1
|
Mondal P, Ishigami I, Yeh SR, Wijeratne GB. The Role of Heme Peroxo Oxidants in the Rational Mechanistic Modeling of Nitric Oxide Synthase: Characterization of Key Intermediates and Elucidation of the Mechanism. Angew Chem Int Ed Engl 2022; 61:e202211521. [PMID: 36169890 PMCID: PMC9675724 DOI: 10.1002/anie.202211521] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Indexed: 11/08/2022]
Abstract
Mammalian nitric oxide synthase (NOS) mediates the two-step O2 -dependent oxidative degradation of arginine, and has been linked to a medley of disease situations in humans. Nonetheless, its exact mechanism of action still remains unclear. This work presents the first NOS model system where biologically proposed heme superoxo and peroxo intermediates are assessed as active oxidants against oxime substrates. Markedly, heme peroxo intermediates engaged in a bioinspired oxime oxidation reaction pathway, converting oximes to ketones and nitroxyl anions (NO- ). Detailed thermodynamic, kinetic, and mechanistic interrogations all evince a rate-limiting step primarily driven by the nucleophilicity of the heme peroxo moiety. Coherent with other findings, 18 O and 15 N isotope substitution experiments herein suffice compelling evidence toward a detailed mechanism, which draw close parallels to one of the enzymatic proposals. Intriguingly, recent enzymatic studies also lend credence to these findings, and several relevant reaction intermediates have been observed during NOS turnover.
Collapse
Affiliation(s)
- Pritam Mondal
- Department of Chemistry and O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35205, USA
| | - Izumi Ishigami
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, The Bronx, NY 10461, USA
| | - Syun-Ru Yeh
- Department of Physiology and Biophysics, Albert Einstein College of Medicine, The Bronx, NY 10461, USA
| | - Gayan B Wijeratne
- Department of Chemistry and O'Neal Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, AL 35205, USA
| |
Collapse
|
2
|
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: 96] [Impact Index Per Article: 32.0] [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.
Collapse
Affiliation(s)
- Nicolai Lehnert
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Eunsuk Kim
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Hai T Dong
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Jill B Harland
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Andrew P Hunt
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Elizabeth C Manickas
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Kady M Oakley
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - John Pham
- Department of Chemistry, Brown University, Providence, Rhode Island 02912, United States
| | - Garrett C Reed
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| | - Victor Sosa Alfaro
- Department of Chemistry and Department of Biophysics, University of Michigan, Ann Arbor, Michigan 48109-1055, United States
| |
Collapse
|
3
|
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.
Collapse
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
| |
Collapse
|
4
|
Chaudhury A. A Hypothesis for Examining Skeletal Muscle Biopsy-Derived Sarcolemmal nNOSμ as Surrogate for Enteric nNOSα Function. Front Med (Lausanne) 2015; 2:48. [PMID: 26284245 PMCID: PMC4517061 DOI: 10.3389/fmed.2015.00048] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 07/10/2015] [Indexed: 12/13/2022] Open
Abstract
The pathophysiology of gastrointestinal motility disorders is controversial and largely unresolved. This provokes empiric approaches to patient management of these so-called functional gastrointestinal disorders. Preliminary evidence demonstrates that defects in neuronal nitric oxide synthase (nNOS) expression and function, the enzyme that synthesizes nitric oxide (NO), the key inhibitory neurotransmitter mediating mechano-electrical smooth muscle relaxation, is the major pathophysiological basis for sluggishness of oro-aboral transit of luminal contents. This opinion is an ansatz of the potential of skeletal muscle biopsy and examining sarcolemmal nNOSμ to provide complementary insights regarding nNOSα expression, localization, and function within enteric nerve terminals, the site of stimulated de novo NO synthesis. The main basis of this thesis is twofold: (a) the molecular similarity of the structures of nNOS α and μ, similar mechanisms of localizations to “active zones” of nitrergic synthesis, and same mechanisms of electron transfers during NO synthesis and (b) pragmatic difficulty to routinely obtain full-thickness biopsies of gastrointestinal tract, even in patients presenting with the most recalcitrant manifestations of stasis and delayed transit of luminal contents. This opinion attempts to provoke dialog whether this approach is feasible as a surrogate to predict catalytic potential of nNOSα and defects in nitrergic neurotransmission. This discussion makes an assumption that similar molecular mechanisms of nNOS defects shall be operant in both the enteric nerve terminals and the skeletal muscles. These overlaps of skeletal and gastrointestinal dysfunction are largely unknown, thus meriting that the thesis be validated in future by proof-of-principle experiments.
