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Tumbic GW, Li J, Jiang T, Hossan MY, Feng C, Thielges MC. Interdomain Interactions Modulate the Active Site Dynamics of Human Inducible Nitric Oxide Synthase. J Phys Chem B 2022; 126:6811-6819. [PMID: 36056879 PMCID: PMC10110350 DOI: 10.1021/acs.jpcb.2c04091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Nitric oxide synthase (NOS) is a homodimeric flavohemoprotein responsible for catalyzing the oxidation of l-arginine (l-Arg) to citrulline and nitric oxide. Electrons are supplied for the reaction via interdomain electron transfer between an N-terminal heme-containing oxygenase domain and a FMN-containing (sub)domain of a C-terminal reductase domain. Extensive attention has focused on elucidating how conformational dynamics regulate electron transfer between the domains. Here we investigate the impact of the interdomain FMN-heme interaction on the heme active site dynamics of inducible NOS (iNOS). Steady state linear and time-resolved two-dimensional infrared (2D IR) spectroscopy was applied to probe a CO ligand at the heme within the oxygenase domain for full-length and truncated or mutated constructs of human iNOS. Whereas the linear IR spectra of the CO ligand were identical among the constructs, 2D IR spectroscopy revealed variation in the frequency dynamics. The wild-type constructs that can properly form the FMN/oxygenase docked state due to the presence of both the FMN and oxygenase domains showed slower dynamics than the oxygenase domain alone. Introduction of the mutation (E546N) predicted to perturb electrostatic interactions between the domains resulted in measured dynamics intermediate between those for the full-length and individual oxygenase domain, consistent with perturbation to the docked/undocked equilibrium. These results indicate that docking of the FMN domain to the oxygenase domain not only brings the FMN cofactor within electron transfer distance of the heme domain but also modulates the dynamics sensed by the CO ligand within the active site in a way expected to promote efficient electron transfer.
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Affiliation(s)
- Goran W Tumbic
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Jinghui Li
- Department of Pharmaceutical Sciences, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Ting Jiang
- Department of Pharmaceutical Sciences, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Md Yeathad Hossan
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
| | - Changjian Feng
- Department of Pharmaceutical Sciences, University of New Mexico, Albuquerque, New Mexico 87131, United States
| | - Megan C Thielges
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States
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2
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Hassett DJ, Kovall RA, Schurr MJ, Kotagiri N, Kumari H, Satish L. The Bactericidal Tandem Drug, AB569: How to Eradicate Antibiotic-Resistant Biofilm Pseudomonas aeruginosa in Multiple Disease Settings Including Cystic Fibrosis, Burns/Wounds and Urinary Tract Infections. Front Microbiol 2021; 12:639362. [PMID: 34220733 PMCID: PMC8245851 DOI: 10.3389/fmicb.2021.639362] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Accepted: 04/07/2021] [Indexed: 11/13/2022] Open
Abstract
The life-threatening pandemic concerning multi-drug resistant (MDR) bacteria is an evolving problem involving increased hospitalizations, billions of dollars in medical costs and a remarkably high number of deaths. Bacterial pathogens have demonstrated the capacity for spontaneous or acquired antibiotic resistance and there is virtually no pool of organisms that have not evolved such potentially clinically catastrophic properties. Although many diseases are linked to such organisms, three include cystic fibrosis (CF), burn/blast wounds and urinary tract infections (UTIs), respectively. Thus, there is a critical need to develop novel, effective antimicrobials for the prevention and treatment of such problematic infections. One of the most formidable, naturally MDR bacterial pathogens is Pseudomonas aeruginosa (PA) that is particularly susceptible to nitric oxide (NO), a component of our innate immune response. This susceptibility sets the translational stage for the use of NO-based therapeutics during the aforementioned human infections. First, we discuss how such NO therapeutics may be able to target problematic infections in each of the aforementioned infectious scenarios. Second, we describe a recent discovery based on years of foundational information, a novel drug known as AB569. AB569 is capable of forming a "time release" of NO from S-nitrosothiols (RSNO). AB569, a bactericidal tandem consisting of acidified NaNO2 (A-NO2 -) and Na2-EDTA, is capable of killing all pathogens that are associated with the aforementioned disorders. Third, we described each disease state in brief, the known or predicted effects of AB569 on the viability of PA, its potential toxicity and highly remote possibility for resistance to develop. Finally, we conclude that AB569 can be a viable alternative or addition to conventional antibiotic regimens to treat such highly problematic MDR bacterial infections for civilian and military populations, as well as the economical burden that such organisms pose.
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Affiliation(s)
- Daniel J Hassett
- Department of Molecular Genetics, Biochemistry and Microbiology, Cincinnati, OH, United States
| | - Rhett A Kovall
- Department of Molecular Genetics, Biochemistry and Microbiology, Cincinnati, OH, United States
| | - Michael J Schurr
- Department of Immunology and Microbiology, University of Colorado Health Sciences, Denver, CO, United States
| | - Nalinikanth Kotagiri
- Division of Pharmacy, University of Colorado Health Sciences, Denver, CO, United States
| | - Harshita Kumari
- Division of Pharmacy, University of Colorado Health Sciences, Denver, CO, United States
| | - Latha Satish
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States.,Shriners Hospitals for Children-Cincinnati, Cincinnati, OH, United States
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3
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Mittal A, Arora R, Kakkar R. Pharmacophore modeling, 3D-QSAR and molecular docking studies of quinazolines and aminopyridines as selective inhibitors of inducible nitric oxide synthase. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2019. [DOI: 10.1142/s0219633619500020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Pharmacophore modeling and 3D-Quantitative Structure Activity Relationship (3D-QSAR) studies have been performed on a dataset of thirty-two quinazoline and aminopyridine derivatives to get an insight into the important structural features required for binding to inducible nitric oxide synthase (iNOS). A four-point CPH (Common Pharmacophore Hypothesis), AHPR.29, with a hydrogen bond acceptor, hydrophobic group, positively charged ionizable group and an aromatic ring, has been obtained as the best pharmacophore model. Satisfactory statistical parameters of correlation ([Formula: see text]) and cross-validated ([Formula: see text]) correlation coefficients, 0.9288 and 0.6353, respectively, show high robustness and good predictive ability of our selected model. The contour maps have been developed from this model and the analysis has provided an interpretable explanation of the effect that various features and substituents have on the potency and selectivity of inhibitors towards iNOS. Docking studies have also been performed in order to analyze the interactions between the enzyme and the inhibitors. Our proposed model can thus be further used for screening a large database of compounds and design new iNOS inhibitors.
