1
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Mammoser CC, LeMasters BE, Edwards SG, McRae EM, Mullins MH, Wang Y, Garcia NM, Edmonds KA, Giedroc DP, Thielges MC. The structure of plastocyanin tunes the midpoint potential by restricting axial ligation of the reduced copper ion. Commun Chem 2023; 6:175. [PMID: 37612467 PMCID: PMC10447441 DOI: 10.1038/s42004-023-00977-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2023] [Accepted: 08/07/2023] [Indexed: 08/25/2023] Open
Abstract
Blue copper proteins are models for illustrating how proteins tune metal properties. Nevertheless, the mechanisms by which the protein controls the metal site remain to be fully elucidated. A hindrance is that the closed shell Cu(I) site is inaccessible to most spectroscopic analyses. Carbon deuterium (C-D) bonds used as vibrational probes afford nonperturbative, selective characterization of the key cysteine and methionine copper ligands in both redox states. The structural integrity of Nostoc plastocyanin was perturbed by disrupting potential hydrogen bonds between loops of the cupredoxin fold via mutagenesis (S9A, N33A, N34A), variably raising the midpoint potential. The C-D vibrations show little change to suggest substantial alteration to the Cu(II) coordination in the oxidized state or in the Cu(I) interaction with the cysteine ligand. They rather indicate, along with visible and NMR spectroscopy, that the methionine ligand distinctly interacts more strongly with the Cu(I) ion, in line with the increases in midpoint potential. Here we show that the protein structure determines the redox properties by restricting the interaction between the methionine ligand and Cu(I) in the reduced state.
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Affiliation(s)
- Claire C Mammoser
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - Brynn E LeMasters
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
- Department of Chemistry, University of Wisconsin, Madison, WI, 53706, USA
| | - Sydney G Edwards
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - Emma M McRae
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - M Hunter Mullins
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
- Indiana University School of Medicine, Indianapolis, IN, 46202, USA
| | - Yiqi Wang
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Nicholas M Garcia
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
- University of Wisconsin School of Medicine and Public Health, Madison, WI, 53726, USA
| | - Katherine A Edmonds
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - David P Giedroc
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA
| | - Megan C Thielges
- Indiana University Department of Chemistry, 800 E. Kirkwood Ave., Bloomington, IN, 47405, USA.
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2
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Calvo JS, Villones RLE, York NJ, Stefaniak E, Hamilton GE, Stelling AL, Bal W, Pierce BS, Meloni G. Evidence for a Long-Lived, Cu-Coupled and Oxygen-Inert Disulfide Radical Anion in the Assembly of Metallothionein-3 Cu(I) 4-Thiolate Cluster. J Am Chem Soc 2022; 144:709-722. [PMID: 34985880 PMCID: PMC9029059 DOI: 10.1021/jacs.1c03984] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The human copper-binding protein metallothionein-3 (MT-3) can reduce Cu(II) to Cu(I) and form a polynuclear Cu(I)4-Cys5-6 cluster concomitant with intramolecular disulfide bonds formation, but the cluster is unusually inert toward O2 and redox-cycling. We utilized a combined array of rapid-mixing spectroscopic techniques to identify and characterize the transient radical intermediates formed in the reaction between Zn7MT-3 and Cu(II) to form Cu(I)4Zn(II)4MT-3. Stopped-flow electronic absorption spectroscopy reveals the rapid formation of transient species with absorption centered at 430-450 nm and consistent with the generation of disulfide radical anions (DRAs) upon reduction of Cu(II) by MT-3 cysteine thiolates. These DRAs are oxygen-stable and unusually long-lived, with lifetimes in the seconds regime. Subsequent DRAs reduction by Cu(II) leads to the formation of a redox-inert Cu(I)4-Cys5 cluster with short Cu-Cu distances (<2.8 Å), as revealed by low-temperature (77 K) luminescence spectroscopy. Rapid freeze-quench Raman and electron paramagnetic resonance (EPR) spectroscopy characterization of the intermediates confirmed the DRA nature of the sulfur-centered radicals and their subsequent oxidation to disulfide bonds upon Cu(II) reduction, generating the final Cu(I)4-thiolate cluster. EPR simulation analysis of the radical g- and A-values indicate that the DRAs are directly coupled to Cu(I), potentially explaining the observed DRA stability in the presence of O2. We thus provide evidence that the MT-3 Cu(I)4-Cys5 cluster assembly process involves the controlled formation of novel long-lived, copper-coupled, and oxygen-stable disulfide radical anion transient intermediates.
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Affiliation(s)
| | | | - Nicholas J. York
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35401, United States
| | - Ewelina Stefaniak
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland; Present Address: National Heart and Lung Institute, Imperial College London, Molecular Sciences Research Hub, White City Campus, London, W12 0BZ, United Kingdom
| | - Grace E. Hamilton
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Allison L. Stelling
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
| | - Wojciech Bal
- Institute of Biochemistry and Biophysics, Polish Academy of Sciences, 02-106 Warsaw, Poland
| | - Brad S. Pierce
- Department of Chemistry and Biochemistry, University of Alabama, Tuscaloosa, Alabama 35401, United States
| | - Gabriele Meloni
- Department of Chemistry and Biochemistry, The University of Texas at Dallas, Richardson, Texas 75080, United States
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3
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Frank P, Benfatto M. Symmetry Breaking in Solution-Phase [Cu(tsc) 2(H 2O) 2] 2+: Emergent Asymmetry in Cu-S Distances and in Covalence. J Phys Chem B 2021; 125:10779-10795. [PMID: 34546762 DOI: 10.1021/acs.jpcb.1c05022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structure of aqueous Cu(II)-bis-thiosemicarbazide, [Cu(tsc)2]2+, is reported following EXAFS and MXAN analyses of the copper K-edge X-ray absorption (XAS) spectrum. The rising K-edge feature at 8987.1 eV is higher energy than those of crystalline models, implying unique electronic and structural solution states. EXAFS analysis (k = 2-13 Å-1; 2 × Cu-N = 2.02 ± 0.01 Å; 2 × Cu-S = 2.27 ± 0.01 Å; Cu-Oax = 2.41 ± 0.04 Å) could not resolve 5- versus 6-coordinate models. However, MXAN fits converged to an asymmetric broken symmetry 6-coordinate model with cis-disposed TSC ligands (Cu-Oax = 2.07 and 2.54 Å; Cu-N = 1.94 Å, 1.98 Å; Cu-S = 2.20 Å, 2.41 Å). Transition dipole integral evaluation of the sulfur K-edge XAS 1s → 3p valence transition feature at 2470.7 eV yielded a Cu-S covalence of 0.66 e-, indicating Cu1.34+. The high Cu-S covalence and short Cu-S bond in aqueous [Cu(tsc)2(H2O)2]2+ again contradict the need for a protein rack to explain the unique structure of the blue copper active site. MXAN models of dissolved Cu(II) complex ions have invariably featured broken centrosymmetry. The potential energy ground state for dissolved Cu(II) evidently includes the extended solvation field, providing a target for improved physical theory. A revised solvation model for aqueous Cu(II), |[Cu(H2O)5]·14H2O|2+, is presented.
