1
|
Flynn AJ, Antonyuk SV, Eady RR, Muench SP, Hasnain SS. A 2.2 Å cryoEM structure of a quinol-dependent NO Reductase shows close similarity to respiratory oxidases. Nat Commun 2023; 14:3416. [PMID: 37296134 PMCID: PMC10256718 DOI: 10.1038/s41467-023-39140-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Accepted: 05/31/2023] [Indexed: 06/12/2023] Open
Abstract
Quinol-dependent nitric oxide reductases (qNORs) are considered members of the respiratory heme-copper oxidase superfamily, are unique to bacteria, and are commonly found in pathogenic bacteria where they play a role in combating the host immune response. qNORs are also essential enzymes in the denitrification pathway, catalysing the reduction of nitric oxide to nitrous oxide. Here, we determine a 2.2 Å cryoEM structure of qNOR from Alcaligenes xylosoxidans, an opportunistic pathogen and a denitrifying bacterium of importance in the nitrogen cycle. This high-resolution structure provides insight into electron, substrate, and proton pathways, and provides evidence that the quinol binding site not only contains the conserved His and Asp residues but also possesses a critical Arg (Arg720) observed in cytochrome bo3, a respiratory quinol oxidase.
Collapse
Affiliation(s)
- Alex J Flynn
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK
| | - Svetlana V Antonyuk
- Molecular Biophysics Group, Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, L69 7ZB, England
| | - Robert R Eady
- Molecular Biophysics Group, Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, L69 7ZB, England
| | - Stephen P Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, UK.
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds, LS2 9JT, UK.
| | - S Samar Hasnain
- Molecular Biophysics Group, Department of Biochemistry and Systems Biology, Institute of Systems, Molecular and Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool, L69 7ZB, England.
| |
Collapse
|
2
|
Kahle M, Appelgren S, Elofsson A, Carroni M, Ädelroth P. Insights into the structure-function relationship of the NorQ/NorD chaperones from Paracoccus denitrificans reveal shared principles of interacting MoxR AAA+/VWA domain proteins. BMC Biol 2023; 21:47. [PMID: 36855050 PMCID: PMC9976466 DOI: 10.1186/s12915-023-01546-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2022] [Accepted: 02/15/2023] [Indexed: 03/02/2023] Open
Abstract
BACKGROUND NorQ, a member of the MoxR-class of AAA+ ATPases, and NorD, a protein containing a Von Willebrand Factor Type A (VWA) domain, are essential for non-heme iron (FeB) cofactor insertion into cytochrome c-dependent nitric oxide reductase (cNOR). cNOR catalyzes NO reduction, a key step of bacterial denitrification. This work aimed at elucidating the specific mechanism of NorQD-catalyzed FeB insertion, and the general mechanism of the MoxR/VWA interacting protein families. RESULTS We show that NorQ-catalyzed ATP hydrolysis, an intact VWA domain in NorD, and specific surface carboxylates on cNOR are all features required for cNOR activation. Supported by BN-PAGE, low-resolution cryo-EM structures of NorQ and the NorQD complex show that NorQ forms a circular hexamer with a monomer of NorD binding both to the side and to the central pore of the NorQ ring. Guided by AlphaFold predictions, we assign the density that "plugs" the NorQ ring pore to the VWA domain of NorD with a protruding "finger" inserting through the pore and suggest this binding mode to be general for MoxR/VWA couples. CONCLUSIONS Based on our results, we present a tentative model for the mechanism of NorQD-catalyzed cNOR remodeling and suggest many of its features to be applicable to the whole MoxR/VWA family.
Collapse
Affiliation(s)
- Maximilian Kahle
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91, Stockholm, Sweden. .,Present Address: Department of Biochemistry, University of Potsdam, 14476, Potsdam, Germany.
| | - Sofia Appelgren
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91, Stockholm, Sweden
| | - Arne Elofsson
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91, Stockholm, Sweden.,Science for Life Laboratory, Stockholm University, Solna, Sweden
| | - Marta Carroni
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91, Stockholm, Sweden. .,Swedish Cryo-EM Facility, Science for Life Laboratory Stockholm University, Solna, Sweden.
| | - Pia Ädelroth
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91, Stockholm, Sweden.
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
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.
Collapse
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
| |
Collapse
|
5
|
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: 101] [Impact Index Per Article: 33.7] [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.
Collapse
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
| |
Collapse
|
6
|
Blomberg MRA. The importance of exact exchange-A methodological investigation of NO reduction in heme-copper oxidases. J Chem Phys 2021; 154:055103. [PMID: 33557557 DOI: 10.1063/5.0035634] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Significant improvements of the density functional theory (DFT) methodology during the past few decades have made DFT calculations a powerful tool in studies of enzymatic reaction mechanisms. For metalloenzymes, however, there are still concerns about the reliability in the DFT-results. Therefore, a systematic study is performed where the fraction of exact exchange in a hybrid DFT functional is used as a parameter. By varying this parameter, a set of different but related functionals are obtained. The various functionals are applied to one of the reactions occurring in the enzyme family heme-copper oxidases, the reduction of nitric oxide (NO) to nitrous oxide (N2O) and water. The results show that, even though certain parts of the calculated energetics exhibit large variations, the qualitative pictures of the reaction mechanisms are quite stable. Furthermore, it is found that the functional with 15% exact exchange (B3LYP*) gives the best agreement with experimental data for the particular reactions studied. An important aspect of the procedure used is that the computational results are carefully combined with a few more general experimental data to obtain a complete description of the entire catalytic cycle of the reactions studied.
Collapse
Affiliation(s)
- Margareta R A Blomberg
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| |
Collapse
|
7
|
Blomberg MRA. Activation of O 2 and NO in heme-copper oxidases - mechanistic insights from computational modelling. Chem Soc Rev 2021; 49:7301-7330. [PMID: 33006348 DOI: 10.1039/d0cs00877j] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Heme-copper oxidases are transmembrane enzymes involved in aerobic and anaerobic respiration. The largest subgroup contains the cytochrome c oxidases (CcO), which reduce molecular oxygen to water. A significant part of the free energy released in this exergonic process is conserved as an electrochemical gradient across the membrane, via two processes, electrogenic chemistry and proton pumping. A deviant subgroup is the cytochrome c dependent NO reductases (cNOR), which reduce nitric oxide to nitrous oxide and water. This is also an exergonic reaction, but in this case none of the released free energy is conserved. Computational studies applying hybrid density functional theory to cluster models of the bimetallic active sites in the heme-copper oxidases are reviewed. To obtain a reliable description of the reaction mechanisms, energy profiles of the entire catalytic cycles, including the reduction steps have to be constructed. This requires a careful combination of computational results with certain experimental data. Computational studies have elucidated mechanistic details of the chemical parts of the reactions, involving cleavage and formation of covalent bonds, which have not been obtainable from pure experimental investigations. Important insights regarding the mechanisms of energy conservation have also been gained. The computational studies show that the reduction potentials of the active site cofactors in the CcOs are large enough to afford electrogenic chemistry and proton pumping, i.e. efficient energy conservation. These results solve a conflict between different types of experimental data. A mechanism for the proton pumping, involving a specific and crucial role for the active site tyrosine, conserved in all CcOs, is suggested. For the cNORs, the calculations show that the low reduction potentials of the active site cofactors are optimized for fast elimination of the toxic NO molecules. At the same time, the low reduction potentials lead to endergonic reduction steps with high barriers. To prevent even higher barriers, which would lead to a too slow reaction, when the electrochemical gradient across the membrane is present, the chemistry must occur in a non-electrogenic manner. This explains why there is no energy conservation in cNOR.
Collapse
Affiliation(s)
- Margareta R A Blomberg
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden.
| |
Collapse
|
8
|
Abstract
Bacteria power their energy metabolism using membrane-bound respiratory enzymes that capture chemical energy and transduce it by pumping protons or Na+ ions across their cell membranes. Recent breakthroughs in molecular bioenergetics have elucidated the architecture and function of many bacterial respiratory enzymes, although key mechanistic principles remain debated. In this Review, we present an overview of the structure, function and bioenergetic principles of modular bacterial respiratory chains and discuss their differences from the eukaryotic counterparts. We also discuss bacterial supercomplexes, which provide central energy transduction systems in several bacteria, including important pathogens, and which could open up possible avenues for treatment of disease.
Collapse
|
9
|
Reed CJ, Lam QN, Mirts EN, Lu Y. Molecular understanding of heteronuclear active sites in heme-copper oxidases, nitric oxide reductases, and sulfite reductases through biomimetic modelling. Chem Soc Rev 2021; 50:2486-2539. [PMID: 33475096 PMCID: PMC7920998 DOI: 10.1039/d0cs01297a] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Heme-copper oxidases (HCO), nitric oxide reductases (NOR), and sulfite reductases (SiR) catalyze the multi-electron and multi-proton reductions of O2, NO, and SO32-, respectively. Each of these reactions is important to drive cellular energy production through respiratory metabolism and HCO, NOR, and SiR evolved to contain heteronuclear active sites containing heme/copper, heme/nonheme iron, and heme-[4Fe-4S] centers, respectively. The complexity of the structures and reactions of these native enzymes, along with their large sizes and/or membrane associations, make it challenging to fully understand the crucial structural features responsible for the catalytic properties of these active sites. In this review, we summarize progress that has been made to better understand these heteronuclear metalloenzymes at the molecular level though study of the native enzymes along with insights gained from biomimetic models comprising either small molecules or proteins. Further understanding the reaction selectivity of these enzymes is discussed through comparisons of their similar heteronuclear active sites, and we offer outlook for further investigations.
