1
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He Y, Haque MM, Stuehr DJ, Lu HP. Conformational States and Fluctuations in Endothelial Nitric Oxide Synthase under Calmodulin Regulation. Biophys J 2021; 120:5196-5206. [PMID: 34748763 DOI: 10.1016/j.bpj.2021.11.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Revised: 09/30/2021] [Accepted: 11/02/2021] [Indexed: 11/30/2022] Open
Abstract
Mechanisms that regulate nitric oxide synthase enzymes (NOS) are of interest in biology and medicine. Although NOS catalysis relies on domain motions and is activated by calmodulin (CaM) binding, the relationships are unclear. We used single-molecule fluorescence resonance energy transfer (FRET) spectroscopy to elucidate the conformational states distribution and associated conformational fluctuation dynamics of the two NOS electron transfer domains in a FRET dye-labeled endothelial NOS reductase domain (eNOSr) and to understand how CaM affects the dynamics to regulate catalysis by shaping the spatial and temporal conformational behaviors of eNOSr. In addition, we developed and applied a new imaging approach capable of recording 3D FRET efficiency vs time images to characterize the impact on dynamic conformal states of the eNOSr enzyme by the binding of CaM, which identifies clearly that CaM binding generates an extra new open state of eNOSr, resolving more detailed NOS conformational states and their fluctuation dynamics. We identified a new output state that has an extra-open FAD-FMN conformation that is only populated in the CaM-bound eNOSr. This may reveal the critical role of CaM in triggering NOS activity as it gives conformational flexibility for eNOSr to assume the electron transfer output FMN-Heme state. Our results provide a dynamic link to recently reported EM static structure analyses and demonstrate a capable approach in probing and simultaneously analyzing all of the conformational states, their fluctuations, and the fluctuation dynamics for understanding the mechanism of NOS electron transfer, involving electron transfer amongst FAD, FMN, and Heme domains, during NO synthesis.
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Affiliation(s)
- Yufan He
- Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403
| | - Mohammad Mahfuzul Haque
- Department of Inflammation and Immunology, Lerner Research Institute, The Cleveland Clinic, 9500 Euclid Avenue, Cleveland Clinic, Cleveland, Ohio, 44195
| | - Dennis J Stuehr
- Department of Inflammation and Immunology, Lerner Research Institute, The Cleveland Clinic, 9500 Euclid Avenue, Cleveland Clinic, Cleveland, Ohio, 44195.
| | - H Peter Lu
- Center for Photochemical Sciences, Department of Chemistry, Bowling Green State University, Bowling Green, Ohio 43403.
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2
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Dao VTV, Elbatreek MH, Fuchß T, Grädler U, Schmidt HHHW, Shah AM, Wallace A, Knowles R. Nitric Oxide Synthase Inhibitors into the Clinic at Last. Handb Exp Pharmacol 2021; 264:169-204. [PMID: 32797331 DOI: 10.1007/164_2020_382] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The 1998 Nobel Prize in Medicine and Physiology for the discovery of nitric oxide, a nitrogen containing reactive oxygen species (also termed reactive nitrogen or reactive nitrogen/oxygen species) stirred great hopes. Clinical applications, however, have so far pertained exclusively to the downstream signaling of cGMP enhancing drugs such as phosphodiesterase inhibitors and soluble guanylate cyclase stimulators. All clinical attempts, so far, to inhibit NOS have failed even though preclinical models were strikingly positive and clinical biomarkers correlated perfectly. This rather casts doubt on our current way of target identification in drug discovery in general and our way of patient stratification based on correlating but not causal biomarkers or symptoms. The opposite, NO donors, nitrite and enhancing NO synthesis by eNOS/NOS3 recoupling in situations of NO deficiency, are rapidly declining in clinical relevance or hold promise but need yet to enter formal therapeutic guidelines, respectively. Nevertheless, NOS inhibition in situations of NO overproduction often jointly with enhanced superoxide (or hydrogen peroxide production) still holds promise, but most likely only in acute conditions such as neurotrauma (Stover et al., J Neurotrauma 31(19):1599-1606, 2014) and stroke (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019). Conversely, in chronic conditions, long-term inhibition of NOS might be too risky because of off-target effects on eNOS/NOS3 in particular for patients with cardiovascular risks or metabolic and renal diseases. Nitric oxide synthases (NOS) and their role in health (green) and disease (red). Only neuronal/type 1 NOS (NOS1) has a high degree of clinical validation and is in late stage development for traumatic brain injury, followed by a phase II safety/efficacy trial in ischemic stroke. The pathophysiology of NOS1 (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016) is likely to be related to parallel superoxide or hydrogen peroxide formation (Kleinschnitz et al., J Cereb Blood Flow Metab 1508-1512, 2016; Casas et al., Proc Natl Acad Sci U S A 114(46):12315-12320, 2017; Casas et al., Proc Natl Acad Sci U S A 116(14):7129-7136, 2019) leading to peroxynitrite and protein nitration, etc. Endothelial/type 3 NOS (NOS3) is considered protective only and its inhibition should be avoided. The preclinical evidence for a role of high-output inducible/type 2 NOS (NOS2) isoform in sepsis, asthma, rheumatic arthritis, etc. was high, but all clinical development trials in these indications were neutral despite target engagement being validated. This casts doubt on the role of NOS2 in humans in health and disease (hence the neutral, black coloring).
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Affiliation(s)
- Vu Thao-Vi Dao
- Department of Psychiatry, Psychosomatic Medicine and Psychotherapy, University Hospital Frankfurt, Goethe University, Frankfurt am Main, Germany
| | - Mahmoud H Elbatreek
- Department of Pharmacology and Personalised Medicine, MeHNS, FHML, Maastricht, The Netherlands.,Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Zagazig, Egypt
| | - Thomas Fuchß
- Takeda GmbH (former Nycomed/Altana Pharma), Konstanz, Germany
| | - Ulrich Grädler
- Takeda GmbH (former Nycomed/Altana Pharma), Konstanz, Germany
| | - Harald H H W Schmidt
- Department of Pharmacology and Personalised Medicine, MeHNS, FHML, Maastricht, The Netherlands
| | - Ajay M Shah
- King's College London British Heart Foundation Centre, School of Cardiovascular Medicine and Sciences, London, UK
| | - Alan Wallace
- Health and Life Sciences, Coventry University, Coventry, UK
| | - Richard Knowles
- Knowles Consulting Ltd., The Stevenage Bioscience Catalyst, Stevenage, UK.
