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Ledray AP, Dwaraknath S, Chakarawet K, Sponholtz MR, Merchen C, Van Stappen C, Rao G, Britt RD, Lu Y. Tryptophan Can Promote Oxygen Reduction to Water in a Biosynthetic Model of Heme Copper Oxidases. Biochemistry 2023; 62:388-395. [PMID: 36215733 DOI: 10.1021/acs.biochem.2c00300] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Heme-copper oxidases (HCOs) utilize tyrosine (Tyr) to donate one of the four electrons required for the reduction of O2 to water in biological respiration, while tryptophan (Trp) is speculated to fulfill the same role in cyt bd oxidases. We previously engineered myoglobin into a biosynthetic model of HCOs and demonstrated the critical role that Tyr serves in the oxygen reduction reaction (ORR). To address the roles of Tyr and Trp in these oxidases, we herein report the preparation of the same biosynthetic model with the Tyr replaced by Trp and further demonstrate that Trp can also promote the ORR, albeit with lower activity. An X-ray crystal structure of the Trp variant shows a hydrogen-bonding network involving two water molecules that are organized by Trp, similar to that in the Tyr variant, which is absent in the crystal structure with the native Phe residue. Additional electron paramagnetic resonance measurements are consistent with the formation of a Trp radical species upon reacting with H2O2. We attribute the lower activity of the Trp variant to Trp's higher reduction potential relative to Tyr. Together, these findings demonstrate, for the first time, that Trp can indeed promote the ORR and provides a structural basis for the observation of varying activities. The results support a redox role for the conserved Trp in bd oxidase while suggesting that HCOs use Tyr instead of Trp to achieve higher reactivity.
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Affiliation(s)
- Aaron P Ledray
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Sudharsan Dwaraknath
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Khetpakorn Chakarawet
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Madeline R Sponholtz
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Claire Merchen
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Casey Van Stappen
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States
| | - Guodong Rao
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - R David Britt
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Yi Lu
- Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.,Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States.,Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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Reed CJ, Lam QN, Mirts EN, Lu Y. Molecular understanding of heteronuclear active sites in heme-copper oxidases, nitric oxide reductases, and sulfite reductases through biomimetic modelling. Chem Soc Rev 2021; 50:2486-2539. [PMID: 33475096 PMCID: PMC7920998 DOI: 10.1039/d0cs01297a] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Heme-copper oxidases (HCO), nitric oxide reductases (NOR), and sulfite reductases (SiR) catalyze the multi-electron and multi-proton reductions of O2, NO, and SO32-, respectively. Each of these reactions is important to drive cellular energy production through respiratory metabolism and HCO, NOR, and SiR evolved to contain heteronuclear active sites containing heme/copper, heme/nonheme iron, and heme-[4Fe-4S] centers, respectively. The complexity of the structures and reactions of these native enzymes, along with their large sizes and/or membrane associations, make it challenging to fully understand the crucial structural features responsible for the catalytic properties of these active sites. In this review, we summarize progress that has been made to better understand these heteronuclear metalloenzymes at the molecular level though study of the native enzymes along with insights gained from biomimetic models comprising either small molecules or proteins. Further understanding the reaction selectivity of these enzymes is discussed through comparisons of their similar heteronuclear active sites, and we offer outlook for further investigations.
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Affiliation(s)
- Christopher J Reed
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA.
| | - Quan N Lam
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA
| | - Evan N Mirts
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA and Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA. and Department of Biochemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA and Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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3
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Kitagishi H, Kano K. Synthetic heme protein models that function in aqueous solution. Chem Commun (Camb) 2021; 57:148-173. [DOI: 10.1039/d0cc07044k] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Supramolecular porphyrin–cyclodextrin complexes act as biomimetic heme protein models in aqueous solution.