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Affiliation(s)
- Patrick Frank
- Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Menlo Park, California 94025, United States.,Department of Chemistry, Stanford University, Stanford, California 94305, United States
| | - Maurizio Benfatto
- Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
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4
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First-principles study on the structure and optical spectroscopy of the redox-active center of blue copper proteins. Chem Phys 2020. [DOI: 10.1016/j.chemphys.2020.110859] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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5
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Pinter TBJ, Koebke KJ, Pecoraro VL. Catalysis and Electron Transfer in De Novo Designed Helical Scaffolds. Angew Chem Int Ed Engl 2020; 59:7678-7699. [PMID: 31441170 PMCID: PMC7035182 DOI: 10.1002/anie.201907502] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2019] [Indexed: 12/31/2022]
Abstract
The relationship between protein structure and function is one of the greatest puzzles within biochemistry. De novo metalloprotein design is a way to wipe the board clean and determine what is required to build in function from the ground up in an unrelated structure. This Review focuses on protein design efforts to create de novo metalloproteins within alpha-helical scaffolds. Examples of successful designs include those with carbonic anhydrase or nitrite reductase activity by incorporating a ZnHis3 or CuHis3 site, or that recapitulate the spectroscopic properties of unique electron-transfer sites in cupredoxins (CuHis2 Cys) or rubredoxins (FeCys4 ). This work showcases the versatility of alpha helices as scaffolds for metalloprotein design and the progress that is possible through careful rational design. Our studies cover the invariance of carbonic anhydrase activity with different site positions and scaffolds, refinement of our cupredoxin models, and enhancement of nitrite reductase activity up to 1000-fold.
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Affiliation(s)
- Tyler B. J. Pinter
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, United States, 48109-1055
| | - Karl J. Koebke
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, United States, 48109-1055
| | - Vincent L. Pecoraro
- Department of Chemistry, University of Michigan, Ann Arbor, Michigan, United States, 48109-1055
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6
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Pinter TBJ, Koebke KJ, Pecoraro VL. Katalyse und Elektronentransfer in helikalen De‐novo‐Gerüststrukturen. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201907502] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Tyler B. J. Pinter
- Department of Chemistry University of Michigan Ann Arbor Michigan 48109-1055 USA
| | - Karl J. Koebke
- Department of Chemistry University of Michigan Ann Arbor Michigan 48109-1055 USA
| | - Vincent L. Pecoraro
- Department of Chemistry University of Michigan Ann Arbor Michigan 48109-1055 USA
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7
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Stroscio GD, Ribson RD, Hadt RG. Quantifying Entatic States in Photophysical Processes: Applications to Copper Photosensitizers. Inorg Chem 2019; 58:16800-16817. [DOI: 10.1021/acs.inorgchem.9b02976] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Gautam D. Stroscio
- Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Ryan D. Ribson
- Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
| | - Ryan G. Hadt
- Division of Chemistry and Chemical Engineering, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, United States
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8
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Mehra R, Kepp KP. Contribution of substrate reorganization energies of electron transfer to laccase activity. Phys Chem Chem Phys 2019; 21:15805-15814. [DOI: 10.1039/c9cp01012b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Laccase substrate reorganization energies computed by DFT show that electronic structure changes of these substrates contribute to enzymatic proficiency.
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Affiliation(s)
- Rukmankesh Mehra
- Technical University of Denmark
- DTU Chemistry
- 2800 Kgs. Lyngby
- Denmark
| | - Kasper P. Kepp
- Technical University of Denmark
- DTU Chemistry
- 2800 Kgs. Lyngby
- Denmark
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9
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Knorr M, Bonnot A, Lapprand A, Khatyr A, Strohmann C, Kubicki MM, Rousselin Y, Harvey PD. Reactivity of CuI and CuBr toward Dialkyl Sulfides RSR: From Discrete Molecular Cu4I4S4 and Cu8I8S6 Clusters to Luminescent Copper(I) Coordination Polymers. Inorg Chem 2015; 54:4076-93. [DOI: 10.1021/acs.inorgchem.5b00327] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Michael Knorr
- Institut UTINAM,
UMR CNRS 6213, Université de Franche-Comté, 16 Route de Gray, 25030 Besançon, France
| | - Antoine Bonnot
- Département de Chimie, Université de Sherbrooke, 2500 Boulevard Université, Sherbrooke, Quebec J1K 2R1, Canada
| | - Antony Lapprand
- Institut UTINAM,
UMR CNRS 6213, Université de Franche-Comté, 16 Route de Gray, 25030 Besançon, France
- Département de Chimie, Université de Sherbrooke, 2500 Boulevard Université, Sherbrooke, Quebec J1K 2R1, Canada
| | - Abderrahim Khatyr
- Institut UTINAM,
UMR CNRS 6213, Université de Franche-Comté, 16 Route de Gray, 25030 Besançon, France
| | - Carsten Strohmann
- Anorganische Chemie, Technische Universität Dortmund, Otto-Hahn-Strasse 6, 44227 Dortmund, Germany
| | - Marek M. Kubicki
- Institut de Chimie
Moléculaire, UMR CNRS 6302, Université de Bourgogne, 9 Avenue
A. Savary, 21087 Dijon, France
| | - Yoann Rousselin
- Institut de Chimie
Moléculaire, UMR CNRS 6302, Université de Bourgogne, 9 Avenue
A. Savary, 21087 Dijon, France
| | - Pierre D. Harvey
- Département de Chimie, Université de Sherbrooke, 2500 Boulevard Université, Sherbrooke, Quebec J1K 2R1, Canada
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10
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Frank P, Benfatto M, Qayyam M, Hedman B, Hodgson KO. A high-resolution XAS study of aqueous Cu(II) in liquid and frozen solutions: pyramidal, polymorphic, and non-centrosymmetric. J Chem Phys 2015; 142:084310. [PMID: 25725734 PMCID: PMC4349298 DOI: 10.1063/1.4908266] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Accepted: 02/04/2015] [Indexed: 11/15/2022] Open
Abstract