Collapse
Affiliation(s)
- Christopher J Reed
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA.
| | - Quan N Lam
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA
| | - Evan N Mirts
- Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA and Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| | - Yi Lu
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA. and Department of Biochemistry, University of Illinois at Urbana-Champaign, Urban, IL 61801, USA and Center for Biophysics and Quantitative Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA and Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
| |
Collapse
|
10
|
Blomberg MRA. Role of the Two Metals in the Active Sites of Heme Copper Oxidases-A Study of NO Reduction in cbb3 Cytochrome c Oxidase. Inorg Chem 2020; 59:11542-11553. [PMID: 32799475 DOI: 10.1021/acs.inorgchem.0c01351] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The superfamily of heme copper oxidases reduces molecular oxygen or nitric oxide, and the active sites comprise a high-spin heme group (a3 or b3) and a non-heme metal (CuB or FeB). The cbb3 C family of cytochrome c oxidases, with the high-spin heme b3 and CuB in the active site, is a subfamily of the heme copper oxidases that can reduce both molecular oxygen, which is the main substrate, and nitric oxide. The mechanism for NO reduction in cbb3 oxidase is studied here using hybrid density functional theory and compared to other cytochrome c oxidases (A and B families), with a high-spin heme a3 and CuB in the active site, and to cytochrome c dependent NO reductase, with a high-spin heme b3 and a non-heme FeB in the active site. It is found that the reaction mechanism and the detailed reaction energetics of the cbb3 oxidases are not similar to those of cytochrome c dependent NO reductase, which has the same type of high-spin heme group but a different non-heme metal. This is in contrast to earlier expectations. Instead, the NO reduction mechanism in cbb3 oxidases is very similar to that in the other cytochrome c oxidases, with the same non-heme metal, CuB, and is independent of the type of high-spin heme group. The conclusion is that the type of non-heme metal (CuB or FeB) in the active site of the heme copper oxidases is more important for the reaction mechanisms than the type of high-spin heme, at least for the NO reduction reaction. The reason is that the proton-coupled reduction potentials of the active site cofactors determine the energetics for the NO reduction reaction, and they depend to a larger extent on the non-heme metal. Observed differences in NO reduction reactivity among the various cytochrome c oxidases may be explained by differences outside the BNC, affecting the rate of proton transfer, rather than in the BNC itself.
Collapse
|
11
|
Takeda H, Kimura T, Nomura T, Horitani M, Yokota A, Matsubayashi A, Ishii S, Shiro Y, Kubo M, Tosha T. Timing of NO Binding and Protonation in the Catalytic Reaction of Bacterial Nitric Oxide Reductase as Established by Time-Resolved Spectroscopy. BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 2020. [DOI: 10.1246/bcsj.20200038] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Affiliation(s)
- Hanae Takeda
- Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
- RIKEN SPring-8 Center, Hyogo 679-5148, Japan
| | - Tetsunari Kimura
- RIKEN SPring-8 Center, Hyogo 679-5148, Japan
- Department of Chemistry, Graduate School of Science, Kobe University, Kobe 657-8501, Japan
| | - Takashi Nomura
- Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
- RIKEN SPring-8 Center, Hyogo 679-5148, Japan
| | - Masaki Horitani
- Department of Applied Biochemistry & Food Science, Saga University, Saga 840-8502, Japan
| | - Azusa Yokota
- Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
| | - Akiko Matsubayashi
- Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
| | - Shoko Ishii
- Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
- RIKEN SPring-8 Center, Hyogo 679-5148, Japan
| | - Yoshitsugu Shiro
- Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
- RIKEN SPring-8 Center, Hyogo 679-5148, Japan
| | - Minoru Kubo
- Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
- RIKEN SPring-8 Center, Hyogo 679-5148, Japan
| | - Takehiko Tosha
- Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
- RIKEN SPring-8 Center, Hyogo 679-5148, Japan
| |
Collapse
|
12
|
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.
Collapse
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
| |
Collapse
|
13
|
Functional interactions between nitrite reductase and nitric oxide reductase from Paracoccus denitrificans. Sci Rep 2019; 9:17234. [PMID: 31754148 PMCID: PMC6872814 DOI: 10.1038/s41598-019-53553-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 10/29/2019] [Indexed: 12/25/2022] Open
Abstract
Denitrification is a microbial pathway that constitutes an important part of the nitrogen cycle on earth. Denitrifying organisms use nitrate as a terminal electron acceptor and reduce it stepwise to nitrogen gas, a process that produces the toxic nitric oxide (NO) molecule as an intermediate. In this work, we have investigated the possible functional interaction between the enzyme that produces NO; the cd1 nitrite reductase (cd1NiR) and the enzyme that reduces NO; the c-type nitric oxide reductase (cNOR), from the model soil bacterium P. denitrificans. Such an interaction was observed previously between purified components from P. aeruginosa and could help channeling the NO (directly from the site of formation to the side of reduction), in order to protect the cell from this toxic intermediate. We find that electron donation to cNOR is inhibited in the presence of cd1NiR, presumably because cd1NiR binds cNOR at the same location as the electron donor. We further find that the presence of cNOR influences the dimerization of cd1NiR. Overall, although we find no evidence for a high-affinity, constant interaction between the two enzymes, our data supports transient interactions between cd1NiR and cNOR that influence enzymatic properties of cNOR and oligomerization properties of cd1NiR. We speculate that this could be of particular importance in vivo during metabolic switches between aerobic and denitrifying conditions.
Collapse
|
14
|
Wijeratne GB, Bhadra M, Siegler MA, Karlin KD. Copper(I) Complex Mediated Nitric Oxide Reductive Coupling: Ligand Hydrogen Bonding Derived Proton Transfer Promotes N 2O (g) Release. J Am Chem Soc 2019; 141:17962-17967. [PMID: 31621325 DOI: 10.1021/jacs.9b07286] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
A cuprous chelate bearing a secondary sphere hydrogen bonding functionality, [(PV-tmpa)CuI]+, transforms •NO(g) to N2O(g) in high-yields in methanol. Ligand derived proton transfer facilitates N-O bond cleavage of a putative hyponitrite intermediate releasing N2O(g), underscoring the crucial balance between H-bonding capabilities and acidities in (bio)chemical •NO(g) coupling systems.
Collapse
Affiliation(s)
- Gayan B Wijeratne
- Department of Chemistry , The Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Mayukh Bhadra
- Department of Chemistry , The Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Maxime A Siegler
- Department of Chemistry , The Johns Hopkins University , Baltimore , Maryland 21218 , United States
| | - Kenneth D Karlin
- Department of Chemistry , The Johns Hopkins University , Baltimore , Maryland 21218 , United States
| |
Collapse
|
15
|
Gopalasingam CC, Johnson RM, Chiduza GN, Tosha T, Yamamoto M, Shiro Y, Antonyuk SV, Muench SP, Hasnain SS. Dimeric structures of quinol-dependent nitric oxide reductases (qNORs) revealed by cryo-electron microscopy. SCIENCE ADVANCES 2019; 5:eaax1803. [PMID: 31489376 PMCID: PMC6713497 DOI: 10.1126/sciadv.aax1803] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2019] [Accepted: 07/24/2019] [Indexed: 06/10/2023]
Abstract
Quinol-dependent nitric oxide reductases (qNORs) are membrane-integrated, iron-containing enzymes of the denitrification pathway, which catalyze the reduction of nitric oxide (NO) to the major ozone destroying gas nitrous oxide (N2O). Cryo-electron microscopy structures of active qNOR from Alcaligenes xylosoxidans and an activity-enhancing mutant have been determined to be at local resolutions of 3.7 and 3.2 Å, respectively. They unexpectedly reveal a dimeric conformation (also confirmed for qNOR from Neisseria meningitidis) and define the active-site configuration, with a clear water channel from the cytoplasm. Structure-based mutagenesis has identified key residues involved in proton transport and substrate delivery to the active site of qNORs. The proton supply direction differs from cytochrome c-dependent NOR (cNOR), where water molecules from the cytoplasm serve as a proton source similar to those from cytochrome c oxidase.