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Affiliation(s)
- Hiroaki Kitagishi
- Department of Molecular Chemistry and Biochemistry
- Faculty of Science and Engineering
- Doshisha University
- Kyoto 610-0321
- Japan
| | - Koji Kano
- Department of Molecular Chemistry and Biochemistry
- Faculty of Science and Engineering
- Doshisha University
- Kyoto 610-0321
- Japan
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Ehudin MA, Schaefer AW, Adam SM, Quist DA, Diaz DE, Tang JA, Solomon EI, Karlin KD. Influence of intramolecular secondary sphere hydrogen-bonding interactions on cytochrome c oxidase inspired low-spin heme-peroxo-copper complexes. Chem Sci 2019; 10:2893-2905. [PMID: 30996867 PMCID: PMC6431958 DOI: 10.1039/c8sc05165h] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Accepted: 01/03/2019] [Indexed: 11/21/2022] Open
Abstract
Dioxygen reduction by heme-copper oxidases is a critical biochemical process, wherein hydrogen bonding is hypothesized to participate in the critical step involving the active-site reductive cleavage of the O-O bond. Sixteen novel synthetic heme-(μ-O2 2-)-Cu(XTMPA) complexes, whose design is inspired by the cytochrome c oxidase active site structure, were generated in an attempt to form the first intramolecular H-bonded complexes. Derivatives of the "parent" ligand (XTMPA, TMPA = (tris((2-pyridyl)methyl)amine)) possessing one or two amine pendants preferentially form an H-bond with the copper-bound O-atom of the peroxide bridge. This is evidenced by a characteristic blue shift in the ligand-to-metal charge transfer (LMCT) bands observed in UV-vis spectroscopy (consistent with lowering of the peroxo π* relative to the iron orbitals) and a weakening of the O-O bond determined by resonance Raman spectroscopy (rR), with support from Density Functional Theory (DFT) calculations. Remarkably, with the TMPA-based infrastructure (versus similar heme-peroxo-copper complexes with different copper ligands), the typically undetected Cu-O stretch for these complexes was observed via rR, affording critical insights into the nature of the O-O peroxo core for the complexes studied. While amido functionalities have been shown to have greater H-bonding capabilities than their amino counterparts, in these heme-peroxo-copper complexes amido substituents distort the local geometry such that H-bonding with the peroxo core only imparts a weak electronic effect; optimal H-bonding interactions are observed by employing two amino groups on the copper ligand. The amino-substituted systems presented in this work reveal a key orientational anisotropy in H-bonding to the peroxo core for activating the O-O bond, offering critical insights into effective O-O cleavage chemistry. These findings indirectly support computational and protein structural studies suggesting the presence of an interstitial H-bonding water molecule in the CcO active site, which is critical for the desired reactivity. The results are evaluated with appropriate controls and discussed with respect to potential O2-reduction capabilities.
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Affiliation(s)
- Melanie A Ehudin
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Andrew W Schaefer
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA .
| | - Suzanne M Adam
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - David A Quist
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Daniel E Diaz
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Joel A Tang
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
| | - Edward I Solomon
- Department of Chemistry , Stanford University , Stanford , California 94305 , USA .
| | - Kenneth D Karlin
- Department of Chemistry , Johns Hopkins University , Baltimore , Maryland 21218 , USA .
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Adam SM, Wijeratne GB, Rogler PJ, Diaz DE, Quist DA, Liu JJ, Karlin KD. Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function. Chem Rev 2018; 118:10840-11022. [PMID: 30372042 PMCID: PMC6360144 DOI: 10.1021/acs.chemrev.8b00074] [Citation(s) in RCA: 145] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e- reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper-O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme-Cu models, evaluating experimental and computational results, which highlight important fundamental structure-function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.
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Affiliation(s)
- Suzanne M. Adam
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Gayan B. Wijeratne
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Patrick J. Rogler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Daniel E. Diaz
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - David A. Quist
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Jeffrey J. Liu
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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Kitagishi H, Shimoji D, Ohta T, Kamiya R, Kudo Y, Onoda A, Hayashi T, Weiss J, Wytko JA, Kano K. A water-soluble supramolecular complex that mimics the heme/copper hetero-binuclear site of cytochrome c oxidase. Chem Sci 2018; 9:1989-1995. [PMID: 29675246 PMCID: PMC5892347 DOI: 10.1039/c7sc04732k] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Accepted: 01/12/2018] [Indexed: 01/16/2023] Open
Abstract
The O2 adduct of an aqueous synthetic heme/copper model system built on a porphyrin/cyclodextrin supramolecular complex has been characterized.