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Affiliation(s)
- Anshika Mittal
- Computational Chemistry Laboratory, Department of Chemistry, University of Delhi, Delhi-110007, India
| | - Ritu Arora
- Computational Chemistry Laboratory, Department of Chemistry, University of Delhi, Delhi-110007, India
| | - Rita Kakkar
- Computational Chemistry Laboratory, Department of Chemistry, University of Delhi, Delhi-110007, India
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4
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Bacon BA, Liu Y, Kincaid JR, Boon EM. Spectral Characterization of a Novel NO Sensing Protein in Bacteria: NosP. Biochemistry 2018; 57:6187-6200. [PMID: 30272959 DOI: 10.1021/acs.biochem.8b00451] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A novel family of bacterial hemoproteins named NosP has been discovered recently; its members are proposed to function as nitric oxide (NO) responsive proteins involved in bacterial group behaviors such as quorum sensing and biofilm growth and dispersal. Currently, little is known about molecular activation mechanisms in NosP. Here, functional studies were performed utilizing the distinct spectroscopic characteristics associated with the NosP heme cofactor. NosPs from Pseudomonas aeruginosa ( Pa), Vibrio cholerae ( Vc), and Legionella pneumophila ( Lpg) were studied in their ferrous unligated forms as well as their ferrous CO, ferrous NO, and ferric CN adducts. The resonance Raman (rR) data collected on the ferric forms strongly support the existence of a distorted heme cofactor, which is a common feature in NO sensors. The ferrous spectra exhibit a 213 cm-1 feature, which is assigned to the Fe-Nhis stretching mode. The Fe-C and C-O frequencies in the spectra of ferrous CO NosP complexes are inversely correlated with relatively similar frequencies, consistent with a proximal histidine ligand and a relatively hydrophobic environment. The rR spectra obtained for isotopically labeled ferrous NO adducts provide evidence of formation of a 5-coordinate NO complex, resulting from proximal Fe-Nhis cleavage, which is believed to play a role in biological heme-NO signal transduction. Additionally, we found that of the three NosPs studied, Lpg NosP contains the most electropositive ligand binding pocket, while Pa NosP has the most electronegative ligand binding pocket. This pattern is also observed in the measured heme reduction potentials for these three proteins, which may indicate distinct functions for each.
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Affiliation(s)
- Bezalel A Bacon
- Graduate program in Biochemistry and Structural Biology , Stony Brook University , Stony Brook , New York 11790-3400 , United States
| | - Yilin Liu
- Department of Chemistry , Marquette University , Milwaukee , Wisconsin 53233 , United States
| | - James R Kincaid
- Department of Chemistry , Marquette University , Milwaukee , Wisconsin 53233 , United States
| | - Elizabeth M Boon
- Graduate program in Biochemistry and Structural Biology , Stony Brook University , Stony Brook , New York 11790-3400 , United States.,Department of Chemistry and Institute of Chemical Biology and Drug Discovery , Stony Brook University , Stony Brook , New York 11794-3400 , United States
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5
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Onzuka M, Sekine Y, Uchida T, Ishimori K, Ozaki SI. HmuS from Yersinia pseudotuberculosis is a non-canonical heme-degrading enzyme to acquire iron from heme. Biochim Biophys Acta Gen Subj 2017; 1861:1870-1878. [PMID: 28385652 DOI: 10.1016/j.bbagen.2017.04.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2016] [Revised: 03/22/2017] [Accepted: 04/02/2017] [Indexed: 01/28/2023]
Abstract
Some Gram-negative pathogens import host heme into the cytoplasm and utilize it as an iron source for their survival. We report here that HmuS, encoded by the heme utilizing system (hmu) locus, cleaves the protoporphyrin ring to release iron from heme. A liquid chromatography/mass spectrometry analysis revealed that the degradation products of this reaction are two biliverdin isomers that result from transformation of a verdoheme intermediate. This oxidative heme degradation by HmuS required molecular oxygen and electrons supplied by either ascorbate or NADPH. Electrons could not be directly transferred from NADPH to heme; instead, ferredoxin-NADP+ reductase (FNR) functioned as a mediator. Although HmuS does not share amino acid sequence homology with heme oxygenase (HO), a well-known heme-degrading enzyme, absorption and resonance Raman spectral analyses suggest that the heme iron is coordinated with an axial histidine residue and a water molecule in both enzymes. The substitution of axial His196 or distal Arg102 with an alanine residue in HmuS almost completely eliminated heme-degradation activity, suggesting that Fe-His coordination and interaction of a distal residue with water molecules in the heme pocket are important for this activity.
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Affiliation(s)
- Masato Onzuka
- Department of Biological Chemistry, Graduate School of Science and Technology for Innovation, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan
| | - Yukari Sekine
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan
| | - Takeshi Uchida
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan; Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Koichiro Ishimori
- Graduate School of Chemical Sciences and Engineering, Hokkaido University, Sapporo, Hokkaido 060-8628, Japan; Department of Chemistry, Faculty of Science, Hokkaido University, Sapporo 060-0810, Japan
| | - Shin-Ichi Ozaki
- Department of Biological Chemistry, Graduate School of Science and Technology for Innovation, Yamaguchi University, Yoshida, Yamaguchi 753-8515, Japan.
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6
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Draganova EB, Adrian SA, Lukat-Rodgers GS, Keutcha CS, Schmitt MP, Rodgers KR, Dixon DW. Corynebacterium diphtheriae HmuT: dissecting the roles of conserved residues in heme pocket stabilization. J Biol Inorg Chem 2016; 21:875-86. [PMID: 27561288 DOI: 10.1007/s00775-016-1386-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2016] [Accepted: 08/10/2016] [Indexed: 12/30/2022]
Abstract
The heme-binding protein HmuT is part of the Corynebacterium diphtheriae heme uptake pathway and is responsible for the delivery of heme to the HmuUV ABC transporter. HmuT binds heme with a conserved His/Tyr heme axial ligation motif. Sequence alignment revealed additional conserved residues of potential importance for heme binding: R237, Y272 and M292. In this study, site-directed mutations at these three positions provided insight into the nature of axial heme binding to the protein and its effect on the thermal stability of the heme-loaded protein fold. UV-visible absorbance, resonance Raman (rR) and thermal unfolding experiments, along with collision-induced dissociation electrospray ionization mass spectrometry, were used to probe the contributions of each mutated residue to the stability of ϖ HmuT. Thermal unfolding and rR experiments revealed that R237 and M292 are important residues for heme binding. Arginine 237 is a hydrogen-bond donor to the phenol side chain of Y235, which serves as an axial heme ligand. Methionine 292 serves a supporting structural role, favoring the R237 hydrogen-bond donation, which elicits a, heretofore, unobserved modulating influence on π donation by the axial tyrosine ligand in the heme carbonyl complex, HmuT-CO.
