1
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de Lichtenberg C, Rapatskiy L, Reus M, Heyno E, Schnegg A, Nowaczyk MM, Lubitz W, Messinger J, Cox N. Assignment of the slowly exchanging substrate water of nature's water-splitting cofactor. Proc Natl Acad Sci U S A 2024; 121:e2319374121. [PMID: 38437550 PMCID: PMC10945779 DOI: 10.1073/pnas.2319374121] [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: 11/06/2023] [Accepted: 02/12/2024] [Indexed: 03/06/2024] Open
Abstract
Identifying the two substrate water sites of nature's water-splitting cofactor (Mn4CaO5 cluster) provides important information toward resolving the mechanism of O-O bond formation in Photosystem II (PSII). To this end, we have performed parallel substrate water exchange experiments in the S1 state of native Ca-PSII and biosynthetically substituted Sr-PSII employing Time-Resolved Membrane Inlet Mass Spectrometry (TR-MIMS) and a Time-Resolved 17O-Electron-electron Double resonance detected NMR (TR-17O-EDNMR) approach. TR-MIMS resolves the kinetics for incorporation of the oxygen-isotope label into the substrate sites after addition of H218O to the medium, while the magnetic resonance technique allows, in principle, the characterization of all exchangeable oxygen ligands of the Mn4CaO5 cofactor after mixing with H217O. This unique combination shows i) that the central oxygen bridge (O5) of Ca-PSII core complexes isolated from Thermosynechococcus vestitus has, within experimental conditions, the same rate of exchange as the slowly exchanging substrate water (WS) in the TR-MIMS experiments and ii) that the exchange rates of O5 and WS are both enhanced by Ca2+→Sr2+ substitution in a similar manner. In the context of previous TR-MIMS results, this shows that only O5 fulfills all criteria for being WS. This strongly restricts options for the mechanism of water oxidation.
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Affiliation(s)
- Casper de Lichtenberg
- Department of Chemistry- Ångström Laboratorium, Uppsala University, UppsalaS-75120, Sweden
- Department of Chemistry, Chemical Biological Centre, Umeå University, UmeåS-90187, Sweden
| | - Leonid Rapatskiy
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der RuhrD-45470, Germany
| | - Michael Reus
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der RuhrD-45470, Germany
| | - Eiri Heyno
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der RuhrD-45470, Germany
| | - Alexander Schnegg
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der RuhrD-45470, Germany
| | - Marc M. Nowaczyk
- Department of Plant Biochemistry, Ruhr-Universität Bochum, BochumD-44780, Germany
| | - Wolfgang Lubitz
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der RuhrD-45470, Germany
| | - Johannes Messinger
- Department of Chemistry- Ångström Laboratorium, Uppsala University, UppsalaS-75120, Sweden
- Department of Chemistry, Chemical Biological Centre, Umeå University, UmeåS-90187, Sweden
| | - Nicholas Cox
- Max Planck Institute for Chemical Energy Conversion, Mülheim an der RuhrD-45470, Germany
- Research School of Chemistry, Australian National University, Acton ACT2601, Australia
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2
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Famulari A, Correddu D, Di Nardo G, Gilardi G, Mitrikas G, Chiesa M, García-Rubio I. Heme Spin Distribution in the Substrate-Free and Inhibited Novel CYP116B5hd: A Multifrequency Hyperfine Sublevel Correlation (HYSCORE) Study. Molecules 2024; 29:518. [PMID: 38276601 PMCID: PMC10819608 DOI: 10.3390/molecules29020518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 12/29/2023] [Accepted: 01/16/2024] [Indexed: 01/27/2024] Open
Abstract
The cytochrome P450 family consists of ubiquitous monooxygenases with the potential to perform a wide variety of catalytic applications. Among the members of this family, CYP116B5hd shows a very prominent resistance to peracid damage, a property that makes it a promising tool for fine chemical synthesis using the peroxide shunt. In this meticulous study, we use hyperfine spectroscopy with a multifrequency approach (X- and Q-band) to characterize in detail the electronic structure of the heme iron of CYP116B5hd in the resting state, which provides structural details about its active site. The hyperfine dipole-dipole interaction between the electron and proton nuclear spins allows for the locating of two different protons from the coordinated water and a beta proton from the cysteine axial ligand of heme iron with respect to the magnetic axes centered on the iron. Additionally, since new anti-cancer therapies target the inhibition of P450s, here we use the CYP116B5hd system-imidazole as a model for studying cytochrome P450 inhibition by an azo compound. The effects of the inhibition of protein by imidazole in the active-site geometry and electron spin distribution are presented. The binding of imidazole to CYP116B5hd results in an imidazole-nitrogen axial coordination and a low-spin heme FeIII. HYSCORE experiments were used to detect the hyperfine interactions. The combined interpretation of the gyromagnetic tensor and the hyperfine and quadrupole tensors of magnetic nuclei coupled to the iron electron spin allowed us to obtain a precise picture of the active-site geometry, including the orientation of the semi-occupied orbitals and magnetic axes, which coincide with the porphyrin N-Fe-N axes. The electronic structure of the iron does not seem to be affected by imidazole binding. Two different possible coordination geometries of the axial imidazole were observed. The angles between gx (coinciding with one of the N-Fe-N axes) and the projection of the imidazole plane on the heme were determined to be -60° and -25° for each of the two possibilities via measurement of the hyperfine structure of the axially coordinated 14N.
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Affiliation(s)
- Antonino Famulari
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, C/Pedro Cerbuna 12, 50009 Zaragoza, Spain;
- Department of Chemistry, University of Turin, Via Giuria 9, 10125 Torino, Italy;
| | - Danilo Correddu
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123 Torino, Italy (G.D.N.); (G.G.)
| | - Giovanna Di Nardo
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123 Torino, Italy (G.D.N.); (G.G.)
| | - Gianfranco Gilardi
- Department of Life Sciences and Systems Biology, University of Turin, Via Accademia Albertina 13, 10123 Torino, Italy (G.D.N.); (G.G.)
| | - George Mitrikas
- Institute of Nanoscience and Nanotechnology, NCSR Demokritos, 15341 Athens, Greece;
| | - Mario Chiesa
- Department of Chemistry, University of Turin, Via Giuria 9, 10125 Torino, Italy;
| | - Inés García-Rubio
- Departamento de Física de la Materia Condensada, Universidad de Zaragoza, C/Pedro Cerbuna 12, 50009 Zaragoza, Spain;
- Instituto de Nanociencia y Materiales de Aragón (INMA), CSIC-Universidad de Zaragoza, 50009 Zaragoza, Spain
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3
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EPR characterization of the heme domain of a self-sufficient cytochrome P450 (CYP116B5). J Inorg Biochem 2022; 231:111785. [DOI: 10.1016/j.jinorgbio.2022.111785] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Revised: 02/25/2022] [Accepted: 02/26/2022] [Indexed: 11/19/2022]
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4
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Podgorski MN, Harbort JS, Coleman T, Stok JE, Yorke JA, Wong LL, Bruning JB, Bernhardt PV, De Voss JJ, Harmer JR, Bell SG. Biophysical Techniques for Distinguishing Ligand Binding Modes in Cytochrome P450 Monooxygenases. Biochemistry 2020; 59:1038-1050. [PMID: 32058707 DOI: 10.1021/acs.biochem.0c00027] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The cytochrome P450 superfamily of heme monooxygenases catalyzes important chemical reactions across nature. The changes in the optical spectra of these enzymes, induced by the addition of substrates or inhibitors, are critical for assessing how these molecules bind to the P450, enhancing or inhibiting the catalytic cycle. Here we use the bacterial CYP199A4 enzyme (Uniprot entry Q2IUO2), from Rhodopseudomonas palustris HaA2, and a range of substituted benzoic acids to investigate different binding modes. 4-Methoxybenzoic acid elicits an archetypal type I spectral response due to a ≥95% switch from the low- to high-spin state with concomitant dissociation of the sixth aqua ligand. 4-(Pyridin-3-yl)- and 4-(pyridin-2-yl)benzoic acid induced different type II ultraviolet-visible (UV-vis) spectral responses in CYP199A4. The former induced a greater red shift in the Soret wavelength (424 nm vs 422 nm) along with a larger overall absorbance change and other differences in the α-, β-, and δ-bands. There were also variations in the ferrous UV-vis spectra of these two substrate-bound forms with a spectrum indicative of Fe-N bond formation with 4-(pyridin-3-yl)benzoic acid. The crystal structures of CYP199A4, with the pyridinyl compounds bound, revealed that while the nitrogen of 4-(pyridin-3-yl)benzoic acid is coordinated to the heme, with 4-(pyridin-2-yl)benzoic acid an aqua ligand remains. Continuous wave and pulse electron paramagnetic resonance data in frozen solution revealed that the substrates are bound in the active site in a form consistent with the crystal structures. The redox potential of each CYP199A4-substrate combination was measured, allowing correlation among binding modes, spectroscopic properties, and the observed biochemical activity.