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3
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Garcia V, Park EJ, Siragusa M, Frohlich F, Mahfuzul Haque M, Pascale JV, Heberlein KR, Isakson BE, Stuehr DJ, Sessa WC. Unbiased proteomics identifies plasminogen activator inhibitor-1 as a negative regulator of endothelial nitric oxide synthase. Proc Natl Acad Sci U S A 2020; 117:9497-9507. [PMID: 32300005 PMCID: PMC7196906 DOI: 10.1073/pnas.1918761117] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Nitric oxide (NO) produced by endothelial nitric oxide synthase (eNOS) is a critical mediator of vascular function. eNOS is tightly regulated at various levels, including transcription, co- and posttranslational modifications, and by various protein-protein interactions. Using stable isotope labeling with amino acids in cell culture (SILAC) and mass spectrometry (MS), we identified several eNOS interactors, including the protein plasminogen activator inhibitor-1 (PAI-1). In cultured human umbilical vein endothelial cells (HUVECs), PAI-1 and eNOS colocalize and proximity ligation assays demonstrate a protein-protein interaction between PAI-1 and eNOS. Knockdown of PAI-1 or eNOS eliminates the proximity ligation assay (PLA) signal in endothelial cells. Overexpression of eNOS and HA-tagged PAI-1 in COS7 cells confirmed the colocalization observations in HUVECs. Furthermore, the source of intracellular PAI-1 interacting with eNOS was shown to be endocytosis derived. The interaction between PAI-1 and eNOS is a direct interaction as supported in experiments with purified proteins. Moreover, PAI-1 directly inhibits eNOS activity, reducing NO synthesis, and the knockdown or antagonism of PAI-1 increases NO bioavailability. Taken together, these findings place PAI-1 as a negative regulator of eNOS and disruptions in eNOS-PAI-1 binding promote increases in NO production and enhance vasodilation in vivo.
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Affiliation(s)
- Victor Garcia
- Vascular Biology and Therapeutics Program, Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520
| | - Eon Joo Park
- Vascular Biology and Therapeutics Program, Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520
| | - Mauro Siragusa
- Institute for Vascular Signaling, Centre for Molecular Medicine, Goethe University, 60596 Frankfurt am Main, Germany
| | - Florian Frohlich
- Vascular Biology and Therapeutics Program, Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520
- Department of Biology/Chemistry, Molecular Membrane Biology Section, University of Osnabrück, 49076 Osnabrück, Germany
| | - Mohammad Mahfuzul Haque
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - Jonathan V Pascale
- Department of Pharmacology, New York Medical College, Valhalla, NY 10595
| | - Katherine R Heberlein
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Brant E Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Dennis J Stuehr
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195
| | - William C Sessa
- Vascular Biology and Therapeutics Program, Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520;
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4
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Gantner BN, LaFond KM, Bonini MG. Nitric oxide in cellular adaptation and disease. Redox Biol 2020; 34:101550. [PMID: 32438317 PMCID: PMC7235643 DOI: 10.1016/j.redox.2020.101550] [Citation(s) in RCA: 92] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Revised: 04/15/2020] [Accepted: 04/20/2020] [Indexed: 02/07/2023] Open
Abstract
Nitric oxide synthases are the major sources of nitric oxide, a critical signaling molecule involved in a wide range of cellular and physiological processes. These enzymes comprise a family of genes that are highly conserved across all eukaryotes. The three family members found in mammals are important for inter- and intra-cellular signaling in tissues that include the nervous system, the vasculature, the gut, skeletal muscle, and the immune system, among others. We summarize major advances in the understanding of biochemical and tissue-specific roles of nitric oxide synthases, with a focus on how these mechanisms enable tissue adaptation and health or dysfunction and disease. We highlight the unique mechanisms and processes of neuronal nitric oxide synthase, or NOS1. This was the first of these enzymes discovered in mammals, and yet much remains to be understood about this highly conserved and complex gene. We provide examples of two areas that will likely be of increasing importance in nitric oxide biology. These include the mechanisms by which these critical enzymes promote adaptation or disease by 1) coordinating communication by diverse cell types within a tissue and 2) directing cellular differentiation/activation decisions processes.
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Affiliation(s)
- Benjamin N Gantner
- Department of Medicine, Division of Endocrinology, Medical College of Wisconsin, USA.
| | - Katy M LaFond
- Department of Medicine, Division of Endocrinology, Medical College of Wisconsin, USA
| | - Marcelo G Bonini
- Department of Medicine, Division of Endocrinology, Medical College of Wisconsin, USA; Feinberg School of Medicine, Division of Hematology and Oncology, Robert H. Lurie Comprehensive Cancer Center, Northwestern University, USA
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5
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Tavolieri AM, Murray DT, Askenasy I, Pennington JM, McGarry L, Stanley CB, Stroupe ME. NADPH-dependent sulfite reductase flavoprotein adopts an extended conformation unique to this diflavin reductase. J Struct Biol 2019; 205:170-179. [DOI: 10.1016/j.jsb.2019.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 12/30/2018] [Accepted: 01/03/2019] [Indexed: 11/17/2022]
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6
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Stuehr DJ, Haque MM. Nitric oxide synthase enzymology in the 20 years after the Nobel Prize. Br J Pharmacol 2019; 176:177-188. [PMID: 30402946 PMCID: PMC6295403 DOI: 10.1111/bph.14533] [Citation(s) in RCA: 94] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2018] [Revised: 10/25/2018] [Accepted: 10/31/2018] [Indexed: 12/31/2022] Open
Abstract
This review briefly summarizes what was known about NOS enzymology at the time of the Nobel Prize award in 1998 and then discusses from the author's perspective some of the advances in NOS enzymology over the subsequent 20 years, focused on five aspects: the maturation process of NOS enzymes and its regulation; the mechanism of NO synthesis; the redox roles played by the 6R-tetrahydrobiopterin cofactor; the role of protein conformational behaviour in enabling NOS electron transfer and its regulation by NOS structural elements and calmodulin, and the catalytic cycling pathways of NOS enzymes and their influence on NOS activity. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.