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Affiliation(s)
| | - Seth A Adrian
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108-6050, USA
| | - Gudrun S Lukat-Rodgers
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108-6050, USA
| | - Cyrianne S Keutcha
- Department of Chemistry, Georgia State University, Atlanta, GA, 30302-3965, USA
| | - Michael P Schmitt
- Laboratory of Respiratory and Special Pathogens, Division of Bacterial, Parasitic, and Allergenic Products, Center for Biologics Evaluation, and Research, Food and Drug Administration, Silver Spring, MD, 20993, USA
| | - Kenton R Rodgers
- Department of Chemistry and Biochemistry, North Dakota State University, Fargo, ND, 58108-6050, USA
| | - Dabney W Dixon
- Department of Chemistry, Georgia State University, Atlanta, GA, 30302-3965, USA.
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7
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Everett W, Scurr DJ, Rammou A, Darbyshire A, Hamilton G, de Mel A. A Material Conferring Hemocompatibility. Sci Rep 2016; 6:26848. [PMID: 27264087 PMCID: PMC4893622 DOI: 10.1038/srep26848] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2015] [Accepted: 05/09/2016] [Indexed: 12/15/2022] Open
Abstract
There is a need for biomimetic materials for use in blood-contacting devices. Blood contacting surfaces maintain their patency through physico-chemical properties of a functional endothelium. A poly(carbonate-urea) urethane (PCU) is used as a base material to examine the feasibility of L-Arginine methyl ester (L-AME) functionalized material for use in implants and coatings. The study hypothesizes that L-AME, incorporated into PCU, functions as a bioactive porogen, releasing upon contact with blood to interact with endothelial nitric oxide synthase (eNOS) present in blood. Endothelial progenitor cells (EPC) were successfully cultured on L-AME functionalized material, indicating that L-AME -increases cell viability. L-AME functionalized material potentially has broad applications in blood-contacting medical devices, as well as various other applications requiring endogenous up-regulation of nitric oxide, such as wound healing. This study presents an in-vitro investigation to demonstrate the novel anti-thrombogenic properties of L-AME, when in solution and when present within a polyurethane-based polymer.
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Affiliation(s)
- William Everett
- Centre for Nanotechnology & Regenerative Medicine, University College London, London, UK
| | - David J Scurr
- Interface and Surface Analysis Centre, Boots Science Building, University of Nottingham, University Park, Nottingham, UK
| | - Anna Rammou
- Centre for Nanotechnology & Regenerative Medicine, University College London, London, UK
| | - Arnold Darbyshire
- Centre for Nanotechnology & Regenerative Medicine, University College London, London, UK
| | | | - Achala de Mel
- Centre for Nanotechnology & Regenerative Medicine, University College London, London, UK
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8
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Tang K, Knipp M, Liu BB, Cox N, Stabel R, He Q, Zhou M, Scheer H, Zhao KH, Gärtner W. Redox-dependent Ligand Switching in a Sensory Heme-binding GAF Domain of the Cyanobacterium Nostoc sp. PCC7120. J Biol Chem 2015; 290:19067-80. [PMID: 26063806 DOI: 10.1074/jbc.m115.654087] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2015] [Indexed: 11/06/2022] Open
Abstract
The genome of the cyanobacterium Nostoc sp. PCC7120 carries three genes (all4978, all7016, and alr7522) encoding putative heme-binding GAF (cGMP-specific phosphodiesterases, adenylyl cyclases, and FhlA) proteins that were annotated as transcriptional regulators. They are composed of an N-terminal cofactor domain and a C-terminal helix-turn-helix motif. All4978 showed the highest affinity for protoheme binding. The heme binding capability of All7016 was moderate, and Alr7522 did not bind heme at all. The "as isolated" form of All4978, identified by Soret band (λmax = 427 nm), was assigned by electronic absorption, EPR, and resonance Raman spectroscopy as a hexa-coordinated low spin Fe(III) heme with a distal cysteine ligand (absorption of δ-band around 360 nm). The protoheme cofactor is noncovalently incorporated. Reduction of the heme could be accomplished by chemically using sodium dithionite and electrospectrochemically; this latter method yielded remarkably low midpoint potentials of -445 and -453 mV (following Soret and α-band absorption changes, respectively). The reduced form of the heme (Fe(II) state) binds both NO and CO. Cysteine coordination of the as isolated Fe(III) protein is unambiguous, but interestingly, the reduced heme instead displays spectral features indicative of histidine coordination. Cys-His ligand switches have been reported as putative signaling mechanisms in other heme-binding proteins; however, these novel cyanobacterial proteins are the first where such a ligand-switch mechanism has been observed in a GAF domain. DNA binding of the helix-turn-helix domain was investigated using a DNA sequence motif from its own promoter region. Formation of a protein-DNA complex preferentially formed in ferric state of the protein.
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Affiliation(s)
- Kun Tang
- From the State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China, the Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim, Germany
| | - Markus Knipp
- the Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim, Germany, Resolv, Faculty for Chemistry and Biochemistry, Ruhr University Bochum, D-44780 Bochum, Germany, and
| | - Bing-Bing Liu
- From the State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China
| | - Nicholas Cox
- the Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim, Germany
| | - Robert Stabel
- the Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim, Germany
| | - Qi He
- From the State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China
| | - Ming Zhou
- From the State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China
| | - Hugo Scheer
- the Department of Biologie I, Ludwig-Maximilians-Universität, Menzinger Strasse 67, D-80638 München, Germany
| | - Kai-Hong Zhao
- From the State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, China,
| | - Wolfgang Gärtner
- the Max Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, D-45470 Mülheim, Germany,
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9
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Ozaki SI, Sato T, Sekine Y, Migita CT, Uchida T, Ishimori K. Spectroscopic studies on HasA from Yersinia pseudotuberculosis. J Inorg Biochem 2014; 138:31-38. [DOI: 10.1016/j.jinorgbio.2014.04.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2013] [Revised: 04/21/2014] [Accepted: 04/21/2014] [Indexed: 10/25/2022]
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10
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Santolini J, Maréchal A, Boussac A, Dorlet P. EPR characterisation of the ferrous nitrosyl complex formed within the oxygenase domain of NO synthase. Chembiochem 2013; 14:1852-7. [PMID: 23943262 PMCID: PMC4159581 DOI: 10.1002/cbic.201300233] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2013] [Indexed: 11/10/2022]
Abstract
Nitric oxide is produced in mammals by a class of enzymes called NO synthases (NOSs). It plays a central role in cellular signalling but also has deleterious effects, as it leads to the production of reactive oxygen and nitrogen species. NO forms a relatively stable adduct with ferrous haem proteins, which, in the case of NOS, is also a key catalytic intermediate. Despite extensive studies on the ferrous nitrosyl complex of other haem proteins (in particular myoglobin), little characterisation has been performed in the case of NOS. We report here a temperature-dependent EPR study of the ferrous nitrosyl complex of the inducible mammalian NOS and the bacterial NOS-like protein from Bacillus subtilis. The results show that the overall behaviours are similar to those observed for other haem proteins, but with distinct ratios between axial and rhombic forms in the case of the two NOS proteins. The distal environment appears to control the existence of the axial form and the evolution of the rhombic form.