Collapse
Affiliation(s)
- Chai C. Gopalasingam
- Molecular Biophysics Group, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 7ZB, UK
| | - Rachel M. Johnson
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - George N. Chiduza
- Molecular Biophysics Group, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 7ZB, UK
| | - Takehiko Tosha
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Masaki Yamamoto
- RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo, Hyogo 679-5148, Japan
| | - Yoshitsugu Shiro
- Graduate School of Life Science, University of Hyogo, 3-2-1 Kouto, Kamigori, Ako, Hyogo 678-1297, Japan
| | - Svetlana V. Antonyuk
- Molecular Biophysics Group, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 7ZB, UK
| | - Stephen P. Muench
- School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds LS2 9JT, UK
- Astbury Centre for Structural and Molecular Biology, University of Leeds, Leeds LS2 9JT, UK
| | - S. Samar Hasnain
- Molecular Biophysics Group, Institute of Integrative Biology, Faculty of Health and Life Sciences, University of Liverpool, Liverpool L69 7ZB, UK
| |
Collapse
|
16
|
Kahle M, Blomberg MRA, Jareck S, Ädelroth P. Insights into the mechanism of nitric oxide reductase from a Fe B -depleted variant. FEBS Lett 2019; 593:1351-1359. [PMID: 31077353 DOI: 10.1002/1873-3468.13436] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Revised: 04/29/2019] [Accepted: 05/09/2019] [Indexed: 11/06/2022]
Abstract
A key step of denitrification, the reduction of toxic nitric oxide to nitrous oxide, is catalysed by cytochrome c-dependent NO reductase (cNOR). cNOR contains four redox-active cofactors: three hemes and a nonheme iron (FeB ). Heme b3 and FeB constitute the active site, but the specific mechanism of NO-binding events and reduction is under debate. Here, we used a recently constructed, fully folded and hemylated cNOR variant that lacks FeB to investigate the role of FeB during catalysis. We show that in the FeB -less cNOR, binding of both NO and O2 to heme b3 still occurs but further reduction is impaired, although to a lesser degree for O2 than for NO. Implications for the catalytic mechanisms of cNOR are discussed.
Collapse
Affiliation(s)
- Maximilian Kahle
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
| | | | - Sascha Jareck
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
| | - Pia Ädelroth
- Department of Biochemistry and Biophysics, Stockholm University, Sweden
| |
Collapse
|
17
|
Blomberg MRA, Ädelroth P. Mechanisms for enzymatic reduction of nitric oxide to nitrous oxide - A comparison between nitric oxide reductase and cytochrome c oxidase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:1223-1234. [PMID: 30248312 DOI: 10.1016/j.bbabio.2018.09.368] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 08/23/2018] [Accepted: 09/17/2018] [Indexed: 12/22/2022]
Abstract
Cytochrome c oxidases (CcO) reduce O2 to H2O in the respiratory chain of mitochondria and many aerobic bacteria. In addition, some species of CcO can also reduce NO to N2O and water while others cannot. Here, the mechanism for NO-reduction in CcO is investigated using quantum mechanical calculations. Comparison is made to the corresponding reaction in a "true" cytochrome c-dependent NO reductase (cNOR). The calculations show that in cNOR, where the reduction potentials are low, the toxic NO molecules are rapidly reduced, while the higher reduction potentials in CcO lead to a slower or even impossible reaction, consistent with experimental observations. In both enzymes the reaction is initiated by addition of two NO molecules to the reduced active site, forming a hyponitrite intermediate. In cNOR, N2O can then be formed using only the active-site electrons. In contrast, in CcO, one proton-coupled reduction step most likely has to occur before N2O can be formed, and furthermore, proton transfer is most likely rate-limiting. This can explain why different CcO species with the same heme a3-Cu active site differ with respect to NO reduction efficiency, since they have a varying number and/or properties of proton channels. Finally, the calculations also indicate that a conserved active site valine plays a role in reducing the rate of NO reduction in CcO.
Collapse
Affiliation(s)
- Margareta R A Blomberg
- Department of Organic Chemistry, Arrhenius Laboratory, Stockholm University, Stockholm SE-106 91, Sweden.
| | - Pia Ädelroth
- Department of Biochemistry and Biophysics, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| |
Collapse
|
18
|
Mahinthichaichan P, Gennis RB, Tajkhorshid E. Bacterial denitrifying nitric oxide reductases and aerobic respiratory terminal oxidases use similar delivery pathways for their molecular substrates. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:712-724. [PMID: 29883591 DOI: 10.1016/j.bbabio.2018.06.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Revised: 05/05/2018] [Accepted: 06/04/2018] [Indexed: 10/14/2022]
Abstract
The superfamily of heme‑copper oxidoreductases (HCOs) include both NO and O2 reductases. Nitric oxide reductases (NORs) are bacterial membrane enzymes that catalyze an intermediate step of denitrification by reducing nitric oxide (NO) to nitrous oxide (N2O). They are structurally similar to heme‑copper oxygen reductases (HCOs), which reduce O2 to water. The experimentally observed apparent bimolecular rate constant of NO delivery to the deeply buried catalytic site of NORs was previously reported to approach the diffusion-controlled limit (108-109 M-1 s-1). Using the crystal structure of cytochrome-c dependent NOR (cNOR) from Pseudomonas aeruginosa, we employed several protocols of molecular dynamics (MD) simulation, which include flooding simulations of NO molecules, implicit ligand sampling and umbrella sampling simulations, to elucidate how NO in solution accesses the catalytic site of this cNOR. The results show that NO partitions into the membrane, enters the enzyme from the lipid bilayer and diffuses to the catalytic site via a hydrophobic tunnel that is resolved in the crystal structures. This is similar to what has been found for O2 diffusion through the closely related O2 reductases. The apparent second order rate constant approximated using the simulation data is ~5 × 108 M-1 s-1, which is optimized by the dynamics of the amino acid side chains lining in the tunnel. It is concluded that both NO and O2 reductases utilize well defined hydrophobic tunnels to assure that substrate diffusion to the buried catalytic sites is not rate limiting under physiological conditions.
Collapse
Affiliation(s)
- Paween Mahinthichaichan
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Street, Urbana, IL 61801, USA; NIH Center for Macromolecular Modeling and Bioinformatics, 405 North Mathews Avenue, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, 405 N. Mathews Avenue, Urbana, IL 61801, USA
| | - Robert B Gennis
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Street, Urbana, IL 61801, USA; Center for Biophysics and Quantitative Biology, 179 Looomis, MC-704, 1110 Green Street, Urbana, IL 61801, USA.
| | - Emad Tajkhorshid
- Department of Biochemistry, University of Illinois at Urbana-Champaign, 600 South Mathews Street, Urbana, IL 61801, USA; NIH Center for Macromolecular Modeling and Bioinformatics, 405 North Mathews Avenue, Urbana, IL 61801, USA; Beckman Institute for Advanced Science and Technology, 405 N. Mathews Avenue, Urbana, IL 61801, USA; Center for Biophysics and Quantitative Biology, 179 Looomis, MC-704, 1110 Green Street, Urbana, IL 61801, USA.
| |
Collapse
|
19
|
Kahle M, Ter Beek J, Hosler JP, Ädelroth P. The insertion of the non-heme Fe B cofactor into nitric oxide reductase from P. denitrificans depends on NorQ and NorD accessory proteins. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2018; 1859:1051-1058. [PMID: 29874552 DOI: 10.1016/j.bbabio.2018.05.020] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/27/2018] [Accepted: 05/31/2018] [Indexed: 10/14/2022]
Abstract
Bacterial NO reductases (NOR) catalyze the reduction of NO into N2O, either as a step in denitrification or as a detoxification mechanism. cNOR from Paracoccus (P.) denitrificans is expressed from the norCBQDEF operon, but only the NorB and NorC proteins are found in the purified NOR complex. Here, we established a new purification method for the P. denitrificans cNOR via a His-tag using heterologous expression in E. coli. The His-tagged enzyme is both structurally and functionally very similar to non-tagged cNOR. We were also able to express and purify cNOR from the structural genes norCB only, in absence of the accessory genes norQDEF. The produced protein is a stable NorCB complex containing all hemes and it can bind gaseous ligands (CO) to heme b3, but it is catalytically inactive. We show that this deficient cNOR lacks the non-heme iron cofactor FeB. Mutational analysis of the nor gene cluster revealed that it is the norQ and norD genes that are essential to form functional cNOR. NorQ belongs to the family of MoxR P-loop AAA+ ATPases, which are in general considered to facilitate enzyme activation processes often involving metal insertion. Our data indicates that NorQ and NorD work together in order to facilitate non-heme Fe insertion. This is noteworthy since in many cases Fe cofactor binding occurs spontaneously. We further suggest a model for NorQ/D-facilitated metal insertion into cNOR.
