Structure's Influence on Reactivity in Metalloenzymes

Summary

Principal Investigator: JULIA A KOVACS
Abstract: DESCRIPTION (provided by applicant): Our research program focuses on understanding how thiolate ligands promote N-O and O-O (O2- and O2) bond activation. Nitric oxide (NO) is frequently used to probe O2 binding sites, and form stable analogues of key metastable Fe-O2 intermediates. The ?NO stretching frequency provides a measure of N-O, and thus O-O bond activating properties. A growing number of metalloenzymes use Mn and Fe interchangeably without altering function, and a majority of these promote O-O bond activation and cleavage, and involve M-dioxygen, -superoxo, -peroxo, and -oxo (M= Mn, Fe) species as key intermediates. These enzymes function to remove toxic O2- radicals implicated in cancer, Alzheimer's, Parkinson's disease, and synthesize key biomolecules such as DNA, neurotransmitters, fatty acids, and steroids. The spectroscopic and reactivity properties of thiolate-ligated Fe- and Mn-peroxo, superoxo, and oxo species remain largely unexplored, and the O2 and O2- chemistry of Mn and Fe is complementary with respect to the spectroscopic visibility and stability of reactive intermediates. For the proposed project period we will design and synthesize new, readily derivatized thiolate ligands, and their corresponding Mn and Fe complexes. By systematically altering substituents we will fine-tune the electronic and steric properties of the molecule, and adjust the redox potential, metal ion Lewis acidity, and relative pKa of the distal versus proximal peroxo oxygens. Using a systematic approach we will attempt to determine which properties are key to promoting reactivity and function. By probing redox potentials and ?NO of structurally analogous Mn/Fe pairs we will examine the tunable nature of the M- SR bond, and establish whether cysteinates can facilitate the interchangeability of Mn and Fe while maintaining function. We will fully characterize our new pyridine/thiolate-ligated Fe-peroxo intermediates formed via O2- reduction, and continue to explore the O2- reactivity of additional pyridine- substituted derivatives. Ultimately we will be looking for correlations between Hammett parameters and reactivity, and determining which properties are key to promoting Fe-O versus O-O bond cleavage. We will continue to look for M3+ (M= Mn, Fe) promoted O2- oxidation activity by monitoring for O2 evolution. Ultimately we will be looking for a catalytic SOD mimic. We will fully characterize our new Mn-dioxygen and Mn-OOR (R= tBu, Cm) intermediates using XAS, MCD, resonance Raman, parallel- mode EPR, and DFT, and examine the kinetics and mechanism of the Mn-dioxygen species formation. We wil attempt to stabilize these intermediates, as well as our new Mn=O, by incorporating steric bulk into the ligand. We will continue to explore the reactivity of our new Mn-dioxygen, Mn-oxo, and Mn- OOR intermediates with oxidizable substrates.
Funding Period: 1992-02-01 - 2015-07-31
more information: NIH RePORT