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Affiliation(s)
- Matthew N Podgorski
- Department of Chemistry, University of Adelaide, Adelaide, SA 5005, Australia
| | - Joshua S Harbort
- Center for Advanced Imaging, University of Queensland, Brisbane, QLD 4072, Australia
| | - Tom Coleman
- Department of Chemistry, University of Adelaide, Adelaide, SA 5005, Australia
| | - Jeanette E Stok
- School of Chemistry and Molecular Bioscience, University of Queensland, Brisbane, QLD 4072, Australia
| | - Jake A Yorke
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - Luet-Lok Wong
- Inorganic Chemistry Laboratory, Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, U.K
| | - John B Bruning
- School of Biological Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Paul V Bernhardt
- School of Chemistry and Molecular Bioscience, University of Queensland, Brisbane, QLD 4072, Australia
| | - James J De Voss
- School of Chemistry and Molecular Bioscience, University of Queensland, Brisbane, QLD 4072, Australia
| | - Jeffrey R Harmer
- Center for Advanced Imaging, University of Queensland, Brisbane, QLD 4072, Australia
| | - Stephen G Bell
- Department of Chemistry, University of Adelaide, Adelaide, SA 5005, Australia
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5
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Colaneri MJ, Vitali J. Probing Axial Water Bound to Copper in Tutton Salt Using Single Crystal 17O-ESEEM Spectroscopy. J Phys Chem A 2018; 122:6214-6224. [PMID: 29989412 DOI: 10.1021/acs.jpca.8b04075] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Electron spin-echo envelope modulation (ESEEM) signals attributed to axial water bound to Cu2+ have been detected and analyzed in Cu(II)-doped 17O-water-enriched potassium zinc sulfate hexahydrate (Tutton salt) crystals. The magnetic field orientation dependences of low frequency modulations were measured to fit hyperfine and quadrupole coupling tensors of a 17O ( I = 5/2) nucleus. The hyperfine tensor ( A xx, A yy, A zz: 0.13, 0.23, -3.81 MHz) exhibits almost axial symmetry with the largest value directed normal to the metal equatorial plane in the host structure. Comparisons with quantum chemical calculations position this nucleus about 2.3 Å from the copper. The isotropic coupling (-1.15 MHz) is small and reflects the weak axial water interaction with a dx2-y2 unshared orbital of copper. The 17O-water quadrupole interaction parameters ( e2 qQ/ h = 6.4 MHz and η = 0.93) are close to the average of those found in a variety of solid hydrates. In addition, the coupling tensor directions correlate very closely with the O8 water geometry, with the maximum quadrupole direction 3° from the water plane normal, and its minimum coupling about 2° from the H-H direction. In almost all previous magnetic resonance 17O-water studies, the quadrupole tensor orientation was based on theoretical considerations. This work represents one of the few experimental confirmations of its principal axis frame. When Cu2+ dopes into the Tutton salt, a Jahn-Teller distortion interchanges the relative long and intermediate metal O7 and O8 bond lengths of the zinc host. Therefore, only those unit cells containing the impurity conform to the pure copper Tutton structure. This study provides further support for this model. Moreover, coupling interactions from distant H217O such as in the present case have important implications in studies of copper enzymes and proteins where substrates have been proposed to displace weakly bound water in the active site.
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Affiliation(s)
- Michael J Colaneri
- Department of Chemistry and Physics , State University of New York at Old Westbury , Old Westbury , New York 11568 , United States
| | - Jacqueline Vitali
- Department of Physics and Department of Biological, Geological and Environmental Sciences , Cleveland State University , Cleveland , Ohio 44115 , United States
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6
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Lockart MM, Rodriguez CA, Atkins WM, Bowman MK. CW EPR parameters reveal cytochrome P450 ligand binding modes. J Inorg Biochem 2018. [PMID: 29530595 DOI: 10.1016/j.jinorgbio.2018.02.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cytochrome P450 (CYP) monoxygenses utilize heme cofactors to catalyze oxidation reactions. They play a critical role in metabolism of many classes of drugs, are an attractive target for drug development, and mediate several prominent drug interactions. Many substrates and inhibitors alter the spin state of the ferric heme by displacing the heme's axial water ligand in the resting enzyme to yield a five-coordinate iron complex, or they replace the axial water to yield a nitrogen-ligated six-coordinate iron complex, which are traditionally assigned by UV-vis spectroscopy. However, crystal structures and recent pulsed electron paramagnetic resonance (EPR) studies find a few cases where molecules hydrogen bond to the axial water. The water-bridged drug-H2O-heme has UV-vis spectra similar to nitrogen-ligated, six-coordinate complexes, but are closer to "reverse type I" complexes described in older liteature. Here, pulsed and continuous wave (CW) EPR demonstrate that water-bridged complexes are remarkably common among a range of nitrogenous drugs or drug fragments that bind to CYP3A4 or CYP2C9. Principal component analysis reveals a distinct clustering of CW EPR spectral parameters for water-bridged complexes. CW EPR reveals heterogeneous mixtures of ligated states, including multiple directly-coordinated complexes and water-bridged complexes. These results suggest that water-bridged complexes are under-represented in CYP structural databases and can have energies similar to other ligation modes. The data indicates that water-bridged binding modes can be identified and distinguished from directly-coordinated binding by CW EPR.
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Affiliation(s)
- Molly M Lockart
- Department of Chemistry and Biochemistry, Box 870336, University of Alabama, Tuscaloosa, AL 35487-0336, United States
| | - Carlo A Rodriguez
- Department of Chemistry and Biochemistry, Box 870336, University of Alabama, Tuscaloosa, AL 35487-0336, United States
| | - William M Atkins
- Department of Medicinal Chemistry, Box 357610, University of Washington, Seattle, WA 98195-7610, United States
| | - Michael K Bowman
- Department of Chemistry and Biochemistry, Box 870336, University of Alabama, Tuscaloosa, AL 35487-0336, United States.