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Affiliation(s)
- Jérôme Santolini
- CNRS, UMR 8221, CEA/iBiTec-S/SB2SM, Bât. 532, CEA Saclay, 91191 Gif-sur-Yvette Cedex (France).
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11
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Peltier MR, Koo HC, Gurzenda EM, Arita Y, Klimova NG, Olgun N, Hanna N. Can Carbon Monoxide Prevent Infection-Mediated Preterm Birth in a Mouse Model? Am J Reprod Immunol 2013; 70:31-7. [DOI: 10.1111/aji.12105] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2012] [Accepted: 01/29/2013] [Indexed: 01/19/2023] Open
Affiliation(s)
| | - Hschi-Chi Koo
- Women and Children's Research Laboratory; Winthrop University Hospital; Mineola; NY; USA
| | - Ellen M. Gurzenda
- Women and Children's Research Laboratory; Winthrop University Hospital; Mineola; NY; USA
| | - Yuko Arita
- Women and Children's Research Laboratory; Winthrop University Hospital; Mineola; NY; USA
| | - Natalia G. Klimova
- Women and Children's Research Laboratory; Winthrop University Hospital; Mineola; NY; USA
| | - Niccole Olgun
- Women and Children's Research Laboratory; Winthrop University Hospital; Mineola; NY; USA
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12
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Spiro TG, Soldatova AV, Balakrishnan G. CO, NO and O 2 as Vibrational Probes of Heme Protein Interactions. Coord Chem Rev 2013; 257:511-527. [PMID: 23471138 PMCID: PMC3587108 DOI: 10.1016/j.ccr.2012.05.008] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
The gaseous XO molecules (X = C, N or O) bind to the heme prosthetic group of heme proteins, and thereby activate or inhibit key biological processes. These events depend on interactions of the surrounding protein with the FeXO adduct, interactions that can be monitored via the frequencies of the Fe-X and X-O bond stretching modes, νFeX and νXO. The frequencies can be determined by vibrational spectroscopy, especially resonance Raman spectroscopy. Backbonding, the donation of Fe dπ electrons to the XO π* orbitals, is a major bonding feature in all the FeXO adducts. Variations in backbonding produce negative νFeX/νXO correlations, which can be used to gauge electrostatic and H-bonding effects in the protein binding pocket. Backbonding correlations have been established for all the FeXO adducts, using porphyrins with electron donating and withdrawing substituents. However the adducts differ in their response to variations in the nature of the axial ligand, and to specific distal interactions. These variations provide differing vantages for evaluating the nature of protein-heme interactions. We review experimental studies that explore these variations, and DFT computational studies that illuminate the underlying physical mechanisms.
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Affiliation(s)
- Thomas G. Spiro
- Department of Chemistry, University of Washington Box 351700, Seattle, Washington 98195
| | | | - Gurusamy Balakrishnan
- Department of Chemistry, University of Washington Box 351700, Seattle, Washington 98195
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13
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Mechanisms of the vasorelaxing effects of CORM-3, a water-soluble carbon monoxide-releasing molecule: interactions with eNOS. Naunyn Schmiedebergs Arch Pharmacol 2013; 386:185-96. [DOI: 10.1007/s00210-012-0829-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Accepted: 12/14/2012] [Indexed: 10/27/2022]
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14
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Mak PJ, Yang Y, Im S, Waskell LA, Kincaid JR. Experimental Documentation of the Structural Consequences of Hydrogen-Bonding Interactions to the Proximal Cysteine of a Cytochrome P450. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201205912] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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15
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Mak PJ, Yang Y, Im S, Waskell LA, Kincaid JR. Experimental documentation of the structural consequences of hydrogen-bonding interactions to the proximal cysteine of a cytochrome P450. Angew Chem Int Ed Engl 2012; 51:10403-7. [PMID: 22968976 DOI: 10.1002/anie.201205912] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Indexed: 11/09/2022]
Affiliation(s)
- Piotr J Mak
- Department of Chemistry, Marquette University, Milwaukee, WI 53233, USA
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16
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Marçal AC, Leonelli M, Fiamoncini J, Deschamps FC, Rodrigues MAM, Curi R, Carpinelli AR, Britto LRG, Carvalho CRO. Diet-induced obesity impairs AKT signalling in the retina and causes retinal degeneration. Cell Biochem Funct 2012; 31:65-74. [PMID: 22915345 DOI: 10.1002/cbf.2861] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2011] [Revised: 06/18/2012] [Accepted: 07/05/2012] [Indexed: 11/06/2022]
Abstract
Retinopathy, a common complication of diabetes, is characterized by an unbalanced production of nitric oxide (NO), a process regulated by nitric oxide synthase (NOS). We hypothesized that retinopathy might stem from changes in the insulin receptor substrate (IRS)/PI3K/AKT pathway and/or expression of NOS isoforms. Thus, we analysed the morphology and apoptosis index in retinas of obese rats in whom insulin resistance had been induced by a high-fat diet (HFD). Immunoblotting analysis revealed that the retinal tissue of HFD rats had lower levels of AKT(1) , eNOS and nNOS protein than those of samples taken from control animals. Furthermore, immunohistochemical analyses indicated higher levels of iNOS and 4-hydroxynonenal and a larger number of apoptotic nuclei in HFD rats. Finally, both the inner and outer retinal layers of HFD rats were thinner than those in their control counterparts. When considered alongside previous results, these patterns suggest two major ways in which HFD might impact animals: direct activity of ingested fatty acids and/or via insulin-resistance-induced changes in intracellular pathways. We discuss these possibilities in further detail and advocate the use of this animal model for further understanding relationships between retinopathy, metabolic syndrome and type 2 diabetes.
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Affiliation(s)
- Anderson C Marçal
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas (ICB), Universidade de São Paulo (USP), SP, Brazil.
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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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19
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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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Carbon monoxide and nitric oxide modulate hyperosmolality-induced oxytocin secretion by the hypothalamus in vitro. Biosci Rep 2010. [DOI: 10.1042/bsr20090010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
OT (oxytocin) is secreted from the posterior pituitary gland, and its secretion has been shown to be modulated by NO (nitric oxide). In rats, OT secretion is also stimulated by hyperosmolarity of the extracellular fluid. Furthermore, NOS (nitric oxide synthase) is located in hypothalamic areas involved in fluid balance control. In the present study, we evaluated the role of the NOS/NO and HO (haem oxygenase)/CO (carbon monoxide) systems in the osmotic regulation of OT release from rat hypothalamus in vitro. We conducted experiments on hypothalamic fragments to determine the following: (i) whether NO donors and NOS inhibitors modulate OT release and (ii) whether the changes in OT response occur concurrently with changes in NOS or HO activity in the hypothalamus. Hyperosmotic stimulation induced a significant increase in OT release that was associated with a reduction in nitrite production. Osmotic stimulation of OT release was inhibited by NO donors. NOS inhibitors did not affect either basal or osmotically stimulated OT release. Blockade of HO inhibited both basal and osmotically stimulated OT release, and induced a marked increase in NOS activity. These results indicate the involvement of CO in the regulation of NOS activity. The present data demonstrate that hypothalamic OT release induced by osmotic stimuli is modulated, at least in part, by interactions between NO and CO.
