1
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Poptic AL, Klinger JK, Carter SL, Moore CE, Zhang S. Nitrite Formation at a Diiron Dinitrosyl Complex. J Am Chem Soc 2023; 145:22993-22999. [PMID: 37815989 DOI: 10.1021/jacs.3c05155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/12/2023]
Abstract
Pathogenic bacteria employ iron-containing enzymes to detoxify nitric oxide (NO•) produced by mammals as part of their immune response. Two classes of diiron proteins, flavodiiron nitric oxide reductases (FNORs) and the hemerythrin-like proteins from mycobacteria (HLPs), are upregulated in bacteria in response to an increased local NO• concentration. While FNORs reduce NO• to nitrous oxide (N2O), the HLPs have been found to either reduce nitrite to NO• (YtfE), or oxidize NO• to nitrite (Mka-HLP). Various structural and functional models of the diiron site in FNORs have been developed over the years. However, the NO• oxidation reactivity of Mka-HLP has yet to be replicated with a synthetic complex. Compared to the FNORs, the coordination environment of the diiron site in Mka-HLP contains one less carboxylate ligand and, therefore, is expected to be more electron-poor. Herein, we synthesized a new diiron complex that models the electron-poor coordination environment of the Mka-HLP diiron site. The diferrous precursor FeIIFeII reacts with NO• to form a diiron dinitrosyl species ({FeNO}72), which is in equilibrium with a mononitrosyl diiron species (FeII{FeNO}7) in solution. Both complexes can be isolated and fully characterized. However, only oxidation of {FeNO}72 produced nitrite in high yield (71%). Our study provides the first model that reproduces the NO• oxidase reactivity of Mka-HLP and suggests intermediacy of an {FeNO}6/{FeNO}7 species.
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Affiliation(s)
- Anna L Poptic
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio43210, United States
| | - Jeffrey K Klinger
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio43210, United States
| | - Samantha L Carter
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio43210, United States
| | - Curtis E Moore
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio43210, United States
| | - Shiyu Zhang
- Department of Chemistry & Biochemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio43210, United States
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2
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Takeda H, Shimba K, Horitani M, Kimura T, Nomura T, Kubo M, Shiro Y, Tosha T. Trapping of a Mononitrosyl Nonheme Intermediate of Nitric Oxide Reductase by Cryo-Photolysis of Caged Nitric Oxide. J Phys Chem B 2023; 127:846-854. [PMID: 36602896 DOI: 10.1021/acs.jpcb.2c05852] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Characterization of short-lived reaction intermediates is essential for elucidating the mechanism of the reaction catalyzed by metalloenzymes. Here, we demonstrated that the photolysis of a caged compound under cryogenic temperature followed by thermal annealing is an invaluable technique for trapping of short-lived reaction intermediates of metalloenzymes through the study of membrane-integrated nitric oxide reductase (NOR) that catalyzes reductive coupling of two NO molecules to N2O at its heme/nonheme FeB binuclear center. Although NO produced by the photolysis of caged NO did not react with NOR under cryogenic temperature, annealing to ∼160 K allowed NO to diffuse and react with NOR, which was evident from the appearance of EPR signals assignable to the S = 3/2 state. This indicates that the nonheme FeB-NO species can be trapped as the intermediate. Time-resolved IR spectroscopy with the use of the photolysis of caged NO as a reaction trigger showed that the intermediate formed at 10 μs gave the NO stretching frequency at 1683 cm-1 typical of nonheme Fe-NO, confirming that the combination of the cryo-photolysis of caged NO and annealing enabled us to trap the reaction intermediate. Thus, the cryo-photolysis of the caged compound has great potential for the characterization of short-lived reaction intermediates.
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Affiliation(s)
- Hanae Takeda
- Graduate School of Life Science, University of Hyogo, Ako, Hyogo 678-1297, Japan.,RIKEN SPring-8 center, Sayo, Hyogo 679-5148, Japan
| | - Kanji Shimba
- Graduate School of Life Science, University of Hyogo, Ako, Hyogo 678-1297, Japan.,RIKEN SPring-8 center, Sayo, Hyogo 679-5148, Japan
| | - Masaki Horitani
- Department of Applied Biochemistry & Food Science, Saga University, Saga 840-8502, Japan.,The United Graduate School of Agricultural Science, Kagoshima University, 1-21-24 Korimoto, Kagoshima 890-0065, Japan
| | - Tetsunari Kimura
- Department of Chemistry, Graduate School of Science, Kobe University, Kobe 657-8501, Japan
| | - Takashi Nomura
- Graduate School of Life Science, University of Hyogo, Ako, Hyogo 678-1297, Japan
| | - Minoru Kubo
- Graduate School of Life Science, University of Hyogo, Ako, Hyogo 678-1297, Japan
| | - Yoshitsugu Shiro
- Graduate School of Life Science, University of Hyogo, Ako, Hyogo 678-1297, Japan
| | - Takehiko Tosha
- Graduate School of Life Science, University of Hyogo, Ako, Hyogo 678-1297, Japan.,RIKEN SPring-8 center, Sayo, Hyogo 679-5148, Japan
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3
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Bhadra M, Albert T, Franke A, Josef V, Ivanović-Burmazović I, Swart M, Moënne-Loccoz P, Karlin KD. Reductive Coupling of Nitric Oxide by Cu(I): Stepwise Formation of Mono- and Dinitrosyl Species En Route to a Cupric Hyponitrite Intermediate. J Am Chem Soc 2023; 145:2230-2242. [PMID: 36652374 PMCID: PMC10122266 DOI: 10.1021/jacs.2c09874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Transition-metal-mediated reductive coupling of nitric oxide (NO(g)) to nitrous oxide (N2O(g)) has significance across the fields of industrial chemistry, biochemistry, medicine, and environmental health. Herein, we elucidate a density functional theory (DFT)-supplemented mechanism of NO(g) reductive coupling at a copper-ion center, [(tmpa)CuI(MeCN)]+ (1) {tmpa = tris(2-pyridylmethyl)amine}. At -110 °C in EtOH (<-90 °C in MeOH), exposing 1 to NO(g) leads to a new binuclear hyponitrite intermediate [{(tmpa)CuII}2(μ-N2O22-)]2+ (2), exhibiting temperature-dependent irreversible isomerization to the previously characterized κ2-O,O'-trans-[(tmpa)2Cu2II(μ-N2O22-)]2+ (OOXray) complex. Complementary stopped-flow kinetic analysis of the reaction in MeOH reveals an initial mononitrosyl species [(tmpa)Cu(NO)]+ (1-(NO)) that binds a second NO molecule, forming a dinitrosyl species [(tmpa)CuII(NO)2] (1-(NO)2). The decay of 1-(NO)2 requires an available starting complex 1 to form a dicopper-dinitrosyl species hypothesized to be [{(tmpa)Cu}2(μ-NO)2]2+ (D) bearing a diamond-core motif, en route to the formation of hyponitrite intermediate 2. In contrast, exposing 1 to NO(g) in 2-MeTHF/THF (v/v 4:1) at <-80 °C leads to the newly observed transient metastable dinitrosyl species [(tmpa)CuII(NO)2] (1-(NO)2) prior to its disproportionation-mediated transformation to the nitrite product [(tmpa)CuII(NO2)]+. Our study furnishes a near-complete profile of NO(g) activation at a reduced Cu site with tripodal tetradentate ligation in two distinctly different solvents, aided by detailed spectroscopic characterization of metastable intermediates, including resonance Raman characterization of the new dinitrosyl and hyponitrite species detected.