In mitochondria, cytochrome c oxidase (CcO) catalyses the reduction of oxygen (O2) to water by using a heme/copper hetero-binuclear active site. Here we report a highly efficient supramolecular approach for the construction of a water-soluble biomimetic model for the active site of CcO. A tridentate copper(ii) complex was fixed onto 5,10,15,20-tetrakis(4-sulfonatophenyl)porphinatoiron(iii) (FeIIITPPS) through supramolecular complexation between FeIIITPPS and a per-O-methylated β-cyclodextrin dimer linked by a (2,2′:6′,2′′-terpyridyl)copper(ii) complex (CuIITerpyCD2). The reduced FeIITPPS/CuITerpyCD2 complex reacted with O2 in an aqueous solution at pH 7 and 25 °C to form a superoxo-type FeIII–O2–/CuI complex in a manner similar to CcO. The pH-dependent autoxidation of the O2 complex suggests that water molecules gathered at the distal Cu site are possibly involved in the FeIII–O2–/CuI superoxo complex in an aqueous solution. Electrochemical analysis using a rotating disk electrode demonstrated the role of the FeTPPS/CuTerpyCD2 hetero-binuclear structure in the catalytic O2 reduction reaction.
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Affiliation(s)
- Hiroaki Kitagishi
- Department of Molecular Chemistry and Biochemistry , Faculty of Science and Engineering , Doshisha University , Kyotanabe , Kyoto 610-0321 , Japan .
| | - Daiki Shimoji
- Department of Molecular Chemistry and Biochemistry , Faculty of Science and Engineering , Doshisha University , Kyotanabe , Kyoto 610-0321 , Japan .
| | - Takehiro Ohta
- Picobiology Institute , Graduate School of Life Science , University of Hyogo , RSC-UH LP Center , Hyogo 679-5148 , Japan
| | - Ryo Kamiya
- Department of Molecular Chemistry and Biochemistry , Faculty of Science and Engineering , Doshisha University , Kyotanabe , Kyoto 610-0321 , Japan .
| | - Yasuhiro Kudo
- Department of Molecular Chemistry and Biochemistry , Faculty of Science and Engineering , Doshisha University , Kyotanabe , Kyoto 610-0321 , Japan .
| | - Akira Onoda
- Department of Applied Chemistry , Graduate School of Engineering , Osaka University , 2-1 Yamadaoka , Suita 565-0871 , Japan
| | - Takashi Hayashi
- Department of Applied Chemistry , Graduate School of Engineering , Osaka University , 2-1 Yamadaoka , Suita 565-0871 , Japan
| | - Jean Weiss
- Institut de Chimie de Strasbourg , UMR 7177 , CNRS , Université de Strasbourg , 4 Rue Blaise Pascal , 67000 Strasbourg , France
| | - Jennifer A Wytko
- Institut de Chimie de Strasbourg , UMR 7177 , CNRS , Université de Strasbourg , 4 Rue Blaise Pascal , 67000 Strasbourg , France
| | - Koji Kano
- Department of Molecular Chemistry and Biochemistry , Faculty of Science and Engineering , Doshisha University , Kyotanabe , Kyoto 610-0321 , Japan .