Collapse
|
5
|
Conner KP, Cruce AA, Krzyaniak MD, Schimpf AM, Frank DJ, Ortiz de Montellano P, Atkins WM, Bowman MK. Drug modulation of water-heme interactions in low-spin P450 complexes of CYP2C9d and CYP125A1. Biochemistry 2015; 54:1198-207. [PMID: 25591012 DOI: 10.1021/bi501402k] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Azoles and pyridines are commonly incorporated into small molecule inhibitor scaffolds that target cytochromes P450 (CYPs) as a strategy to increase drug binding affinity, impart isoform-dependent selectivity, and improve metabolic stability. Optical absorbance spectra of the CYP-inhibitor complex are widely used to infer whether these inhibitors are ligated directly to the heme iron as catalytically inert, low-spin (type II) complexes. Here, we show that the low-spin complex between a drug-metabolizing CYP2C9 variant and 4-(3-phenylpropyl)-1H-1,2,3-triazole (PPT) retains an axial water ligand despite exhibiting elements of "classic" type II optical behavior. Hydrogens of the axial water ligand are observed by pulsed electron paramagnetic resonance (EPR) spectroscopy for both inhibitor-free and inhibitor-bound species and show that inhibitor binding does not displace the axial water. A (15)N label incorporated into PPT is 0.444 nm from the heme iron, showing that PPT is also in the active site. The reverse type I inhibitor, LP10, of CYP125A1 from Mycobacterium tuberculosis, known from X-ray crystal structures to form a low-spin water-bridged complex, is found by EPR and by visible and near-infrared magnetic circular dichroism spectroscopy to retain the axial water ligand in the complex in solution.
Collapse
Affiliation(s)
- Kip P Conner
- Department of Medicinal Chemistry, Box 357610, and Department of Chemistry, Box 351700, University of Washington , Seattle, Washington 98195, United States
| | | | | | | | | | | | | | | |
Collapse
|
6
|
|
7
|
Affiliation(s)
- Thomas L. Poulos
- Departments of Molecular Biology & Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California Irvine, Irvine, California 92697-3900
| |
Collapse
|
8
|
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.
Collapse
Affiliation(s)
- Tzanko Doukov
- Macromolecular Crystallographic Group, The Stanford Synchrotron Radiation Lightsource, SLAC, Stanford University, Stanford, California 94309, USA
| | | | | | | |
Collapse
|
9
|
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.
Collapse
Affiliation(s)
- Roman Davydov
- Chemistry Department, Northwestern University, Evanston, Illinois 60208-3113, USA
| | | | | | | | | |
Collapse
|
10
|
Myers WK, Duesler EN, Tierney DL. Integrated paramagnetic resonance of high-spin Co(II) in axial symmetry: chemical separation of dipolar and contact electron-nuclear couplings. Inorg Chem 2008; 47:6701-10. [PMID: 18605690 DOI: 10.1021/ic800245k] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Integrated paramagnetic resonance, utilizing electron paramagnetic resonance (EPR), NMR, and electron-nuclear double resonance (ENDOR), of a series of cobalt bis-trispyrazolylborates, Co(Tp ( x )) 2, are reported. Systematic substitutions at the ring carbons and on the apical boron provide a unique opportunity to separate through-bond and through-space contributions to the NMR hyperfine shifts for the parent, unsubstituted Tp complex. A simple relationship between the chemical shift difference (delta H - delta Me) and the contact shift of the proton in that position is developed. This approach allows independent extraction of the isotropic hyperfine coupling, A iso, for each proton in the molecule. The Co..H contact coupling energies derived from the NMR, together with the known metrics of the compounds, were used to predict the ENDOR couplings at g perpendicular. Proton ENDOR data is presented that shows good agreement with the NMR-derived model. ENDOR signals from all other magnetic nuclei in the complex ( (14)N, coordinating and noncoordinating, (11)B and (13)C) are also reported.