Top Publications

  1. pmc A functional model for the cysteinate-ligated non-heme iron enzyme superoxide reductase (SOR)
    Terutaka Kitagawa
    Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
    J Am Chem Soc 128:14448-9. 2006
  2. pmc Synthesis and structural characterization of a series of Mn(III)OR complexes, including a water-soluble Mn(III)OH that promotes aerobic hydrogen-atom transfer
    Michael K Coggins
    Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 1700, United States
    Inorg Chem 52:12383-93. 2013
  3. pmc Characterization of metastable intermediates formed in the reaction between a Mn(II) complex and dioxygen, including a crystallographic structure of a binuclear Mn(III)-peroxo species
    Michael K Coggins
    Department of Chemistry, University of Washington, Campus Box 351700 Seattle, Washington 98195 1700, USA
    J Am Chem Soc 135:5631-40. 2013
  4. pmc Correlation between structural, spectroscopic, and reactivity properties within a series of structurally analogous metastable manganese(III)-alkylperoxo complexes
    Michael K Coggins
    The Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 1700, USA
    J Am Chem Soc 135:4260-72. 2013
  5. pmc Characterization and dioxygen reactivity of a new series of coordinatively unsaturated thiolate-ligated manganese(II) complexes
    Michael K Coggins
    The Department of Chemistry, University of Washington, Campus Box 351700, Seattle, Washington 98195 1700, USA
    Inorg Chem 51:6633-44. 2012
  6. pmc Structural and spectroscopic characterization of metastable thiolate-ligated manganese(III)-alkylperoxo species
    Michael K Coggins
    Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
    J Am Chem Soc 133:12470-3. 2011
  7. pmc Nitrile hydration by thiolate- and alkoxide-ligated Co-NHase analogues. Isolation of Co(III)-amidate and Co(III)-iminol intermediates
    Rodney D Swartz
    The Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 1700, United States
    J Am Chem Soc 133:3954-63. 2011
  8. pmc Investigation of the mechanism of formation of a thiolate-ligated Fe(III)-OOH
    Elaine Nam
    Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 1700, USA
    Inorg Chem 50:1592-602. 2011
  9. pmc S K-edge X-ray absorption spectroscopy and density functional theory studies of high and low spin {FeNO}7 thiolate complexes: exchange stabilization of electron delocalization in {FeNO}7 and {FeO2}8
    Ning Sun
    Department of Chemistry, Stanford University, Stanford, California 94305, United States
    Inorg Chem 50:427-36. 2011
  10. pmc Properties of square-pyramidal alkyl-thiolate Fe(III) complexes, including an analogue of the unmodified form of nitrile hydratase
    Priscilla Lugo-Mas
    The Department of Chemistry, University of Washington, Box 351700 Seattle, Washington 98195 1700, USA
    Inorg Chem 47:11228-36. 2008

