1
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Chatterjee S, Nochebuena J, Cisneros GA. Impact of an Ionic Liquid Solution on Horseradish Peroxidase Activity. J Am Chem Soc 2024; 146:13247-13257. [PMID: 38701006 DOI: 10.1021/jacs.4c01100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2024]
Abstract
Horseradish peroxidase (HRP) is an enzyme that oxidizes pollutants from wastewater. A previous report indicated that peroxidases can have an enhancement in initial enzymatic activity in an aqueous solution of 0.26 M 1-ethyl-3-methylimidazolium ethyl sulfate ([EMIm][EtSO4]) at neutral pH. However, the atomistic details remain elusive. In the enzymatic landscape of HRP, compound II (Cpd II) plays a key role and involves a histidine (H42) residue. Cpd II exists as oxoferryl (2a) or hydroxoferryl (2b(FeIV)) forms, where 2a is the predominantly observed form in experimental studies. Intriguingly, the ferric 2b(FeIII) form seen in synthetic complexes has not been observed in HRP. Here, we have investigated the structure and dynamics of HRP in pure water and aqueous [EMIm][EtSO4] (0.26 M), as well as the reaction mechanism of 2a to 2b conversion using polarizable molecular dynamics (MD) simulations and quantum mechanics/molecular mechanics (QM/MM) calculations. When HRP is solvated in aq [EMIm][EtSO4], the catalytic water displaces, and H42 directly orients over the ferryl moiety, allowing a direct proton transfer (PT) with a significant energy barrier reduction. Conversely, in neat water, the reaction of 2a to 2b follows the previously reported mechanism. We further investigated the deprotonated form of H42. Analysis of the electric fields at the active site indicates that the aq [EMIm][EtSO4] medium facilitates the reaction by providing a more favorable environment compared with the system solvated in neat water. Overall, the atomic level supports the previous experimental observations and underscores the importance of favorable electric fields in the active site to promote catalysis.
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Affiliation(s)
- Shubham Chatterjee
- Department of Chemistry and Biochemistry, University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Jorge Nochebuena
- Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, United States
| | - G Andrés Cisneros
- Department of Chemistry and Biochemistry, University of Texas at Dallas, Richardson, Texas 75080, United States
- Department of Physics, University of Texas at Dallas, Richardson, Texas 75080, United States
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2
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Ansari M, Bhattacharjee S, Pantazis DA. Correlating Structure with Spectroscopy in Ascorbate Peroxidase Compound II. J Am Chem Soc 2024; 146:9640-9656. [PMID: 38530124 PMCID: PMC11009960 DOI: 10.1021/jacs.3c13169] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 03/15/2024] [Accepted: 03/15/2024] [Indexed: 03/27/2024]
Abstract
Structural and spectroscopic investigations of compound II in ascorbate peroxidase (APX) have yielded conflicting conclusions regarding the protonation state of the crucial Fe(IV) intermediate. Neutron diffraction and crystallographic data support an iron(IV)-hydroxo formulation, whereas Mössbauer, X-ray absorption (XAS), and nuclear resonance vibrational spectroscopy (NRVS) studies appear consistent with an iron(IV)-oxo species. Here we examine APX with spectroscopy-oriented QM/MM calculations and extensive exploration of the conformational space for both possible formulations of compound II. We establish that irrespective of variations in the orientation of a vicinal arginine residue and potential reorganization of proximal water molecules and hydrogen bonding, the Fe-O distances for the oxo and hydroxo forms consistently fall within distinct, narrow, and nonoverlapping ranges. The accuracy of geometric parameters is validated by coupled-cluster calculations with the domain-based local pair natural orbital approach, DLPNO-CCSD(T). QM/MM calculations of spectroscopic properties are conducted for all structural variants, encompassing Mössbauer, optical, X-ray absorption, and X-ray emission spectroscopies and NRVS. All spectroscopic observations can be assigned uniquely to an Fe(IV)═O form. A terminal hydroxy group cannot be reconciled with the spectroscopic data. Under no conditions can the Fe(IV)═O distance be sufficiently elongated to approach the crystallographically reported Fe-O distance. The latter is consistent only with a hydroxo species, either Fe(IV) or Fe(III). Our findings strongly support the Fe(IV)═O formulation of APX-II and highlight unresolved discrepancies in the nature of samples used across different experimental studies.
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Affiliation(s)
- Mursaleem Ansari
- Max-Planck-Institut für
Kohlenforschung, Kaiser-Wilhelm-Platz
1, Mülheim an der Ruhr 45470, Germany
| | - Sinjini Bhattacharjee
- Max-Planck-Institut für
Kohlenforschung, Kaiser-Wilhelm-Platz
1, Mülheim an der Ruhr 45470, Germany
| | - Dimitrios A. Pantazis
- Max-Planck-Institut für
Kohlenforschung, Kaiser-Wilhelm-Platz
1, Mülheim an der Ruhr 45470, Germany
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3
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Guo C, Chadwick RJ, Foulis A, Bedendi G, Lubskyy A, Rodriguez KJ, Pellizzoni MM, Milton RD, Beveridge R, Bruns N. Peroxidase Activity of Myoglobin Variants Reconstituted with Artificial Cofactors. Chembiochem 2022; 23:e202200197. [PMID: 35816250 PMCID: PMC9545363 DOI: 10.1002/cbic.202200197] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 07/08/2022] [Indexed: 02/02/2023]
Abstract
Myoglobin (Mb) can react with hydrogen peroxide (H2 O2 ) to form a highly active intermediate compound and catalyse oxidation reactions. To enhance this activity, known as pseudo-peroxidase activity, previous studies have focused on the modification of key amino acid residues of Mb or the heme cofactor. In this work, the Mb scaffold (apo-Mb) was systematically reconstituted with a set of cofactors based on six metal ions and two ligands. These Mb variants were fully characterised by UV-Vis spectroscopy, circular dichroism (CD) spectroscopy, inductively coupled plasma mass spectrometry (ICP-MS) and native mass spectrometry (nMS). The steady-state kinetics of guaiacol oxidation and 2,4,6-trichlorophenol (TCP) dehalogenation catalysed by Mb variants were determined. Mb variants with iron chlorin e6 (Fe-Ce6) and manganese chlorin e6 (Mn-Ce6) cofactors were found to have improved catalytic efficiency for both guaiacol and TCP substrates in comparison with wild-type Mb, i. e. Fe-protoporphyrin IX-Mb. Furthermore, the selected cofactors were incorporated into the scaffold of a Mb mutant, swMb H64D. Enhanced peroxidase activity for both substrates were found via the reconstitution of Fe-Ce6 into the mutant scaffold.
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Affiliation(s)
- Chao Guo
- Department of Pure and Applied ChemistryUniversity of Strathclyde295 Cathedral StreetG1 1XLGlasgowUK
| | - Robert J. Chadwick
- Department of Pure and Applied ChemistryUniversity of Strathclyde295 Cathedral StreetG1 1XLGlasgowUK
| | - Adam Foulis
- Department of Pure and Applied ChemistryUniversity of Strathclyde295 Cathedral StreetG1 1XLGlasgowUK
| | - Giada Bedendi
- Department of Inorganic and Analytical ChemistryUniversity of Geneva1211Geneva 4Switzerland
| | - Andriy Lubskyy
- Adolphe Merkle InstituteUniversity of FribourgChemin des Verdiers 41700FribourgSwitzerland
| | - Kyle J. Rodriguez
- Adolphe Merkle InstituteUniversity of FribourgChemin des Verdiers 41700FribourgSwitzerland
| | - Michela M. Pellizzoni
- Adolphe Merkle InstituteUniversity of FribourgChemin des Verdiers 41700FribourgSwitzerland
| | - Ross D. Milton
- Department of Inorganic and Analytical ChemistryUniversity of Geneva1211Geneva 4Switzerland
| | - Rebecca Beveridge
- Department of Pure and Applied ChemistryUniversity of Strathclyde295 Cathedral StreetG1 1XLGlasgowUK
| | - Nico Bruns
- Department of Pure and Applied ChemistryUniversity of Strathclyde295 Cathedral StreetG1 1XLGlasgowUK,Department of ChemistryTechnical University of DarmstadtAlarich-Weiss-Str. 464287DarmstadtGermany
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4
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Kwon H, Basran J, Pathak C, Hussain M, Freeman SL, Fielding AJ, Bailey AJ, Stefanou N, Sparkes HA, Tosha T, Yamashita K, Hirata K, Murakami H, Ueno G, Ago H, Tono K, Yamamoto M, Sawai H, Shiro Y, Sugimoto H, Raven EL, Moody PCE. XFEL Crystal Structures of Peroxidase Compound II. Angew Chem Int Ed Engl 2021; 60:14578-14585. [PMID: 33826799 PMCID: PMC8251747 DOI: 10.1002/anie.202103010] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2021] [Indexed: 01/07/2023]
Abstract
Oxygen activation in all heme enzymes requires the formation of high oxidation states of iron, usually referred to as ferryl heme. There are two known intermediates: Compound I and Compound II. The nature of the ferryl heme-and whether it is an FeIV =O or FeIV -OH species-is important for controlling reactivity across groups of heme enzymes. The most recent evidence for Compound I indicates that the ferryl heme is an unprotonated FeIV =O species. For Compound II, the nature of the ferryl heme is not unambiguously established. Here, we report 1.06 Å and 1.50 Å crystal structures for Compound II intermediates in cytochrome c peroxidase (CcP) and ascorbate peroxidase (APX), collected using the X-ray free electron laser at SACLA. The structures reveal differences between the two peroxidases. The iron-oxygen bond length in CcP (1.76 Å) is notably shorter than in APX (1.87 Å). The results indicate that the ferryl species is finely tuned across Compound I and Compound II species in closely related peroxidase enzymes. We propose that this fine-tuning is linked to the functional need for proton delivery to the heme.
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Affiliation(s)
- Hanna Kwon
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Jaswir Basran
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Chinar Pathak
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Mahdi Hussain
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Samuel L. Freeman
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Alistair J. Fielding
- Centre for Natural Products Discovery, Pharmacy and Biomolecular SciencesLiverpool John Moores UniversityJames Parsons Building, Byrom StreetLiverpoolL3 3AFUK
| | - Anna J. Bailey
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Natalia Stefanou
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Hazel A. Sparkes
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | | | - Keitaro Yamashita
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
- Present address: MRC Laboratory of Molecular BiologyFrancis Crick Avenue, Cambridge Biomedical CampusCambridgeCB1 0QHUK
| | - Kunio Hirata
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Hironori Murakami
- Japan Synchrotron Radiation Research Institute1-1-1 KoutoSayoHyogo679-5198Japan
| | - Go Ueno
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Hideo Ago
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute1-1-1 KoutoSayoHyogo679-5198Japan
| | | | - Hitomi Sawai
- Graduate School of Life ScienceUniversity of Hyogo3-2-1 Kouto, Kamigori-choAko-gunHyogo678-1297Japan
| | - Yoshitsugu Shiro
- Graduate School of Life ScienceUniversity of Hyogo3-2-1 Kouto, Kamigori-choAko-gunHyogo678-1297Japan
| | | | - Emma L. Raven
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Peter C. E. Moody
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
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5
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Kwon H, Basran J, Pathak C, Hussain M, Freeman SL, Fielding AJ, Bailey AJ, Stefanou N, Sparkes HA, Tosha T, Yamashita K, Hirata K, Murakami H, Ueno G, Ago H, Tono K, Yamamoto M, Sawai H, Shiro Y, Sugimoto H, Raven EL, Moody PCE. XFEL Crystal Structures of Peroxidase Compound II. ANGEWANDTE CHEMIE (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2021; 133:14699-14706. [PMID: 38505375 PMCID: PMC10947387 DOI: 10.1002/ange.202103010] [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: 03/01/2021] [Indexed: 03/21/2024]
Abstract
Oxygen activation in all heme enzymes requires the formation of high oxidation states of iron, usually referred to as ferryl heme. There are two known intermediates: Compound I and Compound II. The nature of the ferryl heme-and whether it is an FeIV=O or FeIV-OH species-is important for controlling reactivity across groups of heme enzymes. The most recent evidence for Compound I indicates that the ferryl heme is an unprotonated FeIV=O species. For Compound II, the nature of the ferryl heme is not unambiguously established. Here, we report 1.06 Å and 1.50 Å crystal structures for Compound II intermediates in cytochrome c peroxidase (CcP) and ascorbate peroxidase (APX), collected using the X-ray free electron laser at SACLA. The structures reveal differences between the two peroxidases. The iron-oxygen bond length in CcP (1.76 Å) is notably shorter than in APX (1.87 Å). The results indicate that the ferryl species is finely tuned across Compound I and Compound II species in closely related peroxidase enzymes. We propose that this fine-tuning is linked to the functional need for proton delivery to the heme.