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7
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Lo FC, Hsieh CC, Maestre-Reyna M, Chen CY, Ko TP, Horng YC, Lai YC, Chiang YW, Chou CM, Chiang CH, Huang WN, Lin YH, Bohle DS, Liaw WF. Crystal Structure Analysis of the Repair of Iron Centers Protein YtfE and Its Interaction with NO. Chemistry 2016; 22:9768-76. [DOI: 10.1002/chem.201600990] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Indexed: 11/07/2022]
Affiliation(s)
- Feng-Chun Lo
- Department of Chemistry; National Tsing Hua University; Hsinchu 30013 Taiwan
| | - Chang-Chih Hsieh
- Department of Chemistry; National Tsing Hua University; Hsinchu 30013 Taiwan
| | | | - Chin-Yu Chen
- Department of Life Sciences; National Central University; Taoyuan Taiwan
| | - Tzu-Ping Ko
- Institute of Biological Chemistry; Academia Sinica; Taipei Taiwan
| | - Yih-Chern Horng
- Department of Chemistry; National Changhua University of Education; Changhua Taiwan
| | - Yei-Chen Lai
- Department of Chemistry; National Tsing Hua University; Hsinchu 30013 Taiwan
| | - Yun-Wei Chiang
- Department of Chemistry; National Tsing Hua University; Hsinchu 30013 Taiwan
| | - Chih-Mao Chou
- Department of Life Sciences; National Central University; Taoyuan Taiwan
| | | | - Wei-Ning Huang
- Department of Biotechnology; Yuanpei University; Hsinchu Taiwan
| | - Yi-Hung Lin
- National Synchrotron Radiation Research Center Hsinchu; Taiwan
| | - D. Scott Bohle
- Department of Chemistry; McGill University; 801 Sherbrooke Street West Montreal QC H3A2K6 Canada
| | - Wen-Feng Liaw
- Department of Chemistry; National Tsing Hua University; Hsinchu 30013 Taiwan
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8
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Rapatskiy L, Ames WM, Pérez-Navarro M, Savitsky A, Griese JJ, Weyhermüller T, Shafaat HS, Högbom M, Neese F, Pantazis DA, Cox N. Characterization of Oxygen Bridged Manganese Model Complexes Using Multifrequency 17O-Hyperfine EPR Spectroscopies and Density Functional Theory. J Phys Chem B 2015. [DOI: 10.1021/acs.jpcb.5b04614] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Leonid Rapatskiy
- Max-Planck Institute for Chemical Energy, Stiftstr. 34-36, Mülheim an der Ruhr, DE-45470 Germany
| | - William M. Ames
- Max-Planck Institute for Chemical Energy, Stiftstr. 34-36, Mülheim an der Ruhr, DE-45470 Germany
| | - Montserrat Pérez-Navarro
- Max-Planck Institute for Chemical Energy, Stiftstr. 34-36, Mülheim an der Ruhr, DE-45470 Germany
| | - Anton Savitsky
- Max-Planck Institute for Chemical Energy, Stiftstr. 34-36, Mülheim an der Ruhr, DE-45470 Germany
| | - Julia J. Griese
- Department
of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden
| | - Thomas Weyhermüller
- Max-Planck Institute for Chemical Energy, Stiftstr. 34-36, Mülheim an der Ruhr, DE-45470 Germany
| | - Hannah S. Shafaat
- Max-Planck Institute for Chemical Energy, Stiftstr. 34-36, Mülheim an der Ruhr, DE-45470 Germany
| | - Martin Högbom
- Department
of Biochemistry and Biophysics, Stockholm University, Stockholm SE-106 91, Sweden
| | - Frank Neese
- Max-Planck Institute for Chemical Energy, Stiftstr. 34-36, Mülheim an der Ruhr, DE-45470 Germany
| | - Dimitrios A. Pantazis
- Max-Planck Institute for Chemical Energy, Stiftstr. 34-36, Mülheim an der Ruhr, DE-45470 Germany
| | - Nicholas Cox
- Max-Planck Institute for Chemical Energy, Stiftstr. 34-36, Mülheim an der Ruhr, DE-45470 Germany
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9
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Conner KP, Cruce AA, Krzyaniak MD, Schimpf AM, Frank DJ, Ortiz de Montellano P, Atkins WM, Bowman MK. Drug modulation of water-heme interactions in low-spin P450 complexes of CYP2C9d and CYP125A1. Biochemistry 2015; 54:1198-207. [PMID: 25591012 DOI: 10.1021/bi501402k] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Azoles and pyridines are commonly incorporated into small molecule inhibitor scaffolds that target cytochromes P450 (CYPs) as a strategy to increase drug binding affinity, impart isoform-dependent selectivity, and improve metabolic stability. Optical absorbance spectra of the CYP-inhibitor complex are widely used to infer whether these inhibitors are ligated directly to the heme iron as catalytically inert, low-spin (type II) complexes. Here, we show that the low-spin complex between a drug-metabolizing CYP2C9 variant and 4-(3-phenylpropyl)-1H-1,2,3-triazole (PPT) retains an axial water ligand despite exhibiting elements of "classic" type II optical behavior. Hydrogens of the axial water ligand are observed by pulsed electron paramagnetic resonance (EPR) spectroscopy for both inhibitor-free and inhibitor-bound species and show that inhibitor binding does not displace the axial water. A (15)N label incorporated into PPT is 0.444 nm from the heme iron, showing that PPT is also in the active site. The reverse type I inhibitor, LP10, of CYP125A1 from Mycobacterium tuberculosis, known from X-ray crystal structures to form a low-spin water-bridged complex, is found by EPR and by visible and near-infrared magnetic circular dichroism spectroscopy to retain the axial water ligand in the complex in solution.
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Affiliation(s)
- Kip P Conner
- Department of Medicinal Chemistry, Box 357610, and Department of Chemistry, Box 351700, University of Washington , Seattle, Washington 98195, United States
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10
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Sainna MA, Sil D, Sahoo D, Martin B, Rath SP, Comba P, de Visser SP. Spin-State Ordering in Hydroxo-Bridged Diiron(III)bisporphyrin Complexes. Inorg Chem 2015; 54:1919-30. [DOI: 10.1021/ic502803b] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Mala A. Sainna
- Manchester Institute
of Biotechnology and School of Chemical Engineering and Analytical
Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
| | - Debangsu Sil
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Dipankar Sahoo
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Bodo Martin
- Anorganisch-Chemisches Institüt and Interdisciplinary
Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer
Feld 270, 69120 Heidelberg, Germany
| | - Sankar Prasad Rath
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Peter Comba
- Anorganisch-Chemisches Institüt and Interdisciplinary
Center for Scientific Computing (IWR), University of Heidelberg, Im Neuenheimer
Feld 270, 69120 Heidelberg, Germany
| | - Sam P. de Visser
- Manchester Institute
of Biotechnology and School of Chemical Engineering and Analytical
Science, The University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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11
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12
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Conner KP, Schimpf AM, Cruce AA, McLean KJ, Munro AW, Frank DJ, Krzyaniak MD, Ortiz de Montellano P, Bowman MK, Atkins WM. Strength of axial water ligation in substrate-free cytochrome P450s is isoform dependent. Biochemistry 2014; 53:1428-34. [PMID: 24576089 PMCID: PMC3985942 DOI: 10.1021/bi401547j] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
The heme-containing cytochrome P450s exhibit isoform-dependent ferric spin equilibria in the resting state and differential substrate-dependent spin equilibria. The basis for these differences is not well understood. Here, magnetic circular dichroism (MCD) reveals significant differences in the resting low spin ligand field of CYPs 3A4, 2E1, 2C9, 125A1, and 51B1, which indicates differences in the strength of axial water ligation to the heme. The near-infrared bands that specifically correspond to charge-transfer porphyrin-to-metal transitions span a range of energies of nearly 2 kcal/mol. In addition, the experimentally determined MCD bands are not entirely in agreement with the expected MCD energies calculated from electron paramagnetic resonance parameters, thus emphasizing the need for the experimental data. MCD marker bands of the high spin heme between 500 and 680 nm were also measured and suggest only a narrow range of energies for this ensemble of high spin Cys(S(-)) → Fe(3+) transitions among these isoforms. The differences in axial ligand energies between CYP isoforms of the low spin states likely contribute to the energetics of substrate-dependent spin state perturbation. However, these ligand field energies do not correlate with the fraction of high spin vs low spin in the resting state enzyme, suggestive of differences in water access to the heme or isoform-dependent differences in the substrate-free high spin states as well.
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Affiliation(s)
- Kip P Conner
- Departments of Medicinal Chemistry Box 357610 and ‡Chemistry Box 351700, University of Washington Seattle , Washington 98195 United States
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13
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Rapatskiy L, Cox N, Savitsky A, Ames WM, Sander J, Nowaczyk MM, Rögner M, Boussac A, Neese F, Messinger J, Lubitz W. Detection of the Water-Binding Sites of the Oxygen-Evolving Complex of Photosystem II Using W-Band 17O Electron–Electron Double Resonance-Detected NMR Spectroscopy. J Am Chem Soc 2012; 134:16619-34. [DOI: 10.1021/ja3053267] [Citation(s) in RCA: 224] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Leonid Rapatskiy
- Max-Planck-Institut für
Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
| | - Nicholas Cox
- Max-Planck-Institut für
Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
| | - Anton Savitsky
- Max-Planck-Institut für
Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
| | - William M. Ames
- Max-Planck-Institut für
Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
| | - Julia Sander
- Plant
Biochemistry, Ruhr University Bochum, Universitätsstrasse
150, D-44780 Bochum, Germany
| | - Marc. M. Nowaczyk
- Plant
Biochemistry, Ruhr University Bochum, Universitätsstrasse
150, D-44780 Bochum, Germany
| | - Matthias Rögner
- Plant
Biochemistry, Ruhr University Bochum, Universitätsstrasse
150, D-44780 Bochum, Germany
| | - Alain Boussac
- iBiTec-S, URA UMR 8221, CEA Saclay,
91191 Gif-sur-Yvette, France
| | - Frank Neese
- Max-Planck-Institut für
Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
| | - Johannes Messinger
- Department of Chemistry, Chemical
Biological Centre (KBC), Umeå University, S-90187 Umeå, Sweden
| | - Wolfgang Lubitz
- Max-Planck-Institut für
Chemische Energiekonversion, Stiftstrasse 34-36, D-45470 Mülheim
an der Ruhr, Germany
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14
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McConnell IL, Grigoryants VM, Scholes CP, Myers WK, Chen PY, Whittaker JW, Brudvig GW. EPR-ENDOR characterization of (17O, 1H, 2H) water in manganese catalase and its relevance to the oxygen-evolving complex of photosystem II. J Am Chem Soc 2012; 134:1504-12. [PMID: 22142421 DOI: 10.1021/ja203465y] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The synthesis of efficient water-oxidation catalysts demands insight into the only known, naturally occurring water-oxidation catalyst, the oxygen-evolving complex (OEC) of photosystem II (PSII). Understanding the water oxidation mechanism requires knowledge of where and when substrate water binds to the OEC. Mn catalase in its Mn(III)-Mn(IV) state is a protein model of the OEC's S(2) state. From (17)O-labeled water exchanged into the di-μ-oxo di-Mn(III,IV) coordination sphere of Mn catalase, CW Q-band ENDOR spectroscopy revealed two distinctly different (17)O signals incorporated in distinctly different time regimes. First, a signal appearing after 2 h of (17)O exchange was detected with a 13.0 MHz hyperfine coupling. From similarity in the time scale of isotope incorporation and in the (17)O μ-oxo hyperfine coupling of the di-μ-oxo di-Mn(III,IV) bipyridine model (Usov, O. M.; Grigoryants, V. M.; Tagore, R.; Brudvig, G. W.; Scholes, C. P. J. Am. Chem. Soc. 2007, 129, 11886-11887), this signal was assigned to μ-oxo oxygen. EPR line broadening was obvious from this (17)O μ-oxo species. Earlier exchange proceeded on the minute or faster time scale into a non-μ-oxo position, from which (17)O ENDOR showed a smaller 3.8 MHz hyperfine coupling and possible quadrupole splittings, indicating a terminal water of Mn(III). Exchangeable proton/deuteron hyperfine couplings, consistent with terminal water ligation to Mn(III), also appeared. Q-band CW ENDOR from the S(2) state of the OEC was obtained following multihour (17)O exchange, which showed a (17)O hyperfine signal with a 11 MHz hyperfine coupling, tentatively assigned as μ-oxo-(17)O by resemblance to the μ-oxo signals from Mn catalase and the di-μ-oxo di-Mn(III,IV) bipyridine model.