High-resolution EXAFS (k = 18 Å(-1)) and MXAN XAS analyses show that axially elongated square pyramidal [Cu(H2O)5](2+) dominates the structure of Cu(II) in aqueous solution, rather than 6-coordinate JT-octahedral [Cu(H2O)6](2+). Freezing produced a shoulder at 8989.6 eV on the rising XAS edge and an altered EXAFS spectrum, while 1s → 3d transitions remained invariant in energy position and intensity. Core square pyramidal [Cu(H2O)5](2+) also dominates frozen solution. Solvation shells were found at ∼3.6 Å (EXAFS) or ∼3.8 Å (MXAN) in both liquid and frozen phases. However, MXAN analysis revealed that about half the time in liquid solution, [Cu(H2O)5](2+) associates with an axially non-bonding 2.9 Å water molecule. This distant water apparently organizes the solvation shell. When the 2.9 Å water molecule is absent, the second shell is undetectable to MXAN. The two structural arrangements may represent energetic minima of fluxional dissolved aqueous [Cu(H2O)5](2+). The 2.9 Å trans-axial water resolves an apparent conflict of the [Cu(H2O)5](2+) core model with a dissociational exchange mechanism. In frozen solution, [Cu(H2O)5](2+) is associated with either a 3.0 Å axial non-bonded water molecule or an axial ClO4(-) at 3.2 Å. Both structures are again of approximately equal presence. When the axial ClO4(-) is present, Cu(II) is ∼0.5 Å above the mean O4 plane. This study establishes [Cu(H2O)5](2+) as the dominant core structure for Cu(II) in water solution, and is the first to both empirically resolve multiple extended solution structures for fluxional [Cu(H2O)5](2+) and to provide direct evidence for second shell dynamics.
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Affiliation(s)
- Patrick Frank
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Maurizio Benfatto
- Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
| | - Munzarin Qayyam
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
| | - Britt Hedman
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Stanford University, Menlo Park, California 94025, USA
| | - Keith O Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305, USA
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11
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Gast P, Broeren FG, Sottini S, Aoki R, Takashina A, Yamaguchi T, Kohzuma T, Groenen EJ. The type 1 copper site of pseudoazurin: Axial and rhombic. J Inorg Biochem 2014; 137:57-63. [DOI: 10.1016/j.jinorgbio.2014.03.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Revised: 03/25/2014] [Accepted: 03/28/2014] [Indexed: 11/29/2022]
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12
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Liu J, Chakraborty S, Hosseinzadeh P, Yu Y, Tian S, Petrik I, Bhagi A, Lu Y. Metalloproteins containing cytochrome, iron-sulfur, or copper redox centers. Chem Rev 2014; 114:4366-469. [PMID: 24758379 PMCID: PMC4002152 DOI: 10.1021/cr400479b] [Citation(s) in RCA: 559] [Impact Index Per Article: 55.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Indexed: 02/07/2023]
Affiliation(s)
- Jing Liu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Saumen Chakraborty
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Parisa Hosseinzadeh
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yang Yu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Shiliang Tian
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Igor Petrik
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Ambika Bhagi
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Yi Lu
- Department of Chemistry, Department of Biochemistry, and Center for Biophysics
and Computational
Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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13
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Yu F, Cangelosi VM, Zastrow ML, Tegoni M, Plegaria JS, Tebo AG, Mocny CS, Ruckthong L, Qayyum H, Pecoraro VL. Protein design: toward functional metalloenzymes. Chem Rev 2014; 114:3495-578. [PMID: 24661096 PMCID: PMC4300145 DOI: 10.1021/cr400458x] [Citation(s) in RCA: 340] [Impact Index Per Article: 34.0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Fangting Yu
- University of Michigan, Ann Arbor, Michigan 48109, United States
| | | | | | | | | | - Alison G. Tebo
- University of Michigan, Ann Arbor, Michigan 48109, United States
| | | | - Leela Ruckthong
- University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Hira Qayyum
- University of Michigan, Ann Arbor, Michigan 48109, United States
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14
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Yu F, Penner-Hahn JE, Pecoraro VL. De novo-designed metallopeptides with type 2 copper centers: modulation of reduction potentials and nitrite reductase activities. J Am Chem Soc 2013; 135:18096-107. [PMID: 24182361 DOI: 10.1021/ja406648n] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Enzymatic reactions involving redox processes are highly sensitive to the local electrostatic environment. Despite considerable effort, the complex interactions among different influential factors in native proteins impede progress toward complete understanding of the structure-function relationship. Of particular interest is the type 2 copper center Cu(His)3, which may act as an electron transfer center in peptidylglycine α-hydroxylating monooxygenase (PHM) or a catalytic center in copper nitrite reductase (CuNiR). A de novo design strategy is used to probe the effect of modifying charged amino acid residues around, but not directly bound to, a Cu(His)3 center embedded in three-stranded coiled coils (TRI-H)3 [TRI-H = Ac-G WKALEEK LKALEEK LKALEEK HKALEEK G-NH2]. Specifically, the peptide TRI-EH (=TRI-HK22E) alters an important lysine to glutamate just above the copper binding center. With a series of TRI-EH peptides mutated below the metal center, we use a variety of spectroscopies (EPR, UV-vis, XAS) to show a direct impact on the protonation equilibria, copper binding affinities, reduction potentials, and nitrite reductase activities of these copper-peptide complexes. The potentials at a specific pH vary by 100 mV, and the nitrite reductase activities range over a factor of 4 in rates. We also observe that the affinities, potentials, and catalytic activities are strongly influenced by the pH conditions (pH 5.8-7.4). In general, Cu(II) affinities for the peptides are diminished at low pH values. The interplay among these factors can lead to a 200 mV shift in reduction potential across these peptides, which is determined by the pH-dependent affinities of copper in both oxidation states. This study illustrates the strength of de novo protein design in elucidating the influence of ionizable residues on a particular redox system, an important step toward understanding the factors that govern the properties of this metalloenzyme with a goal of eventually improving the catalytic activity.
