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Nguyen RC, Davis I, Dasgupta M, Wang Y, Simon PS, Butryn A, Makita H, Bogacz I, Dornevil K, Aller P, Bhowmick A, Chatterjee R, Kim IS, Zhou T, Mendez D, Paley D, Fuller F, Alonso-Mori R, Batyuk A, Sauter NK, Brewster AS, Orville AM, Yachandra VK, Yano J, Kern JF, Liu A. In Situ Structural Observation of a Substrate- and Peroxide-Bound High-Spin Ferric-Hydroperoxo Intermediate in the P450 Enzyme CYP121. J Am Chem Soc 2023; 145:25120-25133. [PMID: 37939223 PMCID: PMC10799213 DOI: 10.1021/jacs.3c04991] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
The P450 enzyme CYP121 from Mycobacterium tuberculosis catalyzes a carbon-carbon (C-C) bond coupling cyclization of the dityrosine substrate containing a diketopiperazine ring, cyclo(l-tyrosine-l-tyrosine) (cYY). An unusual high-spin (S = 5/2) ferric intermediate maximizes its population in less than 5 ms in the rapid freeze-quenching study of CYP121 during the shunt reaction with peracetic acid or hydrogen peroxide in acetic acid solution. We show that this intermediate can also be observed in the crystalline state by EPR spectroscopy. By developing an on-demand-rapid-mixing method for time-resolved serial femtosecond crystallography with X-ray free-electron laser (tr-SFX-XFEL) technology covering the millisecond time domain and without freezing, we structurally monitored the reaction in situ at room temperature. After a 200 ms peracetic acid reaction with the cocrystallized enzyme-substrate microcrystal slurry, a ferric-hydroperoxo intermediate is observed, and its structure is determined at 1.85 Å resolution. The structure shows a hydroperoxyl ligand between the heme and the native substrate, cYY. The oxygen atoms of the hydroperoxo are 2.5 and 3.2 Å from the iron ion. The end-on binding ligand adopts a near-side-on geometry and is weakly associated with the iron ion, causing the unusual high-spin state. This compound 0 intermediate, spectroscopically and structurally observed during the catalytic shunt pathway, reveals a unique binding mode that deviates from the end-on compound 0 intermediates in other heme enzymes. The hydroperoxyl ligand is only 2.9 Å from the bound cYY, suggesting an active oxidant role of the intermediate for direct substrate oxidation in the nonhydroxylation C-C bond coupling chemistry.
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Affiliation(s)
- Romie C. Nguyen
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
| | - Ian Davis
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
| | - Medhanjali Dasgupta
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Yifan Wang
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
| | - Philipp S. Simon
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Agata Butryn
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA, United Kingdom
| | - Hiroki Makita
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Isabel Bogacz
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Kednerlin Dornevil
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
| | - Pierre Aller
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA, United Kingdom
| | - Asmit Bhowmick
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Ruchira Chatterjee
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - In-Sik Kim
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Tiankun Zhou
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA, United Kingdom
| | - Derek Mendez
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Daniel Paley
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Franklin Fuller
- LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, United States
| | - Roberto Alonso-Mori
- LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, United States
| | - Alexander Batyuk
- LCLS, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, United States
| | - Nicholas K. Sauter
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Aaron S. Brewster
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Allen M. Orville
- Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, United Kingdom
- Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, Oxfordshire OX11 0FA, United Kingdom
| | - Vittal K. Yachandra
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Junko Yano
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Jan F. Kern
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, United States
| | - Aimin Liu
- Department of Chemistry, University of Texas, San Antonio, TX 78249, United States
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Davydov R, Herzog AE, Jodts RJ, Karlin KD, Hoffman BM. End-On Copper(I) Superoxo and Cu(II) Peroxo and Hydroperoxo Complexes Generated by Cryoreduction/Annealing and Characterized by EPR/ENDOR Spectroscopy. J Am Chem Soc 2022; 144:377-389. [PMID: 34981938 PMCID: PMC8785356 DOI: 10.1021/jacs.1c10252] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
