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Zheng Y, Deng W, Liu D, Li Y, Peng K, Lorimer GH, Wang J. Redox and spectroscopic properties of mammalian nitrite reductase-like hemoproteins. J Inorg Biochem 2022; 237:111982. [PMID: 36116154 DOI: 10.1016/j.jinorgbio.2022.111982] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 08/24/2022] [Accepted: 08/25/2022] [Indexed: 01/18/2023]
Abstract
Besides the canonical pathway of L-arginine oxidation to produce nitric oxide (NO) in vivo, the nitrate-nitrite-NO pathway has been widely accepted as another source for circulating NO in mammals, especially under hypoxia. To date, there have been at least ten heme-containing nitrite reductase-like proteins discovered in mammals with activities mainly identified in vitro, including four globins (hemoglobin, myoglobin, neuroglobin (Ngb), cytoglobin (Cygb)), three mitochondrial respiratory chain enzymes (cytochrome c oxidase, cytochrome bc1, cytochrome c), and three other heme proteins (endothelial nitric oxide synthase, cytochrome P450 and indoleamine 2,3-dioxygenase 1 (IDO1)). The pathophysiological functions of these proteins are closely related to their redox and spectroscopic properties, as well as their protein structure, although the physiological roles of Ngb, Cygb and IDO1 remain unclear. So far, comprehensive summaries of the redox and spectroscopic properties of these nitrite reductase-like hemoproteins are still lacking. In this review, we have mainly summarized the published data on the application of ultraviolet-visible, electron paramagnetic resonance, circular dichroism and resonance Raman spectroscopies, and X-ray crystallography in studying nitrite reductase-like activity of these 10 proteins, in order to sort out the relationships among enzymatic function, structure and spectroscopic characterization, which might help in understanding their roles in redox biology and medicine.
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Affiliation(s)
- Yunlong Zheng
- Hubei University of Technology Autism & Depression Diagnosis and Intervention Institute, Hubei University of Technology, Wuhan, Hubei, China; International Joint Research Center for General Health, Precision Medicine & Nutrition, Hubei University of Technology, Wuhan, Hubei, China; Department of Biomedicine and Biopharmacology, Hubei University of Technology, Wuhan, Hubei, China
| | - Wenwen Deng
- Hubei University of Technology Autism & Depression Diagnosis and Intervention Institute, Hubei University of Technology, Wuhan, Hubei, China; International Joint Research Center for General Health, Precision Medicine & Nutrition, Hubei University of Technology, Wuhan, Hubei, China; Department of Biomedicine and Biopharmacology, Hubei University of Technology, Wuhan, Hubei, China
| | - Di Liu
- Hubei University of Technology Autism & Depression Diagnosis and Intervention Institute, Hubei University of Technology, Wuhan, Hubei, China; International Joint Research Center for General Health, Precision Medicine & Nutrition, Hubei University of Technology, Wuhan, Hubei, China; Department of Biomedicine and Biopharmacology, Hubei University of Technology, Wuhan, Hubei, China
| | - Youheng Li
- Hubei University of Technology Autism & Depression Diagnosis and Intervention Institute, Hubei University of Technology, Wuhan, Hubei, China; International Joint Research Center for General Health, Precision Medicine & Nutrition, Hubei University of Technology, Wuhan, Hubei, China; Department of Biomedicine and Biopharmacology, Hubei University of Technology, Wuhan, Hubei, China
| | - Kang Peng
- Hubei University of Technology Autism & Depression Diagnosis and Intervention Institute, Hubei University of Technology, Wuhan, Hubei, China; International Joint Research Center for General Health, Precision Medicine & Nutrition, Hubei University of Technology, Wuhan, Hubei, China; Department of Biomedicine and Biopharmacology, Hubei University of Technology, Wuhan, Hubei, China
| | | | - Jun Wang
- Hubei University of Technology Autism & Depression Diagnosis and Intervention Institute, Hubei University of Technology, Wuhan, Hubei, China; International Joint Research Center for General Health, Precision Medicine & Nutrition, Hubei University of Technology, Wuhan, Hubei, China; Department of Biomedicine and Biopharmacology, Hubei University of Technology, Wuhan, Hubei, China.
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2
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Lehnert N, Kim E, Dong HT, Harland JB, Hunt AP, Manickas EC, Oakley KM, Pham J, Reed GC, Alfaro VS. The Biologically Relevant Coordination Chemistry of Iron and Nitric Oxide: Electronic Structure and Reactivity. Chem Rev 2021; 121:14682-14905. [PMID: 34902255 DOI: 10.1021/acs.chemrev.1c00253] [Citation(s) in RCA: 90] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Nitric oxide (NO) is an important signaling molecule that is involved in a wide range of physiological and pathological events in biology. Metal coordination chemistry, especially with iron, is at the heart of many biological transformations involving NO. A series of heme proteins, nitric oxide synthases (NOS), soluble guanylate cyclase (sGC), and nitrophorins, are responsible for the biosynthesis, sensing, and transport of NO. Alternatively, NO can be generated from nitrite by heme- and copper-containing nitrite reductases (NIRs). The NO-bearing small molecules such as nitrosothiols and dinitrosyl iron complexes (DNICs) can serve as an alternative vehicle for NO storage and transport. Once NO is formed, the rich reaction chemistry of NO leads to a wide variety of biological activities including reduction of NO by heme or non-heme iron-containing NO reductases and protein post-translational modifications by DNICs. Much of our understanding of the reactivity of metal sites in biology with NO and the mechanisms of these transformations has come from the elucidation of the geometric and electronic structures and chemical reactivity of synthetic model systems, in synergy with biochemical and biophysical studies on the relevant proteins themselves. This review focuses on recent advancements from studies on proteins and model complexes that not only have improved our understanding of the biological roles of NO but also have provided foundations for biomedical research and for bio-inspired catalyst design in energy science.
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Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Eunsuk Kim
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Hai T Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Jill B Harland
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Andrew P Hunt
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Elizabeth C Manickas
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Kady M Oakley
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - John Pham
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Garrett C Reed
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Victor Sosa Alfaro
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
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3
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Nowaczyk A, Kowalska M, Nowaczyk J, Grześk G. Carbon Monoxide and Nitric Oxide as Examples of the Youngest Class of Transmitters. Int J Mol Sci 2021; 22:ijms22116029. [PMID: 34199647 PMCID: PMC8199767 DOI: 10.3390/ijms22116029] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Revised: 05/29/2021] [Accepted: 05/31/2021] [Indexed: 12/27/2022] Open
Abstract
The year 2021 is the 100th anniversary of the confirmation of the neurotransmission phenomenon by Otto Loewi. Over the course of the hundred years, about 100 neurotransmitters belonging to many chemical groups have been discovered. In order to celebrate the 100th anniversary of the confirmation of neurotransmitters, we present an overview of the first two endogenous gaseous transmitters i.e., nitric oxide, and carbon monoxide, which are often termed as gasotransmitters.
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Affiliation(s)
- Alicja Nowaczyk
- Department of Organic Chemistry, Faculty of Pharmacy, Ludwik Rydygier Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Toruń, 2 dr. A. Jurasza St., 85-094 Bydgoszcz, Poland;
- Correspondence: ; Tel.: +48-52-585-3904
| | - Magdalena Kowalska
- Department of Organic Chemistry, Faculty of Pharmacy, Ludwik Rydygier Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University in Toruń, 2 dr. A. Jurasza St., 85-094 Bydgoszcz, Poland;
| | - Jacek Nowaczyk
- Department of Physical Chemistry and Physicochemistry of Polymers, Faculty of Chemistry, Nicolaus Copernicus University, 7 Gagarina St., 87-100 Toruń, Poland;
| | - Grzegorz Grześk
- Department of Cardiology and Clinical Pharmacology, Faculty of Health Sciences, Ludwik Rydygier Collegium Medicum in Bydgoszcz, Nicolaus Copernicus University, 75 Ujejskiego St., 85-168 Bydgoszcz, Poland;
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4
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Li J, Zheng H, Feng C. Effect of Macromolecular Crowding on the FMN-Heme Intraprotein Electron Transfer in Inducible NO Synthase. Biochemistry 2019; 58:3087-3096. [PMID: 31251033 DOI: 10.1021/acs.biochem.9b00193] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Previous biochemical studies of nitric oxide synthase enzymes (NOSs) were conducted in diluted solutions. However, the intracellular milieu where the proteins perform their biological functions is crowded with macromolecules. The effect of crowding on the electron transfer kinetics of multidomain proteins is much less understood. Herein, we investigated the effect of macromolecular crowding on the FMN-heme intraprotein interdomain electron transfer (IET), an obligatory step in NOS catalysis. A noticeable increase in the IET rate in the bidomain oxygenase/FMN (oxyFMN) and the holoprotein of human inducible NOS (iNOS) was observed upon addition of Ficoll 70 in a nonsaturable manner. Additionally, the magnitude of IET enhancement for the holoenzyme is much higher than that that of the oxyFMN construct. The crowding effect is also evident at different ionic strengths. Importantly, the enhancing extent is similar for the iNOS oxyFMN protein with added Ficoll 70 and Dextran 70 that give the same solution viscosity, showing that specific interactions do not exist between the NOS protein and the crowder. Moreover, the population of the docked FMN-heme state is significantly increased upon addition of Ficoll 70 and the fluorescence lifetime values do not correspond to those in the absence of Ficoll 70. The steady-state cytochrome c reduction by the holoenzyme is noticeably enhanced by the crowder, while the ferricyanide reduction is unchanged. The NO production activity of the iNOS holoenzyme is stimulated by Ficoll 70. The effect of macromolecular crowding on the kinetics can be rationalized on the basis of the excluded volume effect, with an entropic origin. The intraprotein electron transfer kinetics, fluorescence lifetime, and steady-state enzymatic activity results indicate that macromolecular crowding modulates the NOS electron transfer through multiple pathways. Such a mechanism should be applicable to electron transfer in other multidomain redox proteins.