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Lang P, Schwalbe M. Pacman Compounds: From Energy Transfer to Cooperative Catalysis. Chemistry 2017; 23:17398-17412. [DOI: 10.1002/chem.201703675] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2017] [Indexed: 01/08/2023]
Affiliation(s)
- Philipp Lang
- Institut für Chemie; Humboldt-Universität zu Berlin; Brook-Taylor-St. 2 12489 Berlin Germany
| | - Matthias Schwalbe
- Institut für Chemie; Humboldt-Universität zu Berlin; Brook-Taylor-St. 2 12489 Berlin Germany
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Walaszek DJ, Maximova K, Rybicka-Jasińska K, Lipke A, Gryko D. Synthesis of chiral porphyrins and their use in photochemical oxidation of carbonyl compounds. J PORPHYR PHTHALOCYA 2014. [DOI: 10.1142/s1088424614500229] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A series of chiral A4, A2B2, and AB3 porphyrins bearing proline moieties at the meso-phenyl group has been synthesized. Photostability studies revealed that the number of L-proline units and their position on meso-phenyl rings strongly influence the decomposition rate of the catalyst. 5,10,15-Tris(mesityl)-20-(3-prolinanilidylphenyl)-21,23H-porphyrin is the most stable while porphyrin bearing four 3-prolinanilidylphenyl substituents completely decomposes in CHCl 3 within 3 h. Singlet oxygen quantum yields of the conjugates were determined by measuring the peak areas of the NIR emission of 1 O 2 (1280 nm) generated by these compounds and compared to that generated by the reference standard TPP. Selected porphyrins were tested as catalysts in the photooxidation of carbonyl compounds at the α-position.
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Affiliation(s)
- Dominika J. Walaszek
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | - Ksenia Maximova
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
| | | | - Agnieszka Lipke
- Faculty of Chemistry, Maria Curie-Skłodowska University, M. Curie-Skłodowska Sq. 2, 20-031 Lublin, Poland
| | - Dorota Gryko
- Institute of Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw, Poland
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Liu X, Yu Y, Hu C, Zhang W, Lu Y, Wang J. Significant Increase of Oxidase Activity through the Genetic Incorporation of a Tyrosine-Histidine Cross-Link in a Myoglobin Model of Heme-Copper Oxidase. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201108756] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Liu X, Yu Y, Hu C, Zhang W, Lu Y, Wang J. Significant increase of oxidase activity through the genetic incorporation of a tyrosine-histidine cross-link in a myoglobin model of heme-copper oxidase. Angew Chem Int Ed Engl 2012; 51:4312-6. [PMID: 22411709 DOI: 10.1002/anie.201108756] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Indexed: 11/12/2022]
Affiliation(s)
- Xiaohong Liu
- Laboratory of Noncoding RNA, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing, 100101, China
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Mulholland AR, Thordarson P, Mensforth EJ, Langford SJ. Porphyrin dyads linked by a rotatable 3,3′-biphenyl scaffold: a new binding motif for small ditopic molecules. Org Biomol Chem 2012; 10:6045-53. [DOI: 10.1039/c2ob25147g] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Lu C, Zhao X, Lu Y, Rousseau DL, Yeh SR. Role of copper ion in regulating ligand binding in a myoglobin-based cytochrome C oxidase model. J Am Chem Soc 2010; 132:1598-605. [PMID: 20070118 DOI: 10.1021/ja907777f] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cytochrome c oxidase (CcO), the terminal enzyme in the mitochondrial respiratory chain, catalyzes the four-electron reduction of dioxygen to water in a binuclear center comprised of a high-spin heme (heme a(3)) and a copper atom (Cu(B)) coordinated by three histidine residues. As a minimum model for CcO, a mutant of sperm whale myoglobin, named Cu(B)Mb, has been engineered, in which a copper atom is held in the distal heme pocket by the native E7 histidine and two nonnative histidine residues. In this work, the role of the copper in regulating ligand binding in Cu(B)Mb was investigated. Resonance Raman studies show that the presence of copper in CO-bound Cu(B)Mb leads to a CcO-like distal heme pocket. Stopped-flow data show that, upon the initiation of the CO binding reaction, the ligand first binds to the Cu(+); it subsequently transfers from Cu(+) to Fe(2+) in an intramolecular process, similar to that reported for CcO. The high CO affinity toward Cu(+) and the slow intramolecular CO transfer rate between Cu(+) and Fe(2+) in the Cu(B)Mb/Cu(+) complex are analogous to those in Thermus thermophilus CcO (TtCcO) but distinct from those in bovine CcO (bCcO). Additional kinetic studies show that, upon photolysis of the NO-bound Cu(B)Mb/Cu(+) complex, the photolyzed ligand transiently binds to Cu(+) and subsequently rebinds to Fe(2+), accounting for the 100% geminate recombination yield, similar to that found in TtCcO. The data demonstrate that the Cu(B)Mb/Cu(+) complex reproduces essential structural and kinetic features of CcO and that the complex is more akin to TtCcO than to bCcO.