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Affiliation(s)
- Hanna Kwon
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Jaswir Basran
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Chinar Pathak
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Mahdi Hussain
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
| | - Samuel L. Freeman
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Alistair J. Fielding
- Centre for Natural Products Discovery, Pharmacy and Biomolecular SciencesLiverpool John Moores UniversityJames Parsons Building, Byrom StreetLiverpoolL3 3AFUK
| | - Anna J. Bailey
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Natalia Stefanou
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Hazel A. Sparkes
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | | | - Keitaro Yamashita
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
- Present address: MRC Laboratory of Molecular BiologyFrancis Crick Avenue, Cambridge Biomedical CampusCambridgeCB1 0QHUK
| | - Kunio Hirata
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Hironori Murakami
- Japan Synchrotron Radiation Research Institute1-1-1 KoutoSayoHyogo679-5198Japan
| | - Go Ueno
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Hideo Ago
- RIKEN SPring-8 Center1-1-1 KoutoSayoHyogo679-5148Japan
| | - Kensuke Tono
- Japan Synchrotron Radiation Research Institute1-1-1 KoutoSayoHyogo679-5198Japan
| | | | - Hitomi Sawai
- Graduate School of Life ScienceUniversity of Hyogo3-2-1 Kouto, Kamigori-choAko-gunHyogo678-1297Japan
| | - Yoshitsugu Shiro
- Graduate School of Life ScienceUniversity of Hyogo3-2-1 Kouto, Kamigori-choAko-gunHyogo678-1297Japan
| | | | - Emma L. Raven
- School of ChemistryUniversity of BristolCantock's CloseBristolBS8 1TSUK
| | - Peter C. E. Moody
- Department of Molecular and Cell Biology and Leicester Institute of Structural and Chemical BiologyUniversity of LeicesterLancaster RoadLeicesterLE1 7RHUK
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6
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Wang L, Kruse H, Sobolev OV, Moriarty NW, Waller MP, Afonine PV, Biczysko M. Real-space quantum-based refinement for cryo-EM: Q|R#3. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2020; 76:1184-1191. [PMID: 33263324 DOI: 10.1107/s2059798320013194] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/25/2020] [Accepted: 09/29/2020] [Indexed: 11/10/2022]
Abstract
Electron cryo-microscopy (cryo-EM) is rapidly becoming a major competitor to X-ray crystallography, especially for large structures that are difficult or impossible to crystallize. While recent spectacular technological improvements have led to significantly higher resolution three-dimensional reconstructions, the average quality of cryo-EM maps is still at the low-resolution end of the range compared with crystallography. A long-standing challenge for atomic model refinement has been the production of stereochemically meaningful models for this resolution regime. Here, it is demonstrated that including accurate model geometry restraints derived from ab initio quantum-chemical calculations (HF-D3/6-31G) can improve the refinement of an example structure (chain A of PDB entry 3j63). The robustness of the procedure is tested for additional structures with up to 7000 atoms (PDB entry 3a5x and chain C of PDB entry 5fn5) using the less expensive semi-empirical (GFN1-xTB) model. The necessary algorithms enabling real-space quantum refinement have been implemented in the latest version of qr.refine and are described here.
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Affiliation(s)
- Lum Wang
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People's Republic of China
| | - Holger Kruse
- Institute of Biophysics of the Czech Academy of Sciences, Brno, Czech Republic
| | - Oleg V Sobolev
- Molecular Biosciences and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Nigel W Moriarty
- Molecular Biosciences and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Mark P Waller
- Pending AI Pty Ltd, iAccelerat, Innovation Campus, North Wollongong, NSW 2500, Australia
| | - Pavel V Afonine
- Molecular Biosciences and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Malgorzata Biczysko
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People's Republic of China
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7
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Ledray AP, Krest CM, Yosca TH, Mittra K, Green MT. Ascorbate Peroxidase Compound II Is an Iron(IV) Oxo Species. J Am Chem Soc 2020; 142:10.1021/jacs.0c09108. [PMID: 33170000 PMCID: PMC8107191 DOI: 10.1021/jacs.0c09108] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The protonation state of the iron(IV) oxo (or ferryl) form of ascorbate peroxidase compound II (APX-II) is a subject of debate. It has been reported that this intermediate is best described as an iron(IV) hydroxide species. Neutron diffraction data obtained from putative APX-II crystals indicate a protonated oxygenic ligand at 1.88 Å from the heme iron. This finding, if correct, would be unprecedented. A basic iron(IV) oxo species has yet to be spectroscopically observed in a histidine-ligated heme enzyme. The importance of ferryl basicity lies in its connection to our fundamental understanding of C-H bond activation. Basic ferryl species have been proposed to facilitate the oxidation of inert C-H bonds, reactions that are unknown for histidine-ligated hemes enzymes. To provide further insight into the protonation status of APX-II, we examined the intermediate using a combination of Mössbauer and X-ray absorption spectroscopies. Our data indicate that APX-II is an iron(IV) oxo species with an Fe-O bond distance of 1.68 Å, a K-edge pre-edge absorption of 18 units, and Mössbauer parameters of ΔEq = 1.65 mm/s and δ = 0.03 mm/s.
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Affiliation(s)
- Aaron P Ledray
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Courtney M Krest
- Roach & Associates, Limited Liability Company, Seymour, Wisconsin 54942, United States
| | - Timothy H Yosca
- Department of Chemistry, University of California, Irvine, California 92697, United States
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Kaustuv Mittra
- Department of Chemistry, University of California, Irvine, California 92697, United States
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
| | - Michael T Green
- Department of Chemistry, University of California, Irvine, California 92697, United States
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, United States
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8
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Cao L, Ryde U. Quantum refinement with multiple conformations: application to the P-cluster in nitrogenase. Acta Crystallogr D Struct Biol 2020; 76:1145-1156. [PMID: 33135685 PMCID: PMC7604908 DOI: 10.1107/s2059798320012917] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2020] [Accepted: 09/21/2020] [Indexed: 11/17/2022] Open
Abstract
X-ray crystallography is the main source of atomistic information on the structure of proteins. Normal crystal structures are obtained as a compromise between the X-ray scattering data and a set of empirical restraints that ensure chemically reasonable bond lengths and angles. However, such restraints are not always available or accurate for nonstandard parts of the structure, for example substrates, inhibitors and metal sites. The method of quantum refinement, in which these empirical restraints are replaced by quantum-mechanical (QM) calculations, has previously been suggested for small but interesting parts of the protein. Here, this approach is extended to allow for multiple conformations in the QM region by performing separate QM calculations for each conformation. This approach is shown to work properly and leads to improved structures in terms of electron-density maps and real-space difference density Z-scores. It is also shown that the quality of the structures can be gauged using QM strain energies. The approach, called ComQumX-2QM, is applied to the P-cluster in two different crystal structures of the enzyme nitrogenase, i.e. an Fe8S7Cys6 cluster, used for electron transfer. One structure is at a very high resolution (1.0 Å) and shows a mixture of two different oxidation states, the fully reduced PN state (Fe82+, 20%) and the doubly oxidized P2+ state (80%). In the original crystal structure the coordinates differed for only two iron ions, but here it is shown that the two states also show differences in other atoms of up to 0.7 Å. The second structure is at a more modest resolution, 2.1 Å, and was originally suggested to show only the one-electron oxidized state, P1+. Here, it is shown that it is rather a 50/50% mixture of the P1+ and P2+ states and that many of the Fe-Fe and Fe-S distances in the original structure were quite inaccurate (by up to 0.8 Å). This shows that the new ComQumX-2QM approach can be used to sort out what is actually seen in crystal structures with dual conformations and to give locally improved coordinates.
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Affiliation(s)
- Lili Cao
- Department of Theoretical Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden
| | - Ulf Ryde
- Department of Theoretical Chemistry, Lund University, PO Box 124, 221 00 Lund, Sweden
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9
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Cao L, Caldararu O, Ryde U. Does the crystal structure of vanadium nitrogenase contain a reaction intermediate? Evidence from quantum refinement. J Biol Inorg Chem 2020; 25:847-861. [PMID: 32856107 PMCID: PMC7511287 DOI: 10.1007/s00775-020-01813-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 08/14/2020] [Indexed: 12/16/2022]
Abstract
Recently, a crystal structure of V-nitrogenase was presented, showing that one of the µ2 sulphide ions in the active site (S2B) is replaced by a lighter atom, suggested to be NH or NH2, i.e. representing a reaction intermediate. Moreover, a sulphur atom is found 7 Å from the S2B site, suggested to represent a storage site for this ion when it is displaced. We have re-evaluated this structure with quantum refinement, i.e. standard crystallographic refinement in which the empirical restraints (employed to ensure that the final structure makes chemical sense) are replaced by more accurate quantum-mechanical calculations. This allows us to test various interpretations of the structure, employing quantum-mechanical calculations to predict the ideal structure and to use crystallographic measures like the real-space Z-score and electron-density difference maps to decide which structure fits the crystallographic raw data best. We show that the structure contains an OH--bound state, rather than an N2-derived reaction intermediate. Moreover, the structure shows dual conformations in the active site with ~ 14% undissociated S2B ligand, but the storage site seems to be fully occupied, weakening the suggestion that it represents a storage site for the dissociated ligand.
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Affiliation(s)
- Lili Cao
- Department of Theoretical Chemistry, Chemical Centre, Lund University, P. O. Box 124, 221 00, Lund, Sweden
| | - Octav Caldararu
- Department of Theoretical Chemistry, Chemical Centre, Lund University, P. O. Box 124, 221 00, Lund, Sweden
| | - Ulf Ryde
- Department of Theoretical Chemistry, Chemical Centre, Lund University, P. O. Box 124, 221 00, Lund, Sweden.