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Affiliation(s)
- Iain L McConnell
- Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA
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15
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Johnston WA, Hunter DJB, Noble CJ, Hanson GR, Stok JE, Hayes MA, De Voss JJ, Gillam EMJ. Cytochrome P450 is present in both ferrous and ferric forms in the resting state within intact Escherichia coli and hepatocytes. J Biol Chem 2011; 286:40750-9. [PMID: 21976668 DOI: 10.1074/jbc.m111.300871] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cytochrome P450 enzymes (P450s) are exceptionally versatile monooxygenases, mediating hydroxylations of unactivated C-H bonds, epoxidations, dealkylations, and N- and S-oxidations as well as other less common reactions. In the conventional view of the catalytic cycle, based upon studies of P450s in vitro, substrate binding to the Fe(III) resting state facilitates the first 1-electron reduction of the heme. However, the resting state of P450s in vivo has not been examined. In the present study, whole cell difference spectroscopy of bacterial (CYP101A1 and CYP176A1, i.e. P450cam and P450cin) and mammalian (CYP1A2, CYP2C9, CYP2A6, CYP2C19, and CYP3A4) P450s expressed within intact Escherichia coli revealed that both Fe(III) and Fe(II) forms of the enzyme are present in the absence of substrates. The relevance of this finding was supported by similar observations of Fe(II) P450 heme in intact rat hepatocytes. Electron paramagnetic resonance (EPR) spectroscopy of the bacterial forms in intact cells showed that a proportion of the P450 in cells was in an EPR-silent form in the native state consistent with the presence of Fe(II) P450. Coexpression of suitable cognate electron donors increased the degree of endogenous reduction to over 80%. A significant proportion of intracellular P450 remained in the Fe(II) form after vigorous aeration of cells. The addition of substrates increased the proportion of Fe(II) heme, suggesting a kinetic gate to heme reduction in the absence of substrate. In summary, these observations suggest that the resting state of P450s should be regarded as a mixture of Fe(III) and Fe(II) forms in both aerobic and oxygen-limited conditions.
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Affiliation(s)
- Wayne A Johnston
- School of Biomedical Sciences, The University of Queensland, St. Lucia, Brisbane, Queensland 4072, Australia
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16
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Conner KP, Woods C, Atkins WM. Interactions of cytochrome P450s with their ligands. Arch Biochem Biophys 2011; 507:56-65. [PMID: 20939998 PMCID: PMC3041843 DOI: 10.1016/j.abb.2010.10.006] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2010] [Revised: 10/01/2010] [Accepted: 10/04/2010] [Indexed: 01/12/2023]
Abstract
Cytochrome P450s (CYPs) are heme-containing monooxygenases that contribute to an enormous range of enzymatic function including biosynthetic and detoxification roles. This review summarizes recent studies concerning interactions of CYPs with ligands including substrates, inhibitors, and diatomic heme-ligating molecules. These studies highlight the complexity in the relationship between the heme spin state and active site occupancy, the roles of water in directing protein-ligand and ligand-heme interactions, and the details of interactions between heme and gaseous diatomic CYP ligands. Both kinetic and thermodynamic aspects of ligand binding are considered.
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Affiliation(s)
- Kip P. Conner
- Department of Medicinal Chemistry, Box 357610, University of Washington, Seattle, WA 98195-7610
| | - Caleb Woods
- Department of Medicinal Chemistry, Box 357610, University of Washington, Seattle, WA 98195-7610
| | - William M. Atkins
- Department of Medicinal Chemistry, Box 357610, University of Washington, Seattle, WA 98195-7610
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Jiang Y, Sivaramakrishnan S, Hayashi T, Cohen S, Moënne-Loccoz P, Shaik S, Ortiz de Montellano PR. Calculated and experimental spin state of seleno cytochrome P450. Angew Chem Int Ed Engl 2010; 48:7193-5. [PMID: 19718734 DOI: 10.1002/anie.200901485] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Yongying Jiang
- Department of Pharmaceutical Chemistry, University of California, 600 16th street, San Francisco, CA 94158, USA
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18
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Shaik S, Cohen S, Wang Y, Chen H, Kumar D, Thiel W. P450 Enzymes: Their Structure, Reactivity, and Selectivity—Modeled by QM/MM Calculations. Chem Rev 2009; 110:949-1017. [DOI: 10.1021/cr900121s] [Citation(s) in RCA: 791] [Impact Index Per Article: 52.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Sason Shaik
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Shimrit Cohen
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Yong Wang
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Hui Chen
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Devesh Kumar
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
| | - Walter Thiel
- Institute of Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel, and Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
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19
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Balding PR, Porro CS, McLean KJ, Sutcliffe MJ, Maréchal JD, Munro AW, de Visser SP. How do azoles inhibit cytochrome P450 enzymes? A density functional study. J Phys Chem A 2009; 112:12911-8. [PMID: 18563875 DOI: 10.1021/jp802087w] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To examine how azole inhibitors interact with the heme active site of the cytochrome P450 enzymes, we have performed a series of density functional theory studies on azole binding. These are the first density functional studies on azole interactions with a heme center and give fundamental insight into how azoles inhibit the catalytic function of P450 enzymes. Since azoles come in many varieties, we tested three typical azole motifs representing a broad range of azole and azole-type inhibitors: methylimidazolate, methyltriazolate, and pyridine. These structural motifs represent typical azoles, such as econazole, fluconazole, and metyrapone. The calculations show that azole binding is a stepwise mechanism whereby first the water molecule from the resting state of P450 is released from the sixth binding site of the heme to create a pentacoordinated active site followed by coordination of the azole nitrogen to the heme iron. This process leads to the breaking of a hydrogen bond between the resting state water molecule and the approaching inhibitor molecule. Although, formally, the water molecule is released in the first step of the reaction mechanism and a pentacoordinated heme is created, this does not lead to an observed spin state crossing. Thus, we show that release of a water molecule from the resting state of P450 enzymes to create a pentacoordinated heme will lead to a doublet to quartet spin state crossing at an Fe-OH(2) distance of approximately 3.0 A, while the azole substitution process takes place at shorter distances. Azoles bind heme with significantly stronger binding energies than a water molecule, so that these inhibitors block the catalytic cycle of the enzyme and prevent oxygen binding and the catalysis of substrate oxidation. Perturbations within the active site (e.g., a polarized environment) have little effect on the relative energies of azole binding. Studies with an extra hydrogen-bonded ethanol molecule in the model, mimicking the active site of the CYP121 P450, show that the resting state and azole binding structures are close in energy, which may lead to chemical equilibrium between the two structures, as indeed observed with recent protein structural studies that have demonstrated two distinct azole binding mechanisms to P450 heme.