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Affiliation(s)
- Dennis J Stuehr
- Department of Inflammation and Immunity, Lerner Research InstituteThe Cleveland ClinicClevelandOHUSA
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7
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Rios-Ibarra CP, Torres-De La Cruz V, Ochoa-Ruiz AG, Rivas-Estilla AM. Quantification of nitric oxide by high-performance liquid chromatography-fluorometric method in subgenomic hepatitis C virus-replicon expressing Huh7 cells upon treatment with acetylsalicylic acid. Exp Ther Med 2018; 16:2621-2626. [PMID: 30186494 DOI: 10.3892/etm.2018.6515] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 02/22/2018] [Indexed: 12/13/2022] Open
Abstract
As nitric oxide (NO) expression levels are lower in hepatocytes compared with other cell types, it is difficult to quantify this compound via Griess assay. The aim of the present study was to quantify NO concentration in the cell culture medium from a subgenomic hepatitis C virus (HCV)-replicon expressing Huh-7 cell system using a high-performance liquid chromatography (HPLC)-fluorescence detector in the presence or absence of acetylsalicylic acid (ASA) treatment. HCV-replicon cells were incubated with ASA (4 mM) for 24, 48 and 72 h. Thereafter, the medium was collected to measure nitrites (NO2-) as an indirect indicator of NO levels using diaminonaphtalene as a derivate agent. NO levels were significantly higher (1.7-fold) in Huh-7 replicon cells treated with ASA (72 h post-treatment) than untreated cells (P<0.05); NO inhibitor reduced ~30% the level of NO in Huh-7 replicon cells treated with ASA (48 h post-treatment; P<0.05). The findings suggested that the HPLC-fluorescence method provided an accurate and efficient measurement of NO production in Huh-7-HCV-replicon cells culture medium.
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Affiliation(s)
- Clara Patricia Rios-Ibarra
- Department of Biochemistry and Molecular Medicine, School of Medicine, Autonomous University of Nuevo Leon, Monterrey, Nuevo León 64460, México.,Department of Bioengineering, Tecnologico de Monterrey, Campus Guadalajara, Zapopan, Jalisco 45138, México
| | - Victor Torres-De La Cruz
- Biomedical Research Center, Northeast Mexican Social Security Institute, Monterrey, Nuevo León 64720, México
| | - Andrea Gabriela Ochoa-Ruiz
- Department of Bioengineering, Tecnologico de Monterrey, Campus Guadalajara, Zapopan, Jalisco 45138, México
| | - Ana María Rivas-Estilla
- Department of Biochemistry and Molecular Medicine, School of Medicine, Autonomous University of Nuevo Leon, Monterrey, Nuevo León 64460, México
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8
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Freeman SL, Martel A, Devos JM, Basran J, Raven EL, Roberts GCK. Solution structure of the cytochrome P450 reductase-cytochrome c complex determined by neutron scattering. J Biol Chem 2018; 293:5210-5219. [PMID: 29475945 PMCID: PMC5892573 DOI: 10.1074/jbc.ra118.001941] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 02/20/2018] [Indexed: 01/22/2023] Open
Abstract
Electron transfer in all living organisms critically relies on formation of complexes between the proteins involved. The function of these complexes requires specificity of the interaction to allow for selective electron transfer but also a fast turnover of the complex, and they are therefore often transient in nature, making them challenging to study. Here, using small-angle neutron scattering with contrast matching with deuterated protein, we report the solution structure of the electron transfer complex between cytochrome P450 reductase (CPR) and its electron transfer partner cytochrome c This is the first reported solution structure of a complex between CPR and an electron transfer partner. The structure shows that the interprotein interface includes residues from both the FMN- and FAD-binding domains of CPR. In addition, the FMN is close to the heme of cytochrome c but distant from the FAD, indicating that domain movement is required between the electron transfer steps in the catalytic cycle of CPR. In summary, our results reveal key details of the CPR catalytic mechanism, including interactions of two domains of the reductase with cytochrome c and motions of these domains relative to one another. These findings shed light on interprotein electron transfer in this system and illustrate a powerful approach for studying solution structures of protein-protein complexes.
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Affiliation(s)
- Samuel L Freeman
- From the Departments of Chemistry and.,Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble, France.,Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester LE1 7RH, United Kingdom and
| | - Anne Martel
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble, France
| | - Juliette M Devos
- Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble, France
| | - Jaswir Basran
- From the Departments of Chemistry and.,Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester LE1 7RH, United Kingdom and.,Molecular and Cell Biology and
| | - Emma L Raven
- From the Departments of Chemistry and .,Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester LE1 7RH, United Kingdom and
| | - Gordon C K Roberts
- Leicester Institute of Structural and Chemical Biology, University of Leicester, Leicester LE1 7RH, United Kingdom and .,Molecular and Cell Biology and
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9
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Haque MM, Tejero J, Bayachou M, Kenney CT, Stuehr DJ. A cross-domain charge interaction governs the activity of NO synthase. J Biol Chem 2018; 293:4545-4554. [PMID: 29414777 DOI: 10.1074/jbc.ra117.000635] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Revised: 01/17/2018] [Indexed: 11/06/2022] Open
Abstract
NO synthase (NOS) enzymes perform interdomain electron transfer reactions during catalysis that may rely on complementary charge interactions at domain-domain interfaces. Guided by our previous results and a computer-generated domain-docking model, we assessed the importance of cross-domain charge interactions in the FMN-to-heme electron transfer in neuronal NOS (nNOS). We reversed the charge of three residues (Glu-762, Glu-816, and Glu-819) that form an electronegative triad on the FMN domain and then individually reversed the charges of three electropositive residues (Lys-423, Lys-620, and Lys-660) on the oxygenase domain (NOSoxy), to potentially restore a cross-domain charge interaction with the triad, but in reversed polarity. Charge reversal of the triad completely eliminated heme reduction and NO synthesis in nNOS. These functions were partly restored by the charge reversal at oxygenase residue Lys-423, but not at Lys-620 or Lys-660. Full recovery of heme reduction was probably muted by an accompanying change in FMN midpoint potential that made electron transfer to the heme thermodynamically unfavorable. Our results provide direct evidence that cross-domain charge pairing is required for the FMN-to-heme electron transfer in nNOS. The unique ability of charge reversal at position 423 to rescue function indicates that it participates in an essential cross-domain charge interaction with the FMN domain triad. This supports our domain-docking model and suggests that it may depict a productive electron transfer complex formed during nNOS catalysis.