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Affiliation(s)
- Jinghui Li
- College of Pharmacy , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Huayu Zheng
- College of Pharmacy , University of New Mexico , Albuquerque , New Mexico 87131 , United States.,Department of Chemistry and Chemical Biology , University of New Mexico , Albuquerque , New Mexico 87131 , United States
| | - Changjian Feng
- College of Pharmacy , University of New Mexico , Albuquerque , New Mexico 87131 , United States.,Department of Chemistry and Chemical Biology , University of New Mexico , Albuquerque , New Mexico 87131 , United States
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5
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Tejero J, Hunt AP, Santolini J, Lehnert N, Stuehr DJ. Mechanism and regulation of ferrous heme-nitric oxide (NO) oxidation in NO synthases. J Biol Chem 2019; 294:7904-7916. [PMID: 30926606 DOI: 10.1074/jbc.ra119.007810] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Revised: 03/27/2019] [Indexed: 12/12/2022] Open
Abstract
Nitric oxide (NO) synthases (NOSs) catalyze the formation of NO from l-arginine. We have shown previously that the NOS enzyme catalytic cycle involves a large number of reactions but can be characterized by a global model with three main rate-limiting steps. These are the rate of heme reduction by the flavin domain (kr ), of dissociation of NO from the ferric heme-NO complex (kd ), and of oxidation of the ferrous heme-NO complex (k ox). The reaction of oxygen with the ferrous heme-NO species is part of a futile cycle that does not directly contribute to NO synthesis but allows a population of inactive enzyme molecules to return to the catalytic cycle, and thus, enables a steady-state NO synthesis rate. Previously, we have reported that this reaction does involve the reaction of oxygen with the NO-bound ferrous heme complex, but the mechanistic details of the reaction, that could proceed via either an inner-sphere or an outer-sphere mechanism, remained unclear. Here, we present additional experiments with neuronal NOS (nNOS) and inducible NOS (iNOS) variants (nNOS W409F and iNOS K82A and V346I) and computational methods to study how changes in heme access and electronics affect the reaction. Our results support an inner-sphere mechanism and indicate that the particular heme-thiolate environment of the NOS enzymes can stabilize an N-bound FeIII-N(O)OO- intermediate species and thereby catalyze this reaction, which otherwise is not observed or favorable in proteins like globins that contain a histidine-coordinated heme.
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Affiliation(s)
- Jesús Tejero
- From the Department of Pathobiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195 and
| | - Andrew P Hunt
- the Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109
| | - Jérôme Santolini
- From the Department of Pathobiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195 and
| | - Nicolai Lehnert
- the Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109
| | - Dennis J Stuehr
- From the Department of Pathobiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio 44195 and
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6
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Hunt AP, Lehnert N. The Thiolate Trans Effect in Heme {FeNO}6 Complexes and Beyond: Insight into the Nature of the Push Effect. Inorg Chem 2019; 58:11317-11332. [DOI: 10.1021/acs.inorgchem.9b00091] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Andrew P. Hunt
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
| | - Nicolai Lehnert
- Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109, United States
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7
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Olsbu IK, Zoppellaro G, Andersson KK, Boucher JL, Hersleth HP. Importance of Val567 on heme environment and substrate recognition of neuronal nitric oxide synthase. FEBS Open Bio 2018; 8:1553-1566. [PMID: 30186754 PMCID: PMC6120233 DOI: 10.1002/2211-5463.12503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 07/22/2018] [Accepted: 08/01/2018] [Indexed: 12/02/2022] Open
Abstract
Nitric oxide (NO) produced by mammalian nitric oxide synthases (mNOSs) is an important mediator in a variety of physiological functions. Crystal structures of mNOSs have shown strong conservation of the active‐site residue Val567 (numbering for rat neuronal NOS, nNOS). NOS‐like proteins have been identified in several bacterial pathogens, and these display striking sequence identity to the oxygenase domain of mNOS (NOSoxy), with the exception of a Val to Ile mutation at the active site. Preliminary studies have highlighted the importance of this Val residue in NO‐binding, substrate recognition, and oxidation in mNOSs. To further elucidate the role of this valine in substrate and substrate analogue recognition, we generated five Val567 mutants of the oxygenase domain of the neuronal NOS (nNOSoxy) and used UV‐visible and EPR spectroscopy to investigate the effects of these mutations on the heme distal environment, the stability of the heme‐FeII‐CO complexes, and the binding of a series of substrate analogues. Our results are consistent with Val567 playing an important role in preserving the integrity of the active site for substrate binding, stability of heme‐bound gaseous ligands, and potential NO production.
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Affiliation(s)
- Inger K Olsbu
- Department of Biosciences Section for Biochemistry and Molecular Biology University of Oslo Norway
| | - Giorgio Zoppellaro
- Regional Centre of Advanced Technologies and Materials Department of Physical Chemistry Faculty of Science Palacky University in Olomouc Czech Republic
| | - K Kristoffer Andersson
- Department of Biosciences Section for Biochemistry and Molecular Biology University of Oslo Norway
| | | | - Hans-Petter Hersleth
- Department of Biosciences Section for Biochemistry and Molecular Biology University of Oslo Norway.,Department of Chemistry Section for Chemical Life Sciences University of Oslo Norway
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8
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Shamovsky I, Belfield G, Lewis R, Narjes F, Ripa L, Tyrchan C, Öberg L, Sjö P. Theoretical studies of the second step of the nitric oxide synthase reaction: Electron tunneling prevents uncoupling. J Inorg Biochem 2018; 181:28-40. [PMID: 29407906 DOI: 10.1016/j.jinorgbio.2018.01.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2017] [Revised: 12/18/2017] [Accepted: 01/08/2018] [Indexed: 12/27/2022]
Abstract
Nitric oxide (NO·) is a messenger molecule with diverse physiological roles including host defense, neurotransmission and vascular function. The synthesis of NO· from l-arginine is catalyzed by NO-synthases and occurs in two steps through the intermediary Nω-hydroxy-l-arginine (NHA). In both steps the P450-like reaction cycle is coupled with the redox cycle of the cofactor tetrahydrobiopterin (H4B). The mechanism of the second step is studied by Density Functional Theory calculations to ascertain the canonical sequence of proton and electron transfer (PT and ET) events. The proposed mechanism is controlled by the interplay of two electron donors, H4B and NHA. Consistent with experimental data, the catalytic cycle proceeds through the ferric-hydroperoxide complex (Cpd 0) and the following aqua-ferriheme resting state, and involves interim partial oxidation of H4B. The mechanism starts with formation of Cpd 0 from the ferrous-dioxy reactant complex by PT from the C-ring heme propionate coupled with hole transfer to H4B through the highest occupied π-orbital of NHA as a bridge. This enables PT from NHA+· to the proximal oxygen leading to the shallow ferriheme-H2O2 oxidant. Subsequent Fenton-like peroxide bond cleavage triggered by ET from the NHA-derived iminoxy-radical leads to the protonated Cpd II diradicaloid singlet stabilized by spin delocalization in H4B, and the closed-shell coordination complex of HO- with iminoxy-cation. The complex is converted to the transient C-adduct, which releases intended products upon PT to the ferriheme-HO- complex coupled with ET to the H4B+·. Deferred ET from the substrate or undue ET from/to the cofactor leads to side products.
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Affiliation(s)
- Igor Shamovsky
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden.
| | - Graham Belfield
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Richard Lewis
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Frank Narjes
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Lena Ripa
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Christian Tyrchan
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Lisa Öberg
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
| | - Peter Sjö
- Department of Medicinal Chemistry, IMED RIA, AstraZeneca R&D Gothenburg, Pepparedsleden 1, 431 83 Mölndal, Sweden
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9
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Krzyaniak MD, Cruce AA, Vennam P, Lockart M, Berka V, Tsai AL, Bowman MK. The tetrahydrobiopterin radical interacting with high- and low-spin heme in neuronal nitric oxide synthase - A new indicator of the extent of NOS coupling. Free Radic Biol Med 2016; 101:367-377. [PMID: 27989753 PMCID: PMC5362310 DOI: 10.1016/j.freeradbiomed.2016.10.503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/21/2016] [Revised: 10/07/2016] [Accepted: 10/26/2016] [Indexed: 01/10/2023]
Abstract
Reaction intermediates trapped during the single-turnover reaction of the neuronal ferrous nitric oxide synthase oxygenase domain (Fe(II)nNOSOX) show four EPR spectra of free radicals. Fully-coupled nNOSOX with cofactor (tetrahydrobiopterin, BH4) and substrate (l-arginine) forms the typical BH4 cation radical with an EPR spectrum ~4.0mT wide and hyperfine tensors similar to reports for a biopterin cation radical in inducible NOSOX (iNOSOX). With excess thiol, nNOSox lacking BH4 and l-arg is known to produce superoxide. In contrast, we find that nNOSOX with BH4 but no l-arg forms two radicals with rather different, fast (~250μs at 5K) and slower (~500μs at 20K), electron spin relaxation rates and a combined ~7.0mT wide EPR spectrum. Rapid freeze-quench CW- and pulsed-EPR measurements are used to identify these radicals and their origin. These two species are the same radical with identical nuclear hyperfine couplings, but with spin-spin couplings to high-spin (4.0mT component) or low-spin (7.0mT component) Fe(III) heme. Uncoupled reactions of nNOS leave the enzyme in states that can be chemically reduced to sustain unregulated production of NO and reactive oxygen species in ischemia-reperfusion injury. The broad EPR signal is a convenient indicator of uncoupled nNOS reactions producing low-spin Fe(III) heme.
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Affiliation(s)
- Matthew D Krzyaniak
- Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487-0336, USA
| | - Alex A Cruce
- Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487-0336, USA
| | - Preethi Vennam
- Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487-0336, USA
| | - Molly Lockart
- Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487-0336, USA
| | - Vladimir Berka
- Division of Hematology, Department of Internal Medicine, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Ah-Lim Tsai
- Division of Hematology, Department of Internal Medicine, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Michael K Bowman
- Department of Chemistry, The University of Alabama, Tuscaloosa, AL 35487-0336, USA.
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10
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Brunel A, Lang J, Couture M, Boucher JL, Dorlet P, Santolini J. Oxygen activation in NO synthases: evidence for a direct role of the substrate. FEBS Open Bio 2016; 6:386-97. [PMID: 27419044 PMCID: PMC4856417 DOI: 10.1002/2211-5463.12036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2015] [Revised: 12/15/2015] [Accepted: 01/13/2016] [Indexed: 12/13/2022] Open
Abstract
Nitric oxide (NO) and the other reactive nitrogen species (RNOS) play crucial patho‐physiological roles at the interface of oxidative stress and signalling processes. In mammals, the NO synthases (NOSs) are the source of these reactive nitrogen species, and so to understand the precise biological role of RNOS and NO requires elucidation of the molecular functioning of NOS. Oxygen activation, which is at the core of NOS catalysis, involves a sophisticated sequence of electron and proton transfers. While electron transfer in NOS has received much attention, the proton transfer processes has been scarcely investigated. Here, we report an original approach that combines fast‐kinetic techniques coupled to resonance Raman spectroscopy with the use of synthetic analogues of NOS substrate. We characterise FeII‐O2 reaction intermediates in the presence of L‐arginine (Arg), alkyl‐ and aryl‐guanidines. The presence of new reaction intermediates, such as ferric haem‐peroxide, that was formerly postulated, was tracked by analysing the oxygen activation reaction at different times and with different excitation wavelengths. Our results suggest that Arg is not a proton donor, but indirectly intervenes in oxygen activation mechanism by modulating the distal H‐bond network and, in particular, by tuning the position and the role of the distal water molecule. This report supports a catalytic model with two proton transfers in step 1 (Arg hydroxylation) but only one proton transfer in step 2 (Nω‐hydroxy‐L‐arginine oxidation).