In this report, we investigate the physical and chemical properties of monocopper Cu(I) superoxo and Cu(II) peroxo and hydroperoxo complexes. These are prepared by cryoreduction/annealing of the parent [LCuI(O2)]+ Cu(I) dioxygen adducts with the tripodal, N4-coordinating, tetradentate ligands L = PVtmpa, DMMtmpa, TMG3tren and are best described as [LCuII(O2•-)]+ Cu(II) complexes that possess end-on (η1-O2•-) superoxo coordination. Cryogenic γ-irradiation (77 K) of the EPR-silent parent complexes generates mobile electrons from the solvent that reduce the [LCuII(O2•-)]+ within the frozen matrix, trapping the reduced form fixed in the structure of the parent complex. Cryoannealing, namely progressively raising the temperature of a frozen sample in stages and then cooling back to low temperature at each stage for examination, tracks the reduced product as it relaxes its structure and undergoes chemical transformations. We employ EPR and ENDOR (electron-nuclear double resonance) as powerful spectroscopic tools for examining the properties of the states that form. Surprisingly, the primary products of reduction of the Cu(II) superoxo species are metastable cuprous superoxo [LCuI(O2•-)]+ complexes. During annealing to higher temperatures this state first undergoes internal electron transfer (IET) to form the end-on Cu(II) peroxo state, which is then protonated to form Cu(II)-OOH species. This is the first time these methods, which have been used to determine key details of metalloenzyme catalytic cycles and are a powerful tools for tracking PCET reactions, have been applied to copper coordination compounds.
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Affiliation(s)
- Roman Davydov
- Department of Chemistry, Northwestern University, Evanston, Illinois 60201, United States
| | - Austin E Herzog
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Richard J Jodts
- Department of Chemistry, Northwestern University, Evanston, Illinois 60201, United States
| | - Kenneth D Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, Evanston, Illinois 60201, United States
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Valle-Altamirano RG, Baratto MC, Badillo-Ramírez I, Gasteazoro F, Pogni R, Saniger JM, Valderrama B. Identification of Fe( iii)–OH species as a catalytic intermediate in plant peroxidases at high H 2O 2 concentration. NEW J CHEM 2022. [DOI: 10.1039/d1nj04837f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The structure for compound III formed after exposure of plant heme peroxidases to excess H2O2 seems to be a hydroxylated form, providing new evidence for understanding the structural basis of the substrate-induced suicidal behavior of these enzymes.
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Affiliation(s)
- Rodolfo G. Valle-Altamirano
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad, 62210 Morelos, Mexico
- Facultad de Química, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510 Ciudad de México, Mexico
| | - Maria Camilla Baratto
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via A. Moro, 53100 Siena, Italy
| | - Isidro Badillo-Ramírez
- Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, 04510, Ciudad de México, Mexico
| | - Francisco Gasteazoro
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad, 62210 Morelos, Mexico
| | - Rebecca Pogni
- Department of Biotechnology, Chemistry and Pharmacy, University of Siena, Via A. Moro, 53100 Siena, Italy
| | - José M. Saniger
- Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, 04510, Ciudad de México, Mexico
| | - Brenda Valderrama
- Departamento de Medicina Molecular y Bioprocesos, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad, 62210 Morelos, Mexico
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Petrik ID, Davydov R, Kahle M, Sandoval B, Dwaraknath S, Ädelroth P, Hoffman B, Lu Y. An Engineered Glutamate in Biosynthetic Models of Heme-Copper Oxidases Drives Complete Product Selectivity by Tuning the Hydrogen-Bonding Network. Biochemistry 2021; 60:346-355. [PMID: 33464878 PMCID: PMC7888536 DOI: 10.1021/acs.biochem.0c00852] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Efficiently carrying out the oxygen reduction reaction (ORR) is critical for many applications in biology and chemistry, such as bioenergetics and fuel cells, respectively. In biology, this reaction is carried out by large, transmembrane oxidases such as heme-copper oxidases (HCOs) and cytochrome bd oxidases. Common to these oxidases is the presence of a glutamate residue next to the active site, but its precise role in regulating the oxidase activity remains unclear. To gain insight into its role, we herein report that incorporation of glutamate next to a designed heme-copper center in two biosynthetic models of HCOs improves O2 binding affinity, facilitates protonation of reaction intermediates, and eliminates release of reactive oxygen species. High-resolution crystal structures of the models revealed extended, water-mediated hydrogen-bonding networks involving the glutamate. Electron paramagnetic resonance of the cryoreduced oxy-ferrous centers at cryogenic temperature followed by thermal annealing allowed observation of the key hydroperoxo intermediate that can be attributed to the hydrogen-bonding network. By demonstrating these important roles of glutamate in oxygen reduction biochemistry, this work offers deeper insights into its role in native oxidases, which may guide the design of more efficient artificial ORR enzymes or catalysts for applications such as fuel cells.