Collapse
Affiliation(s)
- William K Myers
- Department of Chemistry and Chemical Biology, The University of New Mexico, Albuquerque, New Mexico 87131, USA
| | | | | |
Collapse
|
11
|
Gao YT, Roman LJ, Martásek P, Panda SP, Ishimura Y, Masters BSS. Oxygen metabolism by endothelial nitric-oxide synthase. J Biol Chem 2007; 282:28557-28565. [PMID: 17698846 DOI: 10.1074/jbc.m704890200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nitric-oxide synthase (NOS) catalyzes both coupled and uncoupled reactions that generate nitric oxide and reactive oxygen species. Oxygen is often the overlooked substrate, and the oxygen metabolism catalyzed by NOS has been poorly defined. In this paper we focus on the oxygen stoichiometry and effects of substrate/cofactor binding on the endothelial NOS isoform (eNOS). In the presence of both L-arginine and tetrahydrobiopterin, eNOS is highly coupled (>90%), and the measured stoichiometry of O(2)/NADPH is very close to the theoretical value. We report for the first time that the presence of L-arginine stimulates oxygen uptake by eNOS. The fact that nonhydrolyzable L-arginine analogs are not stimulatory indicates that the occurrence of the coupled reaction, rather than the accelerated uncoupled reaction, is responsible for the L-arginine-dependent stimulation. The presence of 5,6,7,8-tetrahydrobiopterin quenched the uncoupled reactions and resulted in much less reactive oxygen species formation, whereas the presence of redox-incompetent 7,8-dihydrobiopterin demonstrates little quenching effect. These results reveal different mechanisms for oxygen metabolism for eNOS as opposed to nNOS and, perhaps, partially explain their functional differences.
Collapse
Affiliation(s)
- Ying Tong Gao
- Department of Biochemistry, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900
| | - Linda J Roman
- Department of Biochemistry, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900
| | - Pavel Martásek
- Department of Pediatrics, Charles University School of Medicine I, 128 08 Prague, Czech Republic
| | - Satya Prakash Panda
- Department of Biochemistry, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900
| | - Yuzuru Ishimura
- Department of Biochemistry and Integrated Biology, School of Medicine, Keio University, Tokyo 160-8582, Japan
| | - Bettie Sue S Masters
- Department of Biochemistry, The University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900.
| |
Collapse
|
12
|
Katritzky AR, Khashab NM, Bobrov S, Yoshioka M. Synthesis of mono- and symmetrical di-N-hydroxy- and N-aminoguanidines. J Org Chem 2007; 71:6753-8. [PMID: 16930024 DOI: 10.1021/jo060793t] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Novel mono- and symmetrical di-N-hydroxy- and N-aminoguanidines were readily prepared from the reaction of diverse hydroxylamines or hydrazines with reagent classes di(benzotriazol-1-yl)methanimine 6, (bis-benzotriazol-1-yl-methylene)amines 8a,b, benzotriazole-1-carboxamidines 10a-i, benzotriazole-1-carboximidamides 11a,b, and N'-hydroxy-1H-1,2,3-benzotriazole-1-carboximidamide 18. The preparation is described for a variety of N-hydroxy- and N-aminoguanidines with different substitution patterns in good yields.
Collapse
Affiliation(s)
- Alan R Katritzky
- Center for Heterocyclic Compounds, University of Florida, Department of Chemistry, Gainesville, FL 32611-7200, USA.
| | | | | | | |
Collapse
|
13
|
García-Rubio I, Braun M, Gromov I, Thöny-Meyer L, Schweiger A. Axial coordination of heme in ferric CcmE chaperone characterized by EPR spectroscopy. Biophys J 2006; 92:1361-73. [PMID: 17142277 PMCID: PMC1783872 DOI: 10.1529/biophysj.106.098277] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In Escherichia coli cytochrome c maturation requires a set of eight proteins including the heme chaperone CcmE, which binds heme transiently, yet covalently. Several variants of CcmE were purified and analyzed by continuous-wave electron paramagnetic resonance, electron nuclear double resonance, and hyperfine sublevel correlation spectroscopy to investigate the heme axial coordination. Results reveal the presence of a number of coordination environments, two high-spin heme centers with different rhombicities, and at least one low-spin heme center. The low-spin species was shown to be an artifact induced by the presence of available histidines in the vicinity of the iron. Both of the high-spin forms are five-coordinated, and comparison of the spectra of the wild-type CcmE with those of the mutant CcmE(Y134H) proves that the higher-rhombicity form is coordinated by Tyr134. The low-rhombicity (axial) form does not have a histidine residue or a water molecule as an axial ligand. However, we identified exchangeable protons coupled to the iron ion. We propose that the axial form can be coordinated by a carboxyl group of an acidic residue in the flexible domain of the protein. The two species would represent two different conformations of the flexible alpha-helix domain surrounding the heme. This conformational flexibility confers CcmE special dynamic properties that are certainly important for its function.