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21
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Carbon monoxide and nitric oxide modulate hyperosmolality-induced oxytocin secretion by the hypothalamus in vitro. Biosci Rep 2010; 30:351-7. [PMID: 20518746 DOI: 10.1042/bsr2009010] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
OT (oxytocin) is secreted from the posterior pituitary gland, and its secretion has been shown to be modulated by NO (nitric oxide). In rats, OT secretion is also stimulated by hyperosmolarity of the extracellular fluid. Furthermore, NOS (nitric oxide synthase) is located in hypothalamic areas involved in fluid balance control. In the present study, we evaluated the role of the NOS/NO and HO (haem oxygenase)/CO (carbon monoxide) systems in the osmotic regulation of OT release from rat hypothalamus in vitro. We conducted experiments on hypothalamic fragments to determine the following: (i) whether NO donors and NOS inhibitors modulate OT release and (ii) whether the changes in OT response occur concurrently with changes in NOS or HO activity in the hypothalamus. Hyperosmotic stimulation induced a significant increase in OT release that was associated with a reduction in nitrite production. Osmotic stimulation of OT release was inhibited by NO donors. NOS inhibitors did not affect either basal or osmotically stimulated OT release. Blockade of HO inhibited both basal and osmotically stimulated OT release, and induced a marked increase in NOS activity. These results indicate the involvement of CO in the regulation of NOS activity. The present data demonstrate that hypothalamic OT release induced by osmotic stimuli is modulated, at least in part, by interactions between NO and CO.
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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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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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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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Piantadosi CA. Carbon monoxide, reactive oxygen signaling, and oxidative stress. Free Radic Biol Med 2008; 45:562-9. [PMID: 18549826 PMCID: PMC2570053 DOI: 10.1016/j.freeradbiomed.2008.05.013] [Citation(s) in RCA: 200] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2007] [Revised: 05/14/2008] [Accepted: 05/15/2008] [Indexed: 11/22/2022]
Abstract
The ubiquitous gas, carbon monoxide (CO), is of substantial biological importance, but apart from its affinity for reduced transition metals, particularly heme-iron, it is surprisingly nonreactive-as is the ferrous-carbonyl-in living systems. CO does form strong complexes with heme proteins for which molecular O2 is the preferred ligand and to which are attributed diverse physiological, adaptive, and toxic effects. Lately, it has become apparent that both exogenous and endogenous CO produced by heme oxygenase engender a prooxidant milieu in aerobic mammalian cells which initiates signaling related to reactive oxygen species (ROS) generation. ROS signaling contingent on CO can be segregated by CO concentration-time effects on cellular function, by the location of heme proteins, e.g., mitochondrial or nonmitochondrial sites, or by specific oxidation-reduction (redox) reactions. The fundamental responses to CO involve overt physiological regulatory events, such as activation of redox-sensitive transcription factors or stress-activated kinases, which institute compensatory expression of antioxidant enzymes and other adaptations to oxidative stress. In contrast, responses originating from highly elevated or protracted CO exposures tend to be nonspecific, produce untoward biological oxidations, and interfere with homeostasis. This brief overview provides a conceptual framework for understanding CO biology in terms of this physiological-pathological hierarchy.
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Affiliation(s)
- Claude A Piantadosi
- Department of Medicine, Duke University Medical Center, Box 3315 CR II Building White Zone, Trent Drive, Durham, NC 27710, USA.
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26
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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.
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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.
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Hangai-Hoger N, Tsai AG, Cabrales P, Suematsu M, Intaglietta M. Microvascular and systemic effects following top load administration of saturated carbon monoxide-saline solution. Crit Care Med 2007; 35:1123-32. [PMID: 17334240 DOI: 10.1097/01.ccm.0000259533.84180.c7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To determine how top loads with different doses of carbon monoxide (CO)-saturated saline solutions (CO-saline) affect microvascular and systemic hemodynamics and to delineate the corresponding biochemical mechanisms. DESIGN Prospective study. SETTING University research laboratory. SUBJECTS Male Golden Syrian hamsters. INTERVENTIONS Hamsters implemented with a dorsal window chamber were given different volumes (characterized as percent of blood volume, BV) by intravenous injection of CO-saturated saline. MEASUREMENTS AND MAIN RESULTS Hamsters were observed until 90 mins after infusion of CO-saline solution. In the 20% BV CO-saline infusion group, observation was extended until 180 mins. Systemic variables measured included mean arterial pressure, heart rate, systemic arterial blood gases, and cardiac output and index. Microvascular hemodynamic measurements included vessel diameter, red blood cell velocity, and functional capillary density. Cyclic guanosine monophosphate (cGMP) content in the chamber tissue was measured by enzyme immunoassay. 10% BV of CO-saline increased flow maximally in the microcirculation at 30 mins after infusion (207% in arterioles and 238% in venules, p < .05 vs. baseline). Functional capillary density was significantly increased in both 10% and 15% groups (p < .05 vs. baseline), and cardiac index increased 130% (p < .05 vs. baseline) at 10 mins after 10% CO-saline infusion. There were no changes of microhemodynamic variables and functional capillary density with 2.5%, 5%, and 20% CO-saline infusion during the observation period. Microvascular hemodynamic changes by 10% CO-saline infusion were inhibited completely by L-NAME pretreatment and partially by 1H-[1,2,4]oxadiazole[4,3-a]quinoxqalin-1-one pretreatment. cGMP content in skin fold tissues was related to changes of vessel diameter. CONCLUSIONS Intravenous injection of CO-saturated saline caused vasodilation and improved microvascular hemodynamics in the hamster window chamber model in a dose-dependent manner. These changes were related to increased cardiac output and local cGMP content. These results support the possible use of CO-saturated solutions as a vasodilator in critical conditions.
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Affiliation(s)
- Nanae Hangai-Hoger
- Department of Bioengineering, University of California, San Diego, La Jolla, CA, USA.