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10
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Álvarez L, Suárez SA, González PJ, Brondino CD, Doctorovich F, Martí MA. The Underlying Mechanism of HNO Production by the Myoglobin-Mediated Oxidation of Hydroxylamine. Inorg Chem 2020; 59:7939-7952. [DOI: 10.1021/acs.inorgchem.9b02750] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Lucía Álvarez
- Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EHA, Argentina
- INQUIMAE-CONICET, Ciudad Universitaria, Buenos Aires C1428EHA, Argentina
| | - Sebastián A. Suárez
- Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EHA, Argentina
- INQUIMAE-CONICET, Ciudad Universitaria, Buenos Aires C1428EHA, Argentina
| | - Pablo J. González
- Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral y CONICET, S3000ZAA Santa Fe, Argentina
| | - Carlos D. Brondino
- Departamento de Física, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral y CONICET, S3000ZAA Santa Fe, Argentina
| | - Fabio Doctorovich
- Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EHA, Argentina
- INQUIMAE-CONICET, Ciudad Universitaria, Buenos Aires C1428EHA, Argentina
| | - Marcelo A. Martí
- Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EHA, Argentina
- IQUIBICEN-CONICET, Ciudad Universitaria, Buenos Aires C1428EHA, Argentina
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11
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Zheng M, Biczysko M, Xu Y, Moriarty NW, Kruse H, Urzhumtsev A, Waller MP, Afonine PV. Including crystallographic symmetry in quantum-based refinement: Q|R#2. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2020; 76:41-50. [PMID: 31909742 DOI: 10.1107/s2059798319015122] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 11/08/2019] [Indexed: 11/11/2022]
Abstract
Three-dimensional structure models refined using low-resolution data from crystallographic or electron cryo-microscopy experiments can benefit from high-quality restraints derived from quantum-chemical methods. However, nonperiodic atom-centered quantum-chemistry codes do not inherently account for nearest-neighbor interactions of crystallographic symmetry-related copies in a satisfactory way. Here, these nearest-neighbor effects have been included in the model by expanding to a super-cell and then truncating the super-cell to only include residues from neighboring cells that are interacting with the asymmetric unit. In this way, the fragmentation approach can adequately and efficiently include nearest-neighbor effects. It has previously been shown that a moderately sized X-ray structure can be treated using quantum methods if a fragmentation approach is applied. In this study, a target protein (PDB entry 4gif) was partitioned into a number of large fragments. The use of large fragments (typically hundreds of atoms) is tractable when a GPU-based package such as TeraChem is employed or cheaper (semi-empirical) methods are used. The QM calculations were run at the HF-D3/6-31G level. The models refined using a recently developed semi-empirical method (GFN2-xTB) were compared and contrasted. To validate the refinement procedure for a non-P1 structure, a standard set of crystallographic metrics were used. The robustness of the implementation is shown by refining 13 additional protein models across multiple space groups and a summary of the refinement metrics is presented.
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Affiliation(s)
- Min Zheng
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People's Republic of China
| | - Malgorzata Biczysko
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People's Republic of China
| | - Yanting Xu
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People's Republic of China
| | - Nigel W Moriarty
- Molecular Biosciences and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Holger Kruse
- Institute of Biophysics of the Czech Academy of Sciences, Královopolská 135, 612 65 Brno, Czech Republic
| | - Alexandre Urzhumtsev
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS-INSERM-UdS, 1 Rue Laurent Fries, BP 10142, 67404 Illkirch, France
| | - Mark P Waller
- Pending AI Pty Ltd, iAccelerate, Innovation Campus, Squires Way, North Wollongong, NSW 2500, Australia
| | - Pavel V Afonine
- Molecular Biosciences and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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12
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Mechanism of protonation of the over-reduced Mn4CaO5 cluster in photosystem II. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2019; 1860:148059. [DOI: 10.1016/j.bbabio.2019.148059] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 07/18/2019] [Accepted: 08/02/2019] [Indexed: 01/12/2023]
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13
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Lukac I, Abdelhakim H, Ward RA, St-Gallay SA, Madden JC, Leach AG. Predicting protein-ligand binding affinity and correcting crystal structures with quantum mechanical calculations: lactate dehydrogenase A. Chem Sci 2019; 10:2218-2227. [PMID: 30881647 PMCID: PMC6388092 DOI: 10.1039/c8sc04564j] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 12/19/2018] [Indexed: 12/22/2022] Open
Abstract
Accurately computing the geometry and energy of host-guest and protein-ligand interactions requires a physically accurate description of the forces in action. Quantum mechanics can provide this accuracy but the calculations can require a prohibitive quantity of computational resources. The size of the calculations can be reduced by including only the atoms of the receptor that are in close proximity to the ligand. We show that when combined with log P values for the ligand (which can be computed easily) this approach can significantly improve the agreement between computed and measured binding energies. When the approach is applied to lactate dehydrogenase A, it can make quantitative predictions about conformational, tautomeric and protonation state preferences as well as stereoselectivity and even identifies potential errors in structures deposited in the Protein Data Bank for this enzyme. By broadening the evidence base for these structures from only the diffraction data, more chemically realistic structures can be proposed.
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Affiliation(s)
- Iva Lukac
- School of Pharmacy and Biomolecular Sciences , Liverpool John Moores University , Byrom Street , Liverpool , L3 3AF , UK .
| | - Hend Abdelhakim
- School of Pharmacy and Biomolecular Sciences , Liverpool John Moores University , Byrom Street , Liverpool , L3 3AF , UK .
| | - Richard A Ward
- Chemistry, Oncology, IMED Biotech Unit , AstraZeneca , Cambridge , UK
| | - Stephen A St-Gallay
- Sygnature Discovery Ltd , Bio City, Pennyfoot St , Nottingham , NG1 1GF , UK
| | - Judith C Madden
- School of Pharmacy and Biomolecular Sciences , Liverpool John Moores University , Byrom Street , Liverpool , L3 3AF , UK .
| | - Andrew G Leach
- School of Pharmacy and Biomolecular Sciences , Liverpool John Moores University , Byrom Street , Liverpool , L3 3AF , UK .
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14
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Caldararu O, Oksanen E, Ryde U, Hedegård ED. Mechanism of hydrogen peroxide formation by lytic polysaccharide monooxygenase. Chem Sci 2019; 10:576-586. [PMID: 30746099 PMCID: PMC6334667 DOI: 10.1039/c8sc03980a] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 10/18/2018] [Indexed: 12/27/2022] Open
Abstract
Lytic polysaccharide monooxygenases (LPMOs) are copper-containing metalloenzymes that can cleave the glycosidic link in polysaccharides. This could become crucial for production of energy-efficient biofuels from recalcitrant polysaccharides. Although LPMOs are considered oxygenases, recent investigations have shown that H2O2 can also act as a co-substrate for LPMOs. Intriguingly, LPMOs generate H2O2 in the absence of a polysaccharide substrate. Here, we elucidate a new mechanism for H2O2 generation starting from an AA10-LPMO crystal structure with an oxygen species bound, using QM/MM calculations. The reduction level and protonation state of this oxygen-bound intermediate has been unclear. However, this information is crucial to the mechanism. We therefore investigate the oxygen-bound intermediate with quantum refinement (crystallographic refinement enhanced with QM calculations), against both X-ray and neutron data. Quantum refinement calculations suggest a Cu(ii)-O-2 system in the active site of the AA10-LPMO and a neutral protonated -NH2 state for the terminal nitrogen atom, the latter in contrast to the original interpretation. Our QM/MM calculations show that H2O2 generation is possible only from a Cu(i) center and that the most favourable reaction pathway is to involve a nearby glutamate residue, adding two electrons and two protons to the Cu(ii)-O-2 system, followed by dissociation of H2O2.
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Affiliation(s)
- Octav Caldararu
- Division of Theoretical Chemistry , Lund University , Chemical Centre , P. O. Box 124 , SE-221 00 Lund , Sweden . ;
| | - Esko Oksanen
- European Spallation Source ESS ERIC , P. O. Box 176 , SE-221 00 Lund , Sweden
- Department of Biochemistry and Structural Biology , Lund University , Chemical Centre , P. O. Box 124 , SE-221 00 Lund , Sweden
| | - Ulf Ryde
- Division of Theoretical Chemistry , Lund University , Chemical Centre , P. O. Box 124 , SE-221 00 Lund , Sweden . ;
| | - Erik D Hedegård
- Division of Theoretical Chemistry , Lund University , Chemical Centre , P. O. Box 124 , SE-221 00 Lund , Sweden . ;
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15
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Genoni A, Bučinský L, Claiser N, Contreras-García J, Dittrich B, Dominiak PM, Espinosa E, Gatti C, Giannozzi P, Gillet JM, Jayatilaka D, Macchi P, Madsen AØ, Massa L, Matta CF, Merz KM, Nakashima PNH, Ott H, Ryde U, Schwarz K, Sierka M, Grabowsky S. Quantum Crystallography: Current Developments and Future Perspectives. Chemistry 2018; 24:10881-10905. [PMID: 29488652 DOI: 10.1002/chem.201705952] [Citation(s) in RCA: 85] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 02/27/2018] [Indexed: 11/09/2022]
Abstract
Crystallography and quantum mechanics have always been tightly connected because reliable quantum mechanical models are needed to determine crystal structures. Due to this natural synergy, nowadays accurate distributions of electrons in space can be obtained from diffraction and scattering experiments. In the original definition of quantum crystallography (QCr) given by Massa, Karle and Huang, direct extraction of wavefunctions or density matrices from measured intensities of reflections or, conversely, ad hoc quantum mechanical calculations to enhance the accuracy of the crystallographic refinement are implicated. Nevertheless, many other active and emerging research areas involving quantum mechanics and scattering experiments are not covered by the original definition although they enable to observe and explain quantum phenomena as accurately and successfully as the original strategies. Therefore, we give an overview over current research that is related to a broader notion of QCr, and discuss options how QCr can evolve to become a complete and independent domain of natural sciences. The goal of this paper is to initiate discussions around QCr, but not to find a final definition of the field.