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Affiliation(s)
- Igor D. Petrik
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Roman Davydov
- The Department of Chemistry, Northwestern University, Evanston, Illinois 60201
| | - Maximilian Kahle
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Braddock Sandoval
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Sudharsan Dwaraknath
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
| | - Pia Ädelroth
- Department of Biochemistry and Biophysics, Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Brian Hoffman
- The Department of Chemistry, Northwestern University, Evanston, Illinois 60201
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, United States
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Rebelo SL, Moniz T, Medforth CJ, de Castro B, Rangel M. EPR spin trapping studies of H2O2 activation in metaloporphyrin catalyzed oxygenation reactions: Insights on the biomimetic mechanism. MOLECULAR CATALYSIS 2019. [DOI: 10.1016/j.mcat.2019.110500] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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6
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Adam SM, Wijeratne GB, Rogler PJ, Diaz DE, Quist DA, Liu JJ, Karlin KD. Synthetic Fe/Cu Complexes: Toward Understanding Heme-Copper Oxidase Structure and Function. Chem Rev 2018; 118:10840-11022. [PMID: 30372042 PMCID: PMC6360144 DOI: 10.1021/acs.chemrev.8b00074] [Citation(s) in RCA: 132] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Heme-copper oxidases (HCOs) are terminal enzymes on the mitochondrial or bacterial respiratory electron transport chain, which utilize a unique heterobinuclear active site to catalyze the 4H+/4e- reduction of dioxygen to water. This process involves a proton-coupled electron transfer (PCET) from a tyrosine (phenolic) residue and additional redox events coupled to transmembrane proton pumping and ATP synthesis. Given that HCOs are large, complex, membrane-bound enzymes, bioinspired synthetic model chemistry is a promising approach to better understand heme-Cu-mediated dioxygen reduction, including the details of proton and electron movements. This review encompasses important aspects of heme-O2 and copper-O2 (bio)chemistries as they relate to the design and interpretation of small molecule model systems and provides perspectives from fundamental coordination chemistry, which can be applied to the understanding of HCO activity. We focus on recent advancements from studies of heme-Cu models, evaluating experimental and computational results, which highlight important fundamental structure-function relationships. Finally, we provide an outlook for future potential contributions from synthetic inorganic chemistry and discuss their implications with relevance to biological O2-reduction.
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Affiliation(s)
- Suzanne M. Adam
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Gayan B. Wijeratne
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Patrick J. Rogler
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Daniel E. Diaz
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - David A. Quist
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Jeffrey J. Liu
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Kenneth D. Karlin
- Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218, United States
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7
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Abstract
Membrane proteins play a most important part in metabolism, signaling, cell motility, transport, development, and many other biochemical and biophysical processes which constitute fundamentals of life on the molecular level. Detailed understanding of these processes is necessary for the progress of life sciences and biomedical applications. Nanodiscs provide a new and powerful tool for a broad spectrum of biochemical and biophysical studies of membrane proteins and are commonly acknowledged as an optimal membrane mimetic system that provides control over size, composition, and specific functional modifications on the nanometer scale. In this review we attempted to combine a comprehensive list of various applications of nanodisc technology with systematic analysis of the most attractive features of this system and advantages provided by nanodiscs for structural and mechanistic studies of membrane proteins.