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28
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Ioanoviciu A, Yukl ET, Moënne-Loccoz P, Ortiz de Montellano PR. DevS, a heme-containing two-component oxygen sensor of Mycobacterium tuberculosis. Biochemistry 2007; 46:4250-60. [PMID: 17371046 PMCID: PMC2518089 DOI: 10.1021/bi602422p] [Citation(s) in RCA: 68] [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
Mycobacterium tuberculosis can exist in the actively growing state of the overt disease or in a latent quiescent state that can be induced, among other things, by anaerobiosis. Eradication of the latent state is particularly difficult with the available drugs and requires prolonged treatment. DevS is a member of the DevS-DevR two-component regulatory system that is thought to mediate the cellular response to anaerobiosis. Here we report the cloning, expression, and initial characterization of a truncated version of DevS (DevS642) containing only the N-terminal GAF sensor domain (GAF-A) and of the full-length protein DevS. The DevS truncated construct quantitatively binds heme in a 1:1 stoichiometry, and the complex of the protein with ferrous heme reversibly binds O2, NO, and CO. UV-vis and resonance Raman spectroscopy of the wild-type protein and the H149A mutant confirm that His149 is the proximal ligand to the heme iron atom. While the heme-CO complex is present as two conformers in the GAF-A domain, a single set of [Fe-C-O] vibrations is observed with the full-length protein, suggesting that interactions between domains within DevS influence the distal pocket environment of the heme in the GAF-A domain.
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Affiliation(s)
- Alexandra Ioanoviciu
- Department of Pharmaceutical Chemistry, University of California, 600 16th Street, San Francisco, California 94158-2517
| | - Erik T. Yukl
- Department of Environmental & Biomolecular Systems, 20,000 NW Walker Road, OGI School of Science and Engineering, Oregon Health & Sciences University, Beaverton, Oregon 97006-8921
| | - Pierre Moënne-Loccoz
- Department of Environmental & Biomolecular Systems, 20,000 NW Walker Road, OGI School of Science and Engineering, Oregon Health & Sciences University, Beaverton, Oregon 97006-8921
| | - Paul R. Ortiz de Montellano
- Department of Pharmaceutical Chemistry, University of California, 600 16th Street, San Francisco, California 94158-2517
- To whom editorial correspondence should be addressed: Dr. Paul Ortiz de Montellano, University of California, Genentech Hall GH-N572D, 600 16 Street, Box 2280, San Francisco, CA 94158-2517, TEL: (415) 476-2903, FAX: (415) 502-4728, e-mail:
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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.
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Affiliation(s)
- Huiying Li
- Department of Molecular Biology and Biochemistry, Center in Chemical and Structural Biology, University of California, Irvine, CA 92697-3900, USA
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30
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Das TK, Dewilde S, Friedman JM, Moens L, Rousseau DL. Multiple active site conformers in the carbon monoxide complexes of trematode hemoglobins. J Biol Chem 2006; 281:11471-9. [PMID: 16481317 DOI: 10.1074/jbc.m512054200] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sequence alignment of hemoglobins of the trematodes Paramphistomum epiclitum and Gastrothylax crumenifer with myoglobin suggests the presence of an unusual active site structure in which two tyrosine residues occupy the E7 and B10 helical positions. In the crystal structure of P. epiclitum hemoglobin, such an E7-B10 tyrosine pair at the putative helical positions has been observed, although the E7 Tyr is displaced toward CD region of the polypeptide. Resonance Raman data on both P. epiclitum and G. crumenifer hemoglobins show that interactions of heme-bound ligands with neighboring amino acid residues are unusual. Multiple conformers in the CO complex, termed the C, O, and N conformers, are observed. The conformers are separated by a large difference (approximately 60 cm(-1)) in the frequencies of their Fe-CO stretching modes. In the C conformer the Fe-CO stretching frequency is very high, 539 and 535 cm(-1), for the P. epiclitum and G. crumenifer hemoglobins, respectively. The Fe-CO stretching of the N conformer appears at an unusually low frequency, 479 and 476 cm(-1), respectively, for the two globins. A population of an O conformer is seen in both hemoglobins, at 496 and 492 cm(-1), respectively. The C conformer is stabilized by a strong polar interaction of the CO with the distal B10 tyrosine residue. The O conformer is similar to the ones typically seen in mutant myoglobins in which there are no strong interactions between the CO and residues in the distal pocket. The N conformer possesses an unusual configuration in which a negatively charged group, assigned as the oxygen atom of the B10 Tyr side chain, interacts with the CO. In this conformer, the B10 Tyr assumes an alternative conformation consistent with one of the conformers seen the crystal structure. Implications of the multiple configurations on the ligand kinetics are discussed.
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Affiliation(s)
- Tapan K Das
- Pfizer Global Biologics, Chesterfield, Missouri 63017, USA
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32
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Fricker SP. Nitric oxide scavengers as a therapeutic approach to nitric oxide mediated disease. Expert Opin Investig Drugs 2005; 8:1209-22. [PMID: 15992146 DOI: 10.1517/13543784.8.8.1209] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The essential role of nitric oxide (NO) in normal physiology and its involvement in the pathophysiology of a variety of diseases render the compound an attractive therapeutic target. NO donor drugs are used in the treatment of hypotension and angina where abnormalities in the L-arginine-nitric oxide pathway have been implicated. Overproduction of NO has been associated with a number of disease states including septic shock, inflammatory diseases, diabetes, ischaemia-reperfusion injury, adult respiratory distress syndrome, neurodegenerative diseases and allograft rejection. NO is produced by a group of enzymes, the nitric oxide synthases. Selective inhibition of the inducible isoform is one approach to the treatment of diseases where there is an overproduction of NO; an alternative approach is to scavenge or remove excess NO. A number of NO scavenger molecules have demonstrated pharmacological activity in disease models, particularly models of septic shock. These include organic molecules such as PTIO (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide), haemoglobin derivatives such as the pyridoxalated haemoglobin polyoxyethylene conjugate (PHP), low molecular weight iron compounds of diethylenetriaminepentaacetic acid and diethyldithiocarbamate and ruthenium polyaminocarboxylate complexes. The data suggest a potential role for NO scavengers in the treatment of NO mediated disease.
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Affiliation(s)
- S P Fricker
- AnorMED, Inc., 200-20353 64th Avenue, Langley, BC, V2Y 1N5, Canada.