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Affiliation(s)
- Alessandro Genoni
- Université de Lorraine, CNRS, Laboratoire LPCT, 1 Boulevard Arago, F-57078, Metz, France
| | - Lukas Bučinský
- Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology, FCHPT SUT, Radlinského 9, SK-812 37, Bratislava, Slovakia
| | - Nicolas Claiser
- Université de Lorraine, CNRS, Laboratoire CRM2, Boulevard des Aiguillettes, BP 70239, F-54506, Vandoeuvre-lès-Nancy, France
| | - Julia Contreras-García
- Sorbonne Universités, UPMC Université Paris 06, CNRS, Laboratoire de Chimie Théorique (LCT), 4 Place Jussieu, F-75252, Paris Cedex 05, France
| | - Birger Dittrich
- Anorganische und Strukturchemie II, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225, Düsseldorf, Germany
| | - Paulina M Dominiak
- Biological and Chemical Research Centre, Department of Chemistry, University of Warsaw, ul. Żwirki i Wigury 101, 02-089, Warszawa, Poland
| | - Enrique Espinosa
- Université de Lorraine, CNRS, Laboratoire CRM2, Boulevard des Aiguillettes, BP 70239, F-54506, Vandoeuvre-lès-Nancy, France
| | - Carlo Gatti
- CNR-ISTM Istituto di Scienze e Tecnologie Molecolari, via Golgi 19, Milano, I-20133, Italy.,Istituto Lombardo Accademia di Scienze e Lettere, via Brera 28, 20121, Milano, Italy
| | - Paolo Giannozzi
- Department of Mathematics, Computer Science and Physics, University of Udine, Via delle Scienze 208, I-33100, Udine, Italy
| | - Jean-Michel Gillet
- Structure, Properties and Modeling of Solids Laboratory, CentraleSupelec, Paris-Saclay University, 3 rue Joliot-Curie, 91191, Gif-sur-Yvette, France
| | - Dylan Jayatilaka
- School of Molecular Sciences, University of Western Australia, 35 Stirling Highway, Perth, WA, 6009, Australia
| | - Piero Macchi
- Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland
| | - Anders Ø Madsen
- Department of Pharmacy, University of Copenhagen, Universitetsparken 2, 2100, Copenhagen, Denmark
| | - Lou Massa
- Hunter College & the Ph.D. Program of the Graduate Center, City University of New York, New York, USA
| | - Chérif F Matta
- Department of Chemistry and Physics, Mount Saint Vincent University, Halifax, Nova Scotia, B3M 2J6, Canada.,Department of Chemistry, Dalhousie University, Halifax, Nova Scotia, B3H 4J3, Canada.,Department of Chemistry, Saint Mary's University, Halifax, Nova Scotia, B3H 3C3, Canada.,Département de Chimie, Université Laval, Québec, QC G1V 0A6, Canada
| | - Kenneth M Merz
- Department of Chemistry and Department of Biochemistry and Molecular Biology, Michigan State University, 578 South Shaw Lane, East Lansing, Michigan, 48824, USA.,Institute for Cyber Enabled Research, Michigan State University, 567 Wilson Road, Room 1440, East Lansing, Michigan, 48824, USA
| | - Philip N H Nakashima
- Department of Materials Science and Engineering, Monash University, Victoria, 3800, Australia
| | - Holger Ott
- Bruker AXS GmbH, Östliche Rheinbrückenstraße 49, 76187, Karlsruhe, Germany
| | - Ulf Ryde
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P.O. Box 124, SE-22100, Lund, Sweden
| | - Karlheinz Schwarz
- Technische Universität Wien, Institut für Materialwissenschaften, Getreidemarkt 9, A-1060, Vienna, Austria
| | - Marek Sierka
- Otto Schott Institute of Materials Research, Friedrich Schiller University Jena, Löbdergraben 32, 07743, Jena, Germany
| | - Simon Grabowsky
- Fachbereich 2-Biologie/Chemie, Institut für Anorganische Chemie und Kristallographie, Universität Bremen, Leobener Str. 3, 28359, Bremen, Germany
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16
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Zheng M, Moriarty NW, Xu Y, Reimers JR, Afonine PV, Waller MP. Solving the scalability issue in quantum-based refinement: Q|R#1. Acta Crystallogr D Struct Biol 2017; 73:1020-1028. [PMID: 29199981 PMCID: PMC5713877 DOI: 10.1107/s2059798317016746] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2017] [Accepted: 11/20/2017] [Indexed: 12/27/2022] Open
Abstract
Accurately refining biomacromolecules using a quantum-chemical method is challenging because the cost of a quantum-chemical calculation scales approximately as nm, where n is the number of atoms and m (≥3) is based on the quantum method of choice. This fundamental problem means that quantum-chemical calculations become intractable when the size of the system requires more computational resources than are available. In the development of the software package called Q|R, this issue is referred to as Q|R#1. A divide-and-conquer approach has been developed that fragments the atomic model into small manageable pieces in order to solve Q|R#1. Firstly, the atomic model of a crystal structure is analyzed to detect noncovalent interactions between residues, and the results of the analysis are represented as an interaction graph. Secondly, a graph-clustering algorithm is used to partition the interaction graph into a set of clusters in such a way as to minimize disruption to the noncovalent interaction network. Thirdly, the environment surrounding each individual cluster is analyzed and any residue that is interacting with a particular cluster is assigned to the buffer region of that particular cluster. A fragment is defined as a cluster plus its buffer region. The gradients for all atoms from each of the fragments are computed, and only the gradients from each cluster are combined to create the total gradients. A quantum-based refinement is carried out using the total gradients as chemical restraints. In order to validate this interaction graph-based fragmentation approach in Q|R, the entire atomic model of an amyloid cross-β spine crystal structure (PDB entry 2oNA) was refined.
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Affiliation(s)
- Min Zheng
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People’s Republic of China
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, 48149 Münster, Germany
| | - Nigel W. Moriarty
- Molecular Biosciences and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Yanting Xu
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People’s Republic of China
| | - Jeffrey R. Reimers
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People’s Republic of China
- School of Mathematical and Physical Sciences, University of Technology Sydney, NSW 2007 Australia
| | - Pavel V. Afonine
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People’s Republic of China
- Molecular Biosciences and Integrated Bioimaging, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
| | - Mark P. Waller
- International Center for Quantum and Molecular Structures, Shanghai University, Shanghai 200444, People’s Republic of China
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17
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Cao L, Caldararu O, Ryde U. Protonation States of Homocitrate and Nearby Residues in Nitrogenase Studied by Computational Methods and Quantum Refinement. J Phys Chem B 2017; 121:8242-8262. [DOI: 10.1021/acs.jpcb.7b02714] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Lili Cao
- 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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18
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Grabowsky S, Genoni A, Bürgi HB. Quantum crystallography. Chem Sci 2017; 8:4159-4176. [PMID: 28878872 PMCID: PMC5576428 DOI: 10.1039/c6sc05504d] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 03/03/2017] [Indexed: 12/12/2022] Open
Abstract
Approximate wavefunctions can be improved by constraining them to reproduce observations derived from diffraction and scattering experiments. Conversely, charge density models, incorporating electron-density distributions, atomic positions and atomic motion, can be improved by supplementing diffraction experiments with quantum chemically calculated, tailor-made electron densities (form factors). In both cases quantum chemistry and diffraction/scattering experiments are combined into a single, integrated tool. The development of quantum crystallographic research is reviewed. Some results obtained by quantum crystallography illustrate the potential and limitations of this field.
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Affiliation(s)
- Simon Grabowsky
- Universität Bremen , Fachbereich 2 - Biologie/Chemie , Institut für Anorganische Chemie und Kristallographie , Leobener Str. NW2 , 28359 Bremen , Germany .
| | - Alessandro Genoni
- CNRS , Laboratoire SRSMC , UMR 7565 , Vandoeuvre-lès-Nancy , F-54506 , France
- Université de Lorraine , Laboratoire SRSMC , UMR 7565 , Vandoeuvre-lès-Nancy , F-54506 , France .
| | - Hans-Beat Bürgi
- Universität Bern , Departement für Chemie und Biochemie , Freiestr. 3 , CH-3012 Bern , Switzerland .
- Universität Zürich , Institut für Chemie , Winterthurerstrasse 190 , CH-8057 Zürich , Switzerland
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19
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Zheng M, Reimers JR, Waller MP, Afonine PV. Q|R: quantum-based refinement. Acta Crystallogr D Struct Biol 2017; 73:45-52. [PMID: 28045384 PMCID: PMC5331472 DOI: 10.1107/s2059798316019847] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2016] [Accepted: 12/12/2016] [Indexed: 11/10/2022] Open
Abstract
Quantum-based refinement utilizes chemical restraints derived from quantum-chemical methods instead of the standard parameterized library-based restraints used in refinement packages. The motivation is twofold: firstly, the restraints have the potential to be more accurate, and secondly, the restraints can be more easily applied to new molecules such as drugs or novel cofactors. Here, a new project called Q|R aimed at developing quantum-based refinement of biomacromolecules is under active development by researchers at Shanghai University together with PHENIX developers. The central focus of this long-term project is to develop software that is built on top of open-source components. A development version of Q|R was used to compare quantum-based refinements with standard refinement using a small model system.
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Affiliation(s)
- Min Zheng
- Department of Physics and International Centre for Quantum and Molecular Structures, Shanghai University, Shanghai, 200444, People’s Republic of China
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
| | - Jeffrey R. Reimers
- Department of Physics and International Centre for Quantum and Molecular Structures, Shanghai University, Shanghai, 200444, People’s Republic of China
- School of Mathematical and Physical Sciences, University of Technology Sydney, Sydney, 2007, Australia
| | - Mark P. Waller
- Department of Physics and International Centre for Quantum and Molecular Structures, Shanghai University, Shanghai, 200444, People’s Republic of China
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Westfälische Wilhelms-Universität Münster, Corrensstrasse 40, 48149 Münster, Germany
| | - Pavel V. Afonine
- Department of Physics and International Centre for Quantum and Molecular Structures, Shanghai University, Shanghai, 200444, People’s Republic of China
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA
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20
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Goerigk L, Collyer CA, Reimers JR. Recommending Hartree–Fock Theory with London-Dispersion and Basis-Set-Superposition Corrections for the Optimization or Quantum Refinement of Protein Structures. J Phys Chem B 2014; 118:14612-26. [DOI: 10.1021/jp510148h] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Lars Goerigk
- School
of Chemistry, The University of Melbourne, Parkville, Victoria 3010, Australia
| | - Charles A. Collyer
- School
of Molecular Bioscience, The University of Sydney, Sydney, New South Wales 2006, Australia
| | - Jeffrey R. Reimers
- Centre
for Quantum and Molecular Structure, College of Sciences, Shanghai University, Shanghai 200444, China
- School
of Physics and Advanced Materials, The University of Technology, Sydney, New South Wales 2007, Australia
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21
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Shafaat HS, Griese JJ, Pantazis DA, Roos K, Andersson CS, Popović-Bijelić A, Gräslund A, Siegbahn PEM, Neese F, Lubitz W, Högbom M, Cox N. Electronic structural flexibility of heterobimetallic Mn/Fe cofactors: R2lox and R2c proteins. J Am Chem Soc 2014; 136:13399-409. [PMID: 25153930 DOI: 10.1021/ja507435t] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
The electronic structure of the Mn/Fe cofactor identified in a new class of oxidases (R2lox) described by Andersson and Högbom [Proc. Natl. Acad. Sci. U.S.A. 2009, 106, 5633] is reported. The R2lox protein is homologous to the small subunit of class Ic ribonucleotide reductase (R2c) but has a completely different in vivo function. Using multifrequency EPR and related pulse techniques, it is shown that the cofactor of R2lox represents an antiferromagnetically coupled Mn(III)/Fe(III) dimer linked by a μ-hydroxo/bis-μ-carboxylato bridging network. The Mn(III) ion is coordinated by a single water ligand. The R2lox cofactor is photoactive, converting into a second form (R2loxPhoto) upon visible illumination at cryogenic temperatures (77 K) that completely decays upon warming. This second, unstable form of the cofactor more closely resembles the Mn(III)/Fe(III) cofactor seen in R2c. It is shown that the two forms of the R2lox cofactor differ primarily in terms of the local site geometry and electronic state of the Mn(III) ion, as best evidenced by a reorientation of its unique (55)Mn hyperfine axis. Analysis of the metal hyperfine tensors in combination with density functional theory (DFT) calculations suggests that this change is triggered by deprotonation of the μ-hydroxo bridge. These results have important consequences for the mixed-metal R2c cofactor and the divergent chemistry R2lox and R2c perform.