Collapse
Affiliation(s)
- Maximilian Kahle
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Josy Ter Beek
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Jonathan P Hosler
- Department of Cell and Molecular Biology, University of Mississippi Medical Center, Jackson, MS 39216, United States
| | - Pia Ädelroth
- Department of Biochemistry and Biophysics, Stockholm University, SE-106 91 Stockholm, Sweden.
| |
Collapse
|
20
|
Characterization of the quinol-dependent nitric oxide reductase from the pathogen Neisseria meningitidis, an electrogenic enzyme. Sci Rep 2018; 8:3637. [PMID: 29483528 PMCID: PMC5826923 DOI: 10.1038/s41598-018-21804-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Accepted: 02/09/2018] [Indexed: 12/01/2022] Open
Abstract
Bacterial nitric oxide reductases (NORs) catalyse the reduction of NO to N2O and H2O. NORs are found either in denitrification chains, or in pathogens where their primary role is detoxification of NO produced by the immune defense of the host. Although NORs belong to the heme-copper oxidase superfamily, comprising proton-pumping O2-reducing enzymes, the best studied NORs, cNORs (cytochrome c-dependent), are non-electrogenic. Here, we focus on another type of NOR, qNOR (quinol-dependent). Recombinant qNOR from Neisseria meningitidis, a human pathogen, purified from Escherichia coli, showed high catalytic activity and spectroscopic properties largely similar to cNORs. However, in contrast to cNOR, liposome-reconstituted qNOR showed respiratory control ratios above two, indicating that NO reduction by qNOR was electrogenic. Further, we determined a 4.5 Å crystal structure of the N. meningitidis qNOR, allowing exploration of a potential proton transfer pathway from the cytoplasm by mutagenesis. Most mutations had little effect on the activity, however the E-498 variants were largely inactive, while the corresponding substitution in cNOR was previously shown not to induce significant effects. We thus suggest that, contrary to cNOR, the N. meningitidis qNOR uses cytoplasmic protons for NO reduction. Our results allow possible routes for protons to be discussed.
Collapse
|
21
|
Wikström M, Krab K, Sharma V. Oxygen Activation and Energy Conservation by Cytochrome c Oxidase. Chem Rev 2018; 118:2469-2490. [PMID: 29350917 PMCID: PMC6203177 DOI: 10.1021/acs.chemrev.7b00664] [Citation(s) in RCA: 249] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
![]()
This review focuses on the type
A cytochrome c oxidases (CcO), which
are found in all mitochondria
and also in several aerobic bacteria. CcO catalyzes
the respiratory reduction of dioxygen (O2) to water by
an intriguing mechanism, the details of which are fairly well understood
today as a result of research for over four decades. Perhaps even
more intriguingly, the membrane-bound CcO couples
the O2 reduction chemistry to translocation of protons
across the membrane, thus contributing to generation of the electrochemical
proton gradient that is used to drive the synthesis of ATP as catalyzed
by the rotary ATP synthase in the same membrane. After reviewing the
structure of the core subunits of CcO, the active
site, and the transfer paths of electrons, protons, oxygen, and water,
we describe the states of the catalytic cycle and point out the few
remaining uncertainties. Finally, we discuss the mechanism of proton
translocation and the controversies in that area that still prevail.
Collapse
Affiliation(s)
- Mårten Wikström
- Institute of Biotechnology , University of Helsinki , P.O. Box 56 , Helsinki FI-00014 , Finland
| | - Klaas Krab
- Department of Molecular Cell Physiology , Vrije Universiteit , P.O. Box 7161 , Amsterdam 1007 MC , The Netherlands
| | - Vivek Sharma
- Institute of Biotechnology , University of Helsinki , P.O. Box 56 , Helsinki FI-00014 , Finland.,Department of Physics , University of Helsinki , P.O. Box 64 , Helsinki FI-00014 , Finland
| |
Collapse
|
22
|
Ter Beek J, Kahle M, Ädelroth P. Modulation of protein function in membrane mimetics: Characterization of P. denitrificans cNOR in nanodiscs or liposomes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1951-1961. [PMID: 28668220 DOI: 10.1016/j.bbamem.2017.06.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 06/03/2017] [Accepted: 06/27/2017] [Indexed: 10/19/2022]
Abstract
For detailed functional characterization, membrane proteins are usually studied in detergent. However, it is becoming clear that detergent micelles are often poor mimics of the lipid environment in which these proteins function. In this work we compared the catalytic properties of the membrane-embedded cytochrome c-dependent nitric oxide reductase (cNOR) from Paracoccus (P.) denitrificans in detergent, lipid/protein nanodiscs, and proteoliposomes. We used two different lipid mixtures, an extract of soybean lipids and a defined mix of synthetic lipids mimicking the original P. denitrificans membrane. We show that the catalytic activity of detergent-solubilized cNOR increased threefold upon reconstitution from detergent into proteoliposomes with the P. denitrificans lipid mixture, and above two-fold when soybean lipids were used. In contrast, there was only a small activity increase in nanodiscs. We further show that binding of the gaseous ligands CO and O2 are affected differently by reconstitution. In proteoliposomes the turnover rates are affected much more than in nanodiscs, but CO-binding is more significantly accelerated in liposomes with soybean lipids, while O2-binding is faster with the P. denitrificans lipid mix. We also investigated proton-coupled electron transfer during the reaction between fully reduced cNOR and O2, and found that the pKa of the internal proton donor was increased in proteoliposomes but not in nanodiscs. Taking our results together, the liposome-reconstituted enzyme shows significant differences to detergent-solubilized protein. Nanodiscs show much more subtle effects, presumably because of their much lower lipid to protein ratio. Which of these two membrane-mimetic systems best mimics the native membrane is discussed.
Collapse
Affiliation(s)
- Josy Ter Beek
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
| | - Maximilian Kahle
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
| | - Pia Ädelroth
- Department of Biochemistry and Biophysics, Stockholm University, Svante Arrhenius väg 16C, SE-106 91 Stockholm, Sweden.
| |
Collapse
|
23
|
Blomberg MRA. Can Reduction of NO to N2O in Cytochrome c Dependent Nitric Oxide Reductase Proceed through a Trans-Mechanism? Biochemistry 2016; 56:120-131. [DOI: 10.1021/acs.biochem.6b00788] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Margareta R. A. Blomberg
- Department of Organic Chemistry,
Arrhenius Laboratory, Stockholm University, SE-106 91, Stockholm, Sweden
| |
Collapse
|
24
|
Blomberg MRA, Siegbahn PEM. Improved free energy profile for reduction of NO in cytochrome c dependent nitric oxide reductase (cNOR). J Comput Chem 2016; 37:1810-8. [DOI: 10.1002/jcc.24396] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 03/31/2016] [Accepted: 04/02/2016] [Indexed: 12/14/2022]
Affiliation(s)
- Margareta R. A. Blomberg
- Department of Organic Chemistry, Arrhenius Laboratory; Stockholm University; Stockholm SE-106 91 Sweden
| | - Per E. M. Siegbahn
- Department of Organic Chemistry, Arrhenius Laboratory; Stockholm University; Stockholm SE-106 91 Sweden
| |
Collapse
|
25
|
Investigating the Proton Donor in the NO Reductase from Paracoccus denitrificans. PLoS One 2016; 11:e0152745. [PMID: 27030968 PMCID: PMC4816578 DOI: 10.1371/journal.pone.0152745] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Accepted: 03/18/2016] [Indexed: 01/22/2023] Open
Abstract
Variant nomenclature: the variants were made in the NorB subunit if not indicated by the superscript c, which are variants in the NorC subunit (e.g. E122A = exchange of Glu-122 in NorB for an Ala, E71cD; exchange of Glu-71 in NorC for an Asp). Bacterial NO reductases (NORs) are integral membrane proteins from the heme-copper oxidase superfamily. Most heme-copper oxidases are proton-pumping enzymes that reduce O2 as the last step in the respiratory chain. With electrons from cytochrome c, NO reductase (cNOR) from Paracoccus (P.) denitrificans reduces NO to N2O via the following reaction: 2NO+2e-+2H+→N2O+H2O. Although this reaction is as exergonic as O2-reduction, cNOR does not contribute to the electrochemical gradient over the membrane. This means that cNOR does not pump protons and that the protons needed for the reaction are taken from the periplasmic side of the membrane (since the electrons are donated from this side). We previously showed that the P. denitrificans cNOR uses a single defined proton pathway with residues Glu-58 and Lys-54 from the NorC subunit at the entrance. Here we further strengthened the evidence in support of this pathway. Our further aim was to define the continuation of the pathway and the immediate proton donor for the active site. To this end, we investigated the region around the calcium-binding site and both propionates of heme b3 by site directed mutagenesis. Changing single amino acids in these areas often had severe effects on cNOR function, with many variants having a perturbed active site, making detailed analysis of proton transfer properties difficult. Our data does however indicate that the calcium ligation sphere and the region around the heme b3 propionates are important for proton transfer and presumably contain the proton donor. The possible evolutionary link between the area for the immediate donor in cNOR and the proton loading site (PLS) for pumped protons in oxygen-reducing heme-copper oxidases is discussed.
Collapse
|
26
|
Al-Attar S, de Vries S. An electrogenic nitric oxide reductase. FEBS Lett 2015; 589:2050-7. [PMID: 26149211 DOI: 10.1016/j.febslet.2015.06.033] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2015] [Revised: 06/24/2015] [Accepted: 06/24/2015] [Indexed: 10/23/2022]
Abstract
Nitric oxide reductases (Nors) are members of the heme-copper oxidase superfamily that reduce nitric oxide (NO) to nitrous oxide (N₂O). In contrast to the proton-pumping cytochrome oxidases, Nors studied so far have neither been implicated in proton pumping nor have they been experimentally established as electrogenic. The copper-A-dependent Nor from Bacillus azotoformans uses cytochrome c₅₅₁ as electron donor but lacks menaquinol activity, in contrast to our earlier report (Suharti et al., 2001). Employing reduced phenazine ethosulfate (PESH) as electron donor, the main NO reduction pathway catalyzed by Cu(A)Nor reconstituted in liposomes involves transmembrane cycling of the PES radical. We show that Cu(A)Nor reconstituted in liposomes generates a proton electrochemical gradient across the membrane similar in magnitude to cytochrome aa₃, highlighting that bacilli using Cu(A)Nor can exploit NO reduction for increased cellular ATP production compared to organisms using cNor.