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Affiliation(s)
- Mayukh Bhadra
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Alicja Franke
- Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nuremberg, 91058 Erlangen, Germany
- Department of Chemistry, Ludwig-Maximilians University, Munich, 81377 Munich, Germany
| | - Verena Josef
- Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nuremberg, 91058 Erlangen, Germany
| | - Ivana Ivanović-Burmazović
- Department of Chemistry and Pharmacy, Friedrich-Alexander University Erlangen-Nuremberg, 91058 Erlangen, Germany
- Department of Chemistry, Ludwig-Maximilians University, Munich, 81377 Munich, Germany
| | - Marcel Swart
- IQCC & Departament de Química, Universitat de Girona, Campus Montilivi (Ciencies), 17003 Girona, Spain
- ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, Oregon 97239, United States
| | - Kenneth D Karlin
- Department of Chemistry, The Johns Hopkins University, Baltimore, Maryland 21218, United States
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4
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Transue WJ, Snyder RA, Caranto JD, Kurtz DM, Solomon EI. Particle Swarm Fitting of Spin Hamiltonians: Magnetic Circular Dichroism of Reduced and NO-Bound Flavodiiron Protein. Inorg Chem 2022; 61:16520-16527. [PMID: 36223761 PMCID: PMC9942269 DOI: 10.1021/acs.inorgchem.2c02234] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A particle swarm optimization (PSO) algorithm is described for the fitting of ground-state spin Hamiltonian parameters from variable-temperature/variable-field (VTVH) magnetic circular dichroism (MCD) data. This PSO algorithm is employed to define the ground state of two catalytic intermediates from a flavodiiron protein (FDP), a class of enzymes with nitric oxide reductase activity. The bimetallic iron active site of this enzyme proceeds through a biferrous intermediate and a mixed ferrous-{FeNO}7 intermediate during the catalytic cycle, and the MCD spectra of these intermediates are presented and analyzed. The fits of the spin Hamiltonians are shown to provide important geometric and electronic insight into these species that is compared and contrasted with previous reports.
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Affiliation(s)
| | - Rae Ana Snyder
- Department of Chemistry, Stanford University, Stanford, CA 94305
| | - Jonathan D. Caranto
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Donald M. Kurtz
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
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5
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Dey A, Albert T, Kong RY, Macmillan SN, Moënne-Loccoz P, Lancaster KM, Goldberg DP. Direct Reduction of NO to N 2O by a Mononuclear Nonheme Thiolate Ligated Iron(II) Complex via Formation of a Metastable {FeNO} 7 Complex. Inorg Chem 2022; 61:14909-14917. [PMID: 36107151 PMCID: PMC9555345 DOI: 10.1021/acs.inorgchem.2c02383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Addition of NO to a nonheme dithiolate-ligated iron(II) complex, FeII(Me3TACN)(S2SiMe2) (1), results in the generation of N2O. Low-temperature spectroscopic studies reveal a metastable six-coordinate {FeNO}7 intermediate (S = 3/2) that was trapped at -135 °C and was characterized by low-temperature UV-vis, resonance Raman, EPR, Mössbauer, XAS, and DFT studies. Thermal decay of the {FeNO}7 species leads to the evolution of N2O, providing a rare example of a mononuclear thiolate-ligated {FeNO}7 that mediates NO reduction to N2O without the requirement of any exogenous electron or proton sources.
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Affiliation(s)
- Aniruddha Dey
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218, United States
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR 97239, Unites States
| | - Richard Y. Kong
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, Unites States
| | - Samantha N. Macmillan
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, Unites States
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR 97239, Unites States
| | - Kyle M. Lancaster
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, Unites States
| | - David P. Goldberg
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD 21218, United States
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6
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Albert T, Moënne-Loccoz P. Spectroscopic Characterization of a Diferric Mycobacterial Hemerythrin-Like Protein with Unprecedented Reactivity toward Nitric Oxide. J Am Chem Soc 2022; 144:17611-17621. [PMID: 36099449 DOI: 10.1021/jacs.2c07113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hemerythrin-like proteins (HLPs) are broadly distributed across taxonomic groups and appear to play highly diverse functional roles in prokaryotes. Mycobacterial HLPs contribute to the survival of these pathogenic bacteria in mammalian macrophages, but their modes of action remain unclear. A recent crystallographic characterization of Mycobacterium kansasii HLP (Mka-HLP) revealed the unexpected presence of a tyrosine sidechain (Tyr54) near the coordination sphere of one of the two iron centers. Here, we show that Tyr54 is a true ligand to the Fe2(III) ion which, in conjunction with the presence of a μ-oxo group bridging the two iron(III), brings unique reactivity toward nitric oxide (NO). Monitoring the titration of Mka-HLP with NO by Fourier-transform infrared and electron paramagnetic resonance spectroscopies shows that both diferric and diferrous forms of Mka-HLP accumulate an uncoupled high-spin and low-spin {FeNO}7 pair. We assign the reactivity of the diferric protein to an initial radical reaction between NO and the μ-oxo bridge to form nitrite and a mixed-valent diiron center that can react further with NO. Amperometric measurements of NO consumption by Mka-HLP confirm that this reactivity can proceed at low micromolar concentrations of NO, before additional NO consumption, supporting a NO scavenging role for mycobacterial HLPs.
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Affiliation(s)
- Therese Albert
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, School of Medicine, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, Oregon 97239, United States
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7
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Dong HT, Camarena S, Sil D, Lengel MO, Zhao J, Hu MY, Alp EE, Krebs C, Lehnert N. What Is the Right Level of Activation of a High-Spin {FeNO} 7 Complex to Enable Direct N-N Coupling? Mechanistic Insight into Flavodiiron NO Reductases. J Am Chem Soc 2022; 144:16395-16409. [PMID: 36040133 DOI: 10.1021/jacs.2c04292] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Flavodiiron nitric oxide reductases (FNORs), found in pathogenic bacteria, are capable of reducing nitric oxide (NO) to nitrous oxide (N2O) to detoxify NO released by the human immune system. Previously, we reported the first FNOR model system that mediates direct NO reduction (Dong, H. T.; J. Am. Chem. Soc. 2018, 140, 13429-13440), but no intermediate of the reaction could be characterized. Here, we present a new set of model complexes that, depending on the ligand substitution, can either mediate direct NO reduction or stabilize a highly activated high-spin (hs) {FeNO}7 complex, the first intermediate of the reaction. The precursors, [{FeII(MPA-(RPhO)2)}2] (1, R = H and 2, R = tBu, Me), were prepared first and fully characterized. Complex 1 (without steric protection) directly reduces NO to N2O almost quantitatively, which constitutes only the second example of this reaction in model systems. Contrarily, the reaction of sterically protected 2 with NO forms the stable mononitrosyl complex 3, which shows one of the lowest N-O stretching frequencies (1689 cm-1) observed so far for a mononuclear hs-{FeNO}7 complex. This study confirms that an N-O stretch ≤1700 cm-1 represents the appropriate level of activation of the FeNO unit to enable direct NO reduction. The higher activation level of these hs-{FeNO}7 complexes required for NO reduction compared to those formed in FNORs emphasizes the importance of hydrogen bonding residues in the active sites of FNORs to activate the bound NO ligands for direct N-N coupling and N2O formation. The implications of these results for FNORs are further discussed.