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Affiliation(s)
- Philip R Balding
- Manchester Interdisciplinary Biocentre, University of Manchester, 131 Princess Street, Manchester M1 7DN, United Kingdom
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20
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Jiang Y, Sivaramakrishnan S, Hayashi T, Cohen S, Moënne-Loccoz P, Shaik S, Ortiz de Montellano P. Calculated and Experimental Spin State of Seleno Cytochrome P450. Angew Chem Int Ed Engl 2009. [DOI: 10.1002/ange.200901485] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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21
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Fittipaldi M, García-Rubio I, Trandafir F, Gromov I, Schweiger A, Bouwen A, Van Doorslaer S. A multi-frequency pulse EPR and ENDOR approach to study strongly coupled nuclei in frozen solutions of high-spin ferric heme proteins. J Phys Chem B 2008; 112:3859-70. [PMID: 18321089 DOI: 10.1021/jp709854x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In spite of the tremendous progress in the field of pulse electron paramagnetic resonance (EPR) in recent years, these techniques have been scarcely used to investigate high-spin (HS) ferric heme proteins. Several technical and spin-system-specific reasons can be identified for this. Additional problems arise when no single crystals of the heme protein are available. In this work, we use the example of a frozen solution of aquometmyoglobin (metMb) to show how a multi-frequency pulse EPR approach can overcome these problems. In particular, the performance of the following pulse EPR techniques are tested: Davies electron nuclear double resonance (ENDOR), hyperfine correlated ENDOR (HYEND), electron-electron double resonance (ELDOR)-detected NMR, and several variants of hyperfine sublevel correlation (HYSCORE) spectroscopy including matched and SMART HYSCORE. The pulse EPR experiments are performed at X-, Q- and W-band microwave frequencies. The advantages and drawbacks of the different methods are discussed in relation to the nuclear interaction that they intend to reveal. The analysis of the spectra is supported by several simulation procedures, which are discussed. This work focuses on the analysis of the hyperfine and nuclear-quadrupole tensors of the strongly coupled nuclei of the first coordination sphere, namely, the directly coordinating heme and histidine nitrogens and the 17O nucleus of the distal water ligand. For the latter, 17O-isotope labeling was used. The accuracy of our results and the spectral resolution are compared in detail to an earlier single-crystal continuous-wave ENDOR study on metMb, and it will be shown how additional information can be obtained from the multi-frequency approach. The current work is therefore prone to become a template for future EPR/ENDOR investigations of HS ferric heme proteins for which no single crystals are available.
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Affiliation(s)
- M Fittipaldi
- Department of Physics, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk-Antwerp, Belgium
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22
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Altun A, Thiel W. Combined quantum mechanical/molecular mechanical study on the pentacoordinated ferric and ferrous cytochrome P450cam complexes. J Phys Chem B 2007; 109:1268-80. [PMID: 16851091 DOI: 10.1021/jp0459108] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The pentacoordinated ferric and ferrous cytochrome P450(cam) complexes have been investigated by combined quantum mechanical/molecular mechanical (QM/MM) calculations in the presence of a protein/solvent environment and by QM calculations on the isolated QM regions with use of density functional theory. The B3LYP functional has been found more reliable than the BLYP and BHLYP functionals for estimating the relative state energies. The B3LYP/CHARMM calculations with an all-electron basis set for iron give high-spin ground states for the title complexes, in agreement with experiment. The comparison of the B3LYP/CHARMM results of the entire protein system with the B3LYP calculations on the naked QM regions shows that the amount of stabilization by the protein environment is largest for the intermediate-spin states, followed by the high-spin states of the complexes. The calculation of Mössbauer parameters in the presence of the enzyme environment confirms the double occupation of the d(xz) orbital in the quintet spin state of the ferrous complex, consistent with the computed QM/MM energies in the enzyme environment, while the d(x)2(-)(y)2 orbital is doubly occupied in the gas-phase quintet state.
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Affiliation(s)
- Ahmet Altun
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, D-45470 Mülheim an der Ruhr, Germany
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23
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Ahrling KA, Evans MCW, Nugent JHA, Ball RJ, Pace RJ. ESEEM studies of substrate water and small alcohol binding to the oxygen-evolving complex of photosystem II during functional turnover. Biochemistry 2006; 45:7069-82. [PMID: 16752897 DOI: 10.1021/bi052146m] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
We report the first examination of exchangeable proton and MeOH interactions with the Mn catalytic cluster in photosystem II, under functional flash turnover conditions, using 2H ESEEM spectroscopy on the S2 and S0 multiline states. Deuterium-labeled water (D2O) and methyl d3-labeled methanol (DMeOH) are employed. It was discovered that a hyperfine resolved multiline S0 signal could be seen in the presence of D2O, the hyperfine structure of which depended on the presence or absence of methanol (MeOH). In the presence of DMeOH, significant dipolar coupling of the three methyl deuterons to the multiline centers in the S2 and S0 states was seen (S2, 0.65, 0.39(2) MHz; and S0, 0.60, 0.37(2) MHz). These are consistent with direct binding of the methoxy fragment to Mn. Assuming terminal Mn-OMe ligation, the couplings indicated a spin projection coefficient (rho) magnitude of approximately 2 for the ligating Mn in both the S2 and S0 states, with inferred Mn-O distances of approximately 1.9-2.0 A. In the presence of D2O, four classes of exchangeable deuterons were identified by ESEEM in S2 and S0. Three of these classes (1, 2, and 4) exhibited populations and coupling strengths that were essentially constant under various conditions of sample preparation, illumination turnover, and small alcohol addition. Class 3 could be modeled with constant coupling but a highly variable deuteron population (n3 approximately 0-10) depending in part on the preparation used. For all classes, the coupling parameters were very similar in S2 and S0. The favored interpretation is that the two strongest coupling classes (1 and 2) represent close binding of one water molecule to a single Mn which has an oxidation state of II in S0 and III in S2, and rho approximately 2 in both cases. This water is not displaced by MeOH, but either the water or MeOH is singly deprotonated upon MeOH binding. Class 4 represents approximately 2 water molecules which are not closely bound to Mn (Mn-deuteron distances of approximately 3.7-4.7 A). Class 3 probably represents protein matrix protons within approximately 4 A of the Mn in the cluster, which can be variably exchanged in different preparations.
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Affiliation(s)
- Karin A Ahrling
- Research School of Biological Science, Australian National University, Canberra, ACT 0200, Australia
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24
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Enemark JH, Astashkin AV, Raitsimring AM. Investigation of the coordination structures of the molybdenum(v) sites of sulfite oxidizing enzymes by pulsed EPR spectroscopy. Dalton Trans 2006:3501-14. [PMID: 16855750 DOI: 10.1039/b602919a] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sulfite oxidizing enzymes (SOEs) are physiologically vital and occur in all forms of life. During the catalytic cycle the five-coordinate square-pyramidal oxo-molybdenum active site passes through the Mo(v) state, and intimate details of the structure can be obtained from pulsed EPR spectroscopy through the hyperfine interactions (hfi) and nuclear quadrupole interactions (nqi) of nearby magnetic nuclei (e.g., (1)H, (2)H, (17)O, (31)P) of the ligands. By employing spectrometer operational frequencies ranging from approximately 4 to approximately 32 GHz, it is possible to make the nuclear Zeeman interaction significantly greater than the hfi and nqi, and thereby simplify the interpretations of the spectra. The SOEs exhibit three general types of Mo(v) structures which differ in the number of nearby exchangeable protons (one, two or zero). The observed structure depends upon the organism, pH, anions in the medium, and method of reduction. One type of structure has a single exchangeable Mo-OH proton approximately in the equatorial plane and a large isotropic hfi (e.g., low pH form of chicken SOE, low pH form of plant SOE reduced by Ti(iii)); the second type has two exchangeable protons with distributed orientations out of the equatorial plane and very small (or zero) isotropic hfi (e.g., high pH form of chicken SOE, high pH form of plant SOE reduced by sulfite); the third type has no nearby exchangeable protons and a coordinated oxyanion (e.g., phosphate inhibited chicken SOE, low pH form of plant SOE reduced by sulfite). An additional structural conclusion is that the orientation angle of any exchangeable equatorial ligand (OH, OH(2), PO(4)(3-)) is not uniquely fixed, but is distributed around its central value by up to +/-20 degrees (depending on pH, the type of the ligand and the type of enzyme). An unexpected finding was that the axial oxo group of SOEs exchanges with (17)O in solutions enriched in H(2)(17)O. The first determination of oxo (17)O nqi parameters for a well-characterized model compound, [Mo(17)O(SPh)(4)](-), clearly demonstrated that (17)O nqi parameters can distinguish between oxo and OH(2) ligands.