Collapse
Affiliation(s)
- Sinan Al-Attar
- Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, The Netherlands
| | - Simon de Vries
- Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC, The Netherlands.
| |
Collapse
|
27
|
Sharma V, Wikström M. A structural and functional perspective on the evolution of the heme-copper oxidases. FEBS Lett 2014; 588:3787-92. [PMID: 25261254 DOI: 10.1016/j.febslet.2014.09.020] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Revised: 09/10/2014] [Accepted: 09/11/2014] [Indexed: 11/15/2022]
Abstract
The heme-copper oxidases (HCOs) catalyze the reduction of O2 to water, and couple the free energy to proton pumping across the membrane. HCOs are divided into three sub-classes, A, B and C, whose order of emergence in evolution has been controversial. Here we have analyzed recent structural and functional data on HCOs and their homologues, the nitric oxide reductases (NORs). We suggest that the C-type oxidases are ancient enzymes that emerged from the NORs. In contrast, the A-type oxidases are the most advanced from both structural and functional viewpoints, which we interpret as evidence for having evolved later.
Collapse
Affiliation(s)
- Vivek Sharma
- Department of Physics, Tampere University of Technology, PO Box 692, FI-33101 Tampere, Finland.
| | - Mårten Wikström
- Helsinki Bioenergetics Group, Institute of Biotechnology, University of Helsinki, FI-00014 Helsinki, Finland
| |
Collapse
|
28
|
Duarte AG, Cordas CM, Moura JJ, Moura I. Steady-state kinetics with nitric oxide reductase (NOR): New considerations on substrate inhibition profile and catalytic mechanism. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:375-84. [DOI: 10.1016/j.bbabio.2014.01.001] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2013] [Revised: 12/28/2013] [Accepted: 01/02/2014] [Indexed: 10/25/2022]
|
29
|
Terasaka E, Okada N, Sato N, Sako Y, Shiro Y, Tosha T. Characterization of quinol-dependent nitric oxide reductase from Geobacillus stearothermophilus: enzymatic activity and active site structure. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2014; 1837:1019-26. [PMID: 24569054 DOI: 10.1016/j.bbabio.2014.02.017] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/21/2013] [Revised: 02/10/2014] [Accepted: 02/15/2014] [Indexed: 10/25/2022]
Abstract
Nitric oxide reductase (NOR) catalyzes the reduction of nitric oxide to generate nitrous oxide. We recently reported on the crystal structure of a quinol-dependent NOR (qNOR) from Geobacillus stearothermophilus [Y. Matsumoto, T. Tosha, A.V. Pisliakov, T. Hino, H. Sugimoto, S. Nagano, Y. Sugita and Y. Shiro, Nat. Struct. Mol. Biol. 19 (2012) 238-246], and suggested that a water channel from the cytoplasm, which is not observed in cytochrome c-dependent NOR (cNOR), functions as a pathway transferring catalytic protons. Here, we further investigated the functional and structural properties of qNOR, and compared the findings with those for cNOR. The pH optimum for the enzymatic reaction of qNOR was in the alkaline range, whereas Pseudomonas aeruginosa cNOR showed a higher activity at an acidic pH. The considerably slower reduction rate, and a correlation of the pH dependence for enzymatic activity and the reduction rate suggest that the reduction process is the rate-determining step for the NO reduction by qNOR, while the reduction rate for cNOR was very fast and therefore is unlikely to be the rate-determining step. A close examination of the heme/non-heme iron binuclear center by resonance Raman spectroscopy indicated that qNOR has a more polar environment at the binuclear center compared with cNOR. It is plausible that a water channel enhances the accessibility of the active site to solvent water, creating a more polar environment in qNOR. This structural feature could control certain properties of the active site, such as redox potential, which could explain the different catalytic properties of the two NORs. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
Collapse
Affiliation(s)
- Erina Terasaka
- RIKEN SPring-8 Center, Kouto, Sayo, Hyogo 679-5148, Japan; Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
| | - Norihiro Okada
- RIKEN SPring-8 Center, Kouto, Sayo, Hyogo 679-5148, Japan; Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan
| | - Nozomi Sato
- RIKEN SPring-8 Center, Kouto, Sayo, Hyogo 679-5148, Japan; Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshihiko Sako
- Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | - Yoshitsugu Shiro
- RIKEN SPring-8 Center, Kouto, Sayo, Hyogo 679-5148, Japan; Graduate School of Life Science, University of Hyogo, Hyogo 678-1297, Japan.
| | - Takehiko Tosha
- RIKEN SPring-8 Center, Kouto, Sayo, Hyogo 679-5148, Japan.
| |
Collapse
|
30
|
Matsumura H, Hayashi T, Chakraborty S, Lu Y, Moënne-Loccoz P. The production of nitrous oxide by the heme/nonheme diiron center of engineered myoglobins (Fe(B)Mbs) proceeds through a trans-iron-nitrosyl dimer. J Am Chem Soc 2014; 136:2420-31. [PMID: 24432820 PMCID: PMC4004238 DOI: 10.1021/ja410542z] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
![]()
Denitrifying NO reductases are transmembrane
protein complexes
that are evolutionarily related to heme/copper terminal oxidases.
They utilize a heme/nonheme diiron center to reduce two NO molecules
to N2O. Engineering a nonheme FeB site within
the heme distal pocket of sperm whale myoglobin has offered well-defined
diiron clusters for the investigation of the mechanism of NO reduction
in these unique active sites. In this study, we use FTIR spectroscopy
to monitor the production of N2O in solution and to show
that the presence of a distal FeBII is not sufficient
to produce the expected product. However, the addition of a glutamate
side chain peripheral to the diiron site allows for 50% of a productive
single-turnover reaction. Unproductive reactions are characterized
by resonance Raman spectroscopy as dinitrosyl complexes, where one
NO molecule is bound to the heme iron to form a five-coordinate low-spin
{FeNO}7 species with ν(FeNO)heme and ν(NO)heme at 522 and 1660 cm–1, and a second NO
molecule is bound to the nonheme FeB site with a ν(NO)FeB at 1755 cm–1. Stopped-flow UV–vis
absorption coupled with rapid-freeze-quench resonance Raman spectroscopy
provide a detailed map of the reaction coordinates leading to the
unproductive iron-nitrosyl dimer. Unexpectedly, NO binding to FeB is kinetically favored and occurs prior to the binding of
a second NO to the heme iron, leading to a (six-coordinate low-spin
heme-nitrosyl/FeB-nitrosyl) transient dinitrosyl complex
with characteristic ν(FeNO)heme at 570 ± 2 cm–1 and ν(NO)FeB at 1755 cm–1. Without the addition of a peripheral glutamate, the dinitrosyl
complex is converted to a dead-end product after the dissociation
of the proximal histidine of the heme iron, but the added peripheral
glutamate side chain in FeBMb2 lowers the rate of dissociation
of the promixal histidine which in turn allows the (six-coordinate
low-spin heme-nitrosyl/FeB-nitrosyl) transient dinitrosyl
complex to decay with production of N2O at a rate of 0.7
s–1 at 4 °C. Taken together, our results support
the proposed trans mechanism of NO reduction in NORs.
Collapse
Affiliation(s)
- Hirotoshi Matsumura
- Divison of Environmental & Biomolecular Systems, Institute of Environmental Health, Oregon Health & Science University , 3181 SW Sam Jackson Park Road, Portland, Oregon 97239-3098, United States
| | | | | | | | | |
Collapse
|
31
|
Sato N, Ishii S, Sugimoto H, Hino T, Fukumori Y, Sako Y, Shiro Y, Tosha T. Structures of reduced and ligand-bound nitric oxide reductase provide insights into functional differences in respiratory enzymes. Proteins 2014; 82:1258-71. [PMID: 24338896 DOI: 10.1002/prot.24492] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2013] [Revised: 11/27/2013] [Accepted: 12/09/2013] [Indexed: 11/07/2022]
Abstract
Nitric oxide reductase (NOR) catalyzes the generation of nitrous oxide (N2O) via the reductive coupling of two nitric oxide (NO) molecules at a heme/non-heme Fe center. We report herein on the structures of the reduced and ligand-bound forms of cytochrome c-dependent NOR (cNOR) from Pseudomonas aeruginosa at a resolution of 2.3-2.7 Å, to elucidate structure-function relationships in NOR, and compare them to those of cytochrome c oxidase (CCO) that is evolutionarily related to NOR. Comprehensive crystallographic refinement of the CO-bound form of cNOR suggested that a total of four atoms can be accommodated at the binuclear center. Consistent with this, binding of bulky acetaldoxime (CH3-CH=N-OH) to the binuclear center of cNOR was confirmed by the structural analysis. Active site reduction and ligand binding in cNOR induced only ∼0.5 Å increase in the heme/non-heme Fe distance, but no significant structural change in the protein. The highly localized structural change is consistent with the lack of proton-pumping activity in cNOR, because redox-coupled conformational changes are thought to be crucial for proton pumping in CCO. It also permits the rapid decomposition of cytotoxic NO in denitrification. In addition, the shorter heme/non-heme Fe distance even in the bulky ligand-bound form of cNOR (∼4.5 Å) than the heme/Cu distance in CCO (∼5 Å) suggests the ability of NOR to maintain two NO molecules within a short distance in the confined space of the active site, thereby facilitating N-N coupling to produce a hyponitrite intermediate for the generation of N2O.