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Affiliation(s)
- Hannah S Shafaat
- Max-Planck-Institut für Chemische Energiekonversion , Stiftstrasse 34-36, Mülheim an der Ruhr D-45470, Germany
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22
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Yosca TH, Behan RK, Krest CM, Onderko EL, Langston MC, Green MT. Setting an upper limit on the myoglobin iron(IV)hydroxide pK(a): insight into axial ligand tuning in heme protein catalysis. J Am Chem Soc 2014; 136:9124-31. [PMID: 24875119 PMCID: PMC4091272 DOI: 10.1021/ja503588n] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To provide insight into the iron(IV)hydroxide pK(a) of histidine ligated heme proteins, we have probed the active site of myoglobin compound II over the pH range of 3.9-9.5, using EXAFS, Mössbauer, and resonance Raman spectroscopies. We find no indication of ferryl protonation over this pH range, allowing us to set an upper limit of 2.7 on the iron(IV)hydroxide pK(a) in myoglobin. Together with the recent determination of an iron(IV)hydroxide pK(a) ∼ 12 in the thiolate-ligated heme enzyme cytochrome P450, this result provides insight into Nature's ability to tune catalytic function through its choice of axial ligand.
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Affiliation(s)
- Timothy H Yosca
- Department of Chemistry, Pennsylvania State University , University Park, State College, Pennsylvania 16802, United States
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23
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Schmidt TC, Paasche A, Grebner C, Ansorg K, Becker J, Lee W, Engels B. QM/MM investigations of organic chemistry oriented questions. Top Curr Chem (Cham) 2014; 351:25-101. [PMID: 22392477 DOI: 10.1007/128_2011_309] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
About 35 years after its first suggestion, QM/MM became the standard theoretical approach to investigate enzymatic structures and processes. The success is due to the ability of QM/MM to provide an accurate atomistic picture of enzymes and related processes. This picture can even be turned into a movie if nuclei-dynamics is taken into account to describe enzymatic processes. In the field of organic chemistry, QM/MM methods are used to a much lesser extent although almost all relevant processes happen in condensed matter or are influenced by complicated interactions between substrate and catalyst. There is less importance for theoretical organic chemistry since the influence of nonpolar solvents is rather weak and the effect of polar solvents can often be accurately described by continuum approaches. Catalytic processes (homogeneous and heterogeneous) can often be reduced to truncated model systems, which are so small that pure quantum-mechanical approaches can be employed. However, since QM/MM becomes more and more efficient due to the success in software and hardware developments, it is more and more used in theoretical organic chemistry to study effects which result from the molecular nature of the environment. It is shown by many examples discussed in this review that the influence can be tremendous, even for nonpolar reactions. The importance of environmental effects in theoretical spectroscopy was already known. Due to its benefits, QM/MM can be expected to experience ongoing growth for the next decade.In the present chapter we give an overview of QM/MM developments and their importance in theoretical organic chemistry, and review applications which give impressions of the possibilities and the importance of the relevant effects. Since there is already a bunch of excellent reviews dealing with QM/MM, we will discuss fundamental ingredients and developments of QM/MM very briefly with a focus on very recent progress. For the applications we follow a similar strategy.
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Affiliation(s)
- Thomas C Schmidt
- Institut für Phys. und Theor. Chemie, Emil-Fischer-Strasse 42, Campus Hubland Nord, 97074, Würzburg, Germany
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Husberg C, Ryde U. How are hydrogen bonds modified by metal binding? J Biol Inorg Chem 2013; 18:499-522. [DOI: 10.1007/s00775-013-0996-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 03/11/2013] [Indexed: 10/27/2022]
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Fu Z, Li X, Merz KM. Conformational Analysis of Free and Bound Retinoic Acid. J Chem Theory Comput 2012; 8:1436-1448. [PMID: 22844234 DOI: 10.1021/ct200813q] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The conformational profiles of unbound all-trans and 9-cis retinoic acid (RA) have been determined using classical and quantum mechanical calculations. Sixty-six all-trans-RA (ATRA) and forty-eight 9-cis-RA energy minimum conformers were identified via HF/6-31G* geometry optimizations in vacuo. Their relative conformational energies were estimated utilizing the M06, M06-2x and MP2 methods combined with the 6-311+G(d,p), aug-cc-pVDZ and aug-cc-pVTZ basis sets, as well as complete basis set MP2 extrapolations using the latter two basis sets. Single-point energy calculations performed with the M06-2x density functional were found to yield similar results to MP2/CBS for the low-energy retinoic acid conformations. Not unexpectedly, the conformational propensities of retinoic acid were governed by the orientation and arrangement of the torsion angles associated with the polyene tail. We also used previously reported QM/MM X-ray refinement results on four ATRA-protein crystal structures plus one newly refined 9-cis-RA complex (PDB ID 1XDK) in order to investigate the conformational preferences of bound retinoic acid. In the re-refined RA conformers the conjugated double bonds are nearly coplanar, which is consistent with the global minimum identified by the Omega/QM method rather than the corresponding crystallographically determined conformations given in the PDB. Consequently, a 91.3% average reduction of the local strain energy in the gas phase, as well as 92.1% in PCM solvent, was observed using the QM/MM refined structures versus the PDB deposited RA conformations. These results thus demonstrate that our QM/MM X-ray refinement approach can significantly enhance the quality of X-ray crystal structures refined by conventional refinement protocols, thereby providing reliable drug-target structural information for use in structure-based drug discovery applications.
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Affiliation(s)
- Zheng Fu
- Department of Chemistry and the Quantum Theory Project, 2328 New Physics Building, P.O. Box 118435, University of Florida, Gainesville, Florida, 32611-8435
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Sharma V, Wikström M, Kaila VRI. Dynamic water networks in cytochrome cbb3 oxidase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:726-34. [PMID: 21963365 DOI: 10.1016/j.bbabio.2011.09.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Revised: 09/13/2011] [Accepted: 09/15/2011] [Indexed: 12/01/2022]
Abstract
Heme-copper oxidases (HCOs) are terminal electron acceptors in aerobic respiration. They catalyze the reduction of molecular oxygen to water with concurrent pumping of protons across the mitochondrial and bacterial membranes. Protons required for oxygen reduction chemistry and pumping are transferred through proton uptake channels. Recently, the crystal structure of the first C-type member of the HCO superfamily was resolved [Buschmann et al. Science 329 (2010) 327-330], but crystallographic water molecules could not be identified. Here we have used molecular dynamics (MD) simulations, continuum electrostatic approaches, and quantum chemical cluster calculations to identify proton transfer pathways in cytochrome cbb(3). In MD simulations we observe formation of stable water chains that connect the highly conserved Glu323 residue on the proximal side of heme b(3) both with the N- and the P-sides of the membrane. We propose that such pathways could be utilized for redox-coupled proton pumping in the C-type oxidases. Electrostatics and quantum chemical calculations suggest an increased proton affinity of Glu323 upon reduction of high-spin heme b(3). Protonation of Glu323 provides a mechanism to tune the redox potential of heme b(3) with possible implications for proton pumping.
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Affiliation(s)
- Vivek Sharma
- Helsinki Bioenergetics Group, Programme for Structural Biology and Biophysics, Institute of Biotechnology, PB 65 (Viikinkaari 1), University of Helsinki, 00014, Finland.
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Cho KB, Lai W, Hamberg M, Raman C, Shaik S. The reaction mechanism of allene oxide synthase: Interplay of theoretical QM/MM calculations and experimental investigations. Arch Biochem Biophys 2011; 507:14-25. [DOI: 10.1016/j.abb.2010.07.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Revised: 06/28/2010] [Accepted: 07/16/2010] [Indexed: 11/28/2022]
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Wangpradit O, Moman E, Nolan KB, Buettner GR, Robertson LW, Luthe G. Observation of an unusual electronically distorted semiquinone radical of PCB metabolites in the active site of prostaglandin H synthase-2. CHEMOSPHERE 2010; 81:1501-1508. [PMID: 20843536 PMCID: PMC3622869 DOI: 10.1016/j.chemosphere.2010.08.041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 08/18/2010] [Accepted: 08/20/2010] [Indexed: 05/29/2023]
Abstract
The activation of the metabolites of airborne polychlorinated biphenyls (PCBs) into highly reactive radicals is of fundamental importance. We found that human recombinant prostaglandin H synthase-2 (hPGHS-2) biotransforms dihydroxy-PCBs, such as 4-chlorobiphenyl-2',5'-hydroquinone (4-CB-2',5'-H(2)Q), into semiquinone radicals via one-electron oxidation. Using electron paramagnetic resonance (EPR) spectroscopy, we observed the formation of the symmetric quartet spectrum (1:3:3:1 by area) of 4-chlorobiphenyl-2',5'-semiquinone radical (4-CB-2',5'-SQ()(-)) from 4-CB-2',5'-H(2)Q. This spectrum changed to an asymmetric spectrum with time: the change can be explained as the overlap of two different semiquinone radical species. Hindered rotation of the 4-CB-2',5'-SQ()(-) appears not to be a major factor for the change in lineshape because increasing the viscosity of the medium with glycerol produced no significant change in lineshape. Introduction of a fluorine, which increases the steric hindrance for rotation of the dihydroxy-PCB studied, also produced no significant changes. An in silico molecular docking model of 4-CB-2',5'-H(2)Q in the peroxidase site of hPGHS-2 together with ab initio quantum mechanical studies indicate that the close proximity of a negatively charged carboxylic acid in the peroxidase active site may be responsible for the observed perturbation in the spectrum. This study provides new insights into the formation of semiquinones from PCB metabolites and underscores the potential role of PGHS-2 in the metabolic activation of PCBs.
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Affiliation(s)
- Orarat Wangpradit
- Department of Occupational and Environmental Health, The University of Iowa, 100 Oakdale Campus, Iowa City, IA 52242-5000, USA
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, 100 Oakdale Campus, Iowa City, IA 52242-5000, USA
| | - Edelmiro Moman
- ProSciens, Computing & Molecular Sciences, 2-4 rue du Palais de Justice, L-1841, Luxembourg
| | - Kevin B. Nolan
- Department of Pharmaceutical & Medicinal Chemistry, Royal College of Surgeons in Ireland (RCSI), Dublin 2, Ireland
| | - Garry R. Buettner
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, 100 Oakdale Campus, Iowa City, IA 52242-5000, USA
- Free Radical and Radiation Biology Program, The University of Iowa, Iowa City, IA, 52242-1181, USA
| | - Larry W. Robertson
- Department of Occupational and Environmental Health, The University of Iowa, 100 Oakdale Campus, Iowa City, IA 52242-5000, USA
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, 100 Oakdale Campus, Iowa City, IA 52242-5000, USA
| | - Gregor Luthe
- Department of Occupational and Environmental Health, The University of Iowa, 100 Oakdale Campus, Iowa City, IA 52242-5000, USA
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, 100 Oakdale Campus, Iowa City, IA 52242-5000, USA
- Saxion University of Applied Sciences, Institute for Life Science and Technology, Enschede, The Netherlands
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Hersleth HP, Andersson KK. How different oxidation states of crystalline myoglobin are influenced by X-rays. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2010; 1814:785-96. [PMID: 20691815 DOI: 10.1016/j.bbapap.2010.07.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Revised: 07/14/2010] [Accepted: 07/20/2010] [Indexed: 10/19/2022]
Abstract
X-ray induced radiation damage of protein crystals is well known to occur even at cryogenic temperatures. Redox active sites like metal sites seem especially vulnerable for these radiation-induced reductions. It is essential to know correctly the oxidation state of metal sites in protein crystal structures to be able to interpret the structure-function relation. Through previous structural studies, we have tried to characterise and understand the reactions between myoglobin and peroxides. These reaction intermediates are relevant because myoglobin is proposed to take part as scavenger of reactive oxygen species during oxidative stress, and because these intermediates are similar among the haem peroxidases and oxygenases. We have in our previous studies shown that these different myoglobin states are influenced by the X-rays used. In this study, we have in detail investigated the impact that X-rays have on these different oxidation states of myoglobin. An underlying goal has been to find a way to be able to determine mostly unreduced states. We have by using single-crystal light absorption spectroscopy found that the different oxidation states of myoglobin are to a different extent influenced by the X-rays (e.g. ferric Fe(III) myoglobin is faster reduced than ferryl Fe(IV)═O myoglobin). We observe that the higher oxidation states are not reduced to normal ferrous Fe(II) or ferric Fe(III) states, but end up in some intermediate and possibly artificial states. For ferric myoglobin, it seems that annealing of the radiation-induced/reduced state can reversibly more or less give the starting point (ferric myoglobin). Both scavengers and different dose-rates might influence to which extent the different states are affected by the X-rays. Our study shows that it is essential to do a time/dose monitoring of the influence X-rays have on each specific redox-state with spectroscopic techniques like single-crystal light absorption spectroscopy. This will determine to which extent you can collect X-ray diffraction data on your crystal before it becomes too heavily influenced/reduced by X-rays. This article is part of a Special Issue entitled: Protein Structure and Function in the Crystalline State.