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Affiliation(s)
- Mohammad Mahfuzul Haque
- From the Departments of Pathobiology, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195
| | - Jesús Tejero
- the Pittsburgh Heart, Lung, Blood, and Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15213, and
| | - Mekki Bayachou
- the Department of Chemistry, Cleveland State University, Cleveland, Ohio 44115
| | - Claire T Kenney
- From the Departments of Pathobiology, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195
| | - Dennis J Stuehr
- From the Departments of Pathobiology, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195,
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10
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Campelo D, Lautier T, Urban P, Esteves F, Bozonnet S, Truan G, Kranendonk M. The Hinge Segment of Human NADPH-Cytochrome P450 Reductase in Conformational Switching: The Critical Role of Ionic Strength. Front Pharmacol 2017; 8:755. [PMID: 29163152 PMCID: PMC5670117 DOI: 10.3389/fphar.2017.00755] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2017] [Accepted: 10/04/2017] [Indexed: 11/18/2022] Open
Abstract
NADPH-cytochrome P450 reductase (CPR) is a redox partner of microsomal cytochromes P450 and is a prototype of the diflavin reductase family. CPR contains 3 distinct functional domains: a FMN-binding domain (acceptor reduction), a linker (hinge), and a connecting/FAD domain (NADPH oxidation). It has been demonstrated that the mechanism of CPR exhibits an important step in which it switches from a compact, closed conformation (locked state) to an ensemble of open conformations (unlocked state), the latter enabling electron transfer to redox partners. The conformational equilibrium between the locked and unlocked states has been shown to be highly dependent on ionic strength, reinforcing the hypothesis of the presence of critical salt interactions at the interface between the FMN and connecting FAD domains. Here we show that specific residues of the hinge segment are important in the control of the conformational equilibrium of CPR. We constructed six single mutants and two double mutants of the human CPR, targeting residues G240, S243, I245 and R246 of the hinge segment, with the aim of modifying the flexibility or the potential ionic interactions of the hinge segment. We measured the reduction of cytochrome c at various salt concentrations of these 8 mutants, either in the soluble or membrane-bound form of human CPR. All mutants were found capable of reducing cytochrome c yet with different efficiency and their maximal rates of cytochrome c reduction were shifted to lower salt concentration. In particular, residue R246 seems to play a key role in a salt bridge network present at the interface of the hinge and the connecting domain. Interestingly, the effects of mutations, although similar, demonstrated specific differences when present in the soluble or membrane-bound context. Our results demonstrate that the electrostatic and flexibility properties of the hinge segment are critical for electron transfer from CPR to its redox partners.
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Affiliation(s)
- Diana Campelo
- Center for Toxicogenomics and Human Health (ToxOmics), Genetics, Oncology and Human Toxicology, NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Thomas Lautier
- LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France
| | - Philippe Urban
- LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France
| | - Francisco Esteves
- Center for Toxicogenomics and Human Health (ToxOmics), Genetics, Oncology and Human Toxicology, NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
| | - Sophie Bozonnet
- LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France
| | - Gilles Truan
- LISBP, Université de Toulouse, CNRS, INRA, INSA, Toulouse, France
| | - Michel Kranendonk
- Center for Toxicogenomics and Human Health (ToxOmics), Genetics, Oncology and Human Toxicology, NOVA Medical School, Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Lisboa, Portugal
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11
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Ramasamy S, Haque MM, Gangoda M, Stuehr DJ. Tetrahydrobiopterin redox cycling in nitric oxide synthase: evidence supports a through-heme electron delivery. FEBS J 2016; 283:4491-4501. [PMID: 27760279 PMCID: PMC5387691 DOI: 10.1111/febs.13933] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Revised: 10/06/2016] [Accepted: 10/17/2016] [Indexed: 11/30/2022]
Abstract
The nitric oxide synthases (NOS) catalyze a two-step oxidation of l-arginine (Arg) to generate NO. In the first step, O2 activation involves one electron being provided to the heme by an enzyme-bound 6R-tetrahydro-l-biopterin cofactor (H4 B), and the H4 B radical must be reduced back to H4 B in order for NOS to continue catalysis. Although an NADPH-derived electron is used to reduce the H4 B radical, how this occurs is unknown. We hypothesized that the NOS flavoprotein domain might reduce the H4 B radical by utilizing the NOS heme porphyrin as a conduit to deliver the electron. This model predicts that factors influencing NOS heme reduction should also influence the extent and rate of H4 B radical reduction in kind. To test this, we utilized single catalytic turnover and stop-freeze methods, along with electron paramagnetic resonance spectroscopy, to measure the rate and extent of reduction of the 5-methyl-H4 B radical formed in neuronal NOS (nNOS) during Arg hydroxylation. We used several nNOS variants that supported either a slower or faster than normal rate of ferric heme reduction. We found that the rates and extents of nNOS heme reduction correlated well with the rates and extents of 5-methyl-H4 B radical reduction among the various nNOS enzymes. This supports a model where the heme porphyrin transfers an electron from the NOS flavoprotein to the H4 B radical formed during catalysis, revealing that the heme plays a dual role in catalyzing O2 activation or electron transfer at distinct points in the reaction cycle.