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Affiliation(s)
- John H Enemark
- Department of Chemistry, Univesity of Arizona, 1306 E. University Blvd, Tucson, AZ 85721, USA.
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25
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Astashkin AV, Neese F, Raitsimring AM, Cooney JJA, Bultman E, Enemark JH. Pulsed EPR investigations of systems modeling molybdenum enzymes: hyperfine and quadrupole parameters of oxo-17O in [Mo 17O(SPh)4]-. J Am Chem Soc 2006; 127:16713-22. [PMID: 16305262 DOI: 10.1021/ja055472y] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Ka band ESEEM spectroscopy was used to determine the hyperfine (hfi) and nuclear quadrupole (nqi) interaction parameters for the oxo-17O ligand in [Mo 17O(SPh)4]-, a spectroscopic model of the oxo-Mo(V) centers of enzymes. The isotropic hfi constant of 6.5 MHz found for the oxo-17O is much smaller than the values of approximately 20-40 MHz typical for the 17O nucleus of an equatorial OH(2) ligand in molybdenum enzymes. The 17O nqi parameter (e2qQ/h = 1.45 MHz, eta approximately = 0) is the first to be obtained for an oxo group in a metal complex. The parameters of the oxo-17O ligand, as well as other magnetic resonance parameters of [Mo 17O(SPh)4]- predicted by quasi-relativistic DFT calculations, were in good agreement with those obtained in experiment. From the electronic structure of the complex revealed by DFT, it follows that the SOMO is almost entirely molybdenum d(xy) and sulfur p, while the spin density on the oxo-17O is negative, determined by spin polarization mechanisms. The results of this work will enable direct experimental identification of the oxo ligand in a variety of chemical and biological systems.
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Affiliation(s)
- Andrei V Astashkin
- Department of Chemistry, University of Arizona, Tucson, Arizona 85721, USA.
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26
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Baute D, Goldfarb D. The 17O Hyperfine Interaction in V17O(H217O)52+ and Mn(H217O)62+ Determined by High Field ENDOR Aided by DFT Calculations. J Phys Chem A 2005; 109:7865-71. [PMID: 16834167 DOI: 10.1021/jp052132q] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The 17O hyperfine interaction of the water ligands and the V=O oxygen in the vanadyl aquo complex and of the water ligands in the Mn2+ aquo complex in a frozen solution were determined by W-band (95 GHz) electron-nuclear double resonance (ENDOR). Orientation selective ENDOR spectra of the vanadyl complex exhibited two distinct signals assigned to the vanadyl oxygen and the water ligands. The assignment of the signals was done based on the orientation of the principal axis system of the hyperfine interaction and through comparison with the hyperfine interaction predicted by DFT calculations. The latter showed good agreement with the experimental values thus providing clear evidence that the vanadyl oxygen is exchangeable. The interaction of the vanadyl oxygen, especially its anisotropic part, was significantly larger than that of the water oxygens due to a relatively large negative spin density on the oxygen p orbitals. The 17O hyperfine interaction of the water ligand in the Mn2+ complex was found to be similar to that of the water ligand in the vanadyl complex and was in good agreement with earlier single-crystal data. Here, due to the large thermal polarization, it was also possible to determine the absolute sign of the hyperfine coupling by selecting different EPR transitions.
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Affiliation(s)
- Debbie Baute
- Department of Chemical Physics, The Weizmann Institute of Science, Rehovot, Israel
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27
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Groenhof AR, Swart M, Ehlers AW, Lammertsma K. Electronic Ground States of Iron Porphyrin and of the First Species in the Catalytic Reaction Cycle of Cytochrome P450s. J Phys Chem A 2005; 109:3411-7. [PMID: 16833677 DOI: 10.1021/jp0441442] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electronic structures of iron(II) and iron(III) porphyrins are studied with density functional theory (DFT) using the GGA exchange functional OPTX in combination with the correlation functional PBE (OPBE) and with the correlation functional Perdew (OPerdew) together with a triple zeta-type basis set. These functionals, known for accurately predicting the spin ground state of iron complexes, are evaluated against other functionals for their performance in calculating relative energies for the various electronic states of both the iron porphyrins. The calculated energy orderings are triplet < quintet < singlet for the iron(II) porphyrin and quartet < sextet < doublet for the iron(III) porphyrin cation. Complexation by a thiolate ion (SH-) changes the preferred ground state for both species to high spin. This thiolate complex is used as a mimic for the cytochrome P450s active site to model the first step of the catalytic cycle of this enzyme. This first step is believed to concern the removal of an axial oxygen donating ligand from the hexacoordinated aqua-thiolate-porphyrin-iron(III) resting state. The DFT results suggest that this is not a free water molecule, because of its repulsive nature, but that it has instead hydroxy anion character. These calculations are in line with the experimentally observed change in the spin state from low to high spin upon this removal of the axial hydroxo ligand by binding of the substrate in the heme pocket of cytochrome P450.
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Affiliation(s)
- André R Groenhof
- Department of Chemistry, Vrije Universiteit, FEW, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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28
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Shaik S, Kumar D, de Visser SP, Altun A, Thiel W. Theoretical Perspective on the Structure and Mechanism of Cytochrome P450 Enzymes. Chem Rev 2005; 105:2279-328. [PMID: 15941215 DOI: 10.1021/cr030722j] [Citation(s) in RCA: 953] [Impact Index Per Article: 50.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sason Shaik
- Department of Organic Chemistry and the Lise-Meitner-Minerva Center for Computational Quantum Chemistry, The Hebrew University of Jerusalem, Israel.
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29
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Woggon WD. Metalloporphyrines as active site analogues--lessons from enzymes and enzyme models. Acc Chem Res 2005; 38:127-36. [PMID: 15709732 DOI: 10.1021/ar0400793] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Research at the interface of enzyme chemistry and organic chemistry of metal complexes is particularly rewarding employing metal porphyrins as cofactor surrogates. Three examples are discussed: active site analogues of cytochrome P450 and chloroperoxidase (CPO), both heme-thiolate proteins, and enzyme models of beta-carotene monooxygenase, a non-heme iron protein. In all cases, catalytically active synthetic systems could be established displaying chemical reactivity close to the native proteins. Further, it is demonstrated that enzymatic reaction mechanisms can be elucidated by means of active site analogues (CPO) and information can be obtained from enzyme models that is useful to explain certain aspects of Nature's sophisticated approach to develop very efficient catalysts.
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Affiliation(s)
- Wolf-D Woggon
- Department of Chemistry, University of Basel, St. Johanns-Ring 19, CH-4056 Basel, Switzerland
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Raitsimring AM, Astashkin AV, Baute D, Goldfarb D, Caravan P. W-Band 17O Pulsed Electron Nuclear Double Resonance Study of Gadolinium Complexes with Water. J Phys Chem A 2004. [DOI: 10.1021/jp040306i] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
| | | | | | | | - Peter Caravan
- EPIX Medical, Inc., 71 Rogers Street, Cambridge, Massachusetts 02142
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31
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Abstract
▪ Abstract Two current frontiers in EPR research are high-field ([Formula: see text]) electron paramagnetic resonance (EPR) and high-field electron-nuclear double resonance (ENDOR). This review focuses on recent advances in high-field ENDOR and its applications to the study of proteins containing native paramagnetic sites. It concentrates on two aspects; the first concerns the determination of the location of protons and is related to the site geometry, and the second focuses on the spin density distribution within the site, which is inherent to the electronic structure. Both spin density and proton locations can be derived from ligand hyperfine couplings determined by ENDOR measurements. A brief description of the experimental methods is presented along with a discussion of the advantages and disadvantages of high-field ENDOR compared with conventional X-band (∼ 9.5 GHz) experiments. Specific examples of both protein single crystals and frozen solutions are then presented. These include the determination of the coordinates of water ligand protons in the Mn(II) site of concanavalin A, the detection of hydrogen bonds in a quinone radical in the bacterial photosynthetic reaction center as well as in the tyrosyl radical in ribonuclease reductase, and the study of the spin distribution in copper proteins. The copper proteins discussed are the type I copper of azurin and the binuclear CuA center in a number of proteins. The last part of the review presents a brief discussion of the interpretation of hyperfine couplings using quantum chemical calculations, primarily density functional theory (DFT) methods. Such methods are becoming an integral part of the data analysis tools, as they can facilitate signal assignment and provide the ultimate relation between the experimental hyperfine couplings and the electronic wave function.