Detail Information

Publications14

  1. pmc A functional model for the cysteinate-ligated non-heme iron enzyme superoxide reductase (SOR)
    Terutaka Kitagawa
    Department of Chemistry, University of Washington, Seattle, Washington 98195, USA
    J Am Chem Soc 128:14448-9. 2006
    ..Thus we provide critical insight into the relationship between the SOR structure and its function, as well as important benchmark parameters for characterizing highly unstable thiolate-ligated iron-peroxo intermediates...
  2. pmc Synthesis and structural characterization of a series of Mn(III)OR complexes, including a water-soluble Mn(III)OH that promotes aerobic hydrogen-atom transfer
    Michael K Coggins
    Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 1700, United States
    Inorg Chem 52:12383-93. 2013
    ..2 (R = Me) > 13.5 (R = Ph) > 12.2 (R = (p)NO2Ph)] is shown to oppose that of the oxidation potential E(p,c) [-220 (R = (p)NO2Ph) > -300 (R = Ph) > -410 (R = Me) > -600 (R = H) mV vs Fc(+/0)] for this particular series...
  3. pmc Characterization of metastable intermediates formed in the reaction between a Mn(II) complex and dioxygen, including a crystallographic structure of a binuclear Mn(III)-peroxo species
    Michael K Coggins
    Department of Chemistry, University of Washington, Campus Box 351700 Seattle, Washington 98195 1700, USA
    J Am Chem Soc 135:5631-40. 2013
    ..Vibrational and metrical parameters for binuclear Mn-peroxo 3 are compared with those of related binuclear Fe- and Cu-peroxo compounds...
  4. pmc Correlation between structural, spectroscopic, and reactivity properties within a series of structurally analogous metastable manganese(III)-alkylperoxo complexes
    Michael K Coggins
    The Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 1700, USA
    J Am Chem Soc 135:4260-72. 2013
    ..The reported work represents one of very few examples of experimentally verified relationships between structure and function...
  5. pmc Characterization and dioxygen reactivity of a new series of coordinatively unsaturated thiolate-ligated manganese(II) complexes
    Michael K Coggins
    The Department of Chemistry, University of Washington, Campus Box 351700, Seattle, Washington 98195 1700, USA
    Inorg Chem 51:6633-44. 2012
    ..Complexes 3-5, on the other hand, do not form observable intermediates, thus illustrating the effect that relatively minor ligand modifications have upon the stability of metastable dioxygen-derived species...
  6. pmc Structural and spectroscopic characterization of metastable thiolate-ligated manganese(III)-alkylperoxo species
    Michael K Coggins
    Department of Chemistry, University of Washington, Seattle, Washington 98195, United States
    J Am Chem Soc 133:12470-3. 2011
    ..Spectroscopic data, including electronic absorption and IR spectra, and ESI mass spectra for (16)O vs (18)O-labeled metastable Mn(III)-OOR (R = (t)Bu, Cm) are discussed, as well as preliminary reactivity...
  7. pmc Nitrile hydration by thiolate- and alkoxide-ligated Co-NHase analogues. Isolation of Co(III)-amidate and Co(III)-iminol intermediates
    Rodney D Swartz
    The Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 1700, United States
    J Am Chem Soc 133:3954-63. 2011
    ..Comparison of the thiolate versus alkoxide intermediate structures shows that C≡N bond activation and C═O bond formation proceed further along the reaction coordinate when a thiolate is incorporated into the coordination sphere...
  8. pmc Investigation of the mechanism of formation of a thiolate-ligated Fe(III)-OOH
    Elaine Nam
    Department of Chemistry, University of Washington, Box 351700, Seattle, Washington 98195 1700, USA
    Inorg Chem 50:1592-602. 2011
    ..The observed deuterium isotope effect (k(H)/k(D) = 3.1) is also consistent with this mechanism...
  9. pmc S K-edge X-ray absorption spectroscopy and density functional theory studies of high and low spin {FeNO}7 thiolate complexes: exchange stabilization of electron delocalization in {FeNO}7 and {FeO2}8
    Ning Sun
    Department of Chemistry, Stanford University, Stanford, California 94305, United States
    Inorg Chem 50:427-36. 2011
    ..These studies demonstrate how the ligand field of the Fe center defines its spin state and thus changes the electron exchange, an important factor in determining the electron distribution over {FeNO}(7) and {FeO2}(8) sites. ..
  10. pmc Properties of square-pyramidal alkyl-thiolate Fe(III) complexes, including an analogue of the unmodified form of nitrile hydratase
    Priscilla Lugo-Mas
    The Department of Chemistry, University of Washington, Box 351700 Seattle, Washington 98195 1700, USA
    Inorg Chem 47:11228-36. 2008
    ..This is supported by previously reported theoretical (DFT) calculations...
  11. pmc Periodic trends within a series of five-coordinate thiolate-ligated [MII(SMe2N4(tren))]+ (M = Mn, Fe, Co, Ni, Cu, Zn) complexes, including a rare example of a stable CuII-thiolate
    Lisa M Brines
    The Department of Chemistry, University of Washington, Box 351700, Seattle, WA 98195 1700, USA
    Inorg Chem 46:9267-77. 2007
    ..The reduced M(+1) oxidation state is only accessible with copper, and the more oxidized M(+4) oxidation state is only accessible for manganese...
  12. pmc Isolation and characterization of a dihydroxo-bridged iron(III,III)(μ-OH)2 diamond core derived from dioxygen
    Michael K Coggins
    The Department of Chemistry, University of Washington Box 351700 Seattle, Washington 98195 1700, United States
    Inorg Chem 52:13325-31. 2013
    ..Hydroxo-bridged 2 was found to stoichiometrically abstract hydrogen atoms from 9,10-dihydroanthracene (C-H BDE = 76 kcal/mol) at ambient temperatures. ..