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Affiliation(s)
| | | | - Debangsu Sil
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
| | | | - Jiyong Zhao
- Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, Illinois 60439, United States
| | - Michael Y Hu
- Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, Illinois 60439, United States
| | - E Ercan Alp
- Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, Illinois 60439, United States
| | - Carsten Krebs
- Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.,Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, United States
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8
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Repair of Iron Center Proteins—A Different Class of Hemerythrin-like Proteins. Molecules 2022; 27:molecules27134051. [PMID: 35807291 PMCID: PMC9268430 DOI: 10.3390/molecules27134051] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/14/2022] [Accepted: 06/17/2022] [Indexed: 01/27/2023] Open
Abstract
Repair of Iron Center proteins (RIC) form a family of di-iron proteins that are widely spread in the microbial world. RICs contain a binuclear nonheme iron site in a four-helix bundle fold, two basic features of hemerythrin-like proteins. In this work, we review the data on microbial RICs including how their genes are regulated and contribute to the survival of pathogenic bacteria. We gathered the currently available biochemical, spectroscopic and structural data on RICs with a particular focus on Escherichia coli RIC (also known as YtfE), which remains the best-studied protein with extensive biochemical characterization. Additionally, we present novel structural data for Escherichia coli YtfE harboring a di-manganese site and the protein’s affinity for this metal. The networking of protein interactions involving YtfE is also described and integrated into the proposed physiological role as an iron donor for reassembling of stress-damaged iron-sulfur centers.
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9
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Matsumura H, Faponle AS, Hagedoorn PL, Tosha T, de Visser SP, Moënne-Loccoz P. Mechanism of substrate inhibition in cytochrome-c dependent NO reductases from denitrifying bacteria (cNORs). J Inorg Biochem 2022; 231:111781. [DOI: 10.1016/j.jinorgbio.2022.111781] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Revised: 02/21/2022] [Accepted: 02/24/2022] [Indexed: 12/24/2022]
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10
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Kametani Y, Abe T, Yoshizawa K, Shiota Y. Mechanistic study on reduction of nitric oxide to nitrous oxide using a dicopper complex. Dalton Trans 2022; 51:5399-5403. [PMID: 35316312 DOI: 10.1039/d2dt00275b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A density functional theory study was carried out to investigate the reduction mechanisms of NO to N2O using a dicopper complex reported by Zhang and coworkers (J. Am. Chem. Soc., 2019, 141, 10159-10164). The reaction mechanism consists of three steps: N-N bond formation, isomerization of the resultant N2O2 moiety, and cleavage of the N-O bond.
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Affiliation(s)
- Yohei Kametani
- Institute for Materials Chemistry and Engineering and IRCCS, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan.
| | - Tsukasa Abe
- Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Kazunari Yoshizawa
- Institute for Materials Chemistry and Engineering and IRCCS, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan.
| | - Yoshihito Shiota
- Institute for Materials Chemistry and Engineering and IRCCS, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka, Japan.
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11
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Lehnert N, Kim E, Dong HT, Harland JB, Hunt AP, Manickas EC, Oakley KM, Pham J, Reed GC, Alfaro VS. The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity. Chem Rev 2021; 121:14682-14905. [PMID: 34902255 DOI: 10.1021/acs.chemrev.1c00253] [Citation(s) in RCA: 92] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nitric oxide (NO) is an important signaling molecule that is involved in a wide range of physiological and pathological events in biology. Metal coordination chemistry, especially with iron, is at the heart of many biological transformations involving NO. A series of heme proteins, nitric oxide synthases (NOS), soluble guanylate cyclase (sGC), and nitrophorins, are responsible for the biosynthesis, sensing, and transport of NO. Alternatively, NO can be generated from nitrite by heme- and copper-containing nitrite reductases (NIRs). The NO-bearing small molecules such as nitrosothiols and dinitrosyl iron complexes (DNICs) can serve as an alternative vehicle for NO storage and transport. Once NO is formed, the rich reaction chemistry of NO leads to a wide variety of biological activities including reduction of NO by heme or non-heme iron-containing NO reductases and protein post-translational modifications by DNICs. Much of our understanding of the reactivity of metal sites in biology with NO and the mechanisms of these transformations has come from the elucidation of the geometric and electronic structures and chemical reactivity of synthetic model systems, in synergy with biochemical and biophysical studies on the relevant proteins themselves. This review focuses on recent advancements from studies on proteins and model complexes that not only have improved our understanding of the biological roles of NO but also have provided foundations for biomedical research and for bio-inspired catalyst design in energy science.
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Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Eunsuk Kim
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Hai T Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Jill B Harland
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Andrew P Hunt
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Elizabeth C Manickas
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Kady M Oakley
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - John Pham
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Garrett C Reed
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Victor Sosa Alfaro
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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12
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Dey A, Gordon JB, Albert T, Sabuncu S, Siegler MA, MacMillan SN, Lancaster KM, Moënne‐Loccoz P, Goldberg DP. A Nonheme Mononuclear {FeNO}
7
Complex that Produces N
2
O in the Absence of an Exogenous Reductant. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202109062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Aniruddha Dey
- Department of Chemistry The Johns Hopkins University Baltimore MD 21218 USA
| | - Jesse B. Gordon
- Department of Chemistry The Johns Hopkins University Baltimore MD 21218 USA
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry Oregon Health & Science University Portland OR 97239 USA
| | - Sinan Sabuncu
- Department of Chemical Physiology and Biochemistry Oregon Health & Science University Portland OR 97239 USA
| | - Maxime A. Siegler
- Department of Chemistry The Johns Hopkins University Baltimore MD 21218 USA
| | | | - Kyle M. Lancaster
- Department of Chemistry and Chemical Biology Cornell University Ithaca NY 14853 USA
| | - Pierre Moënne‐Loccoz
- Department of Chemical Physiology and Biochemistry Oregon Health & Science University Portland OR 97239 USA
| | - David P. Goldberg
- Department of Chemistry The Johns Hopkins University Baltimore MD 21218 USA
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13
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Dey A, Gordon JB, Albert T, Sabuncu S, Siegler MA, MacMillan SN, Lancaster KM, Moënne-Loccoz P, Goldberg DP. A Nonheme Mononuclear {FeNO} 7 Complex that Produces N 2 O in the Absence of an Exogenous Reductant. Angew Chem Int Ed Engl 2021; 60:21558-21564. [PMID: 34415659 DOI: 10.1002/anie.202109062] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Indexed: 11/09/2022]
Abstract
A new nonheme iron(II) complex, FeII (Me3 TACN)((OSiPh2 )2 O) (1), is reported. Reaction of 1 with NO(g) gives a stable mononitrosyl complex Fe(NO)(Me3 TACN)((OSiPh2 )2 O) (2), which was characterized by Mössbauer (δ=0.52 mm s-1 , |ΔEQ |=0.80 mm s-1 ), EPR (S=3/2), resonance Raman (RR) and Fe K-edge X-ray absorption spectroscopies. The data show that 2 is an {FeNO}7 complex with an S=3/2 spin ground state. The RR spectrum (λexc =458 nm) of 2 combined with isotopic labeling (15 N, 18 O) reveals ν(N-O)=1680 cm-1 , which is highly activated, and is a nearly identical match to that seen for the reactive mononitrosyl intermediate in the nonheme iron enzyme FDPnor (ν(NO)=1681 cm-1 ). Complex 2 reacts rapidly with H2 O in THF to produce the N-N coupled product N2 O, providing the first example of a mononuclear nonheme iron complex that is capable of converting NO to N2 O in the absence of an exogenous reductant.