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Affiliation(s)
- D Goldfarb
- Department of Chemical Physics, Weizmann Institute of Science, Rehovot, Israel 76100.
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33
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Evans MCW, Nugent JHA, Ball RJ, Muhiuddin I, Pace RJ. Evidence for a direct manganese-oxygen ligand in water binding to the S2 state of the photosynthetic water oxidation complex. Biochemistry 2004; 43:989-94. [PMID: 14744143 DOI: 10.1021/bi035489y] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The interaction of water with the water oxidizing Mn complex of photosystem II has been investigated using electron spin-echo envelope modulation spectroscopy in the presence of H(2)(17)O. The spectra show interaction of the (17)O with the preparation in the S(2) state induced by 200 K illumination. The modulation is observed only in the center of the multiline spectrum. The inferred hyperfine coupling terms are compatible with water (not hydroxyl) oxygen bound to a particular quasi-axial Mn(III) center in a coupled Mn cluster.
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Affiliation(s)
- M C W Evans
- Department of Biology, University College London, UK.
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34
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Carmieli R, Manikandan P, Kalb Gilboa AJ, Goldfarb D. Proton positions in the Mn(2+) binding site of concanavalin A as determined by single-crystal high-field ENDOR spectroscopy. J Am Chem Soc 2001; 123:8378-86. [PMID: 11516287 DOI: 10.1021/ja0104305] [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
High-field (95 GHz) pulsed EPR and electron-nuclear double resonance (ENDOR) techniques have been used for the first time to determine coordinates of ligand protons of a high-spin metal center in a protein single crystal. The protein concanavalin A contains a Mn(2+) ion which is coordinated to two water molecules, a histidine residue, and three carboxylates. Single crystals of concanavalin A were grown in H(2)O and in D(2)O to distinguish the exchangeable water protons from the nonexchangeable protons of the imidazole group. Distinct EPR transitions were selected by performing the ENDOR measurements at different magnetic fields within the EPR spectrum. This selection, combined with the large thermal polarization achieved at 4.5 K and a magnetic field of approximately 3.4 T allowed us to assign the ENDOR signals to their respective M(S) manifolds, thus providing the signs of the hyperfine couplings. Rotation patterns were acquired in the ac and ab crystallographic planes. Two distinct crystallographic sites were identified in each plane, and the hyperfine tensors of two of the imidazole protons and the four water protons were determined by simulations of the rotation patterns. All protons have axially symmetric hyperfine tensors and, by applying the point-dipole approximation, the positions of the various protons relative to the Mn(2+) ion were determined. Likewise, the water protons involved in H-bonding to neighboring residues were identified using the published, ultrahigh-resolution X-ray crystallographic coordinates of the protein (Deacon et al. J. Chem. Soc., Faraday Trans. 1997, 93(24), 4305-4312).
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Affiliation(s)
- R Carmieli
- Contribution from the Institute of Science, Rehovot, Israel 76100
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35
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Abstract
Pulsed electron paramagnetic resonance (EPR) methods such as ESEEM, PELDOR, relaxation time measurements, transient EPR, high-field/high-frequency EPR, and pulsed ENDOR, have been used successfully to investigate the local structure and dynamics of paramagnetic centers in biological samples. These methods allow different contributions to the EPR spectra to be distinguished and can help unravel complicated EPR spectra consisting of overlapping resonance lines, as are often found in disordered protein samples. The basic principles, specific potentials, technical requirements, and limitations of these advanced EPR techniques will be reviewed together with recent applications to metal centers, organic radicals, and spin labels in proteins.
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Affiliation(s)
- T Prisner
- Institute for Physical and Theoretical Chemistry, J. W. Goethe-University Frankfurt, Marie-Curie-Strasse 11, Frankfurt am Main, D-60439 Germany.
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36
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Deligiannakis Y, Louloudi M, Hadjiliadis N. Electron spin echo envelope modulation (ESEEM) spectroscopy as a tool to investigate the coordination environment of metal centers. Coord Chem Rev 2000. [DOI: 10.1016/s0010-8545(99)00218-0] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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37
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Harris N, Cohen S, Filatov M, Ogliaro F, Shaik S. Zwei Reaktionswege beim „Wiederanbindungs”-Mechanismus der Alkanhydroxylierung durch Cytochrom P450: Entstehung freier Radikale mit begrenzter Lebensdauer. Angew Chem Int Ed Engl 2000. [DOI: 10.1002/1521-3757(20000602)112:11<2070::aid-ange2070>3.0.co;2-u] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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38
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Astashkin AV, Mader ML, Pacheco A, Enemark JH, Raitsimring AM. Direct Detection of the Proton-Containing Group Coordinated to Mo(V) in the High pH Form of Chicken Liver Sulfite Oxidase by Refocused Primary ESEEM Spectroscopy: Structural and Mechanistic Implications. J Am Chem Soc 2000. [DOI: 10.1021/ja9916761] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Andrei V. Astashkin
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - M. L. Mader
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Andrew Pacheco
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - John H. Enemark
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
| | - Arnold M. Raitsimring
- Contribution from the Department of Chemistry, University of Arizona, Tucson, Arizona 85721-0041
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39
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Loew GH, Harris DL. Role of the heme active site and protein environment in structure, spectra, and function of the cytochrome p450s. Chem Rev 2000; 100:407-20. [PMID: 11749241 DOI: 10.1021/cr980389x] [Citation(s) in RCA: 221] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- G H Loew
- Molecular Research Institute, 2495 Old Middlefield Way, Mountain View, California 94043
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40
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Zum Problem des Low-spin-Charakters von Cytochrom P450cam im „Resting State” – Untersuchungen von Enzymmodellen mit Puls-EPR- und ENDOR-Spektroskopie. Angew Chem Int Ed Engl 1998. [DOI: 10.1002/(sici)1521-3757(19981102)110:21<3191::aid-ange3191>3.0.co;2-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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41
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Andersson LA, Johnson AK, Peterson JA. Active site analysis of P450 enzymes: comparative magnetic circular dichroism spectroscopy. Arch Biochem Biophys 1997; 345:79-87. [PMID: 9281314 DOI: 10.1006/abbi.1997.0248] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Recent structural studies indicate that the substrate- and O2-binding distal pocket of the P450 enzymes are not identical. Thus, P450terp (CYP108) from the alpha-terpineol-metabolizing Pseudomonad differs from P450cam (CYP-101) (C. A. Hasemann et al., J. Mol. Biol. 236, 1169, 1994). In contrast, the distal pockets of P450terp and P450BMP (CYP102 heme domain; Bacillus megaterium) are more closely similar, including novel hydrogen-bonding interactions between the distal H2O ligand and the I helix (C. A. Hasemann et al., Structure, 3, 41-62, 1995). To evaluate the significance of these differences, we have compared solution magnetic circular dichroism (MCD) spectra of P450terp with spectra of other P450 enzymes (e.g., P450cam, P450BMP, P450BM-3holo, and P450BM1), as well as with spectra of chloroperoxidase and NO synthase. Spectra of native P450terp are more similar to those of P450BMP and those of mammalian P450LM-2 than to those of P450cam. Upon substrate-binding, the MCD spectra of ferric P450terp and all other thiolate-ligated heme systems examined to date display a strong Soret band that is distinctly unique relative to the typical Soret MCD pattern(s) of catalases or other 5-coordinate ferric heme systems. This intense negative MCD feature thus appears diagnostic for cysteinate-linked ferric hemes. In the case of ferrous P450s, the intensity of the Soret-region MCD trough varies between substrate-bound and substrate-free enzymes (despite the fact that the substrate is NOT in direct contact with the heme moiety). A novel finding of particular interest is the clear spectral shifts of the Soret MCD band between the substrate-bound and substrate-free forms of ferrous-CO-P450terp. No such observation has been made previously. Furthermore, the band positions for BOTH types of P450terp are red-shifted from known bands of ferrous-CO-P50cam. These data thus indicate a surprising sensitivity of MCD spectra to active-site polarity and to H2O occupancy, concurring with reports of distal pocket effects on CO-binding rates and equilibrium constants. Comparative analysis of the spectral properties of P450terp with MCD spectra of other P450 enzymes, as well as with chloroperoxidase and NO synthase, demonstrates both the expected similarities and the significant differences that reflect active-site structural features. The detailed spectral analysis of P450terp relative to other P450 enzymes presented herein includes the first observation of a substrate-induced spectral shift for a ferrous-CO-P450. Furthermore, testable structural predictions for P450-BM-1 and for the novel NO synthase enzyme (neither of which has been crystallized to date) are made herein. This work thus provides insights into structurally defined P450s and may also lead to understanding of other P450 enzymes.