Research Grants30

  1. Simultaneous Time-Resolved X-ray Spectroscopy and Crystallography: A Mechanistic
    Rosalie Tran; Fiscal Year: 2013
    ..abstract_text> ..
  2. Structure/Function Correlations Over Copper Enzymes
    Edward I Solomon; Fiscal Year: 2013
    ..They are of fundamental importance towards understanding pathogenesis and provide structural and mechanistic insight for drug design, medical device development, and the generation of new catalysts. ..
  3. Synthetic Models of the Oxygen Evolving Complex of Photosystem II
    Theodor Agapie; Fiscal Year: 2013
    ....
  4. The Transmembrane Protein Center
    Brian G Fox; Fiscal Year: 2013
    ..Expanded options for crystallization screening, access to synchrotrons, and improvements in software used to solve structures will also contribute to the increased throughput necessary to achieve PSI:Biology goals. ..
  5. Polynuclear iron complexes as functional mimics of the nitrogenase FeMo-cofactor
    Theodore A Betley; Fiscal Year: 2013
    ..The proposed research will permit the testing of several hypotheses concerning interaction of nitrogenase substrates with polynuclear reaction sites prevalent in FeMoco. ..
  6. Protein Dynamics in Enzymatic Catalysis
    Robert Callender; Fiscal Year: 2013
    ..The Equipment Core (Core A) supports the specialized comprehensive suite of instrumentation for the Program. The Administrative Core (Core B) administers the Program Project. ..
  7. Directed Evolution of Metal-Substituted Carbonic Anhydrases for Catalysis
    LEVI MICHAEL STANLEY; Fiscal Year: 2013
    ..abstract_text> ..
  8. DEGENERATIVE AND DEMENTING DISEASES OF AGING
    Stanley B Prusiner; Fiscal Year: 2013
    ..The ultimate goal of all the proposed studies is to define the molecular events that feature in the formation of human prions in order to develop therapeutics that cure the human prion diseases. ..
  9. Synthetic Modeling of Copper Protein Active Sites
    William B Tolman; Fiscal Year: 2013
    ..In addition to aspiring to a deep understanding of copper enzyme structure/function relationships, the proposed work is aimed at developing novel copper chemistry of fundamental significance. ..
  10. Reactivity of Manganese and Iron Metalloenzyme Models
    David P Goldberg; Fiscal Year: 2013
    ..Fundamental information regarding the mechanisms of biomimetic HAT, OAT, ET and related reactions will be obtained. ..
  11. Asymmetric Synthesis of Biologically Active Marine Natural Products
    Chuo Chen; Fiscal Year: 2013
    ..Inspired by the oxidative metalloenzymes, we will further develop new metal catalysts for C-H and olefin oxidation. Our research will have direct impacts on the discovery and manufacturing of small-molecule drugs. ..
  12. BIOINORGANIC COPPER COORDINATION CHEMISTRY
    Kenneth D Karlin; Fiscal Year: 2013
    ..Potential long-term applications of this basic research include development of enzyme inhibitors and relevant disease therapeutic strategies. ..
  13. Electronic, Structural, and Kinetic Characterizations of Cytochrome P450 Compound
    Michael T Green; Fiscal Year: 2013
    ..Proposed experiments thus provide access to the magnitude of D(O-H), allowing insight into how P450s leverage redox potential and ferryl basicity to activate hydrocarbons. ..
  14. Structural bases of the functions of RNA-protein machines
    THOMAS ARTHUR STEITZ; Fiscal Year: 2013
    ..Also of interest will be the ways in which the structures and properties of RNA molecules can be utilized to carry out various biological functions often analogous to those performed by proteins. ..
  15. Mechanisms of Copper Transport
    Ninian J Blackburn; Fiscal Year: 2013
    ..These studies will lead to a better understanding of the molecular basis of copper trafficking and will aid in combating diseases of aberrant copper homeostasis. ..
  16. EPR and Mossbauer Characterization of Mn and Fe Proteins, Models, Intermediates
    Michael P Hendrich; Fiscal Year: 2013
    ..We have created software for the interpretation of EPR spectra which allows an unprecedented ability to quantitatively characterize virtually all paramagnetic metal sites in proteins and enzymes. ..
  17. Electron Transfer in Iron and Copper Proteins
    Jay R Winkler; Fiscal Year: 2013
    ..Efforts will focus on oxidative generation of Compounds I and II in cytochromes P450 (Aim 3) and a bacterial enzyme that exhibits NOS-like reactivity (Aim 4). ..