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Affiliation(s)
- Aniruddha Dey
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Jesse B Gordon
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Therese Albert
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Sinan Sabuncu
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Maxime A Siegler
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD, 21218, USA
| | - Samantha N MacMillan
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Pierre Moënne-Loccoz
- Department of Chemical Physiology and Biochemistry, Oregon Health & Science University, Portland, OR, 97239, USA
| | - David P Goldberg
- Department of Chemistry, The Johns Hopkins University, Baltimore, MD, 21218, USA
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14
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Pal N, Jana M, Majumdar A. Reduction of NO by diiron complexes in relation to flavodiiron nitric oxide reductases. Chem Commun (Camb) 2021; 57:8682-8698. [PMID: 34373873 DOI: 10.1039/d1cc03149j] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Reduction of nitric oxide (NO) to nitrous oxide (N2O) is associated with immense biological and health implications. Flavodiiron nitric oxide reductases (FNORs) are diiron containing enzymes that catalyze the two electron reduction of NO to N2O and help certain pathogenic bacteria to survive under "nitrosative stress" in anaerobic growth conditions. Consequently, invading bacteria can proliferate inside the body of mammals by bypassing the immune defense mechanism involving NO and may thus lead to harmful infections. Various mechanisms, namely the direct reduction, semireduction, superreduction and hyponitrite mechanisms, have been proposed over time for catalytic NO reduction by FNORs. Model studies in relation to the diiron active site of FNORs have immensely helped to replicate the minimal structure-reactivity relationship and to understand the mechanism of NO reduction. A brief overview of the FNOR activity and the proposed reaction mechanisms followed by a systematic description and detailed analysis of the model studies is presented, which describes the development in the area of NO reduction by diiron complexes and its implications. A great deal of successful modeling chemistry as well as the shortcomings related to the synthesis and reactivity studies is discussed in detail. Finally, future prospects in this particular area of research are proposed, which in due course may bring more clarity in the understanding of this important redox reaction.
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Affiliation(s)
- Nabhendu Pal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Kolkata 700032, India.
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15
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The Amino Acids Motif -32GSSYN36- in the Catalytic Domain of E. coli Flavorubredoxin NO Reductase Is Essential for Its Activity. Catalysts 2021. [DOI: 10.3390/catal11080926] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Flavodiiron proteins (FDPs) are a family of modular and soluble enzymes endowed with nitric oxide and/or oxygen reductase activities, producing N2O or H2O, respectively. The FDP from Escherichia coli, which, apart from the two core domains, possesses a rubredoxin-like domain at the C-terminus (therefore named flavorubredoxin (FlRd)), is a bona fide NO reductase, exhibiting O2 reducing activity that is approximately ten times lower than that for NO. Among the flavorubredoxins, there is a strictly conserved amino acids motif, -G[S,T]SYN-, close to the catalytic diiron center. To assess its role in FlRd’s activity, we designed several site-directed mutants, replacing the conserved residues with hydrophobic or anionic ones. The mutants, which maintained the general characteristics of the wild type enzyme, including cofactor content and integrity of the diiron center, revealed a decrease of their oxygen reductase activity, while the NO reductase activity—specifically, its physiological function—was almost completely abolished in some of the mutants. Molecular modeling of the mutant proteins pointed to subtle changes in the predicted structures that resulted in the reduction of the hydration of the regions around the conserved residues, as well as in the elimination of hydrogen bonds, which may affect proton transfer and/or product release.
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16
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Ferousi C, Majer SH, DiMucci IM, Lancaster KM. Biological and Bioinspired Inorganic N-N Bond-Forming Reactions. Chem Rev 2020; 120:5252-5307. [PMID: 32108471 PMCID: PMC7339862 DOI: 10.1021/acs.chemrev.9b00629] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
The metallobiochemistry underlying the formation of the inorganic N-N-bond-containing molecules nitrous oxide (N2O), dinitrogen (N2), and hydrazine (N2H4) is essential to the lifestyles of diverse organisms. Similar reactions hold promise as means to use N-based fuels as alternative carbon-free energy sources. This review discusses research efforts to understand the mechanisms underlying biological N-N bond formation in primary metabolism and how the associated reactions are tied to energy transduction and organismal survival. These efforts comprise studies of both natural and engineered metalloenzymes as well as synthetic model complexes.
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Affiliation(s)
- Christina Ferousi
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Sean H Majer
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Ida M DiMucci
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
| | - Kyle M Lancaster
- Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853, United States
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17
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Jana M, White CJ, Pal N, Demeshko S, Cordes (née Kupper) C, Meyer F, Lehnert N, Majumdar A. Functional Models for the Mono- and Dinitrosyl Intermediates of FNORs: Semireduction versus Superreduction of NO. J Am Chem Soc 2020; 142:6600-6616. [DOI: 10.1021/jacs.9b13795] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Manish Jana
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
| | - Corey J. White
- Department of Chemistry, The University of Michigan, 930 N. University Avenue, Ann Arbor 48109, Michigan, United States
| | - Nabhendu Pal
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
| | - Serhiy Demeshko
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstraße 4, Göttingen 37077, Germany
| | | | - Franc Meyer
- Institut für Anorganische Chemie, Georg-August-Universität, Tammannstraße 4, Göttingen 37077, Germany
| | - Nicolai Lehnert
- Department of Chemistry, The University of Michigan, 930 N. University Avenue, Ann Arbor 48109, Michigan, United States
| | - Amit Majumdar
- School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
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18
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Lehnert N, Fujisawa K, Camarena S, Dong HT, White CJ. Activation of Non-Heme Iron-Nitrosyl Complexes: Turning Up the Heat. ACS Catal 2019. [DOI: 10.1021/acscatal.9b03219] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Kiyoshi Fujisawa
- Department of Chemistry, Ibaraki University, Mito 310-8512, Japan
| | - Stephanie Camarena
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Hai T. Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Corey J. White
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
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19
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Bikas R, Ajormal F, Emami M, Sanchiz J, Noshiranzadeh N, Kozakiewicz A. Crystal structure and magneto-structural investigation of alkoxido bridged dinuclear Fe(III) complexes with 1,3-oxazolidine ligands. Polyhedron 2019. [DOI: 10.1016/j.poly.2019.01.035] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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20
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Lu J, Bi B, Lai W, Chen H. Origin of Nitric Oxide Reduction Activity in Flavo–Diiron NO Reductase: Key Roles of the Second Coordination Sphere. Angew Chem Int Ed Engl 2019; 58:3795-3799. [DOI: 10.1002/anie.201812343] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2018] [Revised: 01/27/2019] [Indexed: 12/21/2022]
Affiliation(s)
- Jiarui Lu
- Beijing National Laboratory for Molecular Sciences (BNLMS)CAS Key Laboratory of PhotochemistryCAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
- Department of ChemistryRenmin University of China Beijing 100872 China
| | - Bo Bi
- Beijing National Laboratory for Molecular Sciences (BNLMS)CAS Key Laboratory of PhotochemistryCAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
- University of Chinese Academy of Sciences Beijing 100049 China
| | - Wenzhen Lai
- Department of ChemistryRenmin University of China Beijing 100872 China
| | - Hui Chen
- Beijing National Laboratory for Molecular Sciences (BNLMS)CAS Key Laboratory of PhotochemistryCAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
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21
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Emami M, Bikas R, Noshiranzadeh N, Sanchiz J, Ślepokura K, Lis T. Synthesis, characterization and magnetic properties of phenoxido bridged dinuclear iron(III) complex with bis(phenolate) ligand. J Mol Struct 2019. [DOI: 10.1016/j.molstruc.2018.12.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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22