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Affiliation(s)
- L A Andersson
- Department of Chemistry, Vassar College, Poughkeepsie, New York 12604-0589, USA.
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42
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Unno M, Christian JF, Benson DE, Gerber NC, Sligar SG, Champion PM. Resonance Raman Investigations of Cytochrome P450cam Complexed with Putidaredoxin. J Am Chem Soc 1997. [DOI: 10.1021/ja963785a] [Citation(s) in RCA: 73] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Masashi Unno
- Contribution from the Department of Physics, Northeastern University, Boston, Massachusetts 02115, and Departments of Biochemistry and Chemistry, University of Illinois at UrbanaChampaign, Urbana, Illinois 61801
| | - James F. Christian
- Contribution from the Department of Physics, Northeastern University, Boston, Massachusetts 02115, and Departments of Biochemistry and Chemistry, University of Illinois at UrbanaChampaign, Urbana, Illinois 61801
| | - David E. Benson
- Contribution from the Department of Physics, Northeastern University, Boston, Massachusetts 02115, and Departments of Biochemistry and Chemistry, University of Illinois at UrbanaChampaign, Urbana, Illinois 61801
| | - Nancy C. Gerber
- Contribution from the Department of Physics, Northeastern University, Boston, Massachusetts 02115, and Departments of Biochemistry and Chemistry, University of Illinois at UrbanaChampaign, Urbana, Illinois 61801
| | - Stephen G. Sligar
- Contribution from the Department of Physics, Northeastern University, Boston, Massachusetts 02115, and Departments of Biochemistry and Chemistry, University of Illinois at UrbanaChampaign, Urbana, Illinois 61801
| | - Paul M. Champion
- Contribution from the Department of Physics, Northeastern University, Boston, Massachusetts 02115, and Departments of Biochemistry and Chemistry, University of Illinois at UrbanaChampaign, Urbana, Illinois 61801
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Schulze H, Hoa GH, Jung C. Mobility of norbornane-type substrates and water accessibility in cytochrome P-450cam. BIOCHIMICA ET BIOPHYSICA ACTA 1997; 1338:77-92. [PMID: 9074618 DOI: 10.1016/s0167-4838(96)00192-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The behaviour of norbornane-type substrates bound to oxidised cytochrome P-450cam (CYP 101) in 60% (w/w) glycerol-containing phosphate buffer was investigated using electronic absorption spectroscopy. The high-pressure dependence study revealed that the value of the spin-state reaction-volume change decreased from -70 to -22.8 cm3/mol with decreasing high-spin state content from 99 to 63%. Simultaneously, the values for the enthalpy and entropy determined from the low-temperature dependence of the spin-state transition decreased from 73.7 to 24.3 kJ/mol and from 310.4 to 88.9 J/mol K, respectively. Under our experimental conditions the pH-value of the buffer remained at low temperatures and high pressures in the range of pH 7-8, in which no pH-value-induced spin-state conversion occurred. Therefore, the secondary effect of the temperature and pressure-induced pH change can be disregarded as being responsible for the observed spin-state transition effects. Substrate dissociation constants were determined. From the temperature-jump experiments (297 K to 180 K) we found a higher mobility in the active site for the substrates in the sequence (1R)-camphor, (1S)-camphor, camphane, (1R)- and (1S)-camphorquinone, norcamphor, and norbornane. Our findings can be explained by the incomplete fit of the methyl groups of the norbornane-type substrate to the protein, in particular to the I-helix, predominantly determining the substrate mobility and water accessibility to the protein.
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Affiliation(s)
- H Schulze
- Max-Delbrück-Centrum für Molekulare Medizin, Berlin, Germany
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45
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Turconi S, MacLachlan DJ, Bratt PJ, Nugent JH, Evans MC. Analysis of the interaction of water with the manganese cluster of photosystem II using isotopically labeled water. Biochemistry 1997; 36:879-85. [PMID: 9020787 DOI: 10.1021/bi962010b] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The association of water with the Mn of the water oxidizing complex was investigated using H2(17)O- and 2H2O-reconstituted lyophilized photosystem II particles. The pulsed electron paramagnetic resonance (EPR) technique of electron spin echo envelope modulation (ESEEM) was used to investigate the interaction of the magnetic 2H and 17O nuclei with the paramagnetic S2 state of the Mn complex and other photosystem II components. ESEEM offers a much more specific and sensitive detection of this type of interaction than continuous wave (CW) EPR. Unlike earlier reports using CW EPR, these experiments did not detect any interaction of water with the multiline EPR signal from the S2 state of the Mn complex. No signals indicating specific interaction of either H or O with the multiline signal were detected. Signals due to 2H and 17O were detected only at the Larmour frequency, indicating nonspecific "distant ENDOR" effects. A weak interaction with 17O was detected both in S1, when the Mn is EPR silent, and in S2, but only on the high-field side of g = 2. This interaction may be with the Rieske iron-sulfur center in the cytochrome b6f complex. The results were the same whether the multiline signal was generated by 200 K illumination of dark-frozen samples, or by room temperature illumination in the presence of the inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). Illumination at room temperature in the presence of an electron acceptor to allow multiple turnovers of the system with cycling of the S states did not result in the appearance of any new interactions. These results appear to exclude close (less than 6 A) binding of water to the Mn center giving rise to the multiline signal, and also to exclude mechanisms in which water oxidation involves the breaking and re-formation of the mu-oxo bridges of the Mn complex. They cannot, however, exclude models in which water binding to the manganese complex and direct oxidation by the manganese complex occur in the higher S states, or are catalyzed by one bis(mu-oxo) Mn dimer while oxidizing equivalents are accumulated in the S2 state by a second bis(mu-oxo) Mn dimer.
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Affiliation(s)
- S Turconi
- Department of Biology, University College London, U.K
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46
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Schulze H, Hoa GH, Helms V, Wade RC, Jung C. Structural changes in cytochrome P-450cam effected by the binding of the enantiomers (1R)-camphor and (1S)-camphor. Biochemistry 1996; 35:14127-38. [PMID: 8916898 DOI: 10.1021/bi9527303] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A comparative study of the enantiomeric substrate [(1R)-camphor- and (1S)-camphor)-bound cytochrome P-450cam concerns the spin-state equilibrium, substrate dissociation, the thermal unfolding of the protein structure, and the subconformer equilibria observed in the infrared spectra of the carbon monoxide (CO) complex of cytochrome P-450cam. The behavior of the different conformational equilibria in dependence on temperature, pressure, pH-value, cosolvent, and cation binding led us to suggest that (1S)-camphor is more loosely and less optimally bound in the heme pocket, which facilitates the access of solvent molecules into the heme-iron environment. The spin reaction volume difference measured using the high pressure technique is smaller by 16 +/- 9 cm3/mol for (1S)-camphor-bound P-450cam compared to the (1R)-camphor-bound P-450cam, which might indicate a higher water content in the protein and in the heme environment in the (1S)-camphor complex. The half-transition temperature of the thermal unfolding of 53.8 degrees C for the (1S)-camphor-bound oxidized cytochrome P-450cam is one degree lower than the value for the (1R)-camphor-bound protein (54.8 degrees C). In the reduced, CO-bound form of cytochrome P-450cam at 290 K the (1S)-camphor complex reveals another CO stretch vibration population distribution with slightly higher frequencies [1940.2 cm-1 (major band) and 1946.3 cm-1 (minor band)] compared to the (1R)-camphor complex [1939.7 cm-1 (major band) and 1930 cm-1 (minor band)]. A loosening of the contact between the iron-bound CO ligand and amino acids of the I-helix, probably induced by compensating effects of the increased water content, is suggested. Assuming the carbon monoxide complex as a model for the dioxygen complex, the more loosened binding of (1S)-camphor, therefore the increased water accessibility, and the weaker contact of the iron ligand to the I-helix might explain the higher amount of uncoupling of the cytochrome P-450 reaction cycle compared to that when (1R)-camphor is used as substrate.
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Affiliation(s)
- H Schulze
- Max-Delbrück-Centrum für Molekulare Medizin Berlin-Buch, Berlin, Germany
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Aissaoui H, Ghirlanda S, Gmür C, Woggon WD. The synthesis of a new active-site analogue of cytochrome P450 carrying substrate recognition sites and athiolate ligand. ACTA ACUST UNITED AC 1996. [DOI: 10.1016/s1381-1169(96)00166-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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