Collapse
Affiliation(s)
- Inés García-Rubio
- Laboratorium für Physikalische Chemie, ETH Zurich, 8093 Zurich, Switzerland.
| | | | | | | | | |
Collapse
|
14
|
Li H, Igarashi J, Jamal J, Yang W, Poulos TL. Structural studies of constitutive nitric oxide synthases with diatomic ligands bound. J Biol Inorg Chem 2006; 11:753-68. [PMID: 16804678 DOI: 10.1007/s00775-006-0123-8] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2006] [Accepted: 05/18/2006] [Indexed: 10/24/2022]
Abstract
Crystal structures are reported for the endothelial nitric oxide synthase (eNOS)-arginine-CO ternary complex as well as the neuronal nitric oxide synthase (nNOS) heme domain complexed with L: -arginine and diatomic ligands, CO or NO, in the presence of the native cofactor, tetrahydrobiopterin, or its oxidized analogs, dihydrobiopterin and 4-aminobiopterin. The nature of the biopterin has no influence on the diatomic ligand binding. The binding geometries of diatomic ligands to nitric oxide synthase (NOS) follow the {MXY}(n) formalism developed from the inorganic diatomic-metal complexes. The structures reveal some subtle structural differences between eNOS and nNOS when CO is bound to the heme which correlate well with the differences in CO stretching frequencies observed by resonance Raman techniques. The detailed hydrogen-bonding geometries depicted in the active site of nNOS structures indicate that it is the ordered active-site water molecule rather than the substrate itself that would most likely serve as a direct proton donor to the diatomic ligands (CO, NO, as well as O(2)) bound to the heme. This has important implications for the oxygen activation mechanism critical to NOS catalysis.
Collapse
Affiliation(s)
- Huiying Li
- Department of Molecular Biology and Biochemistry, Center in Chemical and Structural Biology, University of California, Irvine, CA 92697-3900, USA
| | | | | | | | | |
Collapse
|
15
|
Goligorsky MS. Endothelial cell dysfunction: can't live with it, how to live without it. Am J Physiol Renal Physiol 2005; 288:F871-80. [PMID: 15821252 DOI: 10.1152/ajprenal.00333.2004] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endothelial cell dysfunction is emerging as an ultimate culprit for diverse cardiovascular diseases and cardiovascular complications of chronic renal diseases, yet the definition of this new syndrome, its pathophysiology, and therapy remain poorly defined. Here, I summarize some molecular mechanisms leading from hyperhomocystinemia, elevated asymmetric dimethylarginine, and advanced glycolation end product-modified protein level to the proatherogenic, prothrombogenic, and proinflammatory endothelial phenotype and offer a model of endothelial dysfunction based on the interconnectedness of diverse functions. Finally, several therapeutic strategies to prevent and correct endothelial dysfunction are discussed in the light of uncertainty of their action modulated by the endothelial dysfunction per se.
Collapse
Affiliation(s)
- Michael S Goligorsky
- Department of Nephrology and Renal Research Institute, Department of Medicine, New York Medical College, Valhalla, New York 10595, USA.
| |
Collapse
|
16
|
Cho KB, Gauld JW. Quantum Chemical Calculations of the NHA Bound Nitric Oxide Synthase Active Site: O2 Binding and Implications for the Catalytic Mechanism. J Am Chem Soc 2004; 126:10267-70. [PMID: 15315438 DOI: 10.1021/ja049186i] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Density functional theory has been employed to model the binding of the intermediate substrate NHA, by nitric oxide synthases. In particular, the orientation and interactions of possibly catalytically important substrate hydrogens, with and without molecular oxygen bound to the active site heme group, are considered. Without O(2), three possible conformers have been found, with the energetically most favored structure being that in which both protons of the -NHOH moiety of NHA are directed toward the heme group. With oxygen bound, four different structures were found. The energetically lowest structure is again found to have both hydrogens of the -NHOH group pointing toward the heme group, thus forming hydrogen bonds between -NH- and the terminal oxygen, and between -OH and the inner oxygen of the heme-O(2) group. In addition, unprotonated structures of the substrate bound to the active site are considered and the proton affinity calculated.