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Affiliation(s)
- Ilia G Denisov
- Department of Biochemistry and Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States
| | - Stephen G Sligar
- Department of Biochemistry and Department of Chemistry, University of Illinois , Urbana, Illinois 61801, United States
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Pearl NM, Wilcoxen J, Im S, Kunz R, Darty J, Britt RD, Ragsdale SW, Waskell L. Protonation of the Hydroperoxo Intermediate of Cytochrome P450 2B4 Is Slower in the Presence of Cytochrome P450 Reductase Than in the Presence of Cytochrome b5. Biochemistry 2016; 55:6558-6567. [PMID: 27797496 DOI: 10.1021/acs.biochem.6b00996] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Microsomal cytochromes P450 (P450) require two electrons and two protons for the oxidation of substrates. Although the two electrons can be provided by cytochrome P450 reductase, the second electron can also be donated by cytochrome b5 (b5). The steady-state activity of P450 2B4 is increased up to 10-fold by b5. To improve our understanding of the molecular basis of the stimulatory effect of b5 and to test the hypothesis that b5 stimulates catalysis by more rapid protonation of the anionic ferric hydroperoxo heme intermediate of P450 (Fe3+OOH)- and subsequent formation of the active oxidizing species (Fe+4═O POR•+), we have freeze-quenched the reaction mixture during a single turnover following reduction of oxyferrous P450 2B4 by each of its redox partners, b5 and P450 reductase. The electron paramagnetic resonance spectra of the freeze-quenched reaction mixtures lacked evidence of a hydroperoxo intermediate when b5 was the reductant presumably because hydroperoxo protonation and catalysis occurred within the dead time of the instrument. However, when P450 reductase was the reductant, a hydroperoxo P450 intermediate was observed. The effect of b5 on the enzymatic efficiency in D2O and the kinetic solvent isotope effect under steady-state conditions are both consistent with the ability of b5 to promote rapid protonation of the hydroperoxo species and more efficient catalysis. In summary, by binding to the proximal surface of P450, b5 stimulates the activity of P450 2B4 by enhancing the rate of protonation of the hydroperoxo intermediate and formation of Compound I, the active oxidizing species, which allows less time for side product formation.
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Affiliation(s)
- Naw May Pearl
- Department of Anesthesiology, University of Michigan Medical School , Ann Arbor, Michigan 48109-0112, United States
| | - Jarett Wilcoxen
- Department of Chemistry, University of California, Davis , Davis, California 95616, United States
| | - Sangchoul Im
- Department of Anesthesiology, University of Michigan Medical School , Ann Arbor, Michigan 48109-0112, United States
| | - Ryan Kunz
- Department of Biological Chemistry, University of Michigan Medical School , Ann Arbor, Michigan 48109-0600, United States
| | - Joseph Darty
- Department of Biological Chemistry, University of Michigan Medical School , Ann Arbor, Michigan 48109-0600, United States
| | - R David Britt
- Department of Chemistry, University of California, Davis , Davis, California 95616, United States
| | - Stephen W Ragsdale
- Department of Biological Chemistry, University of Michigan Medical School , Ann Arbor, Michigan 48109-0600, United States
| | - Lucy Waskell
- Department of Anesthesiology, University of Michigan Medical School , Ann Arbor, Michigan 48109-0112, United States
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Bhagi-Damodaran A, Petrik I, Lu Y. Using Biosynthetic Models of Heme-Copper Oxidase and Nitric Oxide Reductase in Myoglobin to Elucidate Structural Features Responsible for Enzymatic Activities. Isr J Chem 2016; 56:773-790. [PMID: 27994254 PMCID: PMC5161413 DOI: 10.1002/ijch.201600033] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In biology, a heme-Cu center in heme-copper oxidases (HCOs) is used to catalyze the four-electron reduction of oxygen to water, while a heme-nonheme diiron center in nitric oxide reductases (NORs) is employed to catalyze the two-electron reduction of nitric oxide to nitrous oxide. Although much progress has been made in biochemical and biophysical studies of HCOs and NORs, structural features responsible for similarities and differences within the two enzymatic systems remain to be understood. Here, we discuss the progress made in the design and characterization of myoglobin-based enzyme models of HCOs and NORs. In particular, we focus on use of these models to understand the structure-function relations between HCOs and NORs, including the role of nonheme metals, conserved amino acids in the active site, heme types and hydrogen-bonding network in tuning enzymatic activities and total turnovers. Insights gained from these studies are summarized and future directions are proposed.