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Affiliation(s)
- Albane Brunel
- Laboratoire Stress Oxydant et Détoxication Institute for Integrative Biology of the Cell (I2BC) CEA, CNRS, Université Paris-Saclay Gif-sur-Yvette Cedex France
| | - Jérôme Lang
- Département de biochimie, de microbiologie et de bio-informatique, and PROTEO Pavillon Charles-Eugène Marchand Université Laval Québec Canada
| | - Manon Couture
- Département de biochimie, de microbiologie et de bio-informatique, and PROTEO Pavillon Charles-Eugène Marchand Université Laval Québec Canada
| | | | - Pierre Dorlet
- Laboratoire Stress Oxydant et Détoxication Institute for Integrative Biology of the Cell (I2BC) CEA, CNRS, Université Paris-Saclay Gif-sur-Yvette Cedex France
| | - Jérôme Santolini
- Laboratoire Stress Oxydant et Détoxication Institute for Integrative Biology of the Cell (I2BC) CEA, CNRS, Université Paris-Saclay Gif-sur-Yvette Cedex France
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11
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Davydov R, Strushkevich N, Smil D, Yantsevich A, Gilep A, Usanov S, Hoffman BM. Evidence That Compound I Is the Active Species in Both the Hydroxylase and Lyase Steps by Which P450scc Converts Cholesterol to Pregnenolone: EPR/ENDOR/Cryoreduction/Annealing Studies. Biochemistry 2015; 54:7089-97. [PMID: 26603348 DOI: 10.1021/acs.biochem.5b00903] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cytochrome P450scc (CYP 11A1) catalyzes the conversion of cholesterol (Ch) to pregnenolone, the precursor to steroid hormones. This process proceeds via three sequential monooxygenation reactions: two hydroxylations of Ch first form 22(R)-hydroxycholesterol (HC) and then 20α,22(R)-dihydroxycholesterol (DHC); a lyase reaction then cleaves the C20-C22 bond to form pregnenolone. Recent cryoreduction/annealing studies that employed electron paramagnetic resonance (EPR)/electron nuclear double resonance (ENDOR) spectroscopy [Davydov, R., et al. (2012) J. Am. Chem. Soc. 134, 17149] showed that compound I (Cpd I) is the active intermediate in the first step, hydroxylation of Ch. Herein, we have employed EPR and ENDOR spectroscopy to characterize the intermediates in the second and third steps of the enzymatic process, as conducted by 77 K radiolytic one-electron cryoreduction and subsequent annealing of the ternary oxy-cytochrome P450scc complexes with HC and DHC. This procedure is validated by showing that the cryoreduced ternary complexes of oxy-cytochrome P450scc with HC and DHC are catalytically competent and during annealing generate DHC and pregnenolone, respectively. Cryoreduction of the oxy-P450scc-HC ternary complex trapped at 77K produces the superoxo-ferrous P450scc intermediate along with a minor fraction of ferric hydroperoxo intermediates. The superoxo-ferrous intermediate converts into a ferric-hydroperoxo species after annealing at 145 K. During subsequent annealing at 170-180 K, the ferric-hydroperoxo intermediate converts to the primary product complex with the large solvent kinetic isotope effect that indicates Cpd I is being formed, and (1)H ENDOR measurements of the primary product formed in D2O demonstrate that Cpd I is the active species. They show that the primary product contains Fe(III) coordinated to the 20-O(1)H of DHC with the (1)H derived from substrate, the signature of the Cpd I reaction. Hydroperoxo ferric intermediates are the primary species formed during cryoreduction of the oxy-P450scc-DHC ternary complex, and they decay at 185 K with a strong solvent kinetic isotope effect to form low-spin ferric P450scc. Together, these observations indicated that Cpd I also is the active intermediate in the C20,22 lyase final step. In combination with our previous results, this study thus indicates that Cpd I is the active species in each of the three sequential monooxygenation reactions by which P450scc catalytically converts Ch to pregnenolone.
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Affiliation(s)
- Roman Davydov
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208-3113, United States
| | - Natallia Strushkevich
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus , Kuprevicha Street 5/2, Minsk 220141, Belarus
| | - David Smil
- Structural Genomics Consortium, University of Toronto , 101 College Street, Toronto, ON, Canada M5G 1L7
| | - Aliaksei Yantsevich
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus , Kuprevicha Street 5/2, Minsk 220141, Belarus
| | - Andrey Gilep
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus , Kuprevicha Street 5/2, Minsk 220141, Belarus
| | - Sergey Usanov
- Institute of Bioorganic Chemistry, National Academy of Sciences of Belarus , Kuprevicha Street 5/2, Minsk 220141, Belarus
| | - Brian M Hoffman
- Department of Chemistry, Northwestern University , Evanston, Illinois 60208-3113, United States
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12
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Astashkin AV, Chen L, Elmore BO, Kunwar D, Miao Y, Li H, Poulos TL, Roman LJ, Feng C. Probing the Hydrogen Bonding of the Ferrous-NO Heme Center of nNOS by Pulsed Electron Paramagnetic Resonance. J Phys Chem A 2015; 119:6641-9. [PMID: 26035438 DOI: 10.1021/acs.jpca.5b01804] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Oxidation of L-arginine (L-Arg) to nitric oxide (NO) by NO synthase (NOS) takes place at the heme active site. It is of current interest to study structures of the heme species that activates O2 and transforms the substrate. The NOS ferrous-NO complex is a close mimic of the obligatory ferric (hydro)peroxo intermediate in NOS catalysis. In this work, pulsed electron-nuclear double resonance (ENDOR) spectroscopy was used to probe the hydrogen bonding of the NO ligand in the ferrous-NO heme center of neuronal NOS (nNOS) without a substrate and with L-Arg or N-hydroxy-L-arginine (NOHA) substrates. Unexpectedly, no H-bonding interaction connecting the NO ligand to the active site water molecule or the Arg substrate was detected, in contrast to the results obtained by X-ray crystallography for the Arg-bound nNOS heme domain [Li et al. J. Biol. Inorg. Chem. 2006, 11, 753-768]. The nearby exchangeable proton in both the no-substrate and Arg-containing nNOS samples is located outside the H-bonding range and, on the basis of the obtained structural constraints, can belong to the active site water (or OH). On the contrary, in the NOHA-bound sample, the nearby exchangeable hydrogen forms an H-bond with the NO ligand (on the basis of its distance from the NO ligand and a nonzero isotropic hfi constant), but it does not belong to the active site water molecule because the water oxygen atom (detected by (17)O ENDOR) is too far. This hydrogen should therefore come from the NOHA substrate, which is in agreement with the X-ray crystallography work [Li et al. Biochemistry 2009, 48, 10246-10254]. The nearby nonexchangeable hydrogen atom assigned as H(ε) of Phe584 was detected in all three samples. This hydrogen atom may have a stabilizing effect on the NO ligand and probably determines its position.
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Affiliation(s)
- Andrei V Astashkin
- †Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Li Chen
- ‡College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Bradley O Elmore
- ‡College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Deepak Kunwar
- ‡College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Yubin Miao
- ‡College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Huiying Li
- §Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, Irvine, California 92697-3900, United States
| | - Thomas L Poulos
- §Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, Irvine, California 92697-3900, United States
| | - Linda J Roman
- ∥Department of Biochemistry, University of Texas Health Science Center in San Antonio, San Antonio, Texas 78229, United States
| | - Changjian Feng
- ‡College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
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13
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Horn M, Nienhaus K, Nienhaus GU. Fourier transform infrared spectroscopy study of ligand photodissociation and migration in inducible nitric oxide synthase. F1000Res 2014; 3:290. [PMID: 25653844 DOI: 10.12688/f1000research.5836.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 11/27/2014] [Indexed: 03/23/2024] Open
Abstract
Inducible nitric oxide synthase (iNOS) is a homodimeric heme enzyme that catalyzes the formation of nitric oxide (NO) from dioxygen and L-arginine (L-Arg) in a two-step process. The produced NO can either diffuse out of the heme pocket into the surroundings or it can rebind to the heme iron and inhibit enzyme action. Here we have employed Fourier transform infrared (FTIR) photolysis difference spectroscopy at cryogenic temperatures, using the carbon monoxide (CO) and NO stretching bands as local probes of the active site of iNOS. Characteristic changes were observed in the spectra of the heme-bound ligands upon binding of the cofactors. Unlike photolyzed CO, which becomes trapped in well-defined orientations, as indicated by sharp photoproduct bands, photoproduct bands of NO photodissociated from the ferric heme iron were not visible, indicating that NO does not reside in the protein interior in a well-defined location or orientation. This may be favorable for NO release from the enzyme during catalysis because it reduces self-inhibition. Moreover, we used temperature derivative spectroscopy (TDS) with FTIR monitoring to explore the dynamics of NO and carbon monoxide (CO) inside iNOS after photodissociation at cryogenic temperatures. Only a single kinetic photoproduct state was revealed, but no secondary docking sites as in hemoglobins. Interestingly, we observed that intense illumination of six-coordinate ferrous iNOS oxy-NO ruptures the bond between the heme iron and the proximal thiolate to yield five-coordinate ferric iNOS oxy-NO, demonstrating the strong trans effect of the heme-bound NO.