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Affiliation(s)
- Hans-Petter Hersleth
- Department of Molecular Biosciences, University of Oslo, P.O. Box 1041 Blindern, NO-0316 Oslo, Norway.
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Li X, He X, Wang B, Merz K. Conformational variability of benzamidinium-based inhibitors. J Am Chem Soc 2009; 131:7742-54. [PMID: 19435349 DOI: 10.1021/ja9010833] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Determining the structure of a small molecule bound to a biological receptor (e.g., a protein implicated in a disease state) is a necessary step in structure-based drug design. The preferred conformation of a small molecule can change when bound to a protein, and a detailed knowledge of the preferred conformation(s) of a bound ligand can help in optimizing the affinity of a molecule for its receptor. However, the quality of a protein/ligand complex determined using X-ray crystallography is dependent on the size of the protein, the crystal quality, and the realized resolution. The energy restraints used in traditional X-ray refinement procedures typically use "reduced" (i.e., neglect of electrostatics and dispersion interactions) Engh and Huber force field models that, while quite suitable for modeling proteins, often are less suitable for small molecule structures due to a lack of validated parameters. Through the use of ab initio QM/MM-based X-ray refinement procedures, this shortcoming can be overcome especially in the active site or binding site of a small-molecule inhibitor. Herein, we demonstrate that ab initio QM/MM refinement of an inhibitor/protein complex provides insights into the binding of small molecules beyond what is available using more traditional refinement protocols. In particular, QM/MM refinement studies of benzamidinium derivatives show variable conformational preferences depending on the refinement protocol used and the nature of the active-site region.
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Affiliation(s)
- Xue Li
- Department of Chemistry, Quantum Theory Project, 2328 New Physics Building, P.O. Box 118435, University of Florida, Gainesville, Florida 32611-8435, USA
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Yin G, Danby AM, Kitko D, Carter JD, Scheper WM, Busch DH. Oxidative reactivity difference among the metal oxo and metal hydroxo moieties: pH dependent hydrogen abstraction by a manganese(IV) complex having two hydroxide ligands. J Am Chem Soc 2009; 130:16245-53. [PMID: 18998682 DOI: 10.1021/ja804305x] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Clarifying the difference in redox reactivity between the metal oxo and metal hydroxo moieties for the same redox active metal ion in identical structures and oxidation states, that is, M(n+)O and M(n+)-OH, contributes to the understanding of nature's choice between them (M(n+)O or M(n+)-OH) as key active intermediates in redox enzymes and electron transfer enzymes, and provides a basis for the design of synthetic oxidation catalysts. The newly synthesized manganese(IV) complex having two hydroxide ligands, [Mn(Me(2)EBC)(2)(OH)(2)](PF(6))(2), serves as the prototypic example to address this issue, by investigating the difference in the hydrogen abstracting abilities of the Mn(IV)O and Mn(IV)-OH functional groups. Independent thermodynamic evaluations of the O-H bond dissociation energies (BDE(OH)) for the corresponding reduction products, Mn(III)-OH and Mn(III)-OH(2), reveal very similar oxidizing power for Mn(IV)O and Mn(IV)-OH (83 vs 84.3 kcal/mol). Experimental tests showed that hydrogen abstraction proceeds at reasonable rates for substrates having BDE(CH) values less than 82 kcal/mol. That is, no detectable reaction occurred with diphenyl methane (BDE(CH) = 82 kcal/mol) for both manganese(IV) species. However, kinetic measurements for hydrogen abstraction showed that at pH 13.4, the dominant species Mn(Me(2)EBC)(2)(O)(2), having only Mn(IV)O groups, reacts more than 40 times faster than the Mn(IV)-OH unit in Mn(Me(2)EBC)(2)(OH)(2)(2+), the dominant reactant at pH 4.0. The activation parameters for hydrogen abstraction from 9,10-dihydroanthracene were determined for both manganese(IV) moieties: over the temperature range 288-318 K for Mn(IV)(OH)(2)(2+), DeltaH(double dagger) = 13.1 +/- 0.7 kcal/mol, and DeltaS(double dagger) = -35.0 +/- 2.2 cal K(-1) mol(-1); and the temperature range 288-308 K for for Mn(IV)(O)(2), DeltaH(double dagger) = 12.1 +/- 1.8 kcal/mol, and DeltaS(double dagger) = -30.3 +/- 5.9 cal K(-1) mol(-1).
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Affiliation(s)
- Guochuan Yin
- Department of Chemistry, The University of Kansas, Lawrence, Kansas 66045, USA
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Abstract
Combined quantum-mechanics/molecular-mechanics (QM/MM) approaches have become the method of choice for modeling reactions in biomolecular systems. Quantum-mechanical (QM) methods are required for describing chemical reactions and other electronic processes, such as charge transfer or electronic excitation. However, QM methods are restricted to systems of up to a few hundred atoms. However, the size and conformational complexity of biopolymers calls for methods capable of treating up to several 100,000 atoms and allowing for simulations over time scales of tens of nanoseconds. This is achieved by highly efficient, force-field-based molecular mechanics (MM) methods. Thus to model large biomolecules the logical approach is to combine the two techniques and to use a QM method for the chemically active region (e.g., substrates and co-factors in an enzymatic reaction) and an MM treatment for the surroundings (e.g., protein and solvent). The resulting schemes are commonly referred to as combined or hybrid QM/MM methods. They enable the modeling of reactive biomolecular systems at a reasonable computational effort while providing the necessary accuracy.
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Affiliation(s)
- Hans Martin Senn
- Department of Chemistry, WestCHEM and University of Glasgow, Glasgow G12 8QQ, UK.
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Hersleth HP, Hsiao YW, Ryde U, Görbitz CH, Andersson KK. The influence of X-rays on the structural studies of peroxide-derived myoglobin intermediates. Chem Biodivers 2008; 5:2067-2089. [PMID: 18972498 DOI: 10.1002/cbdv.200890189] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In recent years, the awareness of potential radiation damage of metal centers in protein crystals during crystallographic data collection has received increasing attention. The radiation damage can lead to radiation-induced changes and reduction of the metal sites. One of the research fields where these concerns have been comprehensively addressed is the study of the reaction intermediates of the heme peroxidase and oxygenase reaction cycles. For both the resting states and the high-valent intermediates, the X-rays used in the structure determination have given undesired side effects through radiation-induced changes to the trapped intermediates. However, X-rays have been used to generate and trap the peroxy/hydroperoxy state in crystals. In this review, the structural work and the influence of X-rays on these intermediates in myoglobin are summarized and viewed in light of analogous studies on similar intermediates in peroxidases and oxygenases.
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Affiliation(s)
- Hans-Petter Hersleth
- University of Oslo, Department of Molecular Biosciences, P. O. Box 1041 Blindern, N-0316 Oslo
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35
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Hersleth HP, Varnier A, Harbitz E, Røhr ÅK, Schmidt PP, Sørlie M, Cederkvist FH, Marchal S, Gorren AC, Mayer B, Uchida T, Schünemann V, Kitagawa T, Trautwein AX, Shimizu T, Lange R, Görbitz CH, Andersson KK. Reactive complexes in myoglobin and nitric oxide synthase. Inorganica Chim Acta 2008. [DOI: 10.1016/j.ica.2007.09.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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36
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Vidossich P, Alfonso-Prieto M, Carpena X, Loewen PC, Fita I, Rovira C. Versatility of the Electronic Structure of Compound I in Catalase-Peroxidases. J Am Chem Soc 2007; 129:13436-46. [DOI: 10.1021/ja072245i] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Affiliation(s)
- Pietro Vidossich
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Mercedes Alfonso-Prieto
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Xavi Carpena
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Peter C. Loewen
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Ignacio Fita
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
| | - Carme Rovira
- Contribution from the Centre de Recerca en Química Teòrica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Institut de Biologia Molecular (IBMB-CSIC), Institut de Recerca Biomèdica (IRB), Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain, Department of Microbiology, University of Manitoba, Winnipeg MB R3T 2N2, Canada, Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig Lluís Companys, 23, 08018 Barcelona, Spain
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Harvey JN, Bathelt CM, Mulholland AJ. QM/MM modeling of compound I active species in cytochrome P450, cytochrome C peroxidase, and ascorbate peroxidase. J Comput Chem 2007; 27:1352-62. [PMID: 16788912 DOI: 10.1002/jcc.20446] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
QM/MM calculations provide a means for predicting the electronic structure of the metal center in metalloproteins. Two heme peroxidases, Cytochrome c Peroxidase (CcP) and Ascorbate Peroxidase (APX), have a structurally very similar active site, yet have active intermediates with very different electronic structures. We review our recent QM/MM calculations on these systems, and present new computational data. Our results are in good agreement with experiment, and suggest that the difference in electronic structure is due to a large number of small differences in structure from one protein to another. We also discuss recent QM/MM calculations on the active species of cytochrome P450, in which a similar sensitivity of the electronic structure to the environment is found. However, this does not appear to explain different catalytic profiles of the different drug-metabolizing isoforms of this class of enzyme.
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Affiliation(s)
- Jeremy N Harvey
- School of Chemistry and Centre for Computational Chemistry, University of Bristol, Cantock's Close, Bristol BS8 1TS, United Kingdom.
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Hersleth HP, Uchida T, Røhr AK, Teschner T, Schünemann V, Kitagawa T, Trautwein AX, Görbitz CH, Andersson KK. Crystallographic and Spectroscopic Studies of Peroxide-derived Myoglobin Compound II and Occurrence of Protonated FeIV–O. J Biol Chem 2007; 282:23372-86. [PMID: 17565988 DOI: 10.1074/jbc.m701948200] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
High resolution crystal structures of myoglobin in the pH range 5.2-8.7 have been used as models for the peroxide-derived compound II intermediates in heme peroxidases and oxygenases. The observed Fe-O bond length (1.86-1.90 A) is consistent with that of a single bond. The compound II state of myoglobin in crystals was controlled by single-crystal microspectrophotometry before and after synchrotron data collection. We observe some radiation-induced changes in both compound II (resulting in intermediate H) and in the resting ferric state of myoglobin. These radiation-induced states are quite unstable, and compound II and ferric myoglobin are immediately regenerated through a short heating above the glass transition temperature (<1 s) of the crystals. It is unclear how this influences our compound II structures compared with the unaffected compound II, but some crystallographic data suggest that the influence on the Fe-O bond distance is minimal. Based on our crystallographic and spectroscopic data we suggest that for myoglobin the compound II intermediate consists of an Fe(IV)-O species with a single bond. The presence of Fe(IV) is indicated by a small isomer shift of delta = 0.07 mm/s from Mössbauer spectroscopy. Earlier quantum refinements (crystallographic refinement where the molecular-mechanics potential is replaced by a quantum chemical calculation) and density functional theory calculations suggest that this intermediate H species is protonated.