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Affiliation(s)
- Somasundaram Ramasamy
- Department of Pathobiology, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA
| | - Mohammad Mahfuzul Haque
- Department of Pathobiology, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA
| | - Mahinda Gangoda
- Department of Chemistry and Biochemistry, Kent State University, Kent, OH 44242, USA
| | - Dennis J. Stuehr
- Department of Pathobiology, Lerner Research Institute, The Cleveland Clinic, Cleveland, Ohio 44195, USA
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12
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Haque MM, Ray SS, Stuehr DJ. Phosphorylation Controls Endothelial Nitric-oxide Synthase by Regulating Its Conformational Dynamics. J Biol Chem 2016; 291:23047-23057. [PMID: 27613870 DOI: 10.1074/jbc.m116.737361] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Indexed: 11/06/2022] Open
Abstract
The activity of endothelial NO synthase (eNOS) is triggered by calmodulin (CaM) binding and is often further regulated by phosphorylation at several positions in the enzyme. Phosphorylation at Ser1179 occurs in response to diverse physiologic stimuli and increases the NO synthesis and cytochrome c reductase activities of eNOS, thereby enhancing its participation in biological signal cascades. Despite its importance, the mechanism by which Ser1179 phosphorylation increases eNOS activity is not understood. To address this, we used stopped-flow spectroscopy and computer modeling approaches to determine how the phosphomimetic mutation (S1179D) may impact electron flux through eNOS and the conformational behaviors of its reductase domain, both in the absence and presence of bound CaM. We found that S1179D substitution in CaM-free eNOS had multiple effects; it increased the rate of flavin reduction, altered the conformational equilibrium of the reductase domain, and increased the rate of its conformational transitions. We found these changes were equivalent in degree to those caused by CaM binding to wild-type eNOS, and the S1179D substitution together with CaM binding caused even greater changes in these parameters. The modeling indicated that the changes caused by the S1179D substitution, despite being restricted to the reductase domain, are sufficient to explain the stimulation of both the cytochrome c reductase and NO synthase activities of eNOS. This helps clarify how Ser1179 phosphorylation regulates eNOS and provides a foundation to compare its regulation by other phosphorylation events.
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Affiliation(s)
- Mohammad Mahfuzul Haque
- From the Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
| | - Sougata Sinha Ray
- From the Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
| | - Dennis J Stuehr
- From the Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, Ohio 44195
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13
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Wang ZQ, Haque MM, Binder K, Sharma M, Wei CC, Stuehr DJ. Engineering nitric oxide synthase chimeras to function as NO dioxygenases. J Inorg Biochem 2016; 158:122-130. [PMID: 27013266 DOI: 10.1016/j.jinorgbio.2016.03.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 03/10/2016] [Accepted: 03/12/2016] [Indexed: 10/22/2022]
Abstract
Nitric oxide synthases (NOSs) catalyze a two-step oxidation of l-arginine to form nitric oxide (NO) and l-citrulline. NOS contains a N-terminal oxygenase domain (NOSoxy) that is the site of NO synthesis, and a C-terminal reductase domain (NOSred) that binds nicotinamide adenine dinucleotide phosphate (NADPH), flavin adenine dinucleotide (FAD), and flavin mononucleotide (FMN) and provides electrons to the NOSoxy heme during catalysis. The three NOS isoforms in mammals inducible NOS (iNOS), neuronal NOS (nNOS), and endothelial NOS (eNOS) share high structural similarity but differ in NO release rates and catalytic properties due to differences in enzyme kinetic parameters. These parameters must be balanced for NOS enzymes to release NO, rather than consume it in a competing, inherent NO dioxygenase reaction. To improve understanding, we drew on a global catalytic model and previous findings to design three NOS chimeras that may predominantly function as NO dioxygenases: iNOSoxy/nNOSred (Wild type (WT) chimera), V346I iNOSoxy/nNOSred (V346I chimera) and iNOSoxy/S1412D nNOSred (S1412D chimera). The WT and S1412D chimeras had higher NO release than the parent iNOS, while the V346I chimera exhibited much lower NO release, consistent with expectations. Measurements indicated that a greater NO dioxygenase activity was achieved, particularly in the V346I chimera, which dioxygenated an estimated two to four NO per NO that it released, while the other chimeras had nearly equivalent NO dioxygenase and NO release activities. Computer simulations of the global catalytic model using the measured kinetic parameters produced results that mimicked the measured outcomes, and this provided further insights on the catalytic behaviors of the chimeras and basis of their increased NO dioxygenase activities.
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Affiliation(s)
- Zhi-Qiang Wang
- Department of Chemistry and Biochemistry, Kent State University Geauga, Burton, OH 44021, United States.
| | - Mohammad Mahfuzul Haque
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, United States
| | - Katherine Binder
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, United States
| | - Manisha Sharma
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, United States
| | - Chin-Chuan Wei
- Department of Chemistry, Southern Illinois University Edwardsville, Edwardsville, IL 62026, United States
| | - Dennis J Stuehr
- Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, United States.