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Affiliation(s)
- Michael Horn
- Karlsruhe Institute of Technology (KIT), Institute of Applied Physics, Karlsruhe, D-76131, Germany
| | - Karin Nienhaus
- Karlsruhe Institute of Technology (KIT), Institute of Applied Physics, Karlsruhe, D-76131, Germany
| | - Gerd Ulrich Nienhaus
- Karlsruhe Institute of Technology (KIT), Institute of Applied Physics, Karlsruhe, D-76131, Germany ; Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
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14
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Horn M, Nienhaus K, Nienhaus GU. Fourier transform infrared spectroscopy study of ligand photodissociation and migration in inducible nitric oxide synthase. F1000Res 2014; 3:290. [PMID: 25653844 PMCID: PMC4304226 DOI: 10.12688/f1000research.5836.2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/11/2014] [Indexed: 11/20/2022] Open
Abstract
Inducible nitric oxide synthase (iNOS) is a homodimeric heme enzyme that catalyzes the formation of nitric oxide (NO) from dioxygen and L-arginine (L-Arg) in a two-step process. The produced NO can either diffuse out of the heme pocket into the surroundings or it can rebind to the heme iron and inhibit enzyme action. Here we have employed Fourier transform infrared (FTIR) photolysis difference spectroscopy at cryogenic temperatures, using the carbon monoxide (CO) and NO stretching bands as local probes of the active site of iNOS. Characteristic changes were observed in the spectra of the heme-bound ligands upon binding of the cofactors. Unlike photolyzed CO, which becomes trapped in well-defined orientations, as indicated by sharp photoproduct bands, photoproduct bands of NO photodissociated from the ferric heme iron were not visible, indicating that NO does not reside in the protein interior in a well-defined location or orientation. This may be favorable for NO release from the enzyme during catalysis because it reduces self-inhibition. Moreover, we used temperature derivative spectroscopy (TDS) with FTIR monitoring to explore the dynamics of NO and carbon monoxide (CO) inside iNOS after photodissociation at cryogenic temperatures. Only a single kinetic photoproduct state was revealed, but no secondary docking sites as in hemoglobins. Interestingly, we observed that intense illumination of six-coordinate ferrous iNOS oxy-NO ruptures the bond between the heme iron and the proximal thiolate to yield five-coordinate ferric iNOS oxy-NO, demonstrating the strong trans effect of the heme-bound NO.
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Affiliation(s)
- Michael Horn
- Karlsruhe Institute of Technology (KIT), Institute of Applied Physics, Karlsruhe, D-76131, Germany
| | - Karin Nienhaus
- Karlsruhe Institute of Technology (KIT), Institute of Applied Physics, Karlsruhe, D-76131, Germany
| | - Gerd Ulrich Nienhaus
- Karlsruhe Institute of Technology (KIT), Institute of Applied Physics, Karlsruhe, D-76131, Germany
- Department of Physics, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA
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15
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Astashkin AV, Chen L, Zhou X, Li H, Poulos TL, Liu KJ, Guillemette JG, Feng C. Pulsed electron paramagnetic resonance study of domain docking in neuronal nitric oxide synthase: the calmodulin and output state perspective. J Phys Chem A 2014; 118:6864-72. [PMID: 25046446 PMCID: PMC4148148 DOI: 10.1021/jp503547w] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The binding of calmodulin (CaM) to neuronal nitric oxide synthase (nNOS) enables formation of the output state of nNOS for nitric oxide production. Essential to NOS function is the geometry and dynamics of CaM docking to the NOS oxygenase domain, but little is known about these details. In the present work, the domain docking in a CaM-bound oxygenase/FMN (oxyFMN) construct of nNOS was investigated using the relaxation-induced dipolar modulation enhancement (RIDME) technique, which is a pulsed electron paramagnetic resonance technique sensitive to the magnetic dipole interaction between the electron spins. A cysteine was introduced at position 110 of CaM, after which a nitroxide spin label was attached at the position. The RIDME study of the magnetic dipole interaction between the spin label and the ferric heme centers in the oxygenase domain of nNOS revealed that, with increasing [Ca(2+)], the concentration of nNOS·CaM complexes increases and reaches a maximum at [Ca(2+)]/[CaM] ≥ 4. The RIDME kinetics of CaM-bound nNOS represented monotonous decays without well-defined oscillations. The analysis of these kinetics based on the structural models for the open and docked states has shown that only about 15 ± 3% of the CaM-bound nNOS is in the docked state at any given time, while the remaining 85 ± 3% of the protein is in the open conformations characterized by a wide distribution of distances between the bound CaM and the oxygenase domain. The results of this investigation are consistent with a model that the Ca(2+)-CaM interaction causes CaM docking with the oxygenase domain. The low population of the docked state indicates that the CaM-controlled docking between the FMN and heme domains is highly dynamic.
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Affiliation(s)
- Andrei V Astashkin
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
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16
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Heinemann SH, Hoshi T, Westerhausen M, Schiller A. Carbon monoxide--physiology, detection and controlled release. Chem Commun (Camb) 2014; 50:3644-60. [PMID: 24556640 PMCID: PMC4072318 DOI: 10.1039/c3cc49196j] [Citation(s) in RCA: 288] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Carbon monoxide (CO) is increasingly recognized as a cell-signalling molecule akin to nitric oxide (NO). CO has attracted particular attention as a potential therapeutic agent because of its reported anti-hypertensive, anti-inflammatory and cell-protective effects. We discuss recent progress in identifying new effector systems and elucidating the mechanisms of action of CO on, e.g., ion channels, as well as the design of novel methods to monitor CO in cellular environments. We also report on recent developments in the area of CO-releasing molecules (CORMs) and materials for controlled CO application. Novel triggers for CO release, metal carbonyls and degradation mechanisms of CORMs are highlighted. In addition, potential formulations of CORMs for targeted CO release are discussed.
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Affiliation(s)
- Stefan H. Heinemann
- Center for Molecular Biomedicine (CMB), Department of Biophysics, Friedrich Schiller University Jena & Jena University Hospital, Hans-Knöll-Straße 2, D-07745 Jena, Germany
| | - Toshinori Hoshi
- Department of Physiology, University of Pennsylvania, 415 Curie Boulevard, 605 CRB, Philadelphia, PA 19104-6085, USA
| | - Matthias Westerhausen
- Institute for Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Humboldtstr. 8, D-07743 Jena, Germany
| | - Alexander Schiller
- Institute for Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Humboldtstr. 8, D-07743 Jena, Germany
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17
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Heine C, Kolesnik B, Schmidt R, Werner ER, Mayer B, Gorren ACF. Interaction between neuronal nitric-oxide synthase and tetrahydrobiopterin revisited: studies on the nature and mechanism of tight pterin binding. Biochemistry 2014; 53:1284-95. [PMID: 24512289 PMCID: PMC3944803 DOI: 10.1021/bi401307r] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Revised: 02/10/2014] [Indexed: 01/06/2023]
Abstract
Recombinant neuronal nitric-oxide synthase (nNOS) expressed in baculovirus-infected Sf9 cells contains approximately 1 equiv of tightly bound tetrahydrobiopterin (BH4) per dimer and binds a second equivalent with a dissociation constant in the 10(-7)-10(-6) M range. Less is known about the pterin-binding properties of nNOS originating from expression systems such as Escherichia coli that do not produce BH4. We determined the binding properties of E. coli-expressed nNOS for BH4 and several inhibitory pterins by monitoring their effects on enzyme activity. E. coli-expressed nNOS as isolated was activated by BH4 monophasically with EC50 ≈ 2 × 10(-7) M, demonstrating a lack of tight pterin binding. However, overnight incubation with BH4 resulted in tight binding of one BH4 per dimer, yielding an enzyme that resembled Sf9-expressed nNOS. Tight pterin binding was also induced by preincubation with 4-amino-tetrahydrobiopterin, but not by 7,8-dihydrobiopterin or 4-amino-dihydrobiopterin, suggesting that tight-binding site formation requires preincubation with a fully reduced pteridine. Kinetic experiments showed that tight-binding site formation takes approximately 10 min with 1 μM BH4 (2 min with 1 μM 4-amino-BH4) at 4 °C. Anaerobic preincubation experiments demonstrated that O2 is not involved in the process. Gel electrophoretic studies suggest that tight-binding site formation is accompanied by an increase in the strength of the NOS dimer. We propose that incubation of pterin-free nNOS with BH4 creates one tight pterin-binding site per dimer, leaving the other site unaffected, in a reaction that involves redox chemistry.
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Affiliation(s)
- Christian
L. Heine
- Department
of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria
| | - Bernd Kolesnik
- Department
of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria
| | - Renate Schmidt
- Department
of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria
| | - Ernst R. Werner
- Division
of Biological Chemistry, Biocenter, Innsbruck
Medical University, A-6020, Innsbruck, Austria
| | - Bernd Mayer
- Department
of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria
| | - Antonius C. F. Gorren
- Department
of Pharmacology and Toxicology, Institute of Pharmaceutical Sciences, Karl-Franzens-University Graz, A-8010, Graz, Austria
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18
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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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19
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Kinetics of CO recombination to the heme in Geobacillus stearothermophilus nitric oxide synthase. Polyhedron 2013; 58:134-138. [DOI: 10.1016/j.poly.2012.08.079] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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20
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Jansen Labby K, Li H, Roman LJ, Martásek P, Poulos TL, Silverman RB. Methylated N(ω)-hydroxy-L-arginine analogues as mechanistic probes for the second step of the nitric oxide synthase-catalyzed reaction. Biochemistry 2013; 52:3062-73. [PMID: 23586781 DOI: 10.1021/bi301571v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Nitric oxide synthase (NOS) catalyzes the conversion of L-arginine to L-citrulline through the intermediate N(ω)-hydroxy-L-arginine (NHA), producing nitric oxide, an important mammalian signaling molecule. Several disease states are associated with improper regulation of nitric oxide production, making NOS a therapeutic target. The first step of the NOS reaction has been well-characterized and is presumed to proceed through a compound I heme species, analogous to the cytochrome P450 mechanism. The second step, however, is enzymatically unprecedented and is thought to occur via a ferric peroxo heme species. To gain insight into the details of this unique second step, we report here the synthesis of NHA analogues bearing guanidinium methyl or ethyl substitutions and their investigation as either inhibitors of or alternate substrates for NOS. Radiolabeling studies reveal that N(ω)-methoxy-L-arginine, an alternative NOS substrate, produces citrulline, nitric oxide, and methanol. On the basis of these results, we propose a mechanism for the second step of NOS catalysis in which a methylated nitric oxide species is released and is further metabolized by NOS. Crystal structures of our NHA analogues bound to nNOS have been determined, revealing the presence of an active site water molecule only in the presence of singly methylated analogues. Bulkier analogues displace this active site water molecule; a different mechanism is proposed in the absence of the water molecule. Our results provide new insights into the steric and stereochemical tolerance of the NOS active site and substrate capabilities of NOS.
