rhodobacter capsulatus NAD+ dependent formate dehydrogenase (RcFDH) is a molybdoenzyme that catalyses the reversible oxidation of formate to carbon dioxide, and is of interest for biotechnological applications. Here the authors present the cryo-EM structures of RcFDH as isolated from R. capsulatus and in the reduced state with bound NADH, and discuss the enzyme mechanism.
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Affiliation(s)
- Christin Radon
- Institute of Biochemistry and Biology, Department of Biochemistry, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Potsdam-Golm, Germany
| | - Gerd Mittelstädt
- Institute of Biochemistry and Biology, Department of Molecular Enzymology, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Potsdam-Golm, Germany.,Ferrier Research Institute, Victoria University of Wellington, Kelburn Parade, Wellington, 6012, New Zealand
| | - Benjamin R Duffus
- Institute of Biochemistry and Biology, Department of Molecular Enzymology, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Potsdam-Golm, Germany
| | - Jörg Bürger
- Max-Planck Institute of Molecular Genetics, Ihnestrasse 63-73, 14195, Berlin, Germany.,Charité, Institut für Medizinische Physik und Biophysik, Charitéplatz 1, 10117, Berlin, Germany
| | - Tobias Hartmann
- Institute of Biochemistry and Biology, Department of Molecular Enzymology, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Potsdam-Golm, Germany
| | - Thorsten Mielke
- Max-Planck Institute of Molecular Genetics, Ihnestrasse 63-73, 14195, Berlin, Germany
| | - Christian Teutloff
- Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195, Berlin, Germany
| | - Silke Leimkühler
- Institute of Biochemistry and Biology, Department of Molecular Enzymology, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Potsdam-Golm, Germany
| | - Petra Wendler
- Institute of Biochemistry and Biology, Department of Biochemistry, University of Potsdam, Karl-Liebknecht Strasse 24-25, 14476, Potsdam-Golm, Germany.
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10
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Hanazono Y, Takeda K, Miki K. Characterization of perdeuterated high-potential iron-sulfur protein with high-resolution X-ray crystallography. Proteins 2019; 88:251-259. [PMID: 31365157 DOI: 10.1002/prot.25793] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2019] [Revised: 07/23/2019] [Accepted: 07/27/2019] [Indexed: 11/12/2022]
Abstract
Perdeuteration in neutron crystallography is an effective method for determining the positions of hydrogen atoms in proteins. However, there is shortage of evidence that the high-resolution details of perdeuterated proteins are consistent with those of the nondeuterated proteins. In this study, we determined the X-ray structure of perdeuterated high-potential iron-sulfur protein (HiPIP) at a high resolution of 0.85 å resolution. The comparison of the nondeuterated and perdeuterated structures of HiPIP revealed slight differences between the two structures. The spectroscopic and spectroelectrochemical studies also showed that perdeuterated HiPIP has approximately the same characteristics as nondeuterated HiPIP. These results further emphasize the suitability of using perdeuterated proteins in the high-resolution neutron crystallography.
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Affiliation(s)
- Yuya Hanazono
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Kazuki Takeda
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, Japan
| | - Kunio Miki
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, Japan
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11
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Li J, Li H. Mechanical Unfolding Pathway of the High-Potential Iron-Sulfur Protein Revealed by Single-Molecule Atomic Force Microscopy: Toward a General Unfolding Mechanism for Iron-sulfur Proteins. J Phys Chem B 2018; 122:9340-9349. [PMID: 30212202 DOI: 10.1021/acs.jpcb.8b07614] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
High-potential iron-sulfur proteins (HiPIPs) are an important class of metalloproteins with a [4Fe-4S] cluster coordinated by four cysteine residues. Distinct from other iron-sulfur proteins, the cluster in HiPIP has a high reduction potential, making it an essential electron carrier in bacterial photosynthesis. Here, we combined single-molecule atomic force microscopy and protein engineering techniques to investigate the mechanical unfolding mechanism of HiPIP from Chromatium tepidum (cHiPIP). We found that cHiPIP unfolds in a two-step fashion with the protein sequence sequestered by the iron-sulfur center as a stable unfolding intermediate state. The rupture of the iron-sulfur center of cHiPIP proceeds in two distinct parallel pathways; one pathway involves the concurrent rupture of multiple iron-thiolate bonds, and the other one involves the sequential rupture of the iron-thiolate bonds. This mechanistic information was further confirmed by mutational studies. We found that the rupture of the iron-thiolate bonds in reduced and oxidized cHiPIP occurred in the range of 150-180 pN at a pulling speed of 400 nm/s, similar to that measured for iron-thiolate bonds in rubredoxin and ferredoxin. Our results may have important implications for understanding the general unfolding mechanism governing iron-sulfur proteins, as well as the mechanism governing the mechanical rupture of the iron-sulfur center.
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Affiliation(s)
- Jiayu Li
- Department of Chemistry , University of British Columbia , Vancouver , British Columbia V6T 1Z1 , Canada
| | - Hongbin Li
- Department of Chemistry , University of British Columbia , Vancouver , British Columbia V6T 1Z1 , Canada
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12
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Tse ECM, Zwang TJ, Barton JK. The Oxidation State of [4Fe4S] Clusters Modulates the DNA-Binding Affinity of DNA Repair Proteins. J Am Chem Soc 2017; 139:12784-12792. [PMID: 28817778 PMCID: PMC5929122 DOI: 10.1021/jacs.7b07230] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A central question important to understanding DNA repair is how certain proteins are able to search for, detect, and fix DNA damage on a biologically relevant time scale. A feature of many base excision repair proteins is that they contain [4Fe4S] clusters that may aid their search for lesions. In this paper, we establish the importance of the oxidation state of the redox-active [4Fe4S] cluster in the DNA damage detection process. We utilize DNA-modified electrodes to generate repair proteins with [4Fe4S] clusters in the 2+ and 3+ states by bulk electrolysis under an O2-free atmosphere. Anaerobic microscale thermophoresis results indicate that proteins carrying [4Fe4S]3+ clusters bind to DNA 550 times more tightly than those with [4Fe4S]2+ clusters. The measured increase in DNA-binding affinity matches the calculated affinity change associated with the redox potential shift observed for [4Fe4S] cluster proteins upon binding to DNA. We further devise an electrostatic model that shows this change in DNA-binding affinity of these proteins can be fully explained by the differences in electrostatic interactions between DNA and the [4Fe4S] cluster in the reduced versus oxidized state. We then utilize atomic force microscopy (AFM) to demonstrate that the redox state of the [4Fe4S] clusters regulates the ability of two DNA repair proteins, Endonuclease III and DinG, to bind preferentially to DNA duplexes containing a single site of DNA damage (here a base mismatch) which inhibits DNA charge transport. Together, these results show that the reduction and oxidation of [4Fe4S] clusters through DNA-mediated charge transport facilitates long-range signaling between [4Fe4S] repair proteins. The redox-modulated change in DNA-binding affinity regulates the ability of [4Fe4S] repair proteins to collaborate in the lesion detection process.
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Affiliation(s)
- Edmund C. M. Tse
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Theodore J. Zwang
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Jacqueline K. Barton
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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