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Affiliation(s)
| | - Igor Petrik
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL. 61801
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL. 61801
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10
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Davydov R, Khadka N, Yang ZY, Fielding AJ, Lukoyanov D, Dean DR, Seefeldt LC, Hoffman BM. Exploring Electron/Proton Transfer and Conformational Changes in the Nitrogenase MoFe Protein and FeMo-cofactor Through Cryoreduction/EPR Measurements. Isr J Chem 2016; 56:841-851. [PMID: 27777444 DOI: 10.1002/ijch.201600026] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
We combine cryoreduction/annealing/EPR measurements of nitrogenase MoFe protein with results of earlier investigations to provide a detailed view of the electron/proton transfer events and conformational changes that occur during early stages of [e-/H+] accumulation by the MoFe protein. This includes reduction of (i) the non-catalytic state of the iron-molybdenum cofactor (FeMo-co) active site that is generated by chemical oxidation of the resting-state cofactor (S = 3/2)) within resting MoFe (E0), and (ii) the catalytic state that has accumulated n =1 [e-/H+] above the resting-state level, denoted E1(1H) (S ≥ 1) in the Lowe-Thorneley kinetic scheme. FeMo-co does not undergo a major change of conformation during reduction of oxidized FeMo-co. In contrast, FeMo-co undergoes substantial conformational changes during the reduction of E0 to E1(1H), and of E1(1H) to E2(2H) (n = 2; S = 3/2). The experimental results further suggest that the E1(1H) → E2(2H) step involves coupled delivery of a proton and electron (PCET) to FeMo-co of E1(H) to generate a non-equilibrium S = ½ form E2(2H)*. This subsequently undergoes conformational relaxation and attendant change in FeMo-co spin state, to generate the equilibrium E2(2H) (S = 3/2) state. Unexpectedly, these experiments also reveal conformational coupling between FeMo-co and P-cluster, and between Fe protein binding and FeMo-co, which might play a role in gated ET from reduced Fe protein to FeMo-co.
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Affiliation(s)
- Roman Davydov
- Department of Chemistry, Northwestern University, Evanston, IL 60208
| | - Nimesh Khadka
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322
| | - Zhi-Yong Yang
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322
| | - Andrew J Fielding
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322
| | - Dmitriy Lukoyanov
- Department of Chemistry, Northwestern University, Evanston, IL 60208
| | - Dennis R Dean
- Department of Biochemistry, Virginia Tech, 110 Fralin Hall, Blacksburg, VA 24061
| | - Lance C Seefeldt
- Department of Chemistry and Biochemistry, Utah State University, Logan, UT 84322
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University, Evanston, IL 60208
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11
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Davydov R, Im S, Shanmugam M, Gunderson WA, Pearl NM, Hoffman BM, Waskell L. Role of the Proximal Cysteine Hydrogen Bonding Interaction in Cytochrome P450 2B4 Studied by Cryoreduction, Electron Paramagnetic Resonance, and Electron-Nuclear Double Resonance Spectroscopy. Biochemistry 2016; 55:869-83. [PMID: 26750753 DOI: 10.1021/acs.biochem.5b00744] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Crystallographic studies have shown that the F429H mutation of cytochrome P450 2B4 introduces an H-bond between His429 and the proximal thiolate ligand, Cys436, without altering the protein fold but sharply decreases the enzymatic activity and stabilizes the oxyferrous P450 2B4 complex. To characterize the influence of this hydrogen bond on the states of the catalytic cycle, we have used radiolytic cryoreduction combined with electron paramagnetic resonance (EPR) and (electron-nuclear double resonance (ENDOR) spectroscopy to study and compare their characteristics for wild-type (WT) P450 2B4 and the F429H mutant. (i) The