Collapse
Affiliation(s)
- Kyung-Bin Cho
- Contribution from the Department of Chemistry and Biochemistry, University of Windsor, Windsor, Ontario, N9B 3P4 Canada
| | | |
Collapse
|
17
|
Raines KW, Cao GL, Porsuphatana S, Tsai P, Rosen GM, Shapiro P. Nitric Oxide Inhibition of ERK1/2 Activity in Cells Expressing Neuronal Nitric-oxide Synthase. J Biol Chem 2004; 279:3933-40. [PMID: 14602725 DOI: 10.1074/jbc.m304813200] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Neuronal nitric-oxide synthase (nNOS) is a constitutively expressed enzyme responsible for the production of nitric oxide (NO*) from l-arginine and O2. Nitric oxide is an intra- and intercellular messenger that mediates a diversity of signaling pathways in target cells. In the absence of l-arginine, nNOS has been shown to generate superoxide (O2*). Superoxide, either directly or through its self-dismutation to H2O2, is likewise believed to be a cell-signaling agent. Because nNOS can generate NO* and O2*, we examined the activation of cellular signal transduction pathways in nNOS-transfected cells grown in the presence or absence of l-arginine. Spin trapping/EPR spectroscopy confirmed that stimulated nNOS-transfected cells grown in an l-arginine environment secreted NO* into the surrounding milieu. Production of NO* blocked Ca2+ ionophore-induced activation of the ERK1/2 through a mechanism involving inhibition of the Ras G-protein and Raf-1 kinase. In contrast, ERK activation was largely unaffected in nNOS-transfected cells grown in l-arginine-free media. Inhibition of nNOS-generated NO* with the competitive NOS inhibitor, NG-nitro-l-arginine methyl ester, in cells grown in l-arginine restored ERK1/2 activation to levels similar to that found when nNOS was activated in l-arginine-free media. These findings indicate that nNOS can differentially regulate the ERK signal transduction pathway in a manner dependent on the presence of l-arginine and the production of NO*.
Collapse
Affiliation(s)
- Kimberly W Raines
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA
| | | | | | | | | | | |
Collapse
|
18
|
What form of NG-hydroxy-L-arginine is the intermediate in the mechanism of NO synthase? QM and QM/MM calculations of substrate–active site interactions. ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0166-1280(03)00305-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
|
19
|
Pant K, Bilwes AM, Adak S, Stuehr DJ, Crane BR. Structure of a nitric oxide synthase heme protein from Bacillus subtilis. Biochemistry 2002; 41:11071-9. [PMID: 12220171 DOI: 10.1021/bi0263715] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Eukaryotic nitric oxide synthases (NOSs) produce nitric oxide to mediate intercellular signaling and protect against pathogens. Recently, proteins homologous to mammalian NOS oxygenase domains have been found in prokaryotes and one from Bacillus subtilis (bsNOS) has been demonstrated to produce nitric oxide [Adak, S., Aulak, K. S., and Stuehr, D. J. (2002) J. Biol. Chem. 277, 16167-16171]. We present structures of bsNOS complexed with the active cofactor tetrahydrofolate and the substrate L-arginine (L-Arg) or the intermediate N(omega)-hydroxy-L-arginine (NHA) to 1.9 or 2.2 A resolution, respectively. The bsNOS structure is similar to those of the mammalian NOS oxygenase domains (mNOS(ox)) except for the absence of an N-terminal beta-hairpin hook and zinc-binding region that interact with pterin and stabilize the mNOS(ox) dimer. Changes in patterns of residue conservation between bacterial and mammalian NOSs correlate to different binding modes for pterin side chains. Residue conservation on a surface patch surrounding an exposed heme edge indicates a likely interaction site for reductase proteins in all NOSs. The heme pockets of bsNOS and mNOS(ox) recognize L-Arg and NHA similarly, although a change from Val to Ile beside the substrate guanidinium may explain the 10-20-fold slower dissociation of product NO from the bacterial enzyme. Overall, these structures suggest that bsNOS functions naturally to produce nitrogen oxides from L-Arg and NHA in a pterin-dependent manner, but that the regulation and purpose of NO production by NOS may be quite different in B. subtilis than in mammals.