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Lu J, Bi B, Lai W, Chen H. Origin of Nitric Oxide Reduction Activity in Flavo–Diiron NO Reductase: Key Roles of the Second Coordination Sphere. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201812343] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Jiarui Lu
- Beijing National Laboratory for Molecular Sciences (BNLMS)CAS Key Laboratory of PhotochemistryCAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
- Department of ChemistryRenmin University of China Beijing 100872 China
| | - Bo Bi
- Beijing National Laboratory for Molecular Sciences (BNLMS)CAS Key Laboratory of PhotochemistryCAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
- University of Chinese Academy of Sciences Beijing 100049 China
| | - Wenzhen Lai
- Department of ChemistryRenmin University of China Beijing 100872 China
| | - Hui Chen
- Beijing National Laboratory for Molecular Sciences (BNLMS)CAS Key Laboratory of PhotochemistryCAS Research/Education Center for Excellence in Molecular SciencesInstitute of ChemistryChinese Academy of Sciences Beijing 100190 China
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23
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Weitz AC, Giri N, Frederick RE, Kurtz DM, Bominaar EL, Hendrich MP. Spectroscopy and DFT Calculations of Flavo-Diiron Nitric Oxide Reductase Identify Bridging Structures of NO-Coordinated Diiron Intermediates. ACS Catal 2018; 8:11704-11715. [PMID: 31263628 PMCID: PMC6602092 DOI: 10.1021/acscatal.8b03051] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Flavo-diiron proteins (FDPs) are widespread in anaerobic bacteria, archaea, and protozoa, where they serve as the terminal components of dioxygen and nitric oxide reductive scavenging pathways. FDPs contain an N,O-ligated diiron site adjacent to a flavin mononucleotide (FMN) cofactor. The diiron site is structurally similar to those in hemerythrin, ribonucleotide reductase, and methane monooxygenase. However, only FDPs turn over NO to N2O at significant rates and yields. Previous studies revealed sequential binding of two NO molecules to the diferrous site, forming mono- and dinitrosyl intermediates leading to N2O formation. In the present work, these mono- and dinitrosyl intermediates have been characterized by EPR and Mössbauer spectroscopies and DFT calculations. Our results show that the iron proximal to the cofactor binds the first NO to form the diiron mononitrosyl complex, implying the iron distal to the FMN binds the second NO to form the diiron dinitrosyl intermediate. The exchange-coupling constants, J (H = JS1·S2), were found to differ substantially, +17 cm-1 for the diiron mononitrosyl and +60 cm-1 for the diiron dinitrosyl. Notwithstanding this large difference, our findings indicate retention of at least one hydroxo bridge throughout the NOR catalytic cycle. The Mossbauer hyperfine parameters and DFT calculations confirmed a semibridging NO- ligand in the mononitrosyl intermediate that lowers the exchange parameter. The DFT calculations on the dinitrosyl intermediate suggest a contribution to J from direct exchange between the S = 1 spins on the NO- ligands, which could initiate N-N bond formation. Our results provide insight into why FDPs are the only known nonheme diiron enzymes that competently turn over NO to N2O.
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Affiliation(s)
- Andrew C. Weitz
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Nitai Giri
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Rosanne E. Frederick
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Donald M. Kurtz
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Emile L. Bominaar
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Michael P. Hendrich
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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24
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Van Stappen C, Lehnert N. Mechanism of N–N Bond Formation by Transition Metal–Nitrosyl Complexes: Modeling Flavodiiron Nitric Oxide Reductases. Inorg Chem 2018; 57:4252-4269. [DOI: 10.1021/acs.inorgchem.7b02333] [Citation(s) in RCA: 42] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Casey Van Stappen
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055, United States
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25
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White CJ, Speelman AL, Kupper C, Demeshko S, Meyer F, Shanahan JP, Alp EE, Hu M, Zhao J, Lehnert N. The Semireduced Mechanism for Nitric Oxide Reduction by Non-Heme Diiron Complexes: Modeling Flavodiiron Nitric Oxide Reductases. J Am Chem Soc 2018; 140:2562-2574. [DOI: 10.1021/jacs.7b11464] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Corey J. White
- Department
of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Amy L. Speelman
- Department
of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Claudia Kupper
- Institut
für Anorganische Chemie, Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Serhiy Demeshko
- Institut
für Anorganische Chemie, Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - Franc Meyer
- Institut
für Anorganische Chemie, Universität Göttingen, Tammannstrasse
4, D-37077 Göttingen, Germany
| | - James P. Shanahan
- Department
of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - E. Ercan Alp
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Michael Hu
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Jiyong Zhao
- Advanced
Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
| | - Nicolai Lehnert
- Department
of Chemistry, The University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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26
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Jana M, Pal N, White CJ, Kupper C, Meyer F, Lehnert N, Majumdar A. Functional Mononitrosyl Diiron(II) Complex Mediates the Reduction of NO to N2O with Relevance for Flavodiiron NO Reductases. J Am Chem Soc 2017; 139:14380-14383. [DOI: 10.1021/jacs.7b08855] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Manish Jana
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
| | - Nabhendu Pal
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
| | - Corey J. White
- Department of Chemistry, The University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109, United States
| | - Claudia Kupper
- Institute of Inorganic Chemistry, University of Goettingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Franc Meyer
- Institute of Inorganic Chemistry, University of Goettingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Nicolai Lehnert
- Department of Chemistry, The University of Michigan, 930 N. University Ave., Ann Arbor, Michigan 48109, United States
| | - Amit Majumdar
- Department of Inorganic Chemistry, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata 700032, West Bengal, India
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27
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Weitz AC, Giri N, Caranto JD, Kurtz DM, Bominaar EL, Hendrich MP. Spectroscopy and DFT Calculations of a Flavo-diiron Enzyme Implicate New Diiron Site Structures. J Am Chem Soc 2017; 139:12009-12019. [PMID: 28756660 PMCID: PMC5898632 DOI: 10.1021/jacs.7b06546] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Flavo-diiron proteins (FDPs) are non-heme iron containing enzymes that are widespread in anaerobic bacteria, archaea, and protozoa, serving as the terminal components to dioxygen and nitric oxide reductive scavenging pathways in these organisms. FDPs contain a dinuclear iron active site similar to that in hemerythrin, ribonucleotide reductase, and methane monooxygenase, all of which can bind NO and O2. However, only FDP competently turns over NO to N2O. Here, EPR and Mössbauer spectroscopies allow electronic characterization of the diferric and diferrous species of FDP. The exchange-coupling constant J (Hex = JS1·S2) was found to increase from +20 cm-1 to +32 cm-1 upon reduction of the diferric to the diferrous species, indicative of (1) at least one hydroxo bridge between the iron ions for both states and (2) a change to the diiron core structure upon reduction. In comparison to characterized diiron proteins and synthetic complexes, the experimental values were consistent with a dihydroxo bridged diferric core, which loses one hydroxo bridge upon reduction. DFT calculations of these structures gave values of J and Mössbauer parameters in agreement with experiment. Although the crystal structure shows a hydrogen bond between the iron bound aspartate and the bridging solvent molecule, the DFT calculations of structures consistent with the crystal structure gave calculated values of J incompatible with the spectroscopic results. We conclude that the crystal structure of the diferric state does not represent the frozen solution structure and that a mono-μ-hydroxo diferrous species is the catalytically functional state that reacts with NO and O2. The new EPR spectroscopic probe of the diferric state indicated that the diferric structure of FDP prior to and immediately after turnover with NO are flavin mononucleotide (FMN) dependent, implicating an additional proton transfer role for FMN in turnover of NO.