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Affiliation(s)
- Kristin Jansen Labby
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
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21
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Davydov R, Gilep AA, Strushkevich NV, Usanov SA, Hoffman BM. Compound I is the reactive intermediate in the first monooxygenation step during conversion of cholesterol to pregnenolone by cytochrome P450scc: EPR/ENDOR/cryoreduction/annealing studies. J Am Chem Soc 2012; 134:17149-56. [PMID: 23039857 DOI: 10.1021/ja3067226] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cytochrome P450scc (CYP11A1) catalyzes conversion of cholesterol (CH) to pregnenolone, the precursor to all steroid hormones. This process proceeds via three sequential monooxygenation reactions: two stereospecific hydroxylations with formation first of 22R-hydroxycholesterol (22-HC) and then 20α,22R-dihydroxycholesterol (20,22-DHC), followed by C20-C22 bond cleavage. Herein we have employed EPR and ENDOR spectroscopy to characterize the intermediates in the first hydroxylation step by 77 K radiolytic one-electron cryoreduction and subsequent annealing of the ternary oxy-cytochrome P450scc-cholesterol complex. This approach is fully validated by the demonstration that the cryoreduced ternary complex of oxy-P450scc-CH is catalytically competent and hydroxylates cholesterol to form 22-HC with no detectable formation of 20-HC, just as occurs under physiological conditions. Cryoreduction of the ternary complex trapped at 77 K produces predominantly the hydroperoxy-ferriheme P450scc intermediate, along with a minor fraction of peroxo-ferriheme intermediate that converts into a new hydroperoxo-ferriheme species at 145 K. This behavior reveals that the distal pocket of the parent oxy-P450scc-cholesterol complex exhibits an efficient proton delivery network, with an ordered water molecule H-bonded to the distal oxygen of the dioxygen ligand. During annealing of the hydroperoxy-ferric P450scc intermediates at 185 K, they convert to the primary product complex in which CH has been converted to 22-HC. In this process, the hydroperoxy-ferric intermediate decays with a large solvent kinetic isotope effect, as expected when proton delivery to the terminal O leads to formation of Compound I (Cpd I). (1)H ENDOR measurements of the primary product formed in deuterated solvent show that the heme Fe(III) is coordinated to the 22R-O(1)H of 22-HC, where the (1)H is derived from substrate and exchanges to D after annealing at higher temperatures. These observations establish that Cpd I is the agent that hydroxylates CH, rather than the hydroperoxy-ferric heme.
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Affiliation(s)
- Roman Davydov
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA
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22
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Madrona Y, Tripathi S, Li H, Poulos TL. Crystal structures of substrate-free and nitrosyl cytochrome P450cin: implications for O(2) activation. Biochemistry 2012; 51:6623-31. [PMID: 22775403 DOI: 10.1021/bi300666u] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The crystal structure of the P450cin substrate-bound nitric oxide complex and the substrate-free form have been determined revealing a substrate-free structure that adopts an open conformation relative to the substrate-bound structure. The region of the I helix that forms part of the O(2) binding pocket shifts from an α helix in the substrate-free form to a π helix in the substrate-bound form. Unique to P450cin is an active site residue, Asn242, in the I helix that H-bonds with the substrate. In most other P450s this residue is a Thr and plays an important role in O(2) activation by participating in an H-bonding network required for O(2) activation. The π/α I helix transition results in the carbonyl O atom of Gly238 moving in to form an H-bond with the water/hydroxide ligand in the substrate-free form. The corresponding residue, Gly248, in the substrate-free P450cam structure experiences a similar motion. Most significantly, in the oxy-P450cam complex Gly248 adopts a position midway between the substrate-free and -bound states. A comparison between these P450cam and the new P450cin structures provides insights into differences in how the two P450s activate O(2). The structure of P450cin complexed with nitric oxide, a close mimic of the O(2) complex, shows that Gly238 is likely to form tighter interactions with ligands than the corresponding Gly248 in P450cam. Having a close interaction between an H-bond acceptor, the Gly238 carbonyl O atom, and the distal oxygen atom of O(2) will promote protonation and hence further reduction of the oxy complex to the hydroperoxy intermediate resulting in heterolytic cleavage of the peroxide O-O bond and formation of the active ferryl intermediate required for substrate hydroxylation.
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Affiliation(s)
- Yarrow Madrona
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697-3900, USA
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23
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Smith AT, Su Y, Stevens DJ, Majtan T, Kraus JP, Burstyn JN. Effect of the disease-causing R266K mutation on the heme and PLP environments of human cystathionine β-synthase. Biochemistry 2012; 51:6360-70. [PMID: 22738154 DOI: 10.1021/bi300421z] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cystathionine β-synthase (CBS) is an essential pyridoxal 5'-phosphate (PLP)-dependent enzyme of the transsulfuration pathway that condenses serine with homocysteine to form cystathionine; intriguingly, human CBS also contains a heme b cofactor of unknown function. Herein we describe the enzymatic and spectroscopic properties of a disease-associated R266K hCBS variant, which has an altered hydrogen-bonding environment. The R266K hCBS contains a low-spin, six-coordinate Fe(III) heme bearing a His/Cys ligation motif, like that of WT hCBS; however, there is a geometric distortion that exists at the R266K heme. Using rR spectroscopy, we show that the Fe(III)-Cys(thiolate) bond is longer and weaker in R266K, as evidenced by an 8 cm(-1) downshift in the ν(Fe-S) resonance. Presence of this longer and weaker Fe(III)-Cys(thiolate) bond is correlated with alteration of the fluorescence spectrum of the active PLP ketoenamine tautomer. Activity data demonstrate that, relative to WT, the R266K variant is more impaired in the alternative cysteine-synthesis reaction than in the canonical cystathionine-synthesis reaction. This diminished cysteine synthesis activity and a greater sensitivity to exogenous PLP correlate with the change in PLP environment. Fe-S(Cys) bond weakening causes a nearly 300-fold increase in the rate of ligand switching upon reduction of the R266K heme. Combined, these data demonstrate cross talk between the heme and PLP active sites, consistent with previous proposals, revealing that alteration of the Arg(266)-Cys(52) interaction affects PLP-dependent activity and dramatically destabilizes the ferrous thiolate-ligated heme complex, underscoring the importance of this hydrogen-bonding residue pair.
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Affiliation(s)
- Aaron T Smith
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, WI 53706, USA
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Astashkin AV, Elmore BO, Chen L, Fan W, Guillemette JG, Feng C. Pulsed ENDOR determination of the arginine location in the ferrous-NO form of neuronal NOS. J Phys Chem A 2012; 116:6731-9. [PMID: 22667467 DOI: 10.1021/jp302319c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Mammalian nitric oxide synthases (NOSs) are enzymes responsible for oxidation of L-arginine (L-Arg) to nitric oxide (NO). Mechanisms of reactions at the catalytic heme site are not well understood, and it is of current interest to study structures of the heme species that activates O(2) and transforms the substrate. The NOS ferrous-NO complex is a close mimic of the obligatory ferric (hydro)peroxo intermediate in NOS catalysis. In this work, pulsed electron-nuclear double resonance (ENDOR) was used to probe the position of the l-Arg substrate at the NO(•)-coordinated ferrous heme center(s) in the oxygenase domain of rat neuronal NOS (nNOS). The analysis of (2)H and (15)N ENDOR spectra of samples containing d(7)- or guanidino-(15)N(2) labeled L-Arg has resulted in distance estimates for the nearby guanidino nitrogen and the nearby proton (deuteron) at C(δ). The L-Arg position was found to be noticeably different from that in the X-ray crystal structure of nNOS ferrous-NO complex [Li et al. J. Biol. Inorg. Chem.2006, 11, 753-768], with the nearby guanidino nitrogen being ~0.5 Å closer to, and the nearby H(δ) about 1 Å further from, the NO ligand than in the X-ray structure. The difference might be related to the structural constraints imposed on the protein by the crystal. Importantly, in spite of its closer position, the guanidino nitrogen does not form a hydrogen bond with the NO ligand, as evidenced by the absence of significant isotropic hfi constant for N(g1). This is consistent with the previous reports that it is not the L-Arg substrate itself that would most likely serve as a direct proton donor to the diatomic ligands (NO and O(2)) bound to the heme.
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Affiliation(s)
- Andrei V Astashkin
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
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25
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Feng C. Mechanism of Nitric Oxide Synthase Regulation: Electron Transfer and Interdomain Interactions. Coord Chem Rev 2012; 256:393-411. [PMID: 22523434 PMCID: PMC3328867 DOI: 10.1016/j.ccr.2011.10.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Nitric oxide synthase (NOS), a flavo-hemoprotein, tightly regulates nitric oxide (NO) synthesis and thereby its dual biological activities as a key signaling molecule for vasodilatation and neurotransmission at low concentrations, and also as a defensive cytotoxin at higher concentrations. Three NOS isoforms, iNOS, eNOS and nNOS (inducible, endothelial, and neuronal NOS), achieve their key biological functions by tight regulation of interdomain electron transfer (IET) process via 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 O(2) activation at the catalytic heme site. Compelling evidence indicates that calmodulin (CaM) activates NO synthesis in eNOS and nNOS through 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 domains. Another exciting recent development in NOS enzymology is the discovery of importance of the the FMN domain motions in modulating reactivity and structure of the catalytic heme active site (in addition to the primary role of controlling the IET processes). In the absence of a structure of full-length NOS, an integrated approach of spectroscopic (e.g. pulsed EPR, MCD, resonance Raman), rapid kinetics (laser flash photolysis and stopped flow) and mutagenesis methods is critical to unravel the molecular details of the interdomain FMN/heme interactions. This is to investigate the roles of dynamic conformational changes of the FMN domain and the docking between the primary functional FMN and heme domains in regulating NOS activity. The recent developments in understanding of mechanisms of the NOS regulation that are driven by the combined approach are the focuses of this review. An improved understanding of the role of interdomain FMN/heme interaction and CaM binding may serve as the basis for the design of new selective inhibitors of NOS isoforms.
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Affiliation(s)
- Changjian Feng
- Department of Pharmaceutical Sciences, University of New Mexico, Albuquerque, NM 87131 (USA) , Tel: 505-925-4326
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26
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Lang J, Santolini J, Couture M. The conserved Trp-Cys hydrogen bond dampens the "push effect" of the heme cysteinate proximal ligand during the first catalytic cycle of nitric oxide synthase. Biochemistry 2011; 50:10069-81. [PMID: 22023145 DOI: 10.1021/bi200965e] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Residues surrounding and interacting with the heme proximal ligand are important for efficient catalysis by heme proteins. The nitric oxide synthases (NOSs) are thiolate-coordinated enzymes that catalyze the hydroxylation of l-Arg in the first of the two catalytic cycles needed to synthesize nitric oxide. In NOSs, the indole NH group of a conserved tryptophan [W56 of the bacterial NOS-like protein from Staphylococcus aureus (saNOS)] forms a hydrogen bond with the heme proximal cysteinate ligand. The purpose of this study was to determine the impact of increasing (W56F and W56Y variants) or decreasing (W56H variant) the electron density of the proximal cysteinate ligand on molecular oxygen (O(2)) activation using saNOS as a model. We show that the removal of the indole NH···S(-) bond for W56F and W56Y caused an increase in the electron density of the cysteinate. This was probed by the decrease of the midpoint reduction potential (E(1/2)) along with weakened σ-bonding and strengthened π-backbonding with distal ligands (CO and O(2)). On the other hand, the W56H variant showed stronger Fe-OO and Fe-CO bonds (strengthened σ-bonding) along with an elevated E(1/2), which is consistent with the formation of a strong NH···S(-) hydrogen bond from H56. We also show here that changing the electron density of the proximal thiolate controls its "push effect"; whereas the rates of both O(2) activation and autoxidation of the Fe(II)O(2) complex increase with the stronger push effect created by removing the indole NH···S(-) hydrogen bond (W56F and W56Y variants), the W56H variant showed an increased stability of the complex against autoxidation and a slower rate of O(2) activation. These results are discussed with regard to the roles played by the conserved tryptophan-cysteinate interaction in the first catalytic cycle of NOS.