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14
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Jeandroz S, Wipf D, Stuehr DJ, Lamattina L, Melkonian M, Tian Z, Zhu Y, Carpenter EJ, Wong GKS, Wendehenne D. Occurrence, structure, and evolution of nitric oxide synthase–like proteins in the plant kingdom. Sci Signal 2016; 9:re2. [DOI: 10.1126/scisignal.aad4403] [Citation(s) in RCA: 166] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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15
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Leferink NGH, Hay S, Rigby SEJ, Scrutton NS. Towards the free energy landscape for catalysis in mammalian nitric oxide synthases. FEBS J 2014; 282:3016-29. [PMID: 25491181 DOI: 10.1111/febs.13171] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Revised: 12/05/2014] [Accepted: 12/05/2014] [Indexed: 01/30/2023]
Abstract
The general requirement for conformational sampling in biological electron transfer reactions catalysed by multi-domain redox systems has been emphasized in recent years. Crucially, we lack insight into the extent of the conformational space explored and the nature of the energy landscapes associated with these reactions. The nitric oxide synthases (NOS) produce the signalling molecule NO through a series of complex electron transfer reactions. There is accumulating evidence that protein domain dynamics and calmodulin binding are implicated in regulating electron flow from NADPH, through the FAD and FMN cofactors, to the haem oxygenase domain, where NO is generated. Simple models based on static crystal structures of the isolated reductase domain have suggested a role for large-scale motions of the FMN-binding domain in shuttling electrons from the reductase domain to the oxygenase domain. However, detailed insight into the higher-order domain architecture and dynamic structural transitions in NOS enzymes during enzyme turnover is lacking. In this review, we discuss the recent advances made towards mapping the catalytic free energy landscapes of NOS enzymes through integration of both structural techniques (e.g. cryo-electron microscopy) and biophysical techniques (e.g. pulsed-electron paramagnetic resonance). The general picture that emerges from these experiments is that NOS enzymes exist in an equilibrium of conformations, comprising a 'rugged' or 'frustrated' energy landscape, with a key regulatory role for calmodulin in driving vectorial electron transfer by altering the conformational equilibrium. A detailed understanding of these landscapes may provide new opportunities for discovery of isoform-specific inhibitors that bind at the dynamic interfaces of these multi-dimensional energy landscapes.
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Affiliation(s)
- Nicole G H Leferink
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, UK
| | - Sam Hay
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, UK
| | - Stephen E J Rigby
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, UK
| | - Nigel S Scrutton
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, UK
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16
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Haque MM, Bayachou M, Tejero J, Kenney CT, Pearl NM, Im SC, Waskell L, Stuehr DJ. Distinct conformational behaviors of four mammalian dual-flavin reductases (cytochrome P450 reductase, methionine synthase reductase, neuronal nitric oxide synthase, endothelial nitric oxide synthase) determine their unique catalytic profiles. FEBS J 2014; 281:5325-40. [PMID: 25265015 DOI: 10.1111/febs.13073] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 08/27/2014] [Accepted: 09/25/2014] [Indexed: 12/14/2022]
Abstract
Multidomain enzymes often rely on large conformational motions to function. However, the conformational setpoints, rates of domain motions and relationships between these parameters and catalytic activity are not well understood. To address this, we determined and compared the conformational setpoints and the rates of conformational switching between closed unreactive and open reactive states in four mammalian diflavin NADPH oxidoreductases that catalyze important biological electron transfer reactions: cytochrome P450 reductase, methionine synthase reductase and endothelial and neuronal nitric oxide synthase. We used stopped-flow spectroscopy, single turnover methods and a kinetic model that relates electron flux through each enzyme to its conformational setpoint and its rates of conformational switching. The results show that the four flavoproteins, when fully-reduced, have a broad range of conformational setpoints (from 12% to 72% open state) and also vary 100-fold with respect to their rates of conformational switching between unreactive closed and reactive open states (cytochrome P450 reductase > neuronal nitric oxide synthase > methionine synthase reductase > endothelial nitric oxide synthase). Furthermore, simulations of the kinetic model could explain how each flavoprotein can support its given rate of electron flux (cytochrome c reductase activity) based on its unique conformational setpoint and switching rates. The present study is the first to quantify these conformational parameters among the diflavin enzymes and suggests how the parameters might be manipulated to speed or slow biological electron flux.
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Affiliation(s)
- Mohammad M Haque
- Department of Pathobiology, Lerner Research Institute, The Cleveland Clinic, Cleveland, OH, USA
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17
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Gao X, Guo M, Li Q, Peng L, Liu H, Zhang L, Bai X, Wang Y, Li J, Cai C. Plasma metabolomic profiling to reveal antipyretic mechanism of Shuang-huang-lian injection on yeast-induced pyrexia rats. PLoS One 2014; 9:e100017. [PMID: 24940599 PMCID: PMC4062457 DOI: 10.1371/journal.pone.0100017] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 05/21/2014] [Indexed: 01/28/2023] Open
Abstract
Shuang-huang-lian injection (SHLI) is a famous Chinese patent medicine, which has been wildly used in clinic for the treatment of acute respiratory tract infection, pneumonia, influenza, etc. The existing randomized controlled trial (RCT) studies suggested that SHLI could afford a certain anti-febrile action. However, seldom does research concern the pharmacological mechanisms of SHLI. In the current study, we explored plasma metabolomic profiling technique and selected potential metabolic markers to reveal the antipyretic mechanism of SHLI on yeast-induced pyrexia rat model using UPLC-Q-TOF/MS coupled with multivariate statistical analysis and pattern recognition techniques. We discovered a significant perturbance of metabolic profile in the plasma of fever rats and obvious reversion in SHLI-administered rats. Eight potential biomarkers, i.e. 1) 3-hydeoxybutyric acid, 2) leucine, 3) 16:0 LPC, 4) allocholic acid, 5) vitamin B2, 6) Cys-Lys-His, 7) 18:2 LPC, and 8) 3-hydroxychola-7, 22-dien-24-oic acid, were screened out by OPLS-DA approach. Five potential perturbed metabolic pathways, i.e. 1) valine, leucine, and isoleucine biosynthesis, 2) glycerophospholipid metabolism, 3) ketone bodies synthesis and degradation, 4) bile acid biosynthesis, and 5) riboflavin metabolism, were revealed to relate to the antipyretic mechanisms of SHLI. Overall, we investigated antipyretic mechanisms of SHLI at metabolomic level for the first time, and the obtained results highlights the necessity of adopting metabolomics as a reliable tool for understanding the holism and synergism of Chinese patent drug.