Collapse
Affiliation(s)
- Kartikeya Pant
- The Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA
| | | | | | | | | |
Collapse
|
20
|
Chen J, Brodsky SV, Goligorsky DM, Hampel DJ, Li H, Gross SS, Goligorsky MS. Glycated collagen I induces premature senescence-like phenotypic changes in endothelial cells. Circ Res 2002; 90:1290-8. [PMID: 12089067 DOI: 10.1161/01.res.0000022161.42655.98] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Diabetic vasculopathy is central to the development of diverse cardiovascular, renal, retinal, and neurological complications of diabetes. We previously demonstrated that growth of endothelial cells on glycated extracellular matrix proteins (collagen and matrigel) results in a significant decrease in cell proliferation. In the present study, we show that early-passage human umbilical vein endothelial cells (HUVECs) grown on glycated collagen (GC) express hallmarks of premature cell senescence, ie, increase in the proportion of cells expressing senescence-associated beta-galactosidase activity, apoptotic rate, and p53 and p14(AFR) expression, but in contrast to replicative senescence, display neither attrition of telomeres nor decrease in telomerase activity. An increased frequency of prematurely senescent cells was similarly observed in vivo in aortae of young Zucker diabetic rats, compared with lean controls. NO production by HUVECs grown on GC was decreased, despite a 3-fold increase in eNOS expression and was associated with the increased nitrotyrosine-modified proteins. Development of premature senescence of HUVECs on GC could be prevented and reversed by treatments with the peroxynitrite scavenger, ebselen, eNOS intermediate N(omega)-hydroxy-L-arginine (NOHA), or superoxide dismutase mimetic Mn-TBAP. Concomitant with the reversal of senescence, ebselen, and NOHA each restored NO production to levels observed with HUVECs grown on unmodified collagen. Our findings indicate that diabetes mellitus in vivo and GC exposure in vitro elicit premature senescence of the vascular endothelium, a process with distinct pathogenetic mechanisms. Premature senescence of the vascular endothelium is hypothesized to be an important contributor to diabetic vasculopathy and a consequence of reduced NO availability, peroxynitrite, and/or superoxide excess.
Collapse
Affiliation(s)
- Jun Chen
- Department of Medicine, State University of New York, Stony Brook, NY, USA
| | | | | | | | | | | | | |
Collapse
|
21
|
Wang PG, Xian M, Tang X, Wu X, Wen Z, Cai T, Janczuk AJ. Nitric oxide donors: chemical activities and biological applications. Chem Rev 2002; 102:1091-134. [PMID: 11942788 DOI: 10.1021/cr000040l] [Citation(s) in RCA: 972] [Impact Index Per Article: 44.2] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Peng George Wang
- Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
| | | | | | | | | | | | | |
Collapse
|
22
|
Affiliation(s)
- Gerald M Rosen
- Department of Pharmaceutical Sciences, University of Maryland School of Pharmacy, Baltimore, MD 21201, USA
| | | | | |
Collapse
|
23
|
Huang H, Martásek P, Roman LJ, Silverman RB. Synthesis and evaluation of dipeptide amides containing N omega-nitroarginine and D-2,4-diaminobutyric acids as inhibitors of neuronal nitric oxide synthase. JOURNAL OF ENZYME INHIBITION 2002; 16:233-9. [PMID: 11697043 DOI: 10.1080/14756360109162371] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Selective inhibition of the isoforms of nitric oxide synthase (NOS) could be beneficial in the treatment of certain disease states arising from the overproduction of nitric oxide by NOS. Recently, we reported dipeptide amides containing a basic amine side chain as potent and selective inhibitors of neuronal NOS (Huang H. et al. (1999) J. Med. Chem., 42, 3147). The most potent nNOS inhibitor among these compounds is L-ArgNO2-L-Dbu-NH2 (1) (Ki = 130 nM), which also exhibits the highest selectivity over eNOS (> 1500-fold). The D,D-dipeptide, D-Lys-D-ArgNO2-NH2 (3) also shows high potency and selectivity. Here the dipeptide amides containing ArgNO2 and D-Dbu (9-12) were synthesized and evaluated. They are all modest inhibitors of nNOS, but poor inhibitors of eNOS and iNOS. D-Dbu-D-ArgNO2-NH2 (12) exhibits decreased inhibitory potency as compared with 3. A hypothesis regarding the binding at the active site of nNOS is proposed to explain the potency differences between the L- and D-form dipeptide amides.