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Affiliation(s)
- Andrew C. Weitz
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Nitai Giri
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Jonathan D. Caranto
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Donald M. Kurtz
- Department of Chemistry, University of Texas at San Antonio, San Antonio, Texas 78249, United States
| | - Emile L. Bominaar
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Michael P. Hendrich
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States
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28
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Kindermann N, Schober A, Demeshko S, Lehnert N, Meyer F. Reductive Transformations of a Pyrazolate-Based Bioinspired Diiron–Dinitrosyl Complex. Inorg Chem 2016; 55:11538-11550. [DOI: 10.1021/acs.inorgchem.6b02080] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Nicole Kindermann
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Anne Schober
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Serhiy Demeshko
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
| | - Nicolai Lehnert
- Department of Chemistry, The University of Michigan, 930 N. University
Avenue, Ann Arbor, Michigan 48109-1055, United States
| | - Franc Meyer
- Institut für Anorganische Chemie, Georg-August-Universität Göttingen, Tammannstraße 4, 37077 Göttingen, Germany
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29
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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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30
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Romão CV, Vicente JB, Borges PT, Frazão C, Teixeira M. The dual function of flavodiiron proteins: oxygen and/or nitric oxide reductases. J Biol Inorg Chem 2016; 21:39-52. [PMID: 26767750 DOI: 10.1007/s00775-015-1329-4] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2015] [Accepted: 12/28/2015] [Indexed: 12/27/2022]
Abstract
Flavodiiron proteins have emerged in the last two decades as a newly discovered family of oxygen and/or nitric oxide reductases widespread in the three life domains, and present in both aerobic and anaerobic organisms. Herein we present the main features of these fascinating enzymes, with a particular emphasis on the metal sites, as more appropriate for this special issue in memory of the exceptional bioinorganic scientist R. J. P. Williams who pioneered the notion of (metal) element availability-driven evolution. We also compare the flavodiiron proteins with the other oxygen and nitric oxide reductases known until now, highlighting how throughout evolution Nature arrived at different solutions for similar functions, in some cases adding extra features, such as energy conservation. These enzymes are an example of the (bioinorganic) unpredictable diversity of the living world.
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Affiliation(s)
- Célia V Romão
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal
| | - João B Vicente
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal
| | - Patrícia T Borges
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal
| | - Carlos Frazão
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal
| | - Miguel Teixeira
- Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Avenida da República (EAN), 2780-157, Oeiras, Portugal.
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31
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Yeh SW, Tsou CC, Liaw WF. The dinitrosyliron complex [Fe₄(μ₃-S)₂(μ₂-NO)₂(NO)₆]²⁻ containing bridging nitroxyls: ¹⁵N (NO) NMR analysis of the bridging and terminal NO-coordinate ligands. Dalton Trans 2015; 43:9022-5. [PMID: 24821662 DOI: 10.1039/c4dt00450g] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The fluxional terminal and semibridging NO-coordinate ligands of DNIC [Fe4(μ3-S)2(μ2-NO)2(NO)6](2-), a precursor of Roussin's black salt (RBS), are characterized by IR ν(NO), (15)N (NO) NMR and single-crystal X-ray diffraction.
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Affiliation(s)
- Shih-Wey Yeh
- Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
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32
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Affiliation(s)
- Ashley M. Wright
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Trevor W. Hayton
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
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Abstract
The coordination chemistry of metal nitrosyls has expanded rapidly in the past decades due to major advances of nitric oxide and its metal compounds in biology. This review article highlights advances made in the area of multinuclear metal nitrosyl complexes, including Roussin's salts and their ester derivatives from 2003 to present. The review article focuses on isolated multinuclear metal nitrosyl complexes and is organized into different sections by the number of metal centers and bridging ligands.
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34
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Frederick RE, Caranto JD, Masitas CA, Gebhardt LL, MacGowan CE, Limberger RJ, Kurtz DM. Dioxygen and nitric oxide scavenging by Treponema denticola flavodiiron protein: a mechanistic paradigm for catalysis. J Biol Inorg Chem 2015; 20:603-13. [PMID: 25700637 PMCID: PMC4768905 DOI: 10.1007/s00775-015-1248-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 02/13/2015] [Indexed: 10/24/2022]
Abstract
Flavodiiron proteins (FDPs) contain a unique active site consisting of a non-heme diiron carboxylate site proximal to a flavin mononucleotide (FMN). FDPs serve as the terminal components for reductive scavenging of dioxygen (to water) or nitric oxide (to nitrous oxide), which combats oxidative or nitrosative stress in many bacteria. Characterizations of FDPs from spirochetes or from any oral microbes have not been previously reported. Here, we report characterization of an FDP from the anaerobic spirochete, Treponema (T.) denticola, which is associated with chronic periodontitis. The isolated T. denticola FDP exhibited efficient four-electron dioxygen reductase activity and lower but significant anaerobic nitric oxide reductase activity. A mutant T. denticola strain containing the inactivated FDP-encoding gene was significantly more air-sensitive than the wild-type strain. Single turnover reactions of the four-electron-reduced FDP (FMNH2-Fe(II)Fe(II)) (FDPred) with O2 monitored on the milliseconds to seconds time scale indicated initial rapid formation of a spectral feature consistent with a cis-μ-1,2-peroxo-diferric intermediate, which triggered two-electron oxidation of FMNH2. Reaction of FDPred with NO showed apparent cooperativity between binding of the first and second NO to the diferrous site. The resulting diferrous dinitrosyl complex triggered two-electron oxidation of the FMNH2. Our cumulative results on this and other FDPs indicate that smooth two-electron FMNH2 oxidation triggered by the FDPred/substrate complex and overall four-electron oxidation of FDPred to FDPox constitutes a mechanistic paradigm for both dioxygen and nitric oxide reductase activities of FDPs. Four-electron reductive O2 scavenging by FDPs could contribute to oxidative stress protection in many other oral bacteria.
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Affiliation(s)
- Rosanne E. Frederick
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Jonathan D. Caranto
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Cesar A. Masitas
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
| | - Linda L. Gebhardt
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Charles E. MacGowan
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Ronald J. Limberger
- Wadsworth Center, New York State Department of Health, Albany, NY 12201, USA
| | - Donald M. Kurtz
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
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35
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Khatua S, Majumdar A. Flavodiiron nitric oxide reductases: Recent developments in the mechanistic study and model chemistry for the catalytic reduction of NO. J Inorg Biochem 2015; 142:145-53. [DOI: 10.1016/j.jinorgbio.2014.09.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Revised: 09/26/2014] [Accepted: 09/29/2014] [Indexed: 11/24/2022]
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36
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Attia AAA, Silaghi-Dumitrescu R. Super-Reduced Mechanism of Nitric Oxide Reduction in Flavo-Diiron NO Reductases. Eur J Inorg Chem 2014. [DOI: 10.1002/ejic.201402385] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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37
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Victor E, Minier MA, Lippard SJ. Synthesis and Characterization of a Linear Dinitrosyl‐Triiron Complex. Eur J Inorg Chem 2014. [DOI: 10.1002/ejic.201402543] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Eric Victor
- Department of Chemist, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA, USA 02139, http://web.mit.edu/lippardlab/
| | - Mikael A. Minier
- Department of Chemist, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA, USA 02139, http://web.mit.edu/lippardlab/
| | - Stephen J. Lippard
- Department of Chemist, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA, USA 02139, http://web.mit.edu/lippardlab/
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38
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Jiang Y, Hayashi T, Matsumura H, Do LH, Majumdar A, Lippard SJ, Moënne-Loccoz P. Light-induced N₂O production from a non-heme iron-nitrosyl dimer. J Am Chem Soc 2014; 136:12524-7. [PMID: 25158917 PMCID: PMC4160282 DOI: 10.1021/ja504343t] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
![]()
Two
non-heme iron–nitrosyl species, [Fe2(N-Et-HPTB)(O2CPh)(NO)2](BF4)2 (1a) and [Fe2(N-Et-HPTB)(DMF)2(NO)(OH)](BF4)3 (2a), are characterized by FTIR
and resonance Raman spectroscopy. Binding of NO is reversible in both
complexes, which are prone to NO photolysis under visible light illumination.