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Affiliation(s)
- Changyuan Lu
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Liu JG, Ohta T, Yamaguchi S, Ogura T, Sakamoto S, Maeda Y, Naruta Y. Spectroscopic characterization of a hydroperoxo-heme intermediate: conversion of a side-on peroxo to an end-on hydroperoxo complex. Angew Chem Int Ed Engl 2010; 48:9262-7. [PMID: 19882613 DOI: 10.1002/anie.200904572] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
- Jin-Gang Liu
- Institute for Materials Chemistry and Engineering, Kyushu University, Higashi-ku, Fukuoka, 812-8581, Japan
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Liu JG, Ohta T, Yamaguchi S, Ogura T, Sakamoto S, Maeda Y, Naruta Y. Spectroscopic Characterization of a HydroperoxoâHeme Intermediate: Conversion of a Side-On Peroxo to an End-On Hydroperoxo Complex. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200904572] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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16
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Offenbacher A, White KN, Sen I, Oliver AG, Konopelski JP, Barry BA, Einarsdóttir O. A spectroscopic investigation of a tridentate Cu-complex mimicking the tyrosine-histidine cross-link of cytochrome C oxidase. J Phys Chem B 2009; 113:7407-17. [PMID: 19438285 DOI: 10.1021/jp9010795] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Heme-copper oxidases have a crucial role in the energy transduction mechanism, catalyzing the reduction of dioxygen to water. The reduction of dioxygen takes place at the binuclear center, which contains heme a3 and CuB. The X-ray crystal structures have revealed that the C6' of tyrosine 244 (bovine heart numbering) is cross-linked to a nitrogen of histidine 240, a ligand to CuB. The role of the cross-linked tyrosine at the active site still remains unclear. In order to provide insight into the function of the cross-linked tyrosine, we have investigated the spectroscopic and electrochemical properties of chemical analogues of the CuB-His-Tyr site. The analogues, a tridentate histidine-phenol cross-linked ether ligand and the corresponding Cu-containing complex, were previously synthesized in our laboratory (White, K.; et al. Chem. Commun. 2007, 3252-3254). Spectrophotometric titrations of the ligand and the Cu-complex indicate a pKa of the phenolic proton of 8.8 and 7.7, respectively. These results are consistent with the cross-linked tyrosine playing a proton delivery role at the cytochrome c oxidase active site. The presence of the phenoxyl radical was investigated at low temperature using electron paramagnetic resonance (EPR) and Fourier transform infrared (FT-IR) difference spectroscopy. UV photolysis of the ligand, without bound copper, generated a narrow g=2.0047 signal, attributed to the phenoxyl radial. EPR spectra recorded before and after UV photolysis of the Cu-complex showed a g=2 signal characteristic of oxidized copper, suggesting that the copper is not spin-coupled to the phenoxyl radical. An EPR signal from the phenoxyl radical was not observed in the Cu-complex, either due to spin relaxation of the two unpaired electrons or to masking of the narrow phenoxyl radical signal by the strong copper contribution. Stable isotope (13C) labeling of the phenol ring (C1') Cu-complex, combined with photoinduced difference FT-IR spectroscopy, revealed bands at 1485 and 1483 cm(-1) in the 12C-minus-13C-isotope-edited spectra of the ligand and Cu-complex, respectively. These bands are attributed to the radical v7a stretching frequency and are shifted to 1468 and 1472 cm(-1), respectively, with 13C1' labeling. These results show that a radical is generated in both the ligand and the Cu-complex and support the unambiguous assignment of a vibrational band to the phenoxyl radical v7a stretching mode. These data are discussed with respect to a possible role of the cross-linked tyrosine radical in cytochrome c oxidase.