Collapse
Affiliation(s)
- H Huang
- Department of Chemistry and Department of Biochemistry, Molecular Biology, and Cell Biology, Northwestern University, Evanston, Illinois 60208-3113, USA
| | | | | | | |
Collapse
|
24
|
Stevenson TH, Gutierrez AF, Alderton WK, Lian L, Scrutton NS. Kinetics of CO binding to the haem domain of murine inducible nitric oxide synthase: differential effects of haem domain ligands. Biochem J 2001; 358:201-8. [PMID: 11485568 PMCID: PMC1222048 DOI: 10.1042/0264-6021:3580201] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The binding of CO to the murine inducible nitric oxide synthase (iNOS) oxygenase domain has been studied by laser flash photolysis. The effect of the (6R)-5,6,7,8-tetrahydro-L-biopterin (BH(4)) cofactor L-arginine and several Type I L-arginine analogues/ligands on the rates of CO rebinding has been evaluated. The presence of BH(4) in the iNOS active site has little effect on the rebinding of protein-caged haem-CO pairs (geminate recombination), but decreases the bimolecular association rates 2-fold. Addition of L-arginine to the BH(4)-bound complex completely abolishes geminate recombination and results in a further 80-fold decrease in the overall rate of bimolecular association. Three of the Type I ligands, S-ethylisothiourea, L-canavanine and 2,5-lutidine, displaced the CO from the haem iron upon addition to the iNOS oxygenase domain. The Type I ligands significantly decreased the rate of bimolecular binding of CO to the haem iron after photolysis. Most of these ligands also completely abolished geminate recombination. These results are consistent with a relatively open distal pocket that allows CO to bind unhindered in the active site of murine iNOS in the absence of L-arginine or BH(4). In the presence of BH(4) and L-arginine, however, the enzyme adopts a more closed structure that can greatly reduce ligand access to the haem iron. These observations are discussed in terms of the known structure of iNOS haem domain and solution studies of ligand binding in iNOS and neuronal NOS isoenzymes.
Collapse
Affiliation(s)
- T H Stevenson
- Biological NMR Centre, Medical Sciences Building, University of Leicester, Leicester LE1 9HN, UK
| | | | | | | | | |
Collapse
|
25
|
Gilbert D, Doetschman D. Five-coordinate nitrosyl iron(II) tetraphenylporphyrin exhibits porphyrin ring 14N symmetry about the Fe–N–O plane: a hyperfine sublevel correlation spectroscopy study. Chem Phys 2001. [DOI: 10.1016/s0301-0104(01)00362-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
26
|
Li H, Raman CS, Martásek P, Král V, Masters BS, Poulos TL. Mapping the active site polarity in structures of endothelial nitric oxide synthase heme domain complexed with isothioureas. J Inorg Biochem 2000; 81:133-9. [PMID: 11051558 DOI: 10.1016/s0162-0134(00)00099-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Analyzing the active site topology and plasticity of nitric oxide synthase (NOS) and understanding enzyme-drug interactions are crucial for the development of potent, isoform-selective NOS inhibitors. A small hydrophobic pocket in the active site is identified in the bovine eNOS heme domain structures complexed with potent isothiourea inhibitors: seleno analogue of S-ethyl-isothiourea, S-isopropyl-isothiourea, and 2-aminothiazoline, respectively. These structures reveal the importance of nonpolar van der Waals contacts in addition to the well-known hydrogen bonding interactions between inhibitor and enzyme. The scaffold of a potent NOS inhibitor should be capable of donating hydrogen bonds to as well as making nonpolar contacts with amino acids in the NOS active site.
Collapse
Affiliation(s)
- H Li
- Department of Molecular Biology & Biochemistry and Physiology & Biophysics and Program in Macromolecular Structure, University of California, Irvine 92697-3900, USA
| | | | | | | | | | | |
Collapse
|
27
|
Crane BR, Arvai AS, Ghosh S, Getzoff ED, Stuehr DJ, Tainer JA. Structures of the N(omega)-hydroxy-L-arginine complex of inducible nitric oxide synthase oxygenase dimer with active and inactive pterins. Biochemistry 2000; 39:4608-21. [PMID: 10769116 DOI: 10.1021/bi992409a] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Nitric oxide synthases (NOSs) catalyze two mechanistically distinct, tetrahydrobiopterin (H(4)B)-dependent, heme-based oxidations that first convert L-arginine (L-Arg) to N(omega)-hydroxy-L-arginine (NHA) and then NHA to L-citrulline and nitric oxide. Structures of the murine inducible NOS oxygenase domain (iNOS(ox)) complexed with NHA indicate that NHA and L-Arg both bind with the same conformation adjacent to the heme iron and neither interacts directly with it nor with H(4)B. Steric restriction of dioxygen binding to the heme in the NHA complex suggests either small conformational adjustments in the ternary complex or a concerted reaction of dioxygen with NHA and the heme iron. Interactions of the NHA hydroxyl with active center beta-structure and the heme ring polarize and distort the hydroxyguanidinium to increase substrate reactivity. Steric constraints in the active center rule against superoxo-iron accepting a hydrogen atom from the NHA hydroxyl in their initial reaction, but support an Fe(III)-peroxo-NHA radical conjugate as an intermediate. However, our structures do not exclude an oxo-iron intermediate participating in either L-Arg or NHA oxidation. Identical binding modes for active H(4)B, the inactive quinonoid-dihydrobiopterin (q-H(2)B), and inactive 4-amino-H(4)B indicate that conformational differences cannot explain pterin inactivity. Different redox and/or protonation states of q-H(2)B and 4-amino-H(4)B relative to H(4)B likely affect their ability to electronically influence the heme and/or undergo redox reactions during NOS catalysis. On the basis of these structures, we propose a testable mechanism where neutral H(4)B transfers both an electron and a 3,4-amide proton to the heme during the first step of NO synthesis.