Photoproduction of N2O occurs in high yield for 1a but not 2a. Low-temperature FTIR photolysis experiments
with 1a in acetonitrile do not reveal any intermediate
species, but in THF at room temperature, a new {FeNO}7 species
quickly forms under illumination and exhibits a ν(NO) vibration
indicative of nitroxyl-like character. This metastable species reacts
further under illumination to produce N2O. A reaction mechanism
is proposed, and implications for NO reduction in flavodiiron
proteins are discussed.
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Affiliation(s)
- Yunbo Jiang
- Institute of Environmental Health, Oregon Health and Science University , Portland, Oregon 97239, United States
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39
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Caranto JD, Weitz A, Giri N, Hendrich MP, Kurtz DM. A diferrous-dinitrosyl intermediate in the N2O-generating pathway of a deflavinated flavo-diiron protein. Biochemistry 2014; 53:5631-7. [PMID: 25144650 PMCID: PMC4159209 DOI: 10.1021/bi500836z] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
![]()
Flavo-diiron proteins (FDPs) function
as anaerobic nitric oxide
scavengers in some microorganisms, catalyzing reduction of nitric
to nitrous oxide. The FDP from Thermotoga maritima can be prepared in a deflavinated form with an intact diferric site
(deflavo-FDP). Hayashi et al. [(2010) Biochemistry 49, 7040–7049] reported that reaction of NO with reduced deflavo-FDP
produced substoichiometric N2O. Here we report a multispectroscopic
approach to identify the iron species in the reactions of deflavo-FDP
with NO. Mössbauer spectroscopy identified two distinct ferrous
species after reduction of the antiferromagnetically coupled diferric
site. Approximately 60% of the total ferrous iron was assigned to
a diferrous species associated with the N2O-generating
pathway. This pathway proceeds through successive diferrous-mononitrosyl
(S = 1/2 FeII{FeNO}7) and diferrous-dinitrosyl (S = 0 [{FeNO}7]2) species that form within ∼100 ms of
mixing of the reduced protein with NO. The diferrous-dinitrosyl intermediate
converted to an antiferromagnetically coupled diferric species that
was spectroscopically indistinguishable from that in the starting
deflavinated protein. These diiron species closely resembled those
reported for the flavinated FDP [Caranto et al. (2014) J.
Am. Chem. Soc. 136, 7981–7992], and
the time scales of their formation and decay were consistent with
the steady state turnover of the flavinated protein. The remaining
∼40% of ferrous iron was inactive in N2O generation
but reversibly bound NO to give an S = 3/2 {FeNO}7 species. The results demonstrate
that N2O formation in FDPs can occur via conversion of S = 0 [{FeNO}7]2 to a diferric form
without participation of the flavin cofactor.
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Affiliation(s)
- Jonathan D Caranto
- Department of Chemistry, University of Texas at San Antonio , San Antonio, Texas 78249, United States
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40
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Caranto J, Weitz A, Hendrich MP, Kurtz DM. The nitric oxide reductase mechanism of a flavo-diiron protein: identification of active-site intermediates and products. J Am Chem Soc 2014; 136:7981-92. [PMID: 24828196 PMCID: PMC4063189 DOI: 10.1021/ja5022443] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2014] [Indexed: 11/30/2022]
Abstract
The unique active site of flavo-diiron proteins (FDPs) consists of a nonheme diiron-carboxylate site proximal to a flavin mononucleotide (FMN) cofactor. FDPs serve as the terminal components for reductive scavenging of dioxygen or nitric oxide to combat oxidative or nitrosative stress in bacteria, archaea, and some protozoan parasites. Nitric oxide is reduced to nitrous oxide by the four-electron reduced (FMNH2-Fe(II)Fe(II)) active site. In order to clarify the nitric oxide reductase mechanism, we undertook a multispectroscopic presteady-state investigation, including the first Mössbauer spectroscopic characterization of diiron redox intermediates in FDPs. A new transient intermediate was detected and determined to be an antiferromagnetically coupled diferrous-dinitrosyl (S = 0, [{FeNO}(7)]2) species. This species has an exchange energy, J ≥ 40 cm(-1) (JS1 ° S2), which is consistent with a hydroxo or oxo bridge between the two irons. The results show that the nitric oxide reductase reaction proceeds through successive formation of diferrous-mononitrosyl (S = ½, Fe(II){FeNO}(7)) and the S = 0 diferrous-dinitrosyl species. In the rate-determining process, the diferrous-dinitrosyl converts to diferric (Fe(III)Fe(III)) and by inference N2O. The proximal FMNH2 then rapidly rereduces the diferric site to diferrous (Fe(II)Fe(II)), which can undergo a second 2NO → N2O turnover. This pathway is consistent with previous results on the same deflavinated and flavinated FDP, which detected N2O as a product (Hayashi Biochemistry 2010, 49, 7040). Our results do not support other proposed mechanisms, which proceed either via "super-reduction" of [{FeNO}(7)]2 by FMNH2 or through Fe(II){FeNO}(7) directly to a diferric-hyponitrite intermediate. The results indicate that an S = 0 [{FeNO}(7)}]2 complex is a proximal precursor to N-N bond formation and N-O bond cleavage to give N2O and that this conversion can occur without redox participation of the FMN cofactor.
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Affiliation(s)
- Jonathan
D. Caranto
- Department
of Chemistry, University of Texas at San
Antonio, San Antonio, Texas 78249, United
States
| | - Andrew Weitz
- Department
of Chemistry, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Michael P. Hendrich
- Department
of Chemistry, Carnegie-Mellon University, Pittsburgh, Pennsylvania 15213, United States
| | - Donald M. Kurtz
- Department
of Chemistry, University of Texas at San
Antonio, San Antonio, Texas 78249, United
States
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41
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Speelman AL, Lehnert N. Heme versus non-heme iron-nitroxyl {FeN(H)O}⁸ complexes: electronic structure and biologically relevant reactivity. Acc Chem Res 2014; 47:1106-16. [PMID: 24555413 DOI: 10.1021/ar400256u] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Researchers have completed extensive studies on heme and non-heme iron-nitrosyl complexes, which are labeled {FeNO}(7) in the Enemark-Feltham notation, but they have had very limited success in producing corresponding, one-electron reduced, {FeNO}(8) complexes where a nitroxyl anion (NO(-)) is formally bound to an iron(II) center. These complexes, and their protonated iron(II)-NHO analogues, are proposed key intermediates in nitrite (NO2(-)) and nitric oxide (NO) reducing enzymes in bacteria and fungi. In addition, HNO is known to have a variety of physiological effects, most notably in the cardiovascular system. HNO may also serve as a signaling molecule in mammals. For these functions, iron-containing proteins may mediate the production of HNO and serve as receptors for HNO in vivo. In this Account, we highlight recent key advances in the preparation, spectroscopic characterization, and reactivity of ferrous heme and non-heme nitroxyl (NO(-)/HNO) complexes that have greatly enhanced our understanding of the potential biological roles of these species. Low-spin (ls) heme {FeNO}(7) complexes (S = 1/2) can be reversibly reduced to the corresponding {FeNO}(8) species, which are stable, diamagnetic compounds. Because the reduction is ligand (NO) centered in these cases, it occurs at extremely negative redox potentials that are at the edge of the biologically feasible range. Interestingly, the electronic structures of ls-{FeNO}(7) and ls-{FeNO}(8) species are strongly correlated with very similar frontier molecular orbitals (FMOs) and thermodynamically strong Fe-NO bonds. In contrast, high-spin (hs) non-heme {FeNO}(7) complexes (S = 3/2) can be reduced at relatively mild redox potentials. Here, the reduction is metal-centered and leads to a paramagnetic (S = 1) {FeNO}(8) complex. The increased electron density at the iron center in these species significantly decreases the covalency of the Fe-NO bond, making the reduced complexes highly reactive. In the absence of steric bulk, monomeric high-spin {FeNO}(8) complexes decompose rapidly. Notably, in a recently prepared, dimeric [{FeNO}(7)]2 species, we observed that reduction leads to rapid N-N bond formation and N2O generation, which directly models the reactivity of flavodiiron NO reductases (FNORs). We have also made key progress in the preparation and stabilization of corresponding HNO complexes, {FeNHO}(8), using both heme and non-heme ligand sets. In both cases, we have taken advantage of sterically bulky coligands to stabilize these species. ls-{FeNO}(8) complexes are basic and easily form corresponding ls-{FeNHO}(8) species, which, however, decompose rapidly via disproportionation and H2 release. Importantly, we recently showed that we can suppress this reaction via steric protection of the bound HNO ligand. As a result, we have demonstrated that ls-{FeNHO}(8) model complexes are stable and amenable to spectroscopic characterization. Neither ls-{FeNO}(8) nor ls-{FeNHO}(8) model complexes are active for N-N coupling, and hence, seem unsuitable as reactive intermediates in nitric oxide reductases (NORs). Hs-{FeNO}(8) complexes are more basic than their hs-{FeNO}(7) precursors, but their electronic structure and reactivity is not as well characterized.