addition of an H-bond to the axial Cys436 thiolate significantly changes the EPR signals of both low-spin and high-spin heme-iron(III) and the hyperfine couplings of the heme-pyrrole (14)N but has relatively little effect on the (1)H ENDOR spectra of the water ligand in the six-coordinate low-spin ferriheme state. These changes indicate that the H-bond introduced between His and the proximal cysteine decreases the extent of S → Fe electron donation and weakens the Fe(III)-S bond. (ii) The added H-bond changes the primary product of cryoreduction of the Fe(II) enzyme, which is trapped in the conformation of the parent Fe(II) state. In the wild-type enzyme, the added electron localizes on the porphyrin, generating an S = (3)/2 state with the anion radical exchange-coupled to the Fe(II). In the mutant, it localizes on the iron, generating an S = (1)/2 Fe(I) state. (iii) The additional H-bond has little effect on g values and (1)H-(14)N hyperfine couplings of the cryogenerated, ferric hydroperoxo intermediate but noticeably slows its decay during cryoannealing. (iv) In both the WT and the mutant enzyme, this decay shows a significant solvent kinetic isotope effect, indicating that the decay reflects a proton-assisted conversion to Compound I (Cpd I). (v) We confirm that Cpd I formed during the annealing of the cryogenerated hydroperoxy intermediate and that it is the active hydroxylating species in both WT P450 2B4 and the F429H mutant. (vi) Our data also indicate that the added H-bond of the mutation diminishes the reactivity of Cpd I.
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Affiliation(s)
- Roman Davydov
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Sangchoul Im
- Department of Anesthesiology, University of Michigan, and VA Medical Center , 2215 Fuller Road, Ann Arbor, Michigan 48105, United States
| | - Muralidharan Shanmugam
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - William A Gunderson
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Naw May Pearl
- Department of Anesthesiology, University of Michigan, and VA Medical Center , 2215 Fuller Road, Ann Arbor, Michigan 48105, United States
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Lucy Waskell
- Department of Anesthesiology, University of Michigan, and VA Medical Center , 2215 Fuller Road, Ann Arbor, Michigan 48105, United States
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Petrik ID, Davydov R, Ross M, Zhao X, Hoffman B, Lu Y. Spectroscopic and Crystallographic Evidence for the Role of a Water-Containing H-Bond Network in Oxidase Activity of an Engineered Myoglobin. J Am Chem Soc 2016; 138:1134-7. [PMID: 26716352 PMCID: PMC4750474 DOI: 10.1021/jacs.5b12004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Heme-copper oxidases (HCOs) catalyze efficient reduction of oxygen to water in biological respiration. Despite progress in studying native enzymes and their models, the roles of non-covalent interactions in promoting this activity are still not well understood. Here we report EPR spectroscopic studies of cryoreduced oxy-F33Y-CuBMb, a functional model of HCOs engineered in myoglobin (Mb). We find that cryoreduction at 77 K of the O2-bound form, trapped in the conformation of the parent oxyferrous form, displays a ferric-hydroperoxo EPR signal, in contrast to the cryoreduced oxy-wild-type (WT) Mb, which is unable to deliver a proton and shows a signal from the peroxo-ferric state. Crystallography of oxy-F33Y-CuBMb reveals an extensive H-bond network involving H2O molecules, which is absent from oxy-WTMb. This H-bonding proton-delivery network is the key structural feature that transforms the reversible oxygen-binding protein, WTMb, into F33Y-CuBMb, an oxygen-activating enzyme that reduces O2 to H2O. These results provide direct evidence of the importance of H-bond networks involving H2O in conferring enzymatic activity to a designed protein. Incorporating such extended H-bond networks in designing other metalloenzymes may allow us to confer and fine-tune their enzymatic activities.