Collapse
Affiliation(s)
- B R Crane
- The Department of Molecular Biology, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA
| | | | | | | | | | | |
Collapse
|
28
|
Flores M, Wajnberg E, Bemski G. Proton electron nuclear double resonance from nitrosyl horse heart myoglobin: the role of His-E7 and Val-E11. Biophys J 2000; 78:2107-15. [PMID: 10733988 PMCID: PMC1300802 DOI: 10.1016/s0006-3495(00)76757-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
Electron nuclear double resonance (ENDOR) spectroscopy has been used to study protons in nitrosyl horse heart myoglobin (MbNO). (1)H ENDOR spectra were recorded for different settings of the magnetic field. Detailed analysis of the ENDOR powder spectra, using computer simulation, based on the "orientation-selection" principle, leads to the identification of the available protons in the heme pocket. We observe hyperfine interactions of the N(HisF8)-Fe(2+)-N(NO) complex with five protons in axial and with eight protons in the rhombic symmetry along different orientations, including those of the principal axes of the g-tensor. Protons from His-E7 and Val-E11 residues are identified in the two symmetries, rhombic and axial, exhibited by MbNO. Our results indicate that both residues are present inside the heme pocket and help to stabilize one particular conformation.
Collapse
Affiliation(s)
- M Flores
- Centro Brasileiro de Pesquisas Físicas, 22290-180 Rio de Janeiro, Brazil
| | | | | |
Collapse
|
29
|
Masters BS. Structural Variations to Accommodate Functional Themes of the Isoforms of NO Synthases. Nitric Oxide 2000. [DOI: 10.1016/b978-012370420-7/50007-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
|
30
|
Bryk R, Lubeskie A, Wolff DJ. Studies of neuronal nitric oxide synthase inactivation by diverse suicide inhibitors. Arch Biochem Biophys 1999; 369:243-51. [PMID: 10486143 DOI: 10.1006/abbi.1999.1340] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
N(G)-Amino-l-arginine, N(5)-(1-iminoethyl)-l-ornithine, N(6)-(1-iminoethyl)-l-lysine, and aminoguanidine were studied for the mechanisms by which they produce suicidal inactivation of the neuronal nitric oxide synthase isoform (nNOS). All of the inactivators that were amino acid structural analogs targeted the heme residue at the nNOS active site and led to its destruction as evidenced by the time- and concentration-dependent loss of the nNOS heme fluorescence, which reflects the disruption of the protoporphyrin-conjugated structure. The loss of heme was exclusively associated with the dimeric population of the nNOS. This inactivator-mediated loss of the nNOS heme never reached more than 60%, suggesting that only half of the dimeric heme is involved in catalytic activation of mechanism-based inactivators studied. Aminoguanidine-induced nNOS inactivation produced covalent modification of the nNOS protein chain with a stoichiometry of 0.8 mol of aminoguanidine per mole of the nNOS monomer. Specific covalent modification by aminoguanidine was exclusively associated with the oxygenase domain of the nNOS. The mechanisms by which N(6)-(1-iminoethyl)-l-lysine and aminoguanidine inactivate the nNOS and iNOS do not differ between the isoforms. The selectivity of these inactivators toward the iNOS isoform is a reflection of their much lower partition ratios, which were determined to be 0.16 +/- 0. 1 for N(6)-(1-iminoethyl)-l-lysine and 12 +/- 1.5 for aminoguanidine in case of the iNOS isoform while the same inactivators produced the partition ratios of 17 +/- 2 and 206 +/- 4, respectively, for the nNOS isoform.
Collapse
Affiliation(s)
- R Bryk
- Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey, 08854, USA
| | | | | |
Collapse
|