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Affiliation(s)
- Jérôme Lang
- Département de biochimie, de microbiologie et de bioinformatique, PROTEO and IBIS, pavillon Charles-Eugène Marchand, room 3163, Université Laval, Québec, Canada G1V 0A6
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27
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Generation, Translocation, and Action of Nitric Oxide in Living Systems. ACTA ACUST UNITED AC 2011; 18:1211-20. [DOI: 10.1016/j.chembiol.2011.09.009] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Revised: 09/19/2011] [Accepted: 09/20/2011] [Indexed: 01/01/2023]
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28
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Cytochrome P450 BM3, NO binding and real-time NO detection. Nitric Oxide 2011; 25:89-94. [DOI: 10.1016/j.niox.2011.01.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2010] [Revised: 01/27/2011] [Accepted: 01/29/2011] [Indexed: 11/19/2022]
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29
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Li W, Fan W, Elmore BO, Feng C. Effect of solution viscosity on intraprotein electron transfer between the FMN and heme domains in inducible nitric oxide synthase. FEBS Lett 2011; 585:2622-6. [PMID: 21803041 DOI: 10.1016/j.febslet.2011.07.022] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 07/13/2011] [Accepted: 07/14/2011] [Indexed: 11/15/2022]
Abstract
The FMN-heme intraprotein electron transfer (IET) kinetics in a human inducible NOS (iNOS) oxygenase/FMN construct were determined by laser flash photolysis as a function of solution viscosity (1.0-3.0 cP). In the presence of ethylene glycol or sucrose, an appreciable decrease in the IET rate constant value was observed with an increase in the solution viscosity. The IET rate constant is inversely proportional to the viscosity for both viscosogens. This demonstrates that viscosity, and not other properties of the added viscosogens, causes the dependence of IET rates on the solvent concentration. The IET kinetics results indicate that the FMN-heme IET in iNOS is gated by a large conformational change of the FMN domain. The kinetics and NOS flavin fluorescence results together indicate that the docked FMN/heme state is populated transiently.
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Affiliation(s)
- Wenbing Li
- Department of Pharmaceutical Sciences, University of New Mexico, Albuquerque, NM 87131, USA
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30
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Sempombe J, Galinato MGI, Elmore BO, Fan W, Guillemette JG, Lehnert N, Kirk ML, Feng C. Mutation in the flavin mononucleotide domain modulates magnetic circular dichroism spectra of the iNOS ferric cyano complex in a substrate-specific manner. Inorg Chem 2011; 50:6859-61. [PMID: 21718007 DOI: 10.1021/ic200952c] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
We have obtained low-temperature magnetic circular dichroism (MCD) spectra for ferric cyano complexes of the wild type and E546N mutant of a human inducible nitric oxide synthase (iNOS) oxygenase/flavin mononucleotide (oxyFMN) construct. The mutation at the FMN domain has previously been shown to modulate the MCD spectra of the l-arginine-bound ferric iNOS heme (Sempombe, J.; et al. J. Am. Chem. Soc. 2009, 131, 6940-6941). The addition of l-arginine to the wild-type protein causes notable changes in the CN(-)-adduct MCD spectrum, while the E546N mutant spectrum is not perturbed. Moreover, the MCD spectral perturbation observed with l-arginine is absent in the CN(-) complexes incubated with N-hydroxy-L-arginine, which is the substrate for the second step of NOS catalysis. These results indicate that interdomain FMN-heme interactions exert a long-range effect on key heme axial ligand-substrate interactions that determine substrate oxidation pathways of NOS.
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Affiliation(s)
- Joseph Sempombe
- Department of Chemistry and Chemical Biology, The University of New Mexico, New Mexico 87131, USA
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31
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Floquet N, Hernandez JF, Boucher JL, Martinez J. L-arginine binding to human inducible nitric oxide synthase: an antisymmetric funnel route toward isoform-specific inhibitors? J Chem Inf Model 2011; 51:1325-35. [PMID: 21574590 DOI: 10.1021/ci100422v] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nitric oxide (NO) is an important signaling molecule produced by a family of enzymes called nitric oxide synthases (NOS). Because NO is involved in various pathological conditions, the development of potent and isoform-selective NOS inhibitors is an important challenge. In the present study, the dimer of oxygenase domain of human iNOS (iNOSoxy) complexed to its natural substrate L-arginine (L-Arg) and both heme and tetrahydro-L-biopterin (BH4) cofactors was studied through multiple molecular dynamics simulations. Starting from the X-ray structure available for that complex (PDB: 1NSI ), a 16 ns equilibration trajectory was first obtained. Twelve dynamics of slow extraction of L-Arg out from the iNOSoxy active site were then performed. The steered molecular dynamics (SMD) approach was used starting from three different points of the reference trajectory for a total simulation time of 35 ns. A probable unbinding/binding pathway of L-Arg was characterized. It was suggested that a driving force directed the substrate toward the heme pocket. Key intermediate steps/residues along the access route to the active site were identified along this "funnel shape" pathway and compared to existing data. A quasi-normal mode analysis performed on the SMD data suggested that large collective motions of the protein may be involved in L-Arg binding and that opening the route to the active site in one monomer promoted an inverse, closing motion in the second monomer. Finally, our findings might help to rationalize the design of human iNOS isoform competitive inhibitors.
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Affiliation(s)
- Nicolas Floquet
- Institut des Biomolécules Max Mousseron (IBMM), UMR 5247 Université Montpellier 1, Université Montpellier 2, CNRS, Faculté de Pharmacie, Montpellier, France.
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32
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Brunel A, Wilson A, Henry L, Dorlet P, Santolini J. The proximal hydrogen bond network modulates Bacillus subtilis nitric-oxide synthase electronic and structural properties. J Biol Chem 2011; 286:11997-2005. [PMID: 21310962 DOI: 10.1074/jbc.m110.195446] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bacterial nitric-oxide synthase (NOS)-like proteins are believed to be genuine NOSs. As for cytochromes P450 (CYPs), NOS-proximal ligand is a thiolate that exerts a push effect crucial for the process of dioxygen activation. Unlike CYPs, this catalytic electron donation seems controlled by a hydrogen bond (H-bond) interaction between the thiolate ligand and a vicinal tryptophan. Variations of the strength of this H-bond could provide a direct way to tune the stability along with the electronic and structural properties of NOS. We generated five different mutations of bsNOS Trp66, which can modulate this proximal H-bond. We investigated the effects of these mutations on different NOS complexes (FeIII, FeIICO, and FeIINO), using a combination of UV-visible absorption, EPR, FTIR, and resonance Raman spectroscopies. Our results indicate that (i) the proximal H-bond modulation can selectively decrease or increase the electron donating properties of the proximal thiolate, (ii) this modulation controls the σ-competition between distal and proximal ligands, (iii) this H-bond controls the stability of various NOS intermediates, and (iv) a fine tuning of the electron donation by the proximal ligand is required to allow at the same time oxygen activation and to prevent uncoupling reactions.
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Affiliation(s)
- Albane Brunel
- Commissariat à l'Energie Atomique, iBiTec-S, SBSM, F-91191 Gif-sur-Yvette, France
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33
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Ji H, Delker SL, Li H, Martásek P, Roman LJ, Poulos TL, Silverman RB. Exploration of the active site of neuronal nitric oxide synthase by the design and synthesis of pyrrolidinomethyl 2-aminopyridine derivatives. J Med Chem 2010; 53:7804-24. [PMID: 20958055 DOI: 10.1021/jm100947x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Neuronal nitric oxide synthase (nNOS) represents an important therapeutic target for the prevention of brain injury and the treatment of various neurodegenerative disorders. A series of trans-substituted amino pyrrolidinomethyl 2-aminopyridine derivatives (8-34) was designed and synthesized. A structure-activity relationship analysis led to the discovery of low nanomolar nNOS inhibitors ((±)-32 and (±)-34) with more than 1000-fold selectivity for nNOS over eNOS. Four enantiomerically pure isomers of 3'-[2''-(3'''-fluorophenethylamino)ethoxy]pyrrolidin-4'-yl}methyl}-4-methylpyridin-2-amine (4) also were synthesized. It was found that (3'R,4'R)-4 can induce enzyme elasticity to generate a new "hot spot" for ligand binding. The inhibitor adopts a unique binding mode, the same as that observed for (3'R,4'R)-3'-[2''-(3'''-fluorophenethylamino)ethylamino]pyrrolidin-4'-yl}methyl}-4-methylpyridin-2-amine ((3'R,4'R)-3) (J. Am. Chem. Soc. 2010, 132 (15), 5437 - 5442). On the basis of structure-activity relationships of 8-34 and different binding conformations of the cis and trans isomers of 3 and 4, critical structural requirements of the NOS active site for ligand binding are revealed.
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Affiliation(s)
- Haitao Ji
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, and Chemistry of Life Processes Institute, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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34
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Astashkin AV, Elmore BO, Fan W, Guillemette JG, Feng C. Pulsed EPR determination of the distance between heme iron and FMN centers in a human inducible nitric oxide synthase. J Am Chem Soc 2010; 132:12059-67. [PMID: 20695464 DOI: 10.1021/ja104461p] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Mammalian nitric oxide synthase (NOS) is a homodimeric flavo-hemoprotein that catalyzes the oxidation of L-arginine to nitric oxide (NO). Regulation of NO biosynthesis by NOS is primarily through control of interdomain electron transfer (IET) processes in NOS catalysis. The IET from the flavin mononucleotide (FMN) to heme domains is essential in the delivery of electrons required for O(2) activation in the heme domain and the subsequent NO synthesis by NOS. The NOS output state for NO production is an IET-competent complex of the FMN-binding domain and heme domain, and thereby it facilitates the IET from the FMN to the catalytic heme site. The structure of the functional output state has not yet been determined. In the absence of crystal structure data for NOS holoenzyme, it is important to experimentally determine the Fe...FMN distance to provide a key calibration for computational docking studies and for the IET kinetics studies. Here we used the relaxation-induced dipolar modulation enhancement (RIDME) technique to measure the electron spin echo envelope modulation caused by the dipole interactions between paramagnetic FMN and heme iron centers in the [Fe(III)][FMNH(*)] (FMNH(*): FMN semiquinone) form of a human inducible NOS (iNOS) bidomain oxygenase/FMN construct. The FMNH(*)...Fe distance has been directly determined from the RIDME spectrum. This distance (18.8 +/- 0.1 A) is in excellent agreement with the IET rate constant measured by laser flash photolysis [Feng, C. J.; Dupont, A.; Nahm, N.; Spratt, D.; Hazzard, J. T.; Weinberg, J.; Guillemette, J.; Tollin, G.; Ghosh, D. K. J. Biol. Inorg. Chem. 2009, 14, 133-142].