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Affiliation(s)
- Xiaoyan Gao
- Science experiment center for TCM, Beijing University of Chinese Medicine, Beijing, China
| | - Mingxing Guo
- Science experiment center for TCM, Beijing University of Chinese Medicine, Beijing, China
| | - Qiang Li
- School of Chinese material medica, Beijing University of Chinese Medicine, Beijing, China
| | - Long Peng
- Science experiment center for TCM, Beijing University of Chinese Medicine, Beijing, China
| | - Haiyu Liu
- Science experiment center for TCM, Beijing University of Chinese Medicine, Beijing, China
| | - Li Zhang
- Science experiment center for TCM, Beijing University of Chinese Medicine, Beijing, China
| | - Xu Bai
- Waters technologies (Shanghai) Ltd., Shanghai, China
| | - Yingxin Wang
- The 2 Traditional Chinese Medicine factory of Harbin pharm group CO. LTD, Harbin, China
| | - Jian Li
- School of Basic Medical Sciences, Beijing University of Chinese Medicine, Beijing, China
- * E-mail: (JL); (CC)
| | - Chengke Cai
- School of Chinese material medica, Beijing University of Chinese Medicine, Beijing, China
- * E-mail: (JL); (CC)
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18
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Yokom AL, Morishima Y, Lau M, Su M, Glukhova A, Osawa Y, Southworth DR. Architecture of the nitric-oxide synthase holoenzyme reveals large conformational changes and a calmodulin-driven release of the FMN domain. J Biol Chem 2014; 289:16855-65. [PMID: 24737326 DOI: 10.1074/jbc.m114.564005] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Nitric-oxide synthase (NOS) is required in mammals to generate NO for regulating blood pressure, synaptic response, and immune defense. NOS is a large homodimer with well characterized reductase and oxygenase domains that coordinate a multistep, interdomain electron transfer mechanism to oxidize l-arginine and generate NO. Ca(2+)-calmodulin (CaM) binds between the reductase and oxygenase domains to activate NO synthesis. Although NOS has long been proposed to adopt distinct conformations that alternate between interflavin and FMN-heme electron transfer steps, structures of the holoenzyme have remained elusive and the CaM-bound arrangement is unknown. Here we have applied single particle electron microscopy (EM) methods to characterize the full-length of the neuronal isoform (nNOS) complex and determine the structural mechanism of CaM activation. We have identified that nNOS adopts an ensemble of open and closed conformational states and that CaM binding induces a dramatic rearrangement of the reductase domain. Our three-dimensional reconstruction of the intact nNOS-CaM complex reveals a closed conformation and a cross-monomer arrangement with the FMN domain rotated away from the NADPH-FAD center, toward the oxygenase dimer. This work captures, for the first time, the reductase-oxygenase structural arrangement and the CaM-dependent release of the FMN domain that coordinates to drive electron transfer across the domains during catalysis.
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Affiliation(s)
- Adam L Yokom
- From the Department of Biological Chemistry, the Program in Chemical Biology, and
| | | | | | - Min Su
- the Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109
| | | | | | - Daniel R Southworth
- From the Department of Biological Chemistry, the Life Sciences Institute, University of Michigan, Ann Arbor, Michigan 48109
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19
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Sobolewska-Stawiarz A, Leferink NGH, Fisher K, Heyes DJ, Hay S, Rigby SEJ, Scrutton NS. Energy landscapes and catalysis in nitric-oxide synthase. J Biol Chem 2014; 289:11725-11738. [PMID: 24610812 PMCID: PMC4002082 DOI: 10.1074/jbc.m114.548834] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Nitric oxide (NO) plays diverse roles in mammalian physiology. It is involved in blood pressure regulation, neurotransmission, and immune response, and is generated through complex electron transfer reactions catalyzed by NO synthases (NOS). In neuronal NOS (nNOS), protein domain dynamics and calmodulin binding are implicated in regulating electron flow from NADPH, through the FAD and FMN cofactors, to the heme oxygenase domain, the site of NO generation. Simple models based on crystal structures of nNOS reductase have invoked a role for large scale motions of the FMN-binding domain in shuttling electrons from the FAD-binding domain to the heme oxygenase domain. However, molecular level insight of the dynamic structural transitions in NOS enzymes during enzyme catalysis is lacking. We use pulsed electron-electron double resonance spectroscopy to derive inter-domain distance relationships in multiple conformational states of nNOS. These distance relationships are correlated with enzymatic activity through variable pressure kinetic studies of electron transfer and turnover. The binding of NADPH and calmodulin are shown to influence interdomain distance relationships as well as reaction chemistry. An important effect of calmodulin binding is to suppress adventitious electron transfer from nNOS to molecular oxygen and thereby preventing accumulation of reactive oxygen species. A complex landscape of conformations is required for nNOS catalysis beyond the simple models derived from static crystal structures of nNOS reductase. Detailed understanding of this landscape advances our understanding of nNOS catalysis/electron transfer, and could provide new opportunities for the discovery of small molecule inhibitors that bind at dynamic protein interfaces of this multidimensional energy landscape.
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Affiliation(s)
- Anna Sobolewska-Stawiarz
- From the Manchester Institute of Biotechnology and Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, United Kingdom
| | - Nicole G H Leferink
- From the Manchester Institute of Biotechnology and Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, United Kingdom
| | - Karl Fisher
- From the Manchester Institute of Biotechnology and Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, United Kingdom
| | - Derren J Heyes
- From the Manchester Institute of Biotechnology and Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, United Kingdom
| | - Sam Hay
- From the Manchester Institute of Biotechnology and Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, United Kingdom
| | - Stephen E J Rigby
- From the Manchester Institute of Biotechnology and Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, United Kingdom
| | - Nigel S Scrutton
- From the Manchester Institute of Biotechnology and Faculty of Life Sciences, University of Manchester, Manchester M1 7DN, United Kingdom.