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Chartier FJM, Couture M. Stability of the heme environment of the nitric oxide synthase from Staphylococcus aureus in the absence of pterin cofactor. Biophys J 2005; 87:1939-50. [PMID: 15345570 PMCID: PMC1304597 DOI: 10.1529/biophysj.104.042119] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
We have used resonance Raman spectroscopy to probe the heme environment of a recently discovered NOS from the pathogenic bacterium Staphylococcus aureus, named SANOS. We detect two forms of the CO complex in the absence of L-arginine, with nu(Fe-CO) at 482 and 497 cm(-1) and nu(C-O) at 1949 and 1930 cm(-1), respectively. Similarly to mammalian NOS, the binding of L-arginine to SANOS caused the formation of a single CO complex with nu(Fe-CO) and nu(C-O) frequencies at 504 and 1,917 cm(-1), respectively, indicating that L-arginine induced an electrostatic/steric effect on the CO molecule. The addition of pterins to CO-bound SANOS modified the resonance Raman spectra only when they were added in combination with L-arginine. We found that (6R) 5,6,7,8 tetra-hydro-L-biopterin and tetrahydrofolate were not required for the stability of the reduced protein, which is 5-coordinate, and of the CO complex, which does not change with time to a form with a Soret band at 420 nm that is indicative of a change of the heme proximal coordination. Since SANOS is stable in the absence of added pterin, it suggests that the role of the pterin cofactor in the bacterial NOS may be limited to electron/proton transfer required for catalysis and may not involve maintaining the structural integrity of the protein as is the case for mammalian NOS.
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Affiliation(s)
- François J M Chartier
- Department of Biochemistry and Microbiology, Laval University, Quebec City, Quebec G2K 7P4, Canada
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34
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Proskuryakov SY, Konoplyannikov AG, Skvortsov VG, Mandrugin AA, Fedoseev VM. Structure and activity of NO synthase inhibitors specific to the L-arginine binding site. BIOCHEMISTRY (MOSCOW) 2005. [DOI: 10.1007/s10541-005-0048-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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35
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Structure and activity of NO synthase inhibitors specific to the L-arginine binding site. BIOCHEMISTRY (MOSCOW) 2005. [DOI: 10.1007/pl00021750] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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36
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Li D, Stuehr DJ, Yeh SR, Rousseau DL. Heme distortion modulated by ligand-protein interactions in inducible nitric-oxide synthase. J Biol Chem 2004; 279:26489-99. [PMID: 15066989 DOI: 10.1074/jbc.m400968200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The catalytic center of nitric-oxide synthase (NOS) consists of a thiolate-coordinated heme macrocycle, a tetrahydrobiopterin (H4B) cofactor, and an l-arginine (l-Arg)/N-hydroxyarginine substrate binding site. To determine how the interplay between the cofactor, the substrates, and the protein matrix housing the heme regulates the enzymatic activity of NOS, the CO-, NO-, and CN(-)-bound adducts of the oxygenase domain of the inducible isoform of NOS (iNOS(oxy)) were examined with resonance Raman spectroscopy. The Raman data of the CO-bound ferrous protein demonstrated that the presence of l-Arg causes the Fe-C-O moiety to adopt a bent structure because of an H-bonding interaction whereas H4B binding exerts no effect. Similar behavior was found in the CN(-)-bound ferric protein and in the nitric oxide (NO)-bound ferrous protein. In contrast, in the NO-bound ferric complexes, the addition of l-Arg alone does not affect the structural properties of the Fe-N-O moiety, but H4B binding forces it to adopt a bent structure, which is further enhanced by the subsequent addition of l-Arg. The differential interactions between the various heme ligands and the protein matrix in response to l-Arg and/or H4B binding is coupled to heme distortions, as reflected by the development of a variety of out-of-plane heme modes in the low frequency Raman spectra. The extent and symmetry of heme deformation modulated by ligand, substrate, and cofactor binding may provide important control over the catalytic and autoinhibitory properties of the enzyme.
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Affiliation(s)
- David Li
- Department of Physiology and Biophysics, Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10461, USA
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37
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Abstract
The capacity of nitric oxide (NO) to affect biphasic dose responses in pharmacological and toxicological systems was assessed. Numerous examples of such biphasic responses were documented, including osteoclast differentiation, various vascular responses, neutrophil migration, superoxide anion formation, exploratory behavior in rodents, vitamin D3 levels in macrophages, human sperm motility and mobility, myocardial contraction, and other functions. The quantitative features of the dose response indicated a maximum stimulatory response usually less than twofold greater than the controls. While the stimulatory range was variable, ranging from approximately 2.5 to 500-fold, the majority was < or = 10-fold. These findings indicate that biphasic dose-response relationships are common manifestations of the NO-induced effects.
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Affiliation(s)
- E J Calabrese
- Department of Environmental Health Sciences, School of Public Health and Health Sciences, University of Massachusetts, Amherst 01003, USA.
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38
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Sorrenti V, Di Giacomo C, Salerno L, Siracusa MA, Guerrera F, Vanella A. Inhibition of neuronal nitric oxide synthase by N-phenacyl imidazoles. Nitric Oxide 2001; 5:32-8. [PMID: 11178934 DOI: 10.1006/niox.2000.0324] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nitric oxide (NO) mediates a series of physiological processes, including regulation of vascular tone, macrofage-mediated neurotoxicity, platelet aggregation, learning and long-term potentiation, and neuronal transmission. Although NO mediates several physiological functions, overproduction of NO can be detrimental and play multiple roles in several pathological diseases. Accordingly, more potent inhibitors, more selective for neuronal nitric oxide synthase (nNOS) than endothelial NOS (eNOS) or inducible NOS (iNOS), could be useful in the treatment of cerebral ischemia and other neurodegenerative diseases. We recently described the synthesis of a series of imidazole derivatives. Among them N-(4-nitrophenacyl) imidazole (A) and N-(4-nitrophenacyl)-2-methyl-imidazole (B) were considered selective nNOS inhibitors. In the present study the action mechanism of compounds A and B was analyzed. Spectral changes observed in the presence of compound A indicate that this inhibitor exerts its effect without interaction with heme iron. Moreover compounds A and B, inhibit nNOS "noncompetitively" versus arginine, but "competitively" versus BH(4).
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Affiliation(s)
- V Sorrenti
- Department of Biological Chemistry, Medical Chemistry, and Molecular Biology, University of Catania, Italy
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39
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Pevni D, Gurevich J, Frolkis I, Keren G, Shapira I, Paz J, Kramer A, Locker C, Mohr R. Protamine induces vasorelaxation of human internal thoracic artery by endothelial NO-synthase pathway. Ann Thorac Surg 2000; 70:2050-3. [PMID: 11156119 DOI: 10.1016/s0003-4975(00)01678-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
BACKGROUND Protamine is commonly used in cardiac surgery to reverse the anticoagulant effects of heparin. We investigated the role of different nitric oxide synthase pathways in the response of the human internal thoracic artery to protamine and evaluated whether heparin could prevent this effect. METHODS A tension-recording method was used to obtain baseline measurements of contractions of human internal thoracic artery rings achieved with norepinephrine. Isolated internal thoracic artery rings were suspended in two organ chambers. One contained Krebs-Henseleit solution and served as control. The other contained a heparin or Nomega-Nitro-L-arginine (L-NAM, an inhibitor of both endothelial and inducible nitric oxide synthase) or a specific inhibitor of inducible nitric oxide synthase, aminoguanidine. Increasing doses of protamine were added to both chambers and dose-response curves were obtained. RESULTS Protamine was found to relax contracted internal thoracic arteries 56% +/- 4.7% of baseline measurements in a concentration-dependent manner. When L-NAM was added, protamine caused only a slight decrease of tension. There were no differences in the relaxing effect of protamine in the presence of aminoguanidine or heparin. CONCLUSIONS Protamine induces nitric oxide-dependent relaxation of the internal thoracic artery by activation of endothelial nitric oxide synthase pathway. Heparin could not prevent this relaxing effect of protamine.