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Affiliation(s)
- Hans-Petter Hersleth
- Department of Chemistry, University of Oslo, PO Box 1033, Blindern, Oslo N-0315, Norway
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Arcovito A, Benfatto M, Cianci M, Hasnain SS, Nienhaus K, Nienhaus GU, Savino C, Strange RW, Vallone B, Della Longa S. X-ray structure analysis of a metalloprotein with enhanced active-site resolution using in situ x-ray absorption near edge structure spectroscopy. Proc Natl Acad Sci U S A 2007; 104:6211-6. [PMID: 17404234 PMCID: PMC1851025 DOI: 10.1073/pnas.0608411104] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
X-ray absorption spectroscopy is exquisitely sensitive to the coordination geometry of an absorbing atom and therefore allows bond distances and angles of the surrounding atomic cluster to be measured with atomic resolution. By contrast, the accuracy and resolution of metalloprotein active sites obtainable from x-ray crystallography are often insufficient to analyze the electronic properties of the metals that are essential for their biological functions. Here, we demonstrate that the combination of both methods on the same metalloprotein single crystal yields a structural model of the protein with exceptional active-site resolution. To this end, we have collected an x-ray diffraction data set to 1.4-A resolution and Fe K-edge polarized x-ray absorption near edge structure (XANES) spectra on the same cyanomet sperm whale myoglobin crystal. The XANES spectra were quantitatively analyzed by using a method based on the multiple scattering approach, which yielded Fe-heme structural parameters with +/-(0.02-0.07)-A accuracy on the atomic distances and +/-7 degrees on the Fe-CN angle. These XANES-derived parameters were subsequently used as restraints in the crystal structure refinement. By combining XANES and x-ray diffraction, we have obtained an cyanomet sperm whale myoglobin structural model with a higher precision of the bond lengths and angles at the active site than would have been possible with crystallographic analysis alone.
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Affiliation(s)
- Alessandro Arcovito
- Department of Biochemical Sciences and Consiglio Nazionale delle Ricerche, Institute of Molecular Biology and Pathology, University of Rome La Sapienza, P.le A. Moro 5, 00185 Rome, Italy
| | - Maurizio Benfatto
- Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, P.O. Box 13, 00044 Frascati, Italy
| | - Michele Cianci
- Molecular Biophysics Group, Daresbury Laboratory, Central Laboratory of the Research Councils, Warrington WA4 4AD, United Kingdom
| | - S. Samar Hasnain
- Molecular Biophysics Group, Daresbury Laboratory, Central Laboratory of the Research Councils, Warrington WA4 4AD, United Kingdom
| | - Karin Nienhaus
- Institute of Biophysics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
| | - G. Ulrich Nienhaus
- Institute of Biophysics, University of Ulm, Albert-Einstein-Allee 11, 89081 Ulm, Germany
- Department of Physics, University of Illinois at Urbana–Champaign, 1110 West Green Street, Urbana, IL 61801; and
- To whom correspondence may be addressed. E-mail: , , or
| | - Carmelinda Savino
- Department of Biochemical Sciences and Consiglio Nazionale delle Ricerche, Institute of Molecular Biology and Pathology, University of Rome La Sapienza, P.le A. Moro 5, 00185 Rome, Italy
| | - Richard W. Strange
- Molecular Biophysics Group, Daresbury Laboratory, Central Laboratory of the Research Councils, Warrington WA4 4AD, United Kingdom
- To whom correspondence may be addressed. E-mail: , , or
| | - Beatrice Vallone
- Department of Biochemical Sciences and Consiglio Nazionale delle Ricerche, Institute of Molecular Biology and Pathology, University of Rome La Sapienza, P.le A. Moro 5, 00185 Rome, Italy
| | - Stefano Della Longa
- Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, P.O. Box 13, 00044 Frascati, Italy
- Dipartimento di Medicina Sperimentale, Università dell' Aquila, Via Vetoio, 67100 L'Aquila, Italy
- To whom correspondence may be addressed. E-mail: , , or
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40
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Alfonso-Prieto M, Borovik A, Carpena X, Murshudov G, Melik-Adamyan W, Fita I, Rovira C, Loewen PC. The structures and electronic configuration of compound I intermediates of Helicobacter pylori and Penicillium vitale catalases determined by X-ray crystallography and QM/MM density functional theory calculations. J Am Chem Soc 2007; 129:4193-205. [PMID: 17358056 DOI: 10.1021/ja063660y] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The structures of Helicobacter pylori (HPC) and Penicillium vitale (PVC) catalases, each with two subunits in the crystal asymmetric unit, oxidized with peroxoacetic acid are reported at 1.8 and 1.7 A resolution, respectively. Despite the similar oxidation conditions employed, the iron-oxygen coordination length is 1.72 A for PVC, close to what is expected for a Fe=O double bond, and 1.80 and 1.85 A for HPC, suggestive of a Fe-O single bond. The structure and electronic configuration of the oxoferryl heme and immediate protein environment is investigated further by QM/MM density functional theory calculations. Four different active site electronic configurations are considered, Por*+-FeIV=O, Por*+-FeIV=O...HisH+, Por*+-FeIV-OH+ and Por-FeIV-OH (a protein radical is assumed in the latter configuration). The electronic structure of the primary oxidized species, Por*+-FeIV=O, differs qualitatively between HPC and PVC with an A2u-like porphyrin radical delocalized on the porphyrin in HPC and a mixed A1u-like "fluctuating" radical partially delocalized over the essential distal histidine, the porphyrin, and, to a lesser extent, the proximal tyrosine residue. This difference is rationalized in terms of HPC containing heme b and PVC containing heme d. It is concluded that compound I of PVC contains an oxoferryl Por*+-FeIV=O species with partial protonation of the distal histidine and compound I of HPC contains a hydroxoferryl Por-FeIV-OH with the second oxidation equivalent delocalized as a protein radical. The findings support the idea that there is a relation between radical migration to the protein and protonation of the oxoferryl bond in catalase.
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Affiliation(s)
- Mercedes Alfonso-Prieto
- Centre especial de Recerca en Química Teorica, Parc Científic de Barcelona, Josep Samitier 1-5, 08028 Barcelona, Spain
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41
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Yu N, Li X, Cui G, Hayik SA, Merz KM. Critical assessment of quantum mechanics based energy restraints in protein crystal structure refinement. Protein Sci 2007; 15:2773-84. [PMID: 17132861 PMCID: PMC2242432 DOI: 10.1110/ps.062343206] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
A critical evaluation of the performance of X-ray refinement protocols using various energy functions is presented using the bovine pancreatic trypsin inhibitor (BPTI) protein. The four potential energy functions we explored include: (1) fully quantum mechanical calculations; (2) one based on an incomplete molecular mechanics (MM) energy function employed in the Crystallography and NMR System (CNS) with empirical parameters developed by Engh and Huber (EH), which lacks electrostatic and attractive van der Waals terms; (3) one based on a complete MM energy function (AMBER ff99 parameter set); and (4) the same as 3, with the addition of a Generalized Born (GB) implicit solvation term. The R, R (free), real space R values of the refined structures and deviations from the original experimental structure were used to assess the relative performance. It was found that at 1 Angstrom resolution the physically based energy functions 1, 3, and 4 performed better than energy function 2, which we attribute to the better representation of key interactions, particularly electrostatics. The observed departures from the experimental structure were similar for the refinements with physically based energy functions and were smaller than the structure refined with EH. A test refinement was also performed with the reflections truncated at a high-resolution cutoff of 2.5 Angstrom and with random perturbations introduced into the initial coordinates, which showed that low-resolution refinements with physically based energy functions held the structure closer to the experimental structure solved at 1 Angstrom resolution than the EH-based refinements.
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Affiliation(s)
- Ning Yu
- Department of Chemistry, Pennsylvania State University, University Park, Pennsylvania 16802, USA
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42
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Kvist M, Ryabova ES, Nordlander E, Bülow L. An investigation of the peroxidase activity of Vitreoscilla hemoglobin. J Biol Inorg Chem 2007; 12:324-34. [PMID: 17219165 DOI: 10.1007/s00775-006-0190-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Accepted: 10/24/2006] [Indexed: 10/23/2022]
Abstract
In order to investigate the ability of the Vitreoscilla hemoglobin (VHb) to act as a peroxidase, the protein was overexpressed in Escerichia coli and purified using a 6xHis-tag. The peroxidase activity of VHb was studied using 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferrocene carboxylic acid (FcCOOH) dopamine and L-dopa as substrates. The effects of external agents such as pH, salt concentration/ionic strength, and the thermal stability of VHb on the catalytic activity were assessed. The optimum pH for VHb using ABTS as a substrate was estimated to be 6-7. The VHb protein proved to be stable up to 80 degrees C, as judged by its peroxidase activity. Furthermore, NaCl concentrations up to 100 mM did not exert any significant effect on the activity. The catalytic activity against ABTS and FcCOOH was similar to that measured for horseradish peroxidase, whereas in the case of the phenolic substrates dopamine and L-dopa the activity was several orders of magnitude lower. The Michaelis constants, KmH2O2, were in good agreement with the data for human and bovine hemoglobin. No activity could be detected for the negative controls lacking VHb. These results demonstrate that VHb exhibits peroxidase activity, a finding in line with the hypothesis that VHb has cellular functions beyond the role as an oxygen carrier.
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Affiliation(s)
- Malin Kvist
- Center for Chemistry and Chemical Engineering, Pure and Applied Biochemistry, Lund Institute of Technology, Box 124, 221 00, Lund, Sweden
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43
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Ryde U. Accurate metal-site structures in proteins obtained by combining experimental data and quantum chemistry. Dalton Trans 2006:607-25. [PMID: 17268593 DOI: 10.1039/b614448a] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The use of molecular mechanics calculations to supplement experimental data in standard X-ray crystallography and NMR refinements is discussed and it is shown that structures can be locally improved by the use of quantum chemical calculations. Such calculations can also be used to interpret the structures, e.g. to decide the protonation state of metal-bound ligands. They have shown that metal sites in crystal structures are frequently photoreduced or disordered, which makes the interpretation of the structures hard. Similar methods can be used for EXAFS refinements to obtain a full atomic structure, rather than a set of metal-ligand distances.
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Affiliation(s)
- Ulf Ryde
- Department of Theoretical Chemistry, Lund University, Chemical Centre, P. O. Box 124, SE-221 00, Lund, Sweden.