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Affiliation(s)
- Igor D Petrik
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Roman Davydov
- The Department of Chemistry, Northwestern University , Evanston, Illinois 60201, United States
| | - Matthew Ross
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.,The Department of Chemistry, Northwestern University , Evanston, Illinois 60201, United States
| | - Xuan Zhao
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
| | - Brian Hoffman
- The Department of Chemistry, Northwestern University , Evanston, Illinois 60201, United States
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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Davydov R, Strushkevich N, Smil D, Yantsevich A, Gilep A, Usanov S, Hoffman BM. Evidence That Compound I Is the Active Species in Both the Hydroxylase and Lyase Steps by Which P450scc Converts Cholesterol to Pregnenolone: EPR/ENDOR/Cryoreduction/Annealing Studies. Biochemistry 2015; 54:7089-97. [PMID: 26603348 DOI: 10.1021/acs.biochem.5b00903] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytochrome P450scc (CYP 11A1) catalyzes the conversion of cholesterol (Ch) to pregnenolone, the precursor to steroid hormones. This process proceeds via three sequential monooxygenation reactions: two hydroxylations of Ch first form 22(R)-hydroxycholesterol (HC) and then 20α,22(R)-dihydroxycholesterol (DHC); a lyase reaction then cleaves the C20-C22 bond to form pregnenolone. Recent cryoreduction/annealing studies that employed electron paramagnetic resonance (EPR)/electron nuclear double resonance (ENDOR) spectroscopy [Davydov, R., et al. (2012) J. Am. Chem. Soc. 134, 17149] showed that compound I (Cpd I) is the active intermediate in the first step, hydroxylation of Ch. Herein, we have employed EPR and ENDOR spectroscopy to characterize the intermediates in the second and third steps of the enzymatic process, as conducted by 77 K radiolytic one-electron cryoreduction and subsequent annealing of the ternary oxy-cytochrome P450scc complexes with HC and DHC. This procedure is validated by showing that the cryoreduced ternary complexes of oxy-cytochrome P450scc with HC and DHC are catalytically competent and during annealing generate DHC and pregnenolone, respectively. Cryoreduction of the oxy-P450scc-HC ternary complex trapped at 77K produces the superoxo-ferrous P450scc intermediate along with a minor fraction of ferric hydroperoxo intermediates. The superoxo-ferrous intermediate converts into a ferric-hydroperoxo species after annealing at 145 K. During subsequent annealing at 170-180 K, the ferric-hydroperoxo intermediate converts to the primary product complex with the large solvent kinetic isotope effect that indicates Cpd I is being formed, and (1)H ENDOR measurements of the primary product formed in D2O demonstrate that Cpd I is the active species. They show that the primary product contains Fe(III) coordinated to the 20-O(1)H of DHC with the (1)H derived from substrate, the signature of the Cpd I reaction. Hydroperoxo ferric intermediates are the primary species formed during cryoreduction of the oxy-P450scc-DHC ternary complex, and they decay at 185 K with a strong solvent kinetic isotope effect to form low-spin ferric P450scc. Together, these observations indicated that Cpd I also is the active intermediate in the C20,22 lyase final step. In combination with our previous results, this study thus indicates that Cpd I is the active species in each of the three sequential monooxygenation reactions by which P450scc catalytically converts Ch to pregnenolone.
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Affiliation(s)
- Roman Davydov
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208-3113, United States
| | - Natallia Strushkevich
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus , Kuprevicha Street 5/2, Minsk 220141, Belarus
| | - David Smil
- Structural Genomics Consortium, University of Toronto , 101 College Street, Toronto, ON, Canada M5G 1L7
| | - Aliaksei Yantsevich
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus , Kuprevicha Street 5/2, Minsk 220141, Belarus
| | - Andrey Gilep
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus , Kuprevicha Street 5/2, Minsk 220141, Belarus
| | - Sergey Usanov
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus , Kuprevicha Street 5/2, Minsk 220141, Belarus
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208-3113, United States
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