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Affiliation(s)
- Fangting Yu
- Department of Chemistry, University of Michigan , 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
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15
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Chen J, Chen WK, Rentzepis PM. Electron Transfer in Metal-Organic Molecules. A Time Resolved EXAFS and Optical Spectroscopy Study. J CHIN CHEM SOC-TAIP 2011. [DOI: 10.1002/jccs.201190001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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16
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Ligand Field and Molecular Orbital Theories of Transition Metal X-ray Absorption Edge Transitions. MOLECULAR ELECTRONIC STRUCTURES OF TRANSITION METAL COMPLEXES I 2011. [DOI: 10.1007/430_2011_60] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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17
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Lancaster KM, Yokoyama K, Richards JH, Winkler JR, Gray HB. High-potential C112D/M121X (X = M, E, H, L) Pseudomonas aeruginosa azurins. Inorg Chem 2010; 48:1278-80. [PMID: 19113863 DOI: 10.1021/ic802322e] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Site-directed mutagenesis of Pseudomonas aeruginosa azurin C112D at the M121 position has afforded a series of proteins with elevated Cu(II/I) reduction potentials relative to the Cu(II) aquo ion. The high potential and low axial hyperfine splitting (Cu(II) electron paramagnetic resonance A( parallel)) of the C112D/M121L protein are remarkably similar to features normally associated with type 1 copper centers.
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Affiliation(s)
- Kyle M Lancaster
- Beckman Institute, California Institute of Technology, Pasadena, California 91125, USA
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18
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Mankad NP, Antholine WE, Szilagyi RK, Peters JC. Three-coordinate copper(I) amido and aminyl radical complexes. J Am Chem Soc 2009; 131:3878-80. [PMID: 19253942 DOI: 10.1021/ja809834k] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A three-coordinate Cu-NR(2) system (R = p-tolyl) supported by the anionic bis(phosphino)borate ligand [Ph(2)B(CH(2)P(t)Bu(2))(2)](-) has been isolated and structurally characterized in both its anionic Cu(I) and neutral (formally) Cu(II) oxidation states. A large rate constant for the self-exchange electron-transfer reaction (k(S) >or= 10(7) M(-1) s(-1)) makes this system a functional model for the type-1 active sites in blue copper proteins. Multiedge X-ray absorption spectroscopy, multifrequency electron paramagnetic resonance, and density functional theory analyses collectively indicate that the oxidized form is best regarded as a Cu(I)-aminyl radical complex rather than a Cu(II)-amido species, with about 70% localization of the unpaired electron on the NR(2) unit. Hydrogen-atom transfer and C-C coupling reactions are presented as examples of chemical reactivity manifested by this unusual electronic structure.
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Affiliation(s)
- Neal P Mankad
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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Rizzuti B, Sportelli L, Guzzi R. Molecular dynamics of amicyanin reveals a conserved dynamical core for blue copper proteins. Proteins 2009; 74:961-71. [PMID: 18767164 DOI: 10.1002/prot.22204] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Molecular dynamics simulation has been carried out for the blue copper protein amicyanin from two different sources, Paracoccus denitrificans and Paraccocus versutus, to investigate the structural and dynamical properties common to the two molecules and to identify prominent features shared with proteins of the same family, the monomeric cupredoxins. The two amicyanins have almost identical secondary and tertiary structure. In the simulation, they differ for the number of hydrogen bonds in the main chain and the conformation of some beta-strands. However, they strictly maintain the arrangement of the portions of the beta-barrel that are conserved in the folding architecture of the blue copper proteins. Paracoccus versutus amicyanin equilibrates more rapidly, shows lower atomic deviation values, and is less rigid with respect to Paracoccus denitrificans amicyanin. Principal component analysis reveals that the conformational subspaces corresponding to eigenvectors with the same index for each of the two molecules are not necessarily equivalent. Nevertheless, a core scaffold with constrained dynamics exist for both amicyanins. In addition, two fairly flexible regions that are located on the opposite side with respect to the interaction sites with the partner molecules in the redox process have been evidenced in the protein structure. This description of amicyanin, with a few mobile regions remote from the active site and a rigid scaffold including most of the protein beta-barrel, has a close similarity with that of azurin and plastocyanin, two other cupredoxins previously investigated in simulation. Furthermore, similarities in the distribution of the atomic fluctuations indicate that amicyanin, azurin, and plastocyanin possess common dynamical features, in spite of differences in their structure. On the basis of these findings, we suggest that topological constraints imposed by the folding in correspondence of protein regions that are the most conserved determine the protein dynamics of the cupredoxin family. The dynamical properties of the cupredoxins might be controlled for functional advantages that include the binding mechanism with the biological partners and the collective inner motions of the protein matrix required for the electron transfer, whereas long-range conformational changes in the redox reaction should be excluded.
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Affiliation(s)
- Bruno Rizzuti
- Laboratorio Licryl CNR-INFM, Dipartimento di Fisica, Università della Calabria, Rende, Italy
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20
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Copper Proteins as Model Systems for Investigating Intramolecular Electron Transfer Processes. ADVANCES IN CHEMICAL PHYSICS 2007. [DOI: 10.1002/9780470141663.ch10] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/04/2023]
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21
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22
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23
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Bertrand P. Application of electron transfer theories to biological systems. STRUCTURE AND BONDING 2005. [DOI: 10.1007/3-540-53260-9_1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
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24
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Pierloot K. Calculations of Electronic Spectra of Transition Metal Complexes. ACTA ACUST UNITED AC 2005. [DOI: 10.1016/s1380-7323(05)80026-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/07/2023]
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25
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Abstract
Recent applications of density functional theory to biologically relevant metal centers are reviewed. The emphasis is on reaction mechanisms, structures, and modeling. The accuracy of different functionals is discussed for standard benchmark tests of first- and second-row molecules and for transition metal systems. Modeling aspects of the protein metal complexes are discussed regarding both the size of the model being treated quantum mechanically and the treatment of the protein surrounding it. To illustrate the effects, structures computed without the effects of the protein are compared with experimental structures from enzymes, and results from simple dielectric models of the protein for electron transfer processes are described. The choice of spin state is discussed for multimetal complexes. Examples of mechanisms studied recently by density functional theory are described, such as O2 and methane activation in methane monooxygenase and O2 formation in photosystem II.
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Affiliation(s)
- P E Siegbahn
- Department of Physics, Stockholm University, Box 6730, S-113 85 Stockholm, Sweden.