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Affiliation(s)
- Adam Offenbacher
- Department of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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Collman JP, Ghosh S, Dey A, Decréau RA, Yang Y. Catalytic reduction of O2 by cytochrome C using a synthetic model of cytochrome C oxidase. J Am Chem Soc 2009; 131:5034-5. [PMID: 19317484 DOI: 10.1021/ja9001579] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Cytochrome c oxidase (CcO) catalyzes the four-electron reduction of oxygen to water, the one-electron reductant Cytochrome c (Cytc) being the source of electrons. Recently we reported a functional model of CcO that electrochemically catalyzes the four-electron reduction of O(2) to H(2)O (Collman et al. Science 2007, 315, 1565). The current paper shows that the same functional CcO model catalyzes the four-electron reduction of O(2) using the actual biological reductant Cytc in a homogeneous solution. Both single and steady-state turnover kinetics studies indicate that O(2) binding is rate-determining and that O-O bond cleavage and electron transfer from reduced Cytc to the oxidized model complex are relatively fast.
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Affiliation(s)
- James P Collman
- Department of Chemistry, Stanford University, Stanford, California 94305, USA.
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Collman JP, Decréau RA. Functional biomimetic models for the active site in the respiratory enzyme cytochrome c oxidase. Chem Commun (Camb) 2008:5065-76. [PMID: 18956030 DOI: 10.1039/b808070b] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A functional analog of the active site in the respiratory enzyme, cytochrome c oxidase (CcO) reproduces every feature in CcO's active site: a myoglobin-like heme (heme a3), a distal tridentate imidazole copper complex (Cu(B)), a phenol (Tyr244), and a proximal imidazole. When covalently attached to a liquid-crystalline SAM film on an Au electrode, this functional model continuously catalyzes the selective four-electron reduction of dioxygen at physiological potential and pH, under rate-limiting electron flux (as occurs in CcO).
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Affiliation(s)
- James P Collman
- Stanford University, Chemistry Department, Stanford, CA-94305-5080, USA.
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Collman JP, Dey A, Decréau RA, Yang Y. Model studies of azide binding to functional analogues of CcO. Inorg Chem 2008; 47:2916-8. [PMID: 18361486 DOI: 10.1021/ic702294n] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
N3- binding to a functional model of CcO is investigated in its Fe3+, Fe3+Cu+, and Fe3+Cu2+ forms. A combination of EPR and FTIR indicates that N3- binds in a bridging mode in the bimetallic sites and signature N3- bands are identified for several forms of N3- binding to the site. The presence of the distal metal increases the binding affinity of N3-. This bridging enables antiferromagnetic interaction between the two metal centers in the Fe3+Cu2+ state, which results in an EPR-silent ground state.
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Affiliation(s)
- James P Collman
- Department of Chemistry, Stanford University, Stanford, CA 94305, USA.