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Affiliation(s)
- Amy L. Speelman
- Department
of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
| | - Nicolai Lehnert
- Department
of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States
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42
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Wright AM, Zaman HT, Wu G, Hayton TW. Mechanistic Insights into the Formation of N2O by a Nickel Nitrosyl Complex. Inorg Chem 2014; 53:3108-16. [DOI: 10.1021/ic403038e] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- Ashley M. Wright
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Homaira T. Zaman
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Guang Wu
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
| | - Trevor W. Hayton
- Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara, California 93106, United States
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43
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Majumdar A, Lippard SJ. Non-heme mononitrosyldiiron complexes: importance of iron oxidation state in controlling the nature of the nitrosylated products. Inorg Chem 2013; 52:13292-4. [PMID: 24246021 DOI: 10.1021/ic4019508] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Mononitrosyldiiron complexes having either an [Fe(II)·{FeNO}(7)] or an [Fe(III)·{FeNO}(7)] core formulation have been synthesized by methods that rely on redox-state-induced differentiation of the diiron starting materials in an otherwise symmetrical dinucleating ligand environment. The synthesis, X-ray structures, Mössbauer spectroscopy, cyclic voltammetry, and dioxygen reactivity of [Fe(III)·{FeNO}(7)] are described.
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Affiliation(s)
- Amit Majumdar
- Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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44
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Sano Y, Weitz AC, Ziller JW, Hendrich MP, Borovik A. Unsymmetrical bimetallic complexes with M(II)-(μ-OH)-M(III) cores (M(II)M(III) = Fe(II)Fe(III), Mn(II)Fe(III), Mn(II)Mn(III)): structural, magnetic, and redox properties. Inorg Chem 2013; 52:10229-31. [PMID: 23992041 PMCID: PMC3826960 DOI: 10.1021/ic401561k] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Heterobimetallic cores are important units within the active sites of metalloproteins but are often difficult to duplicate in synthetic systems. We have developed a synthetic approach for the preparation of a complex with a Mn(II)-(μ-OH)-Fe(III) core, in which the metal centers have different coordination environments. Structural and physical data support the assignment of this complex as a heterobimetallic system. A comparison with analogous homobimetallic complexes, Mn(II)-(μ-OH)-Mn(III) and Fe(II)-(μ-OH)-Fe(III) cores, further supports this assignment.
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Affiliation(s)
- Yohei Sano
- Department of Chemistry, University of California–Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025
| | - Andrew C. Weitz
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Joseph W. Ziller
- Department of Chemistry, University of California–Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025
| | - Michael P. Hendrich
- Department of Chemistry, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - A.S. Borovik
- Department of Chemistry, University of California–Irvine, 1102 Natural Sciences II, Irvine, California 92697-2025
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45
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Zheng S, Berto TC, Dahl EW, Hoffman MB, Speelman AL, Lehnert N. The functional model complex [Fe2(BPMP)(OPr)(NO)2](BPh4)2 provides insight into the mechanism of flavodiiron NO reductases. J Am Chem Soc 2013; 135:4902-5. [PMID: 23472831 DOI: 10.1021/ja309782m] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Flavodiiron nitric oxide reductases (FNORs), found in many pathogenic bacteria, are able to detoxify NO by reducing it to N2O. In this way, FNORs equip these pathogens with immunity to NO, which is a central immune defense agent in humans. Hence, FNORs are thought to promote infection of the human body, leading to chronic diseases. Despite this importance of FNORs for bacterial pathogenesis, the mechanism of NO reduction by these enzymes is not well understood. Here we present the synthesis and spectroscopic characterization of the diiron dinitrosyl model complex [Fe2(BPMP)(OPr)(NO)2](BPh4)2. The crystal structure of this complex shows two end-on-coordinated {FeNO}(7) units that, based on spectroscopic and electrochemical results, are only weakly electronically coupled. Importantly, reduction of this complex by two electrons leads to the clean formation of N2O in quantitative yield. This complex therefore represents the first example of a functional model system for FNORs. The results provide key mechanistic insight into the mechanism of FNORs and, in particular, represent strong support for the proposed "super-reduced" mechanism for these enzymes.
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Affiliation(s)
- Sheng Zheng
- Department of Chemistry, The University of Michigan , Ann Arbor, Michigan 48109-1055, United States
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46
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Fang H, Caranto JD, Mendoza R, Taylor AB, Hart PJ, Kurtz DM. Histidine ligand variants of a flavo-diiron protein: effects on structure and activities. J Biol Inorg Chem 2012; 17:1231-9. [PMID: 22990880 DOI: 10.1007/s00775-012-0938-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 09/10/2012] [Indexed: 11/30/2022]
Abstract
Flavo-diiron proteins (FDPs) contain non-heme diiron and proximal flavin mononucleotide (FMN) active sites and function as terminal components of a nitric oxide reductase (NOR) and/or a four-electron dioxygen reductase (O(2)R). While most FDPs show similar structural, spectroscopic, and redox properties, O(2)R and NOR activities vary significantly among FDPs. A potential source of this variability is the iron ligation status of a conserved His residue that provides an iron ligand in all known FDP structures but one, where this His residue is rotated away from iron and replaced by a solvent ligand. In order to test the effect of this His ligation status, we changed this ligating His residue (H90) in Thermotoga maritima (Tm) FDP to either Asn or Ala. The wild-type Tm FDP shows significantly higher O(2)R than NOR activity. Single crystal X-ray crystallography revealed a remarkably conserved diiron site structure in the H90N and -A variants, differing mainly by either Asn or solvent coordination, respectively, in place of H90. The steady-state activities were minimally affected by the H90 substitutions, remaining significantly higher for O(2)R versus NOR. The pre-steady-state kinetics of the fully reduced FDP with O(2) were also minimally affected by the H90 substitutions. The results indicate that the coordination status of this His ligand does not significantly modulate the O(2)R or NOR activities, and that FDPs can retain these activities when the individual iron centers are differentiated by His ligand substitution. This differentiation may have implications for the O(2)R and NOR mechanisms of FDPs.
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Affiliation(s)
- Han Fang
- Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, USA
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