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26
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Kataoka K, Yamaguchi K, Sakai S, Takagi K, Suzuki S. Characterization and function of Met150Gln mutant of copper-containing nitrite reductase from Achromobacter cycloclastes IAM1013. Biochem Biophys Res Commun 2003; 303:519-24. [PMID: 12659849 DOI: 10.1016/s0006-291x(03)00381-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The mutant (M150Q-NIR) replacing the Met150 ligand of the type 1 Cu center in Achromobacter cycloclastes nitrite reductase (AcNIR) with Gln has been physicochemically and functionally characterized. The electronic absorption and CD spectra of M150Q-NIR are similar to those of mavicyanin and stellacyanin having the 2His, Cys, and Gln ligands, but the EPR signal has an axial character, although their blue copper proteins show rhombic EPR signals. The mutant has about 80% catalytic activity of AcNIR. Moreover, the midpoint potential (E(1/2)) of M150Q-NIR is +113 mV vs. NHE at pH 7.0, being negatively shifted compared to that of AcNIR (+240 mV). Although the intermolecular electron-transfer process from Achromobacter cycloclastes pseudoazurin (pAz) to M150Q-NIR was not detected, the pAz mutant (M86Q-pAz) replacing the Met86 ligand with Gln transfers one electron to the NIR mutant with an intermolecular electron-transfer rate constant (k(ET)) of 2.3 x 10(5)M(-1)s(-1).
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Affiliation(s)
- Kunishige Kataoka
- Department of Chemistry, Faculty of Science, Kanazawa University, Kakuma, Kanazawa 920-1192, Japan
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27
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Kanbi LD, Antonyuk S, Hough MA, Hall JF, Dodd FE, Hasnain SS. Crystal structures of the Met148Leu and Ser86Asp mutants of rusticyanin from Thiobacillus ferrooxidans: insights into the structural relationship with the cupredoxins and the multi copper proteins. J Mol Biol 2002; 320:263-75. [PMID: 12079384 DOI: 10.1016/s0022-2836(02)00443-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The crystal structures of the Met148Leu and Ser86Asp mutants of rusticyanin are presented at 1.82 and 1.65 A resolution, respectively. Both of these structures have two molecules in the asymmetric unit compared to the one present in the crystal form of the native protein. This provides an opportunity to investigate intramolecular electron transfer pathways in rusticyanin. The redox potential of the Met148Leu mutant ( approximately 800 mV) is elevated compared to that of the native protein ( approximately 670 mV at pH 3.2) while that of the Ser86Asp mutant ( approximately 623 mV at pH 3.2) is decreased. The effect of the Ser86Asp mutation on the hydrogen bonding near the type 1 Cu site is discussed and hence its role in determining acid stability is examined. The type 1 Cu site of Met148Leu mimics the structural and biochemical characteristics of those found in domain II of ceruloplasmin and fungal laccase. Moreover, the native rusticyanin's cupredoxin core and the type 1 Cu site closely resemble those found in ascorbate oxidase and nitrite reductase. Structure based phylogenetic trees have been re-examined in view of the additional structural data on rusticyanin and fungal laccase. We confirm that rusticyanin is in the same class as nitrite reductase domain 2, laccase domain 3 and ceruloplasmin domains 2, 4 and 6.
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Affiliation(s)
- Lalji D Kanbi
- Faculty of Applied Sciences, De Montfort University, The Gateway, Leicester LE1 9BH, UK
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28
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Abstract
Spectroscopic and theoretical investigations of the geometric and electronic structures of mononuclear and binuclear copper sites in proteins help in understanding the contributions of these proteins to biological electron transfer. Spectroscopically calibrated density functional theory calculations, which give reasonable bonding descriptions in both ground- and excited-states, define the role of the protein in determining the geometric and electronic structure of the active site.
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Affiliation(s)
- Robert K Szilagyi
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA
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29
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Ellis MJ, Prudêncio M, Dodd FE, Strange RW, Sawers G, Eady RR, Hasnain SS. Biochemical and crystallographic studies of the Met144Ala, Asp92Asn and His254Phe mutants of the nitrite reductase from Alcaligenes xylosoxidans provide insight into the enzyme mechanism. J Mol Biol 2002; 316:51-64. [PMID: 11829502 DOI: 10.1006/jmbi.2001.5304] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Dissimilatory nitrite reductase catalyses the reduction of nitrite (NO(2)(-)) to nitric oxide (NO). Copper-containing nitrite reductases contain both type 1 and type 2 Cu sites. Electron transfer from redox partners is presumed to be mediated via the type 1 Cu site and used at the catalytic type 2 Cu centre along with the substrate nitrite. At the type 2 Cu site, Asp92 has been identified as a key residue in substrate utilisation, since it hydrogen bonds to the water molecule at the nitrite binding site. We have also suggested that protons enter the catalytic site via Asp92, through a water network that is mediated by His254. The role of these residues has been investigated in the blue copper nitrite reductase from Alcaligenes xylosoxidans (NCIMB 11015) by a combination of point mutation, enzymatic activity measurement and structure determination.In addition, it has been suggested that the enzyme operates via an ordered mechanism where an electron is transferred to the type 2 Cu site largely when the second substrate nitrite is bound and that this is controlled via the lowering of the redox potential of the type 2 site when it is loaded with nitrite. Thus, a small perturbation of the type 1 Cu site should result in a significant effect on the activity of the enzyme. For this reason a mutation of Met144, which is the weakest ligand of the type 1 Cu, is investigated. The structures of H254F, D92N and M144A have been determined to 1.85 A, 1.9 A and 2.2 A resolution, respectively. The D92N and H254F mutants have negligible or no activity, while the M144A mutant has 30 % activity of the native enzyme. Structural and spectroscopic data show that the loss of activity in H254F is due to the catalytic site being occupied by Zn while the loss/reduction of activity in D92N/M144A are due to structural reasons. The D92N mutation results in the loss of the Asp92 hydrogen bond to the Cu-ligated water. Therefore, the ligand is no longer able to perform proton abstraction. Even though the loss of activity in H254F is due to lack of catalytic Cu, the mutation does cause the disruption of the water network, confirming its key role in proton channel. The structure of the H254F mutant is the first case where full occupancy Zn at the type 2 Cu site is observed, but despite the previously noted similarity of this site to the carbonic anhydrase catalytic site, no carbonic anhydrase activity is observed. The H254F and D92N mutant structures provide, for the first time, observation of surface Zn sites which may act as a Zn sink and prevent binding of Zn at the catalytic Cu site in the native enzyme.