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Affiliation(s)
- Andrei V Astashkin
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
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35
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Santolini J. The molecular mechanism of mammalian NO-synthases: a story of electrons and protons. J Inorg Biochem 2010; 105:127-41. [PMID: 21194610 DOI: 10.1016/j.jinorgbio.2010.10.011] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 10/19/2010] [Accepted: 10/22/2010] [Indexed: 02/01/2023]
Abstract
Since its discovery, nitric oxide synthase (NOS), the enzyme responsible for NO biosynthesis in mammals, has been the subject of extensive investigations regarding its catalytic and molecular mechanisms. These studies reveal the high degree of sophistication of NOS functioning and regulation. However, the precise description of the NOS molecular mechanism and in particular of the oxygen activation chemistry is still lacking. The reaction intermediates implicated in NOS catalysis continue to elude identification and the current working paradigm is increasingly contested. Consequently, the last three years has seen the emergence of several competing models. All these models propose the same global reaction scheme consisting of two successive oxidation reactions but they diverge in the details of their reaction sequence. The major discrepancies concern the number, source and characteristics of proton and electron transfer processes. As a result each model proposes distinct reaction pathways with different implied oxidative species. This review aims to examine the different experimental evidence concerning NOS proton and electron transfer events and the role played by the substrates and cofactors in these processes. The resulting discussion should provide a comparative picture of all potential models for the NOS molecular mechanism.
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Affiliation(s)
- Jérôme Santolini
- iBiTec-S; LSOD, C. E. A. Saclay; 91191 Gif-sur-Yvette Cedex, France.
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36
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Feng C, Fan W, Dupont A, Guy Guillemette J, Ghosh DK, Tollin G. Electron transfer in a human inducible nitric oxide synthase oxygenase/FMN construct co-expressed with the N-terminal globular domain of calmodulin. FEBS Lett 2010; 584:4335-8. [PMID: 20868689 DOI: 10.1016/j.febslet.2010.09.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 09/16/2010] [Accepted: 09/16/2010] [Indexed: 11/26/2022]
Abstract
The FMN-heme intraprotein electron transfer (IET) kinetics in a human inducible NOS (iNOS) oxygenase/FMN (oxyFMN) construct co-expressed with NCaM, a truncated calmodulin (CaM) construct that includes only its N-terminal globular domain consisting of residues 1-75, were determined by laser flash photolysis. The IET rate constant is significantly decreased by nearly fourfold (compared to the iNOS oxyFMN co-expressed with full length CaM). This supports an important role of full length CaM in proper interdomain FMN/heme alignment in iNOS. The IET process was not observed with added excess EDTA, suggesting that Ca(2+) depletion results in the FMN domain moving away from the heme domain. The results indicate that a Ca(2+)-dependent reorganization of the truncated CaM construct could cause a major modification of the NCaM/iNOS association resulting in a loss of the IET.
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Affiliation(s)
- Changjian Feng
- College of Pharmacy, University of New Mexico, Albuquerque, NM 87131, USA.
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37
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Yakubovich N, Silva EA, O'Farrell PH. Nitric oxide synthase is not essential for Drosophila development. Curr Biol 2010; 20:R141-2. [PMID: 20178753 DOI: 10.1016/j.cub.2009.12.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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38
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Giroud C, Moreau M, Mattioli TA, Balland V, Boucher JL, Xu-Li Y, Stuehr DJ, Santolini J. Role of arginine guanidinium moiety in nitric-oxide synthase mechanism of oxygen activation. J Biol Chem 2009; 285:7233-45. [PMID: 19951943 DOI: 10.1074/jbc.m109.038240] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Nitric-oxide synthases (NOS) are highly regulated heme-thiolate enzymes that catalyze two oxidation reactions that sequentially convert the substrate L-Arg first to N(omega)-hydroxyl-L-arginine and then to L-citrulline and nitric oxide. Despite numerous investigations, the detailed molecular mechanism of NOS remains elusive and debatable. Much of the dispute in the various proposed mechanisms resides in the uncertainty concerning the number and sources of proton transfers. Although specific protonation events are key features in determining the specificity and efficiency of the two catalytic steps, little is known about the role and properties of protons from the substrate, cofactors, and H-bond network in the vicinity of the heme active site. In this study, we have investigated the role of the acidic proton from the L-Arg guanidinium moiety on the stability and reactivity of the ferrous heme-oxy complex intermediate by exploiting a series of L-Arg analogues exhibiting a wide range of guanidinium pK(a) values. Using electrochemical and vibrational spectroscopic techniques, we have analyzed the effects of the analogues on the heme, including characteristics of its proximal ligand, heme conformation, redox potential, and electrostatic properties of its distal environment. Our results indicate that the substrate guanidinium pK(a) value significantly affects the H-bond network near the heme distal pocket. Our results lead us to propose a new structural model where the properties of the guanidinium moiety finely control the proton transfer events in NOS and tune its oxidative chemistry. This model may account for the discrepancies found in previously proposed mechanisms of NOS oxidation processes.
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Affiliation(s)
- Claire Giroud
- Laboratoire Stress Oxydants et Detoxication, Commissariat à l'Energie Atomique Saclay, Institut de Biologie et de Technologies de Saclay, 91191 Gif-sur-Yvette Cedex, France
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39
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Doukov T, Li H, Soltis M, Poulos TL. Single crystal structural and absorption spectral characterizations of nitric oxide synthase complexed with N(omega)-hydroxy-L-arginine and diatomic ligands. Biochemistry 2009; 48:10246-54. [PMID: 19791770 DOI: 10.1021/bi9009743] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The X-ray structures of neuronal nitric oxide synthase (nNOS) with N(omega)-hydroxy-l-arginine (l-NHA) and CO (or NO) bound have been determined at 1.91-2.2 A resolution. Microspectrophotometric techniques confirmed reduced redox state and the status of diatomic ligand complexes during X-ray diffraction data collection. The structure of nNOS-NHA-NO, a close mimic to the dioxygen complex, provides a picture of the potential interactions between the heme-bound diatomic ligand, substrate l-NHA, and the surrounding protein and solvent structure environment. The OH group of l-NHA in the X-ray structures deviates from the plane of the guanidinium moiety substantially, indicating that the OH-bearing, protonated guanidine N(omega) nitrogen of l-NHA has substantial sp(3) hybridization character. This nitrogen geometry, different from that of the guanidinium N(omega) nitrogen of l-arginine, allows a hydrogen bond to be donated to the proximal oxygen of the heme-bound dioxygen complex, thus preventing cleavage of the O-O bond. Instead, it favors the stabilization of the ferric-hydroperoxy intermediate, Fe(3+)-OOH(-), which serves as the active oxidant in the conversion of l-NHA to NO and citrulline in the second reaction of the NOS.
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Affiliation(s)
- Tzanko Doukov
- Macromolecular Crystallographic Group, The Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford, California 94309, USA
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Davydov R, Sudhamsu J, Lees NS, Crane BR, Hoffman BM. EPR and ENDOR characterization of the reactive intermediates in the generation of NO by cryoreduced oxy-nitric oxide synthase from Geobacillus stearothermophilus. J Am Chem Soc 2009; 131:14493-507. [PMID: 19754116 DOI: 10.1021/ja906133h] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cryoreduction EPR/ENDOR/step-annealing measurements with substrate complexes of oxy-gsNOS (3; gsNOS is nitric oxide synthase from Geobacillus stearothermophilus) confirm that Compound I (6) is the reactive heme species that carries out the gsNOS-catalyzed (Stage I) oxidation of L-arginine to N-hydroxy-L-arginine (NOHA), whereas the active species in the (Stage II) oxidation of NOHA to citrulline and HNO/NO(-) is the hydroperoxy-ferric form (5). When 3 is reduced by tetrahydrobiopterin (BH4), instead of an externally supplied electron, the resulting BH4(+) radical oxidizes HNO/NO(-) to NO. In this report, radiolytic one-electron reduction of 3 and its complexes with Arg, Me-Arg, and NO(2)Arg was shown by EPR and (1)H and (14,15)N ENDOR spectroscopies to generate 5; in contrast, during cryoreduction of 3/NOHA, the peroxo-ferric-gsNOS intermediate (4/NOHA) was trapped. During annealing at 145 K, ENDOR shows that 5/Arg and 5/Me-Arg (but not 5/NO(2)Arg) generate a Stage I primary product species in which the OH group of the hydroxylated substrate is coordinated to Fe(III), characteristic of 6 as the active heme center. Analysis shows that hydroxylation of Arg and Me-Arg is quantitative. Annealing of 4/NOHA at 160 K converts it first to 5/NOHA and then to the Stage II primary enzymatic product. The latter contains Fe(III) coordinated by water, characteristic of 5 as the active heme center. It further contains quantitative amounts of citrulline and HNO/NO(-); the latter reacts with the ferriheme to form the NO-ferroheme upon further annealing. Stage I delivery of the first proton of catalysis to the (unobserved) 4 formed by cryoreduction of 3 involves a bound water that may convey a proton from L-Arg, while the second proton likely derives from the carboxyl side chain of Glu 248 or the heme carboxylates; the process also involves proton delivery by water(s). In the Stage II oxidation of NOHA, the proton that converts 4/NOHA to 5/NOHA likely is derived from NOHA itself, a conclusion supported by the pH invariance of the process. The present results illustrate how the substrate itself modulates the nature and reactivity of intermediates along the monooxygenase reaction pathway.