Collapse
Affiliation(s)
- Nozomi Sato
- Biometal Science Laboratory, RIKEN SPring-8 Center, Kouto, Sayo, Hyogo 679-5148, Japan; Division of Applied Biosciences, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan
| | | | | | | | | | | | | | | |
Collapse
|
32
|
Ter Beek J, Krause N, Reimann J, Lachmann P, Ädelroth P. The nitric-oxide reductase from Paracoccus denitrificans uses a single specific proton pathway. J Biol Chem 2013; 288:30626-30635. [PMID: 24014024 DOI: 10.1074/jbc.m113.497347] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The NO reductase from Paracoccus denitrificans reduces NO to N2O (2NO + 2H(+) + 2e(-) → N2O + H2O) with electrons donated by periplasmic cytochrome c (cytochrome c-dependent NO reductase; cNOR). cNORs are members of the heme-copper oxidase superfamily of integral membrane proteins, comprising the O2-reducing, proton-pumping respiratory enzymes. In contrast, although NO reduction is as exergonic as O2 reduction, there are no protons pumped in cNOR, and in addition, protons needed for NO reduction are derived from the periplasmic solution (no contribution to the electrochemical gradient is made). cNOR thus only needs to transport protons from the periplasm into the active site without the requirement to control the timing of opening and closing (gating) of proton pathways as is needed in a proton pump. Based on the crystal structure of a closely related cNOR and molecular dynamics simulations, several proton transfer pathways were suggested, and in principle, these could all be functional. In this work, we show that residues in one of the suggested pathways (denoted pathway 1) are sensitive to site-directed mutation, whereas residues in the other proposed pathways (pathways 2 and 3) could be exchanged without severe effects on turnover activity with either NO or O2. We further show that electron transfer during single-turnover reduction of O2 is limited by proton transfer and can thus be used to study alterations in proton transfer rates. The exchange of residues along pathway 1 showed specific slowing of this proton-coupled electron transfer as well as changes in its pH dependence. Our results indicate that only pathway 1 is used to transfer protons in cNOR.
Collapse
Affiliation(s)
- Josy Ter Beek
- From the Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Nils Krause
- From the Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Joachim Reimann
- From the Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Peter Lachmann
- From the Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Pia Ädelroth
- From the Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden.
| |
Collapse
|
33
|
Blomberg MR, Siegbahn PE. Why is the reduction of NO in cytochrome c dependent nitric oxide reductase (cNOR) not electrogenic? BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2013; 1827:826-33. [DOI: 10.1016/j.bbabio.2013.04.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 03/27/2013] [Accepted: 04/13/2013] [Indexed: 11/29/2022]
|
34
|
Tosha T, Shiro Y. Crystal structures of nitric oxide reductases provide key insights into functional conversion of respiratory enzymes. IUBMB Life 2013; 65:217-26. [DOI: 10.1002/iub.1135] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Accepted: 12/25/2012] [Indexed: 11/08/2022]
|
35
|
Shiro Y, Sugimoto H, Tosha T, Nagano S, Hino T. Structural basis for nitrous oxide generation by bacterial nitric oxide reductases. Philos Trans R Soc Lond B Biol Sci 2012; 367:1195-203. [PMID: 22451105 DOI: 10.1098/rstb.2011.0310] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The crystal structure of the bacterial nitric oxide reductase (cNOR) from Pseudomonas aeruginosa is reported. Its overall structure is similar to those of the main subunit of aerobic and micro-aerobic cytochrome oxidases (COXs), in agreement with the hypothesis that all these enzymes are members of the haem-copper oxidase superfamily. However, substantial structural differences between cNOR and COX are observed in the catalytic centre and the delivery pathway of the catalytic protons, which should be reflected in functional differences between these respiratory enzymes. On the basis of the cNOR structure, we propose a possible reaction mechanism of nitric oxide reduction to nitrous oxide as a working hypothesis.
Collapse
|
36
|
Ouyang H, Han H, Roh JH, Hemp J, Hosler JP, Gennis RB. Functional importance of a pair of conserved glutamic acid residues and of Ca(2+) binding in the cbb(3)-type oxygen reductases from Rhodobacter sphaeroides and Vibrio cholerae. Biochemistry 2012; 51:7290-6. [PMID: 22913716 DOI: 10.1021/bi3006847] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The cbb(3)-type cytochrome c oxidases are members of the family of heme-copper proton pumping respiratory oxygen reductases. The structure of the cbb(3)-type oxidase from Pseudomonas stutzeri reveals that, in addition to the six redox-active metal centers (two b-type hemes, three c-type hemes, and Cu(B)), the enzyme also contains at least one Ca(2+). The calcium bridges two propionate carboxyls at the interface between the low-spin heme b and the active-site heme b(3) and, in addition, is ligated to a serine in subunit CcoO and by a glutamate in subunit CcoN. The glutamate that is ligated to Ca(2+) is one of a pair of glutamic acid residues that has previously been suggested to be part of a proton exit pathway for pumped protons. In this work, mutations of these glutamates are investigated in the cbb(3)-type oxidases from Vibrio cholerae and Rhodobacter sphaeroides. Metal analysis shows that each of these wild-type enzymes contains Ca(2+). Mutations of the glutamate expected to ligate the Ca(2+) in each of these enzymes (E126 in V. cholerae and E180 in R. sphaeroides) result in a loss of activity as well as a loss of Ca(2+). Mutations of the nearby glutamate (E129 in V. cholerae and E183 in R. sphaeroides) also resulted in a loss of oxidase activity and a loss of Ca(2+). It is concluded that the Ca(2+) is essential for assembly of the fully functional enzyme and that neither of the glutamates is likely to be part of a pathway for pumped protons within the cbb(3)-type oxygen reductases. A more likely role for these glutamates is the maintenance of the structural integrity of the active conformation of the enzyme.
Collapse
Affiliation(s)
- Hanlin Ouyang
- Department of Chemistry, University of Illinois, Urbana, Illinois 61801, United States
| | | | | | | | | | | |
Collapse
|
37
|
Molecular dynamics simulations reveal proton transfer pathways in cytochrome C-dependent nitric oxide reductase. PLoS Comput Biol 2012; 8:e1002674. [PMID: 22956904 PMCID: PMC3431322 DOI: 10.1371/journal.pcbi.1002674] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2012] [Accepted: 07/22/2012] [Indexed: 01/25/2023] Open
Abstract
Nitric oxide reductases (NORs) are membrane proteins that catalyze the reduction of nitric oxide (NO) to nitrous oxide (N2O), which is a critical step of the nitrate respiration process in denitrifying bacteria. Using the recently determined first crystal structure of the cytochrome c-dependent NOR (cNOR) [Hino T, Matsumoto Y, Nagano S, Sugimoto H, Fukumori Y, et al. (2010) Structural basis of biological N2O generation by bacterial nitric oxide reductase. Science 330: 1666–70.], we performed extensive all-atom molecular dynamics (MD) simulations of cNOR within an explicit membrane/solvent environment to fully characterize water distribution and dynamics as well as hydrogen-bonded networks inside the protein, yielding the atomic details of functionally important proton channels. Simulations reveal two possible proton transfer pathways leading from the periplasm to the active site, while no pathways from the cytoplasmic side were found, consistently with the experimental observations that cNOR is not a proton pump. One of the pathways, which was newly identified in the MD simulation, is blocked in the crystal structure and requires small structural rearrangements to allow for water channel formation. That pathway is equivalent to the functional periplasmic cavity postulated in cbb3 oxidase, which illustrates that the two enzymes share some elements of the proton transfer mechanisms and confirms a close evolutionary relation between NORs and C-type oxidases. Several mechanisms of the critical proton transfer steps near the catalytic center are proposed. Denitrification is an anaerobic process performed by several bacteria as an alternative to aerobic respiration. A key intermediate step is catalyzed by the nitric oxide reductase (NOR) enzyme, which is situated in the cytoplasmic membrane. Proton delivery to the catalytic site inside NOR is an important part of its functioning. In this work we use molecular dynamics simulations to describe water distribution and to identify proton transfer pathways in cNOR. Our results reveal two channels from the periplasmic side of the membrane and none from the cytoplasmic side, indicating that cNOR is not a proton pump. It is our hope that these results will provide a basis for further experimental and computational studies aimed to understand details of the NOR mechanism. Furthermore, this work sheds light on the molecular evolution of respiratory enzymes.