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Affiliation(s)
- Mark J Ellis
- Faculty of Applied Science, De Montfort University, Leicester, LE1 9BH, UK
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30
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Rack-induced bonding in blue copper proteins: Spectroscopic properties and reduction potential of the azurin mutant Met-121 → Leu. FEBS Lett 2001. [DOI: 10.1016/0014-5793(89)80938-x] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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31
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32
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Chowdhury A, Peteanu LA, Webb MA, Loppnow GR. Stark Spectroscopic Studies of Blue Copper Proteins: Azurin. J Phys Chem B 2000. [DOI: 10.1021/jp0025227] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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33
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Abstract
Free energy perturbations have been performed on two blue copper proteins, plastocyanin and nitrite reductase. By changing the copper coordination geometry, force constants, and charges, we have estimated the maximum energy with which the proteins may distort the copper coordination sphere. By comparing this energy with the quantum chemical energy cost for the same perturbation on the isolated copper complex, various hypotheses about protein strain have been tested. The calculations show that the protein can only modify the copper-methionine bond length by a modest amount of energy-<5 kJ/mol-and they lend no support to the suggestion that the quite appreciable difference in the copper coordination geometry encountered in the two proteins is a result of the proteins enforcing different Cu-methionine bond lengths. On the contrary, this bond is very flexible, and neither the geometry nor the electronic structure change appreciably when the bond length is changed. Moreover, the proteins are rather indifferent to the length of this bond. Instead, the Cu(II) coordination geometries in the two proteins represent two distinct minima on the potential surface of the copper ligand sphere, characterized by different electronic structures, a tetragonal, mainly sigma-bonded, structure in nitrite reductase and a trigonal, pi-bonded, structure in plastocyanin. In vacuum, the structures have almost the same energy, and they are stabilized in the proteins by a combination of geometric and electrostatic interactions. Plastocyanin favors the bond lengths and electrostatics of the trigonal structure, whereas in nitrite reductase, the angles are the main discriminating factor. Proteins 1999;36:157-174.
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Affiliation(s)
- J O De Kerpel
- Department of Chemistry, University of Leuven, Heverlee-Leuven, Belgium
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35
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36
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37
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Effects of protein folding on metalloprotein redox-active sites: electron-transfer properties of blue and purple copper proteins. Coord Chem Rev 1999. [DOI: 10.1016/s0010-8545(98)00257-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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38
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Xu F, Palmer AE, Yaver DS, Berka RM, Gambetta GA, Brown SH, Solomon EI. Targeted mutations in a Trametes villosa laccase. Axial perturbations of the T1 copper. J Biol Chem 1999; 274:12372-5. [PMID: 10212209 DOI: 10.1074/jbc.274.18.12372] [Citation(s) in RCA: 134] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Trametes villosa laccase was mutated on a tetrapeptide segment near the type 1 site. The mutations F463M and F463L were at the position corresponding to the type 1 copper axial methionine (M517) ligand in Zucchini ascorbate oxidase. The mutations E460S and A461E were near the T1 copper site. The mutated Trametes laccases were expressed in an Aspergillus oryzae host and characterized. The E460S mutation failed to produce a transformant with meaningful expression. The F463L and A461E mutations did not significantly alter the molecular and enzymological properties of the laccase. In contrast, the F463M mutation resulted in a type 1 copper site with an EPR signal intermediate between that of the wild type laccase and plastocyanin, an altered UV-visible spectrum, and a decreased redox potential (by 0.1 V). In oxidizing phenolic substrate, the mutation led to a more basic optimal pH as well as an increase in kcat and Km. These effects are attributed to a significant perturbation of the T1 copper center caused by the coordination of the axial methionine (M463) ligand.
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Affiliation(s)
- F Xu
- Novo Nordisk Biotech, Davis, California 95616, USA.
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39
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Shibata N, Inoue T, Nagano C, Nishio N, Kohzuma T, Onodera K, Yoshizaki F, Sugimura Y, Kai Y. Novel insight into the copper-ligand geometry in the crystal structure of Ulva pertusa plastocyanin at 1.6-A resolution. Structural basis for regulation of the copper site by residue 88. J Biol Chem 1999; 274:4225-30. [PMID: 9933621 DOI: 10.1074/jbc.274.7.4225] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The crystal structure of plastocyanin from a green alga, Ulva pertusa, has been determined at 1.6-A resolution. At its copper site, U. pertusa plastocyanin has a distorted tetrahedral coordination geometry similar to other plastocyanins. In comparison with structures of plastocyanins reported formerly, a Cu(II)-Sdelta(Met92) bond distance (2.69 A) is shorter by about 0.2 A and a Cu(II)-Sgamma(Cys84) distance is longer by less than 0.1 A in U. pertusa plastocyanin. These subtle but significant differences are caused by the structural change at a His-Met loop (His87-Met92) due to an absence of a O(Asp85)-Ogamma(Ser88) hydrogen bond which is found in Enteromorpha prolifera plastocyanin. In addition, poplar and Chlamydomonas reinhardtii plastocyanins with a glutamine at residue 88 have a weak cation-pi interaction with Tyr83. This interaction lengthens the Cu(II)-Sdelta(Met92) bond of poplar and C. reinhardtii plastocyanins by 0.14 and 0.20 A, respectively. As a result of structural differences, U. pertusa plastocyanin has a less distorted geometry than the other plastocyanins. Thus, the cupric geometry is finely tuned by the interactions between residues 85 and 88 and between residues 83 and 88. This result implies that the copper site is more flexible than reported formerly and that the rack mechanism would be preferable to the entatic theory. The His-Met loop may regulate the electron transfer rate within the complex between plastocyanin and cytochrome f.
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Affiliation(s)
- N Shibata
- Department of Applied Chemistry, Faculty of Engineering, Osaka University, Suita, Osaka 565-0871, Japan
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40
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Bonomo RP, Boudet AM, Cozzolino R, Rizzarelli E, Santoro AM, Sterjiades R, Zappalà R. A comparative study of two isoforms of laccase secreted by the "white-rot" fungus Rigidoporus lignosus, exhibiting significant structural and functional differences. J Inorg Biochem 1998; 71:205-11. [PMID: 9833327 DOI: 10.1016/s0162-0134(98)10057-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Two isoforms of laccase were obtained as the predominant phenol-oxidases in defined medium liquid cultures of the "white-rot" fungus Rigidoporus lignosus (R. lignosus). A characterization of the two laccases was made in terms of molecular mass, isoelectric point, metal content and N-terminal sequence. Furthermore, in order to gain information on the structural features related to the metal centers, a study of their geometric arrangement and their redox ability was made. It turned out that the two isoenzymes greatly differed with regard to pH stability, catalytic and copper centers features. It is proposed that all such differences are dependent on the amino acid sequences, which cause a distortion of the copper sites, thus accounting for the redox potential values and kinetic properties.