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Affiliation(s)
- Roman Davydov
- Chemistry Department, Northwestern University, Evanston, Illinois 60208-3113, USA
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41
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Fan B, Stuehr DJ, Rousseau DL. Role of substrate functional groups in binding to nitric oxide synthase. Biochem Biophys Res Commun 2009; 382:21-5. [PMID: 19248772 DOI: 10.1016/j.bbrc.2009.02.084] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2009] [Accepted: 02/10/2009] [Indexed: 10/21/2022]
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Menyhárd DK. Comparative computational analysis of active and inactive cofactors of nitric oxide synthase. J Phys Chem B 2009; 113:3151-9. [PMID: 19708267 DOI: 10.1021/jp8083056] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nitric oxide synthases (NOSs) are heme proteins that catalyze the formation of nitric oxide from L-Arg in the presence of oxygen. Of the two electrons required for the first step of the reaction, the second is primarily donated by the tetrahydrobiopterin (H4B) cofactor bound adjacent to the heme, which is eventually reduced back to resting state by the ultimate electron source of the reaction, the flavins of the NOS reductase domain. Density functional theory calculations were carried out to identify those protonation states of different cofactor molecules that best support radicalization of the cofactor and the coupled increase in the electron density of the heme-bound oxygen molecule. Three cofactor molecules were studied, native H4B, an active analogue, 5-methyl-H4B, and the inactive 4-amino-H4B. Findings support the emerging model where H4B and 5-methyl-H4B are coupled proton/electron sources of NOS catalysis, while 4-amino-H4B is an inhibitor due to its inability to donate the catalytically required proton.
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Affiliation(s)
- Dóra K Menyhárd
- Department of Inorganic and Analytical Chemistry, Budapest University of Technology and Economy, Budapest, Szent Gellért tér 4., H-1111, Hungary.
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43
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Cho KB, Carvajal MA, Shaik S. First Half-Reaction Mechanism of Nitric Oxide Synthase: The Role of Proton and Oxygen Coupled Electron Transfer in the Reaction by Quantum Mechanics/Molecular Mechanics. J Phys Chem B 2008; 113:336-46. [DOI: 10.1021/jp8073199] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Kyung-Bin Cho
- Institute of Chemistry and The Lise Meitner-Minerva Center for Quantum Computational Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Maria Angels Carvajal
- Institute of Chemistry and The Lise Meitner-Minerva Center for Quantum Computational Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
| | - Sason Shaik
- Institute of Chemistry and The Lise Meitner-Minerva Center for Quantum Computational Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel
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Woodward JJ, Chang MM, Martin NI, Marletta MA. The Second Step of the Nitric Oxide Synthase Reaction: Evidence for Ferric-Peroxo as the Active Oxidant. J Am Chem Soc 2008; 131:297-305. [DOI: 10.1021/ja807299t] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Joshua J. Woodward
- Departments of Chemistry, Molecular and Cellular Biology, QB3 Institute, and Division of Physical Biosciences, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720-3220
| | - Michelle M. Chang
- Departments of Chemistry, Molecular and Cellular Biology, QB3 Institute, and Division of Physical Biosciences, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720-3220
| | - Nathaniel I. Martin
- Departments of Chemistry, Molecular and Cellular Biology, QB3 Institute, and Division of Physical Biosciences, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720-3220
| | - Michael A. Marletta
- Departments of Chemistry, Molecular and Cellular Biology, QB3 Institute, and Division of Physical Biosciences, Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720-3220
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45
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Kabir M, Sudhamsu J, Crane BR, Yeh SR, Rousseau DL. Substrate-ligand interactions in Geobacillus stearothermophilus nitric oxide synthase. Biochemistry 2008; 47:12389-97. [PMID: 18956884 PMCID: PMC3403685 DOI: 10.1021/bi801491e] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Nitric oxide synthase (NOS) generates NO via a sequential two-step reaction [l-arginine (l-Arg) --> N-hydroxy-l-arginine (NOHA) --> l-citrulline + NO]. Each step of the reaction follows a distinct mechanism defined by the chemical environment introduced by each substrate bound to the heme active site. The dioxygen complex of the NOS enzyme from a thermophilic bacterium, Geobacillus stearothermophilus (gsNOS), is unusually stable; hence, it provides a unique model for the studies of the mechanistic differences between the two steps of the NOS reaction. By using CO as a structural probe, we found that gsNOS exhibits two conformations in the absence of substrate, as indicated by the presence of two sets of nu(Fe-CO)/nu(C-O) modes in the resonance Raman spectra. In the nu(Fe-CO) versus nu(C-O) inverse correlation plot, one set of data falls on the correlation line characterized by mammalian NOSs (mNOS), whereas the other set of data lies on a new correlation line defined by a bacterial NOS from Bacillus subtilis (bsNOS), reflecting a difference in the proximal Fe-Cys bond strength in the two conformers of gsNOS. The addition of l-Arg stabilizes the conformer associated with the mNOS correlation line, whereas NOHA stabilizes the conformer associated with the bsNOS correlation line, although both substrates introduce a positive electrostatic potential into the distal heme pocket. To assess how substrate binding affects Fe-Cys bond strength, the frequency of the Fe-Cys stretching mode of gsNOS was monitored by resonance Raman spectroscopy with 363.8 nm excitation. In the substrate-free form, the Fe-Cys stretching mode was detected at 342.5 cm(-1), similar to that of bsNOS. The binding of l-Arg and NOHA brings about a small decrease and increase in the Fe-Cys stretching frequency, respectively. The implication of these unique structural features with respect to the oxygen chemistry of NOS is discussed.
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Affiliation(s)
- Mariam Kabir
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Jawahar Sudhamsu
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca NY 14853
| | - Brian R. Crane
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca NY 14853
| | - Syun-Ru Yeh
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Denis L. Rousseau
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, Bronx, NY 10461
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Li H, Das A, Sibhatu H, Jamal J, Sligar SG, Poulos TL. Exploring the electron transfer properties of neuronal nitric-oxide synthase by reversal of the FMN redox potential. J Biol Chem 2008; 283:34762-72. [PMID: 18852262 DOI: 10.1074/jbc.m806949200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
In nitric-oxide synthase (NOS) the FMN can exist as the fully oxidized (ox), the one-electron reduced semiquinone (sq), or the two-electron fully reduced hydroquinone (hq). In NOS and microsomal cytochrome P450 reductase the sq/hq redox potential is lower than that of the ox/sq couple, and hence it is the hq form of FMN that delivers electrons to the heme. Like NOS, cytochrome P450BM3 has the FAD/FMN reductase fused to the C-terminal end of the heme domain, but in P450BM3 the ox/sq and sq/hq redox couples are reversed, so it is the sq that transfers electrons to the heme. This difference is due to an extra Gly residue found in the FMN binding loop in NOS compared with P450BM3. We have deleted residue Gly-810 from the FMN binding loop in neuronal NOS (nNOS) to give Delta G810 so that the shorter binding loop mimics that in cytochrome P450BM3. As expected, the ox/sq redox potential now is lower than the sq/hq couple. Delta G810 exhibits lower NO synthase activity but normal levels of cytochrome c reductase activity. However, unlike the wild-type enzyme, the cytochrome c reductase activity of Delta G810 is insensitive to calmodulin binding. In addition, calmodulin binding to Delta G810 does not result in a large increase in FMN fluorescence as in wild-type nNOS. These results indicate that the FMN domain in Delta G810 is locked in a unique conformation that is no longer sensitive to calmodulin binding and resembles the "on" output state of the calmodulin-bound wild-type nNOS with respect to the cytochrome c reduction activity.
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Affiliation(s)
- Huiying Li
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California 92697, USA
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Whited CA, Belliston-Bittner W, Dunn AR, Winkler JR, Gray HB. Probing the heme-thiolate oxygenase domain of inducible nitric oxide synthase with Ru(II) and Re(I) electron tunneling wires. J PORPHYR PHTHALOCYA 2008; 12:971-978. [PMID: 19759857 PMCID: PMC2744429 DOI: 10.1142/s1088424608000352] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Nitric oxide synthase (NOS) catalyzes the production of nitric oxide from L-arginine and dioxygen at a thiolate-ligated heme active site. Although many of the reaction intermediates are as yet unidentified, it is well established that the catalytic cycle begins with substrate binding and rate-limiting electron transfer to the heme. Here we show that Ru(II)-diimine and Re(I)-diimine electron tunneling wires trigger nanosecond photoreduction of the active-site heme in the enzyme. Very rapid generation of a reduced thiolate-ligated heme opens the way for direct observation of short-lived intermediates in the NOS reaction cycle.
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Affiliation(s)
| | | | - Alexander R. Dunn
- Beckman Institute, California Institute of Technology, Pasadena, 91125, USA
| | - Jay R. Winkler
- Beckman Institute, California Institute of Technology, Pasadena, 91125, USA
| | - Harry B. Gray
- Beckman Institute, California Institute of Technology, Pasadena, 91125, USA
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Rose MJ, Mascharak PK. A photosensitive {Ru–NO}6 nitrosyl bearing dansyl chromophore: novel NO donor with a fluorometric on/off switch. Chem Commun (Camb) 2008:3933-5. [DOI: 10.1039/b805332d] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
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49
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Chartier FJM, Couture M. Substrate-specific Interactions with the Heme-bound Oxygen Molecule of Nitric-oxide Synthase. J Biol Chem 2007; 282:20877-86. [PMID: 17537725 DOI: 10.1074/jbc.m701800200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
We report the characterization by resonance Raman spectroscopy of the oxygenated complex (Fe(II)O(2)) of nitric-oxide synthases of Staphylococcus aureus (saNOS) and Bacillus subtilis (bsNOS) saturated with N(omega)-hydroxy-l-arginine. The frequencies of the nu(Fe-O) and nu(O-O) modes were 530 and 1135 cm(-), respectively, in both the presence and absence of tetrahydrobiopterin. On the basis of a comparison of these frequencies with those of saNOS and bsNOS saturated with l-arginine (nu(Fe-O) at 517 cm(-1) and nu(O-O) at 1123 cm(-1)) and those of substrate-free saNOS (nu(Fe-O) at 517 and nu(O-O) at 1135 cm(-1)) (Chartier, F. J. M., Blais, S. P., and Couture, M. (2006) J. Biol. Chem. 281, 9953-9962), we propose two models that account for the frequency shift of nu(Fe-O) (but not nu(O-O)) upon N(omega)-hydroxy-l-arginine binding as well as the frequency shift of nu(O-O) (but not nu(Fe-O)) upon l-arginine binding. The implications of these substrate-specific interactions with respect to catalysis by NOSs are discussed.
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Affiliation(s)
- François J M Chartier
- Département de Biochimie et de Microbiologie and the Centre de Recherche sur la Fonction, la Structure, et l'Ingénierie des Protéines, Université Laval, Quebec City, Quebec G1K 7P4, Canada
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