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20
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Liu JG, Naruta Y, Tani F. Synthetic Models of the Active Site of Cytochromec Oxidase: Influence of Tridentate or Tetradentate Copper Chelates Bearing a HisTyr Linkage Mimic on Dioxygen Adduct Formation by Heme/Cu Complexes. Chemistry 2007; 13:6365-78. [PMID: 17503416 DOI: 10.1002/chem.200601884] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Two synthetic models of the active site of cytochrome c oxidase--[(LN4-OH)CuI-FeII(TMP)]+ (1 a) and [(LN3-OH)CuI-FeII(TMP)]+ (2 a)-have been designed and synthesized. These models each contain a heme and a covalently attached copper moiety supported either by a tetradentate N4-copper chelate or by a tridentate N3-copper chelate including a moiety that acts as a mimic of the crosslinked His-Tyr component of cytochrome c oxidase. Low-temperature oxygenation reactions of these models have been investigated by spectroscopic methods including UV/Vis, resonance Raman, ESI-MS, and EPR spectroscopy. Oxygenation of the tetradentate model 1 a in MeCN and in other solvents produces a low-temperature-stable dioxygen-bridged peroxide [(LN4-OH)CuII-O2-FeIII(TMP)]+ {nuO--O=799 (16O2)/752 cm(-1) (18O2)}, while a heme superoxide species [(TMP)FeIII(O2-)CuIILN3-OH] {nuFe--O2: 576 (16O2)/551 cm(-1) (18O2)} is generated when the tridentate model 2 a is oxygenated in EtCN solution under similar experimental conditions. The coexistence of a heme superoxide species [(TMP)FeIII(O2-)CuIILN3-OH] and a bridged peroxide [(LN3-OH)CuII-O2-FeIII(TMP)]+ species in equal amounts is observed when the oxygenation reaction of 2 a is performed in CH2Cl(2)/7 % EtCN, while the percentage of the peroxide (approximately 70 %) in relation to superoxide (approximately 30 %) increases further when the crosslinked phenol moiety in 2 a is deprotonated to produce the bridged peroxide [(LN3-OH)CuII-O2-FeIII(TMP)]+ {nuO--O: 812 (16O2)/765 cm(-1) (18O2)} as the main dioxygen intermediate. The weak reducibility and decreased O2 reactivity of the tricoordinated CuI site in 2 a are responsible for the solvent-dependent formation of dioxygen adducts. The initial binding of dioxygen to the copper site en route to the formation of a bridged heme-O2-Cu intermediate by model 2 a is suggested and the deprotonated crosslinked His-Tyr moiety might contribute to enhancement of the O2 affinity of the CuI site at an early stage of the dioxygen-binding process.
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Affiliation(s)
- Jin-Gang Liu
- Institute for Materials Chemistry and Engineering, Kyushu University, Higashi-ku, Fukuoka, 812-8581, Japan
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21
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Collman JP, Decréau RA, Yan Y, Yoon J, Solomon EI. Intramolecular single-turnover reaction in a cytochrome C oxidase model bearing a Tyr244 mimic. J Am Chem Soc 2007; 129:5794-5. [PMID: 17429972 PMCID: PMC2512969 DOI: 10.1021/ja0690969] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- James P Collman
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, USA.
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22
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A strategic approach for the synthesis of new porphyrin rings, attractive for heme model purpose. Tetrahedron 2007. [DOI: 10.1016/j.tet.2007.01.036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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White KN, Sen I, Szundi I, Landaverry YR, Bria LE, Konopelski JP, Olmstead MM, Einarsdóttir O. Synthesis and structural characterization of cross-linked histidine–phenol Cu(ii) complexes as cytochrome c oxidase active site models. Chem Commun (Camb) 2007:3252-4. [PMID: 17668091 DOI: 10.1039/b703835f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Tridentate cross-linked histidine-phenol Cu(ii) ether and ester complexes, chemical analogs of the active site of several heme-copper oxidases, have been synthesized and crystallized.
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Affiliation(s)
- Kimberly N White
- Department of Chemistry and Biochemistry, University of California, Santa Cruz, CA 95064, USA
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24
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Melin F, Choua S, Bernard M, Turek P, Weiss J. Built-in Axial Base Binding on Phenanthroline-Strapped Zinc(II) and Iron(III) Porphyrins. Inorg Chem 2006; 45:10750-7. [PMID: 17173432 DOI: 10.1021/ic0611185] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In addition to the need for functional models of cytochrome c oxidase, structural models are still required for a better understanding of the small reorganizations occurring during the catalytic cycle. An efficient synthetic approach has been designed to prepare several phenanthroline-strapped porphyrins, two of them bearing two pendant imidazoles. These built-in bases are both potentially able to act as axial bases for the metalloporphyrin and as complementary ligands for copper if necessary. Diamagnetic zinc(II) was used to demonstrate that the distal/proximal selectivity demonstrated by exogenic bases binding studies can be extended to the coordination of iron(III). Combination of EPR and paramagnetic 1H NMR shows that the imidazole binding on the zinc species can be further extended to the iron(III) species in dilute conditions.