Collapse
|
38
|
Blomberg MRA, Siegbahn PEM. Mechanism for N2O Generation in Bacterial Nitric Oxide Reductase: A Quantum Chemical Study. Biochemistry 2012; 51:5173-86. [DOI: 10.1021/bi300496e] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Margareta R. A. Blomberg
- Department of Physics, AlbaNova university
center,
and Department of Biochemistry and Biophysics, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Per E. M. Siegbahn
- Department of Physics, AlbaNova university
center,
and Department of Biochemistry and Biophysics, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| |
Collapse
|
39
|
Salomonsson L, Reimann J, Tosha T, Krause N, Gonska N, Shiro Y, Adelroth P. Proton transfer in the quinol-dependent nitric oxide reductase from Geobacillus stearothermophilus during reduction of oxygen. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1914-20. [PMID: 22538294 DOI: 10.1016/j.bbabio.2012.04.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Revised: 04/04/2012] [Accepted: 04/10/2012] [Indexed: 12/17/2022]
Abstract
Bacterial nitric oxide reductases (NOR) are integral membrane proteins that catalyse the reduction of nitric oxide to nitrous oxide, often as a step in the process of denitrification. Most functional data has been obtained with NORs that receive their electrons from a soluble cytochrome c in the periplasm and are hence termed cNOR. Very recently, the structure of a different type of NOR, the quinol-dependent (q)-NOR from the thermophilic bacterium Geobacillus stearothermophilus was solved to atomic resolution [Y. Matsumoto, T. Tosha, A.V. Pisliakov, T. Hino, H. Sugimoto, S. Nagano, Y. Sugita and Y. Shiro, Nat. Struct. Mol. Biol. 19 (2012) 238-246]. In this study, we have investigated the reaction between this qNOR and oxygen. Our results show that, like some cNORs, the G. stearothermophilus qNOR is capable of O(2) reduction with a turnover of ~3electronss(-1) at 40°C. Furthermore, using the so-called flow-flash technique, we show that the fully reduced (with three available electrons) qNOR reacts with oxygen in a reaction with a time constant of 1.8ms that oxidises the low-spin heme b. This reaction is coupled to proton uptake from solution and presumably forms a ferryl intermediate at the active site. The pH dependence of the reaction is markedly different from a corresponding reaction in cNOR from Paracoccus denitrificans, indicating that possibly the proton uptake mechanism and/or pathway differs between qNOR and cNOR. This study furthermore forms the basis for investigation of the proton transfer pathway in qNOR using both variants with putative proton transfer elements modified and measurements of the vectorial nature of the proton transfer. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).
Collapse
Affiliation(s)
- Lina Salomonsson
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, Stockholm, Sweden
| | | | | | | | | | | | | |
Collapse
|
40
|
Lee HJ, Reimann J, Huang Y, Ädelroth P. Functional proton transfer pathways in the heme–copper oxidase superfamily. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:537-44. [DOI: 10.1016/j.bbabio.2011.10.007] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Revised: 10/19/2011] [Accepted: 10/21/2011] [Indexed: 12/21/2022]
|
41
|
Shiro Y. Structure and function of bacterial nitric oxide reductases: nitric oxide reductase, anaerobic enzymes. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1907-13. [PMID: 22425814 DOI: 10.1016/j.bbabio.2012.03.001] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 03/01/2012] [Accepted: 03/01/2012] [Indexed: 10/28/2022]
Abstract
The crystal structures of bacterial nitric oxide reductases (NOR) from Pseudomonas aeruginosa and Geobacillus stearothermophilus were reported. The structural characteristics of these enzymes, especially at the catalytic site and on the pathway that catalytic protons are delivered, are compared, and the corresponding regions of aerobic and micro-aerobic cytochrome oxidases, O(2) reducing enzymes, which are evolutionarily related to NOR are discussed. On the basis of these structural comparisons, a mechanism for the reduction of NO to produce N(2)O by NOR, and the possible molecular evolution of the proton pumping ability of the respiratory enzymes is discussed. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).
Collapse
|
42
|
Matsumoto Y, Tosha T, Pisliakov AV, Hino T, Sugimoto H, Nagano S, Sugita Y, Shiro Y. Crystal structure of quinol-dependent nitric oxide reductase from Geobacillus stearothermophilus. Nat Struct Mol Biol 2012; 19:238-45. [PMID: 22266822 DOI: 10.1038/nsmb.2213] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Accepted: 11/22/2011] [Indexed: 11/09/2022]
Abstract
The structure of quinol-dependent nitric oxide reductase (qNOR) from G. stearothermophilus, which catalyzes the reduction of NO to produce the major ozone-depleting gas N(2)O, has been characterized at 2.5 Å resolution. The overall fold of qNOR is similar to that of cytochrome c-dependent NOR (cNOR), and some structural features that are characteristic of cNOR, such as the calcium binding site and hydrophilic cytochrome c domain, are observed in qNOR, even though it harbors no heme c. In contrast to cNOR, structure-based mutagenesis and molecular dynamics simulation studies of qNOR suggest that a water channel from the cytoplasm can serve as a proton transfer pathway for the catalytic reaction. Further structural comparison of qNOR with cNOR and aerobic and microaerobic respiratory oxidases elucidates their evolutionary relationship and possible functional conversions.
Collapse
Affiliation(s)
- Yushi Matsumoto
- Biometal Science Laboratory, RIKEN SPring-8 Center, Sayo, Hyogo, Japan
| | | | | | | | | | | | | | | |
Collapse
|
43
|
Abstract
Heme-copper oxidases (HCuOs) are the last components of the respiratory chain in mitochondria and many bacteria. They catalyze O(2) reduction and couple it to the maintenance of a proton-motive force across the membrane in which they are embedded. In the mitochondrial-like, A family of HCuOs, there are two well established proton transfer pathways leading from the cytosol to the active site, the D and the K pathways. In the C family (cbb(3)) HCuOs, recent work indicated the use of only one pathway, analogous to the K pathway. In this work, we have studied the functional importance of the suggested entry point of this pathway, the Glu-25 (Rhodobacter sphaeroides cbb(3) numbering) in the accessory subunit CcoP (E25(P)). We show that catalytic turnover is severely slowed in variants lacking the protonatable Glu-25. Furthermore, proton uptake from solution during oxidation of the fully reduced cbb(3) by O(2) is specifically and severely impaired when Glu-25 was exchanged for Ala or Gln, with rate constants 100-500 times slower than in wild type. Thus, our results support the role of E25(P) as the entry point to the proton pathway in cbb(3) and that this pathway is the main proton pathway. This is in contrast to the A-type HCuOs, where the D (and not the K) pathway is used during O(2) reduction. The cbb(3) is in addition to O(2) reduction capable of NO reduction, an activity that was largely retained in the E25(P) variants, consistent with a scenario where NO reduction in cbb(3) uses protons from the periplasmic side of the membrane.
Collapse
|
44
|
Hino T, Nagano S, Sugimoto H, Tosha T, Shiro Y. Molecular structure and function of bacterial nitric oxide reductase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:680-7. [PMID: 22001779 DOI: 10.1016/j.bbabio.2011.09.021] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2011] [Revised: 09/29/2011] [Accepted: 09/29/2011] [Indexed: 10/17/2022]
Abstract
The crystal structure of the membrane-integrated nitric oxide reductase cNOR from Pseudomonas aeruginosa was determined. The smaller NorC subunit of cNOR is comprised of 1 trans-membrane helix and a hydrophilic domain, where the heme c is located, while the larger NorB subunit consists of 12 trans-membrane helices, which contain heme b and the catalytically active binuclear center (heme b(3) and non-heme Fe(B)). The roles of the 5 well-conserved glutamates in NOR are discussed, based on the recently solved structure. Glu211 and Glu280 appear to play an important role in the catalytic reduction of NO at the binuclear center by functioning as a terminal proton donor, while Glu215 probably contributes to the electro-negative environment of the catalytic center. Glu135, a ligand for Ca(2+) sandwiched between two heme propionates from heme b and b(3), and the nearby Glu138 appears to function as a structural factor in maintaining a protein conformation that is suitable for electron-coupled proton transfer from the periplasmic region to the active site. On the basis of these observations, the possible molecular mechanism for the reduction of NO by cNOR is discussed. This article is part of a Special Issue entitled: Respiratory Oxidases.