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20
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Feng C, Chen L, Li W, Elmore BO, Fan W, Sun X. Dissecting regulation mechanism of the FMN to heme interdomain electron transfer in nitric oxide synthases. J Inorg Biochem 2013; 130:130-40. [PMID: 24084585 DOI: 10.1016/j.jinorgbio.2013.09.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 08/12/2013] [Accepted: 09/05/2013] [Indexed: 11/25/2022]
Abstract
Nitric oxide synthase (NOS), a flavo-hemoprotein, is responsible for biosynthesis of nitric oxide (NO) in mammals. Three NOS isoforms, iNOS, eNOS and nNOS (inducible, endothelial, and neuronal NOS), achieve their biological functions by tight control of interdomain electron transfer (IET) process through interdomain interactions. In particular, the FMN-heme IET is essential in coupling electron transfer in the reductase domain with NO synthesis in the heme domain by delivery of electrons required for O2 activation at the catalytic heme site. Emerging evidence indicates that calmodulin (CaM) activates NO synthesis in eNOS and nNOS by a conformational change of the FMN domain from its shielded electron-accepting (input) state to a new electron-donating (output) state, and that CaM is also required for proper alignment of the FMN and heme domains in the three NOS isoforms. In the absence of a structure of full-length NOS, an integrated approach of spectroscopic, rapid kinetic and mutagenesis methods is required to unravel regulation mechanism of the FMN-heme IET process. This is to investigate the roles of the FMN domain motions and the docking between the primary functional FMN and heme domains in regulating NOS activity. The recent developments in this area that are driven by the combined approach are the focuses of this review. A better understanding of the roles of interdomain FMN/heme interactions and CaM binding may serve as a basis for the rational design of new selective modulators of the NOS enzymes.
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Affiliation(s)
- Changjian Feng
- Department of Pharmaceutical Sciences, University of New Mexico, Albuquerque, NM 87131, USA.
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21
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Huang WC, Ellis J, Moody P, Raven E, Roberts G. Redox-linked domain movements in the catalytic cycle of cytochrome p450 reductase. Structure 2013; 21:1581-9. [PMID: 23911089 PMCID: PMC3763376 DOI: 10.1016/j.str.2013.06.022] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2013] [Revised: 06/24/2013] [Accepted: 06/26/2013] [Indexed: 11/17/2022]
Abstract
NADPH-cytochrome P450 reductase is a key component of the P450 mono-oxygenase drug-metabolizing system. There is evidence for a conformational equilibrium involving large-scale domain motions in this enzyme. We now show, using small-angle X-ray scattering (SAXS) and small-angle neutron scattering, that delivery of two electrons to cytochrome P450 reductase leads to a shift in this equilibrium from a compact form, similar to the crystal structure, toward an extended form, while coenzyme binding favors the compact form. We present a model for the extended form of the enzyme based on nuclear magnetic resonance and SAXS data. Using the effects of changes in solution conditions and of site-directed mutagenesis, we demonstrate that the conversion to the extended form leads to an enhanced ability to transfer electrons to cytochrome c. This structural evidence shows that domain motion is linked closely to the individual steps of the catalytic cycle of cytochrome P450 reductase, and we propose a mechanism for this.
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Affiliation(s)
- Wei-Cheng Huang
- Henry Wellcome Laboratories for Structural Biology, Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK
| | - Jacqueline Ellis
- Henry Wellcome Laboratories for Structural Biology, Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK
| | - Peter C.E. Moody
- Henry Wellcome Laboratories for Structural Biology, Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK
| | - Emma L. Raven
- Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK
| | - Gordon C.K. Roberts
- Henry Wellcome Laboratories for Structural Biology, Department of Biochemistry, University of Leicester, Henry Wellcome Building, Leicester LE1 9HN, UK
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Abstract
Diflavin reductases are essential proteins capable of splitting the two-electron flux from reduced pyridine nucleotides to a variety of one electron acceptors. The primary sequence of diflavin reductases shows a conserved domain organization harboring two catalytic domains bound to the FAD and FMN flavins sandwiched by one or several non-catalytic domains. The catalytic domains are analogous to existing globular proteins: the FMN domain is analogous to flavodoxins while the FAD domain resembles ferredoxin reductases. The first structural determination of one member of the diflavin reductases family raised some questions about the architecture of the enzyme during catalysis: both FMN and FAD were in perfect position for interflavin transfers but the steric hindrance of the FAD domain rapidly prompted more complex hypotheses on the possible mechanisms for the electron transfer from FMN to external acceptors. Hypotheses of domain reorganization during catalysis in the context of the different members of this family were given by many groups during the past twenty years. This review will address the recent advances in various structural approaches that have highlighted specific dynamic features of diflavin reductases.
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Affiliation(s)
- Louise Aigrain
- Gene Machines Group, Clarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK; E-Mail:
| | - Fataneh Fatemi
- Institut de Chimie des Substances Naturelles, CNRS, UPR 2301, Centre de Recherche de Gif, 1 Av. de la Terrasse, 91198 Gif-sur-Yvette Cedex, France; E-Mails: (F.F.); (O.F.); (E.L.)
| | - Oriane Frances
- Institut de Chimie des Substances Naturelles, CNRS, UPR 2301, Centre de Recherche de Gif, 1 Av. de la Terrasse, 91198 Gif-sur-Yvette Cedex, France; E-Mails: (F.F.); (O.F.); (E.L.)
| | - Ewen Lescop
- Institut de Chimie des Substances Naturelles, CNRS, UPR 2301, Centre de Recherche de Gif, 1 Av. de la Terrasse, 91198 Gif-sur-Yvette Cedex, France; E-Mails: (F.F.); (O.F.); (E.L.)
| | - Gilles Truan
- Université de Toulouse; INSA, UPS, INP; LISBP, 135 Avenue de Rangueil, F-31077 Toulouse, France
- INRA, UMR792 Ingénierie des Systèmes Biologiques et des Procédés, F-31400 Toulouse, France
- CNRS, UMR5504, F-31400 Toulouse, France
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +33-567048813; Fax: +33-567048814
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