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Affiliation(s)
- Frédéric Melin
- Chimie des Ligands à Architecture Contrôlée, LC3 CNRS-ULP, Institut Le Bel, 4 rue Blaise Pascal, 67070 Strasbourg Cedex, France
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25
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Liu JG, Naruta Y, Tani F. A functional model of the cytochrome c oxidase active site: unique conversion of a heme-mu-peroxo-Cu(II) intermediate into heme- superoxo/Cu(I). Angew Chem Int Ed Engl 2006; 44:1836-40. [PMID: 15723432 DOI: 10.1002/anie.200462582] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Jin-Gang Liu
- Institute for Materials Chemistry and Engineering, Kyushu University, Higashi-ku, Fukuoka, 812-8581, Japan
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26
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Pesavento RP, Pratt DA, Jeffers J, van der Donk WA. Model studies of the CuBsite of cytochrome c oxidase utilizing a Zn(ii) complex containing an imidazole–phenol cross-linked ligand. Dalton Trans 2006:3326-37. [PMID: 16820845 DOI: 10.1039/b516090a] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cytochrome c oxidase, the enzyme complex responsible for the four-electron reduction of O2 to H2O, contains an unusual histidine-tyrosine cross-link in its bimetallic heme a3-CuB active site. We have synthesised an unhindered, tripodal chelating ligand, BPAIP, containing the unusual ortho-imidazole-phenol linkage, which mimics the coordination environment of the CuB center. The ligand was used to investigate the physicochemical (pKa, oxidation potential) and coordination properties of the imidazole-phenol linkage when bound to a dication. Zn(II) coordination lowers the pKa of the phenol by 0.6 log units, and increases the potential of the phenolate/phenoxyl radical couple by approximately 50 mV. These results are consistent with inductive withdrawal of electron density from the phenolic ring. Spectroscopic data and theoretical calculations (DFT) were used to establish that the cationic complex [Zn(BPAIP)Br]+ has an axially distorted trigonal bipyramidal structure, with three coordinating nitrogen ligands (two pyridine and one imidazole) occupying the equatorial plane and the bromide and the tertiary amine nitrogen of the tripod in the axial positions. Interestingly, the Zn-Namine bonding interaction is weak or absent in [Zn(BPAIP)Br]+ and the complex gains stability in basic solutions, as indicated by 1H NMR spectroscopy. These observations are supported by theoretical calculations (DFT), which suggest that the electron-donating capacity of the equatorial imidazole ligand can be varied by modulation of the protonation and/or redox state of the cross-linked phenol. Deprotonation of the phenol makes the equatorial imidazole a stronger sigma-donor, resulting in an increased Zn-Nimd interaction and thereby leading to distortion of the axial ligand axis toward a more tetrahedral geometry.
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Affiliation(s)
- Russell P Pesavento
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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27
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Collman JP, Decréau RA, Sunderland CJ. Single-turnover intermolecular reaction between a Feiii–superoxide–Cuicytochrome c oxidase model and exogeneous Tyr244 mimics. Chem Commun (Camb) 2006:3894-6. [PMID: 17268662 DOI: 10.1039/b607277a] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
An Fe(III)-superoxide-Cu(I) cytochrome c oxidase model reacts intermolecularly with hindered phenols leading to phenoxyl radicals, as was observed in the enzyme and evidence for the formation of an Fe(IV)-oxo is presented.
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Affiliation(s)
- James P Collman
- Stanford University, Chemistry Department, Stauffer II, Stanford, CA-94306, USA.
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28
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Liu JG, Naruta Y, Tani F. A Functional Model of the Cytochromec Oxidase Active Site: Unique Conversion of a Heme-?-peroxo-CuII Intermediate into Heme- superoxo/CuI. Angew Chem Int Ed Engl 2005. [DOI: 10.1002/ange.200462582] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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29
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Nagano Y, Liu JG, Naruta Y, Kitagawa T. UV resonance Raman study of model complexes of the CuB site of cytochrome c oxidase. J Mol Struct 2005. [DOI: 10.1016/j.molstruc.2004.11.012] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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