Collapse
|
45
|
Sousa FL, Alves RJ, Ribeiro MA, Pereira-Leal JB, Teixeira M, Pereira MM. The superfamily of heme-copper oxygen reductases: types and evolutionary considerations. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2011; 1817:629-37. [PMID: 22001780 DOI: 10.1016/j.bbabio.2011.09.020] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 09/13/2011] [Accepted: 09/29/2011] [Indexed: 11/24/2022]
Abstract
Heme-copper oxygen reductases (HCO) reduce O(2) to water being the last enzymatic complexes of most aerobic respiratory chains. These enzymes promote energy conservation coupling the catalytic reaction to charge separation and charge translocation across the prokaryotic cytoplasmatic or mitochondrial membrane. In this way they contribute to the establishment and maintenance of the transmembrane difference of electrochemical potential, which is vital for solute/nutrient cell import, synthesis of ATP and motility. The HCO enzymes most probably share with the nitric oxide reductases, NORs, a common ancestor. We have proposed the classification of HCOs into three different types, A, B and C; based on the constituents of their proton channels (Pereira, Santana and Teixeira (2001) Biochim Biophys Acta, 1505, 185-208). This classification was recently challenged by the suggestion of other different types of HCOs. Using an enlarged sampling we performed an exhaustive bioinformatic reanalysis of HCOs family. Our results strengthened our previously proposed classification and showed no need for the existence of more divisions. Now, we analyze the taxonomic distribution of HCOs and NORs and the congruence of their sequence trees with the 16S rRNA tree. We observed that HCOs are widely distributed in the two prokaryotic domains and that the different types of enzymes are not confined to a specific taxonomic group or environmental niche.
Collapse
Affiliation(s)
- Filipa L Sousa
- Universidade Nova de Lisboa, Av. da República, Oeiras, Portugal
| | | | | | | | | | | |
Collapse
|
46
|
Hayashi T, Miner KD, Yeung N, Lin YW, Lu Y, Moënne-Loccoz P. Spectroscopic characterization of mononitrosyl complexes in heme--nonheme diiron centers within the myoglobin scaffold (Fe(B)Mbs): relevance to denitrifying NO reductase. Biochemistry 2011; 50:5939-47. [PMID: 21634416 DOI: 10.1021/bi200409a] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Denitrifying NO reductases are evolutionarily related to the superfamily of heme--copper terminal oxidases. These transmembrane protein complexes utilize a heme-nonheme diiron center to reduce two NO molecules to N(2)O. To understand this reaction, the diiron site has been modeled using sperm whale myoglobin as a scaffold and mutating distal residues Leu-29 and Phe-43 to histidines and Val-68 to a glutamic acid to create a nonheme Fe(B) site. The impact of incorporation of metal ions at this engineered site on the reaction of the ferrous heme with one NO was examined by UV-vis absorption, EPR, resonance Raman, and FTIR spectroscopies. UV--vis absorption and resonance Raman spectra demonstrate that the first NO molecule binds to the ferrous heme, but while the apoproteins and Cu(I)- or Zn(II)-loaded proteins show characteristic EPR signatures of S = 1/2 six-coordinate heme {FeNO}(7) species that can be observed at liquid nitrogen temperature, the Fe(II)-loaded proteins are EPR silent at ≥30 K. Vibrational modes from the heme [Fe-N-O] unit are identified in the RR and FTIR spectra using (15)NO and (15)N(18)O. The apo and Cu(I)-bound proteins exhibit ν(FeNO) and ν(NO) that are only marginally distinct from those reported for native myoglobin. However, binding of Fe(II) at the Fe(B) site shifts the heme ν(FeNO) by 17 cm(-1) and the ν(NO) by -50 cm(-1) to 1549 cm(-1). This low ν(NO) is without precedent for a six-coordinate heme {FeNO}(7) species and suggests that the NO group adopts a strong nitroxyl character stabilized by electrostatic interaction with the nearby nonheme Fe(II). Detection of a similarly low ν(NO) in the Zn(II)-loaded protein supports this interpretation.
Collapse
Affiliation(s)
- Takahiro Hayashi
- Division of Environmental and Biomolecular Systems, Oregon Health and Science University, Beaverton, Oregon 97006, United States
| | | | | | | | | | | |
Collapse
|
47
|
Sousa FL, Alves RJ, Pereira-Leal JB, Teixeira M, Pereira MM. A bioinformatics classifier and database for heme-copper oxygen reductases. PLoS One 2011; 6:e19117. [PMID: 21559461 PMCID: PMC3084760 DOI: 10.1371/journal.pone.0019117] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2010] [Accepted: 03/22/2011] [Indexed: 12/02/2022] Open
Abstract
Background Heme-copper oxygen reductases (HCOs) are the last enzymatic complexes of most aerobic respiratory chains, reducing dioxygen to water and translocating up to four protons across the inner mitochondrial membrane (eukaryotes) or cytoplasmatic membrane (prokaryotes). The number of completely sequenced genomes is expanding exponentially, and concomitantly, the number and taxonomic distribution of HCO sequences. These enzymes were initially classified into three different types being this classification recently challenged. Methodology We reanalyzed the classification scheme and developed a new bioinformatics classifier for the HCO and Nitric oxide reductases (NOR), which we benchmark against a manually derived gold standard sequence set. It is able to classify any given sequence of subunit I from HCO and NOR with a global recall and precision both of 99.8%. We use this tool to classify this protein family in 552 completely sequenced genomes. Conclusions We concluded that the new and broader data set supports three functional and evolutionary groups of HCOs. Homology between NORs and HCOs is shown and NORs closest relationship with C Type HCOs demonstrated. We established and made available a classification web tool and an integrated Heme-Copper Oxygen reductase and NOR protein database (www.evocell.org/hco).
Collapse
Affiliation(s)
- Filipa L. Sousa
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | | | | | - Miguel Teixeira
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
| | - Manuela M. Pereira
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Oeiras, Portugal
- * E-mail:
| |
Collapse
|
48
|
Lachmann P, Huang Y, Reimann J, Flock U, Adelroth P. Substrate control of internal electron transfer in bacterial nitric-oxide reductase. J Biol Chem 2010; 285:25531-7. [PMID: 20547487 DOI: 10.1074/jbc.m110.123984] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nitric -oxide reductase (NOR) from Paracoccus denitrificans catalyzes the reduction of nitric oxide (NO) to nitrous oxide (N(2)O) (2NO + 2H(+) + 2e(-) -->N(2)O + H(2)O) by a poorly understood mechanism. NOR contains two low spin hemes c and b, one high spin heme b(3), and a non-heme iron Fe(B). Here, we have studied the reaction between fully reduced NOR and NO using the "flow-flash" technique. Fully (four-electron) reduced NOR is capable of two turnovers with NO. Initial binding of NO to reduced heme b(3) occurs with a time constant of approximately 1 micros at 1.5 mM NO, in agreement with earlier studies. This reaction is [NO]-dependent, ruling out an obligatory binding of NO to Fe(B) before ligation to heme b(3). Oxidation of hemes b and c occurs in a biphasic reaction with rate constants of 50 s(-1) and 3 s(-1) at 1.5 mM NO and pH 7.5. Interestingly, this oxidation is accelerated as [NO] is lowered; the rate constants are 120 s(-1) and 12 s(-1) at 75 microM NO. Protons are taken up from solution concomitantly with oxidation of the low spin hemes, leading to an acceleration at low pH. This effect is, however, counteracted by a larger degree of substrate inhibition at low pH. Our data thus show that substrate inhibition in NOR, previously observed during multiple turnovers, already occurs during a single oxidative cycle. Thus, NO must bind to its inhibitory site before electrons redistribute to the active site. The further implications of our data for the mechanism of NO reduction by NOR are discussed.
Collapse
Affiliation(s)
- Peter Lachmann
- Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Stockholm University, SE-106 91 Stockholm, Sweden
| | | | | | | | | |
Collapse
|
49
|
Huang Y, Reimann J, Singh LM, Ädelroth P. Substrate binding and the catalytic reactions in cbb3-type oxidases: The lipid membrane modulates ligand binding. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:724-31. [DOI: 10.1016/j.bbabio.2010.03.016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2010] [Revised: 03/11/2010] [Accepted: 03/12/2010] [Indexed: 11/25/2022]
|
50
|
Roles of glutamates and metal ions in a rationally designed nitric oxide reductase based on myoglobin. Proc Natl Acad Sci U S A 2010; 107:8581-6. [PMID: 20421510 DOI: 10.1073/pnas.1000526107] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A structural and functional model of bacterial nitric oxide reductase (NOR) has been designed by introducing two glutamates (Glu) and three histidines (His) in sperm whale myoglobin. X-ray structural data indicate that the three His and one Glu (V68E) residues bind iron, mimicking the putative Fe(B) site in NOR, while the second Glu (I107E) interacts with a water molecule and forms a hydrogen bonding network in the designed protein. Unlike the first Glu (V68E), which lowered the heme reduction potential by approximately 110 mV, the second Glu has little effect on the heme potential, suggesting that the negatively charged Glu has a different role in redox tuning. More importantly, introducing the second Glu resulted in a approximately 100% increase in NOR activity, suggesting the importance of a hydrogen bonding network in facilitating proton delivery during NOR reactivity. In addition, EPR and X-ray structural studies indicate that the designed protein binds iron, copper, or zinc in the Fe(B) site, each with different effects on the structures and NOR activities, suggesting that both redox activity and an intermediate five-coordinate heme-NO species are important for high NOR activity. The designed protein offers an excellent model for NOR and demonstrates the power of using designed proteins as a simpler and more well-defined system to address important chemical and biological issues.
Collapse
|