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Affiliation(s)
- R P Bonomo
- Dipartimento di Scienze Chimiche, Università di Catania, Italy.
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41
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Messerschmidt A, Wever R. X-ray structures of apo and tungstate derivatives of vanadium chloroperoxidase from the fungus Curvularia inaequalis. Inorganica Chim Acta 1998. [DOI: 10.1016/s0020-1693(97)05919-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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42
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Schlag EW, Lin SH, Weinkauf R, Rentzepis PM. Dynamical principles in biological processes. Proc Natl Acad Sci U S A 1998; 95:1358-62. [PMID: 9465019 PMCID: PMC19004 DOI: 10.1073/pnas.95.4.1358] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The purpose of this paper is to propose certain dynamical principles in biological systems, which can be used to explain the effectiveness of charge transfer or excitation transfer in biological systems. Some of these systems are accessible experimentally.
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Affiliation(s)
- E W Schlag
- Institute for Physical and Theoretical Chemistry, Technical University of Munich, D-86748 Garching, Germany
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43
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Metal sites in small blue copper proteins, blue copper oxidases and vanadium-containing enzymes. STRUCTURE AND BONDING 1998. [DOI: 10.1007/3-540-62888-6_2] [Citation(s) in RCA: 69] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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44
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Leckner J, Bonander N, Wittung-Stafshede P, Malmström BG, Karlsson BG. The effect of the metal ion on the folding energetics of azurin: a comparison of the native, zinc and apoprotein. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1342:19-27. [PMID: 9366266 DOI: 10.1016/s0167-4838(97)00074-5] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The unfolding by guanidine hydrochloride (GuHCl) and the refolding on dilution of zinc and apoazurin have been monitored by far-UV circular dichroism (CD). With the native protein, the unfolding was followed by CD and optical absorption in the visible spectral region. With the zinc protein, the reversible unfolding has also been followed by tryptophan fluorescence and NMR. The zinc and Cu2+ metal ions remain associated with the protein in the unfolded state. When the unfolding of the native protein is followed by CD, the initial, reversible transition due to unfolding is followed by a slow change associated with the reduction of Cu2+ by the thiol group of the ligand Cys112. The unfolding of apoazurin displays two CD transitions, which evidence suggests represent different folding domains, the least stable one including the metal-binding site and the other one the rest of the beta-sheet structure. Both occur at a lower GuHCl concentration than the unfolding of the native protein. The CD titrations also demonstrate that zinc azurin has a lower stability than the copper protein. Unfolding of zinc azurin followed by tryptophan fluorescence occurs at a much lower GuHCl concentration than the CD changes, and NMR spectra show that there is no loss of secondary and tertiary structure at this concentration, whereas the CD-detected loss of secondary structure correlates with the NMR changes. Thus, the fluorescence change is ascribed to a small local perturbation of the structure around the single tryptophan residue. The differences in stability of the three forms of azurin are discussed in terms of the rack mechanism. A bound metal ion stabilizes the native fold, and this stabilization is larger for Cu(II) than for Zn(II), reflecting the higher affinity of the protein for Cu(II).
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Affiliation(s)
- J Leckner
- Department of Biochemistry and Biophysics, Göteborg University and Chalmers University of Technology, Sweden
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45
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Subramanian V, Shankaranarayanan C, Nair BU, Kanthimathi M, Manickkavachagam R, Ramasami T. Development of a force field for some copper(II) Schiff-base complexes. Chem Phys Lett 1997. [DOI: 10.1016/s0009-2614(97)00663-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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46
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Winkler JR, Wittung-Stafshede P, Leckner J, Malmström BG, Gray HB. Effects of folding on metalloprotein active sites. Proc Natl Acad Sci U S A 1997; 94:4246-9. [PMID: 9113974 PMCID: PMC20707 DOI: 10.1073/pnas.94.9.4246] [Citation(s) in RCA: 135] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Experimental data for the unfolding of cytochrome c and azurin by guanidinium chloride (GuHCl) are used to construct free-energy diagrams for the folding of the oxidized and reduced proteins. With cytochrome c, the driving force for folding the reduced protein is larger than that for the oxidized form. Both the oxidized and the reduced folded forms of yeast cytochrome c are less stable than the corresponding states of the horse protein. Due to the covalent attachment of the heme and its fixed tetragonal coordination geometry, cytochrome c folding can be described by a two-state model. A thermodynamic cycle leads to an expression for the difference in self-exchange reorganization energies for the folded and unfolded proteins. The reorganization energy for electron exchange in the folded protein is approximately 0.5 eV smaller than that for a heme in aqueous solution. The finding that reduced azurin unfolds at lower GuHCl concentrations than the oxidized protein suggests that the coordination structure of copper is different in oxidized and reduced unfolded states: it is likely that the geometry of CuI in the unfolded protein is linear or trigonal, whereas CuII prefers to be tetragonal. The evidence indicates that protein folding lowers the azurin reorganization energy by roughly 1.7 eV relative to an aqueous Cu(1, 10-phenanthroline)22+/+ reference system.
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Affiliation(s)
- J R Winkler
- Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA
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47
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Bonander N, Vänngård T, Tsai LC, Langer V, Nar H, Sjölin L. The metal site of Pseudomonas aeruginosa azurin, revealed by a crystal structure determination of the Co(II) derivative and Co-EPR spectroscopy. Proteins 1997; 27:385-94. [PMID: 9094740 DOI: 10.1002/(sici)1097-0134(199703)27:3<385::aid-prot6>3.0.co;2-c] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The crystal structure of cobalt-substituted azurin from Pseudomonas aeruginosa has been determined to final crystallographic R value of 0.175 at 1.9 A resolution. There are four molecules in the asymmetric unit in the structure, and these four molecules are packed as a dimer of dimers. The dimer packing is very similar to that of the wild-type Pseudomonas aeruginosa azurin dimer. Replacement of the native copper by the cobalt ion has only small effects on the metal binding site presumably because of the existence of an extensive network of hydrogen bonds in its immediate neighborhood. Some differences are obvious, however. In wild-type azurin the copper atom occupies a distorted trigonal bipyramidal site, while cobalt similar to zinc and nickel occupy a distorted tetrahedral site, in which the distance to the Met121,S(delta) atom is increased to 3.3-3.5 A and the distance to the carbonyl oxygen of Gly45 has decreased to 2.1-2.4 A. The X-band EPR spectrum of the high-spin Co(II) in azurin is well resolved (apparent g values gx' = 5.23; gy' = 3.83; gz' = 1.995, and hyperfine splittings Ax' = 31; Ay' = 20-30; Az' = 53 G) and indicates that the ligand field is close to axial.