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44
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Söderhjelm P, Ryde U. Combined computational and crystallographic study of the oxidised states of [NiFe] hydrogenase. ACTA ACUST UNITED AC 2006. [DOI: 10.1016/j.theochem.2006.06.008] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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45
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Yu N, Hayik SA, Wang B, Liao N, Reynolds CH, Merz KM. Assigning the protonation states of the key aspartates in β-Secretase using QM/MM X-ray structure refinement. J Chem Theory Comput 2006; 2:1057-1069. [PMID: 19079786 DOI: 10.1021/ct0600060] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
β-Secretase, a.k.a. β-APP cleaving enzyme (BACE), is an aspartyl protease that has been implicated as a key target in the pathogenesis of Alzheimer's disease (AD). The identification of the protonation states of the key aspartates in β-secretase is of great interest both in understanding the reaction mechanism and in guiding the design of drugs against AD. However, the resolutions of currently available crystal structures for BACE are not sufficient to determine the hydrogen atom locations. We have assigned the protonation states of the key aspartates using a novel method, QM/MM X-ray refinement. In our approach, an energy function is introduced to the refinement where the atoms in the active site are modeled by quantum mechanics (QM) and the other atoms are represented by molecular mechanics (MM). The gradients derived from the QM/MM energy function are combined with those from the X-ray target to refine the crystal structure of a complex containing BACE and an inhibitor. A total number of 8 protonation configurations of the aspartyl dyad were considered and QM/MM X-ray refinements were performed for all of them. The relative stability of the refined structures was scored by constructing the thermodynamic cycle using the energetics calculated by fully quantum mechanical self-consistent reaction field (QM/SCRF) calculations. While all 8 refined structures fit the observed electron density about equally well, we find the mono-protonated configurations to be strongly favored energetically, especially the configuration with the inner oxygen of Asp32 protonated and the hydroxyl of the inhibitor pointing towards Asp228. It was also found that these results depend on the constraints imposed by the X-ray data. We suggest that one of the strengths of this approach is that the resulting structures are a consensus of theoretical and experimental data and remark on the significance of our results in structure based drug design and mechanistic studies.
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Affiliation(s)
- Ning Yu
- Department of Chemistry, the Pennsylvania State University, 104 Chemistry Research Building, University Park, PA 16802
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46
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Derat E, Shaik S. Two-State Reactivity, Electromerism, Tautomerism, and “Surprise” Isomers in the Formation of Compound II of the Enzyme Horseradish Peroxidase from the Principal Species, Compound I. J Am Chem Soc 2006; 128:8185-98. [PMID: 16787083 DOI: 10.1021/ja0600734] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
QM and QM/MM calculations on Compound II, the enigmatic species in the catalytic cycle of the horseradish peroxidase enzyme, reveal six low-lying isomers. The principal isomer is the triplet oxo-ferryl form (PorFe(IV)=O) that yields the hydroxo-ferryl isomer (PorFe(IV)-OH+). These are the only forms observed in experimental studies. Theory shows, however, that these are the least stable isomers of Compound II. The two most stable forms are the singlet and triplet states of the Por+*Fe(III)-OH electromer. In addition, theory reveals species never considered in heme enzymes: the singlet and triplet states of the Por+*Fe(III)-OH2 electromer. The computational results reproduce the experimental features of the known isomers and enable us to draw relationships and make predictions regarding the missing ones. For example, while the "surprise" species, singlet and triplet Por+*Fe(III)-OH2, have never been considered in heme chemistry, the calculated Fe-O bond lengths indicate that these isomers may have, in fact, been observed in one of the two opposing EXAFS studies reported previously. Furthermore, these ferric-aqua complexes could be responsible for the reported 18O exchange with bulk water. It is clear, therefore, that the role of Compound II in the HRP cycle is considerably more multi-faceted than has been revealed so far. Our suggested multi-state reactivity scheme provides a paradigm for Compound II species. The calculated Mössbauer parameters may be helpful toward eventual characterization of these missing isomers of Compound II.
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Affiliation(s)
- Etienne Derat
- Department of Organic Chemistry and the Lise Meitner-Minerva Center for Computational Quantum Chemistry, Hebrew University of Jerusalem, Givat Ram Campus, 91904 Jerusalem, Israel
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47
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Hersleth HP, Ryde U, Rydberg P, Görbitz CH, Andersson KK. Structures of the high-valent metal-ion haem–oxygen intermediates in peroxidases, oxygenases and catalases. J Inorg Biochem 2006; 100:460-76. [PMID: 16510192 DOI: 10.1016/j.jinorgbio.2006.01.018] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Revised: 01/09/2006] [Accepted: 01/09/2006] [Indexed: 11/22/2022]
Abstract
Peroxidases, oxygenases and catalases have similar high-valent metal-ion intermediates in their respective reaction cycles. In this review, haem-based examples will be discussed. The intermediates of the haem-containing enzymes have been extensively studied for many years by different spectroscopic methods like UV-Vis, EPR (electron paramagnetic resonance), resonance Raman, Mössbauer and MCD (magnetic circular dichroism). The first crystal structure of one of these high-valent intermediates was on cytochrome c peroxidase in 1987. Since then, structures have appeared for catalases in 1996, 2002, 2003, putatively for cytochrome P450 in 2000, for myoglobin in 2002, for horseradish peroxidase in 2002 and for cytochrome c peroxidase again in 1994 and 2003. This review will focus on the most recent structural investigations for the different intermediates of these proteins. The structures of these intermediates will also be viewed in light of quantum mechanical (QM) calculations on haem models. In particular quantum refinement, which is a combination of QM calculations and crystallography, will be discussed. Only small structural changes accompany the generation of these intermediates. The crystal structures show that the compound I state, with a so called pi-cation radical on the haem group, has a relatively short iron-oxygen bond (1.67-1.76A) in agreement with a double-bond character, while the compound II state or the compound I state with a radical on an amino acid residue have a relatively long iron-oxygen bond (1.86-1.92A) in agreement with a single-bond character where the oxygen-atom is protonated.
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Affiliation(s)
- Hans-Petter Hersleth
- Department of Chemistry, University of Oslo, P.O. Box 1033 Blindern, N-0315 Oslo, Norway
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48
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Terner J, Palaniappan V, Gold A, Weiss R, Fitzgerald MM, Sullivan AM, Hosten CM. Resonance Raman spectroscopy of oxoiron(IV) porphyrin π-cation radical and oxoiron(IV) hemes in peroxidase intermediates. J Inorg Biochem 2006; 100:480-501. [PMID: 16513173 DOI: 10.1016/j.jinorgbio.2006.01.008] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Accepted: 01/04/2006] [Indexed: 11/15/2022]
Abstract
The catalytic cycle intermediates of heme peroxidases, known as compounds I and II, have been of long standing interest as models for intermediates of heme proteins, such as the terminal oxidases and cytochrome P450 enzymes, and for non-heme iron enzymes as well. Reports of resonance Raman signals for compound I intermediates of the oxo-iron(IV) porphyrin pi-cation radical type have been sometimes contradictory due to complications arising from photolability, causing compound I signals to appear similar to those of compound II or other forms. However, studies of synthetic systems indicated that protein based compound I intermediates of the oxoiron(IV) porphyrin pi-cation radical type should exhibit vibrational signatures that are different from the non-radical forms. The compound I intermediates of horseradish peroxidase (HRP), and chloroperoxidase (CPO) from Caldariomyces fumago do in fact exhibit unique and characteristic vibrational spectra. The nature of the putative oxoiron(IV) bond in peroxidase intermediates has been under discussion in the recent literature, with suggestions that the Fe(IV)O unit might be better described as Fe(IV)-OH. The generally low Fe(IV)O stretching frequencies observed for proteins have been difficult to mimic in synthetic ferryl porphyrins via electron donation from trans axial ligands alone. Resonance Raman studies of iron-oxygen vibrations within protein species that are sensitive to pH, deuteration, and solvent oxygen exchange, indicate that hydrogen bonding to the oxoiron(IV) group within the protein environment contributes to substantial lowering of Fe(IV)O frequencies relative to those of synthetic model compounds.
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Affiliation(s)
- James Terner
- Department of Chemistry, Virginia Commonwealth University, Richmond, VA 23284-2006, USA.
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49
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De Jesús-Bonilla W, Cruz A, Lewis A, Cerda J, Bacelo DE, Cadilla CL, López-Garriga J. Hydrogen-bonding conformations of tyrosine B10 tailor the hemeprotein reactivity of ferryl species. J Biol Inorg Chem 2006; 11:334-42. [PMID: 16468033 DOI: 10.1007/s00775-006-0082-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2005] [Accepted: 01/16/2006] [Indexed: 10/25/2022]
Abstract
Ferryl compounds [Fe(IV)=O] in living organisms play an essential role in the radical catalytic cycle and degradation processes of hemeproteins. We studied the reactions between H2O2 and hemoglobin II (HbII) (GlnE7, TyrB10, PheCD1, PheE11), recombinant hemoglobin I (HbI) (GlnE7, PheB10, PheCD1, PheE11), and the HbI PheB10Tyr mutant of L. pectinata. We found that the tyrosine residue in the B10 position tailors, in two very distinct ways, the reactivity of the ferryl species, compounds I and II. First, increasing the reaction pH from 4.86 to 7.50, and then to 11.2, caused the the second-order rate constant for HbII to decrease from 141.60 to 77.78 M-1 s-1, and to 2.96 M-1 s-1, respectively. This pH dependence is associated with the disruption of the heme-tyrosine (603 nm) protein moiety, which controls the access of the H2O2 to the hemeprotein active center, thus regulating the formation of the ferryl species. Second, the presence of compound I was evident in the UV-vis spectra (648-nm band) in the reactions of HbI and recombinant HbI with H2O2, This band, however, is completely absent in the analogous reaction with HbII and the HbI PheB10Tyr mutant. Therefore, the existence of a hydrogen-bonding network between the heme pocket amino acids (i.e., TyrB10) and the ferryl compound I created a path much faster than 3.0x10(-2) s-1 for the decay of compound I to compound II. Furthermore, the decay of the heme ferryl compound I to compound II was independent of the proximal HisF8 trans-ligand strength. Thus, the pH dependence of the heme-tyrosine moiety complex determined the overall reaction rate of the oxidative reaction limiting the interaction with H2O2 at neutral pH. The hydrogen-bonding strength between the TyrB10 and the heme ferryl species suggests the presence of a cycle where the ferryl consumption by the ferric heme increases significantly the pseudoperoxidase activity of these hemeproteins.
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50
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Green MT. Application of Badger's Rule to Heme and Non-Heme Iron−Oxygen Bonds: An Examination of Ferryl Protonation States. J Am Chem Soc 2006; 128:1902-6. [PMID: 16464091 DOI: 10.1021/ja054074s] [Citation(s) in RCA: 112] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
To gain insight into the protonation state of enzymatic ferryl species we have examined the applicability of Badger's rule to heme and non-heme iron-oxygen bonds. Using density functional theory we have calculated r(e) and nu(e) for the Fe-O bonds of complexes with different axial ligands, iron-oxidation, oxygen-protonation, and spin states. Our results indicate that Badger's rule holds for heme and non-heme oxo and hydroxo complexes. We find that the long Fe-O bonds that have been reported in the crystal structures of the ferryl forms of myoglobin, horseradish peroxidase, cytochrome c peroxidase, and catalase deviate substantially from the values predicted by Badger's rule, while the short Fe-O bonds obtained from X-ray absorption measurements are in good agreement with Badger's rule. In light of our analysis we conclude that the ferryl forms of myoglobin, horseradish peroxidase, and cytochrome c peroxidase are authentic iron(IV)oxos with Fe-O bonds on the order of 1.66 A and pKa's < 4.
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Affiliation(s)
- Michael T Green
- Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA.
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