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Affiliation(s)
- N Bonander
- Department of Biochemistry, Göteborg University, Sweden.
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48
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Battistuzzi G, Borsari M, Dallari D, Lancellotti I, Sola M. Anion binding to mitochondrial cytochromes c studied through electrochemistry. Effects of the neutralization of surface charges on the redox potential. EUROPEAN JOURNAL OF BIOCHEMISTRY 1996; 241:208-14. [PMID: 8898908 DOI: 10.1111/j.1432-1033.1996.0208t.x] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The redox potential of horse and bovine heart cytochromes c determined through cyclic voltammetry is exploited to probe for anion-protein interactions, using a Debye-Hückel-based model. In parallel, protein charge neutralization resulting from specific anion binding allows monitoring for surface-charge/E(o) relationships. This approach shows that a number of anions, most of which are of biological relevance, namely CI-, HPO(2-)4, HCO3-, NO3, SO(2-)4, CIO4-, citrate3- and oxalate2-, bind specifically to the protein surface, often in a sequential manner as a result of the presence of multiple sites with different affinities. The binding stoichiometries of the various anions toward a given cytochrome are in general different. Chloride and phosphate appear to bind to a greater extent to both proteins as compared to the other anions. Differences in binding specificity toward the two cytochromes, although highly sequence-related, are observed for a few anions. The data are discussed comparatively in terms of electrostatic and geometric properties of the anions and by reference to the proposed location and amino acid composition of the anion binding sites, when available. Specific binding of this large set of anions bearing different charges allows the electrostatic effect on Eo due to neutralization of net positive protein surface charge(s) to be monitored. (J)H NMR indeed indicates the absence of significant salt-induced structural perturbations, hence the above change in Eo is predominantly electrostatic in origin. A systematic study of protein surface-charge/Eo relationships using this approach is unprecedented. Values of 15-25 mV (extrapolated at zero ionic strength) are obtained for the decrease in Eo due to neutralization of one positive surface charge, which are of the same order of magnitude as previous estimates obtained with either mutation or chemical modification of surface lysines. The effects of the anion-induced decrease of net positive charge on Eo persist also at a relatively high ionic strength and add to the general effects related to the charge shielding of the protein as a whole due to the surrounding ionic atmosphere: hence the ionic strength dependence of the rate of electron transfer between cytochromes c and redox partners could also involve salt-induced changes in the driving force.
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Affiliation(s)
- G Battistuzzi
- Department of Chemistry, University of Modena, Italy
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49
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Xu F, Shin W, Brown SH, Wahleithner JA, Sundaram UM, Solomon EI. A study of a series of recombinant fungal laccases and bilirubin oxidase that exhibit significant differences in redox potential, substrate specificity, and stability. BIOCHIMICA ET BIOPHYSICA ACTA 1996; 1292:303-11. [PMID: 8597577 DOI: 10.1016/0167-4838(95)00210-3] [Citation(s) in RCA: 367] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
A series of fungal laccases (Polyporus pinsitus, Rhizoctonia solani, Myceliophthora thermophila, Scytalidium thermophilum) and one bilirubin oxidase (Myrothecium verrucaria) have been studied to determine their redox potential, specificity, and stability. Polyporus and Rhizoctonia laccases possess potentials near 0.7-0.8 V (vs. NHE), while other oxidases have potentials near 0.5 V. It is observed that higher redox potential correlates with higher activity. By EPR, no significant change in the geometry of type 1 copper (II) site is observed over this series. At the optimal pH, the two substrates studied, 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulfonic acid) and syringaldazine, show Km values ranging form 10 to 120 and from 1 to 45 microM; and kcat values ranging from 50 to 16 000 and 200 to 3000 per min, respectively. The enzymes are more stable in the neutral-alkaline pH range. The thermal stability is in the order of bilirubin oxidase equivalent to Myceliophthora laccase equivalent to Scytalidium laccase > Polyporus laccase > Rhizoctonia laccase. Based on these results and the sequence alignments made against Zucchini ascorbate oxidase it is speculated that structural differences in the substrate-activation site (a 'blue', type 1 copper center) control the redox potential range as well as substrate specificity, and the cystine content contributes to stability.
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Affiliation(s)
- F Xu
- Novo Nordisk Biotech, Davis, CA 95616 USA
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50
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Kofman V, Farver O, Pecht I, Goldfarb D. Two-Dimensional Pulsed EPR Spectroscopy of the Copper Protein Azurin. J Am Chem Soc 1996. [DOI: 10.1021/ja952704s] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- V. Kofman
- Contribution from the Departments of Chemical Physics and Chemical Immunology, The Weizmann Institute of Science, Rehovot, Israel, and Department of Analytical and Pharmaceutical Chemistry, Royal Danish School of Pharmacy, Copenhagen, Denmark
| | - O. Farver
- Contribution from the Departments of Chemical Physics and Chemical Immunology, The Weizmann Institute of Science, Rehovot, Israel, and Department of Analytical and Pharmaceutical Chemistry, Royal Danish School of Pharmacy, Copenhagen, Denmark
| | - I. Pecht
- Contribution from the Departments of Chemical Physics and Chemical Immunology, The Weizmann Institute of Science, Rehovot, Israel, and Department of Analytical and Pharmaceutical Chemistry, Royal Danish School of Pharmacy, Copenhagen, Denmark
| | - D. Goldfarb
- Contribution from the Departments of Chemical Physics and Chemical Immunology, The Weizmann Institute of Science, Rehovot, Israel, and Department of Analytical and Pharmaceutical Chemistry, Royal Danish School of Pharmacy, Copenhagen, Denmark
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