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Affiliation(s)
- D Pevni
- Department of Thoracic and Cardiovascular Surgery, Tel Aviv Sourasky Medical Center and Sackler Faculty of Medicine, Tel Aviv University, Israel
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40
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Couture M, Stuehr DJ, Rousseau DL. The ferrous dioxygen complex of the oxygenase domain of neuronal nitric-oxide synthase. J Biol Chem 2000; 275:3201-5. [PMID: 10652305 DOI: 10.1074/jbc.275.5.3201] [Citation(s) in RCA: 48] [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
The mechanisms by which nitric-oxide synthases (NOSs) bind and activate oxygen at their P450-type heme active site in order to synthesize nitric oxide from the substrate L-arginine are mostly unknown. To obtain information concerning the structure and properties of the first oxygenated intermediate of the enzymatic cycle, we have used a rapid continuous flow mixer and resonance Raman spectroscopy to generate and identify the ferrous dioxygen complex of the oxygenase domain of nNOS (Fe(2+)O(2) nNOSoxy). We detect a line at 1135 cm(-1) in the resonance Raman spectrum of the intermediate formed from 0.6 to 3.0 ms after the rapid mixing of the ferrous enzyme with oxygen that is shifted to 1068 cm(-1) with (18)O(2). This line is assigned as the O-O stretching mode (nu(O-O)) of the oxygenated complex of nNOSoxy. Rapid mixing experiments performed with nNOSoxy saturated with L-arginine or N(omega)-hydroxy-L-arginine, in the presence or absence of (6R)-5,6, 7,8-tetrahydro-L-biopterin, reveal that the nu(O-O) line is insensitive to the presence of the substrate and the pterin. The optical spectrum of this ferrous dioxygen species, with a Soret band wavelength maximum at 430 nm, confirms the identification of the previously reported oxygenated complexes generated by stopped flow techniques.
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Affiliation(s)
- M Couture
- Department of Physiology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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41
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Thorup C, Jones CL, Gross SS, Moore LC, Goligorsky MS. Carbon monoxide induces vasodilation and nitric oxide release but suppresses endothelial NOS. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:F882-9. [PMID: 10600935 DOI: 10.1152/ajprenal.1999.277.6.f882] [Citation(s) in RCA: 124] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The vascular effects of carbon monoxide (CO) resemble those of nitric oxide (NO), but it is unknown whether the two messengers converge or exhibit reciprocal feedback regulation. These questions were examined in microdissected perfused renal resistance arteries (RRA) studied using NO-sensitive microelectrodes. Perfusion of RRA with buffers containing increasing concentrations of CO resulted in a biphasic release of NO. The NO response peaked at 100 nM CO and then declined to virtually zero at 10 microM. When a series of 50-s pulses of 100 nM CO were applied repeatedly (150-s interval), the amplitude of consecutive NO responses was diminished. NO release from RRA showed dependence on L-arginine but not D-arginine, and the responses to CO were inhibited by pretreatment with NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO synthases (NOS). CO (100 nM) also suppressed NO release induced by 100 microM carbachol, a potent agonist for endothelial NOS (eNOS). RRA from rats in which endogenous CO production from inducible HO was elevated (cobalt chloride 12 h prior to study) also showed suppressed responses to carbachol. Furthermore, responses consistent with these findings were obtained in juxtamedullary afferent arterioles perfused in vitro, where the vasodilatory response to CO was biphasic and the response to acetylcholine was blunted. Collectively, these data suggest that the CO-induced NO release could be attributed to either stimulation of eNOS or to NO displacement from a cellular storage pool. To address this, direct in vitro measurements with an NO-selective electrode of NO production by recombinant eNOS revealed that CO dose-dependently inhibits NO synthesis. Together, the above data demonstrate that, whereas high levels of CO inhibit NOS activity and NO generation, lower concentrations of CO induce release of NO from a large intracellular pool and, therefore, may mimic the vascular effects of NO.
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Affiliation(s)
- C Thorup
- Department of Physiology, Göteborg University, S-41390 Göteborg, Sweden
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42
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Bryk R, Wolff DJ. Pharmacological modulation of nitric oxide synthesis by mechanism-based inactivators and related inhibitors. Pharmacol Ther 1999; 84:157-78. [PMID: 10596904 DOI: 10.1016/s0163-7258(99)00030-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Nitric oxide synthase (NOS) (EC 1.14.13.39) is a homodimeric cytochrome P450 monooxygenase analog that generates nitric oxide (NO) from the amino acid L-arginine. Enzymatically produced NO acts as an intracellular messenger in neuronal networks, blood pressure regulatory mechanisms, and immune responses. Isoform-selective pharmacological modulation of NO synthesis has emerged as a new therapeutic strategy for the treatment of diverse clinical conditions associated with NO overproduction. Mechanism-based inactivators (MBIs) represent a class of NOS mechanistic inhibitors that require catalytic turnover to produce irreversible inactivation of the ability of NOS to generate NO. Diverse isoform-selective NOS MBIs have been characterized with respect to their kinetic parameters and chemical mechanisms of inactivation. In studies with isolated and purified NOS isoforms, MBIs produce irreversible inactivation of NOS enzymatic activities. The inactivation process is associated with covalent modification of the NOS active site and proceeds either through heme destruction, its structural alteration, or covalent modification of the NOS protein chain. The behavior of NOS MBIs in intact cells is different from their behavior observed with the isolated NOS isoforms. In cytokine-induced RAW 264.7 macrophages, treatment with MBIs produces a complete loss of cellular NOS synthetic competence and inducible NOS activity. However, following drug removal, cells can recover at least partially in the absence of protein synthesis. In GH3 cells containing the neuronal NOS isoform, calcium transients are too low and abbreviated to allow significant NOS inactivation; hence, the cellular effects of MBIs on the neuronal isoform are almost completely and immediately reversible.
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Affiliation(s)
- R Bryk
- Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway 08854, USA
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43
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Abstract
In the 4 years since our first article, there has been considerable progress in our understanding of the pathophysiology of acute ischaemic stroke, and the results of well-conducted trials have at last begun to change everyday clinical practice. The timing of the various processes of the ischaemic cascade and the potential time windows for different interventions are better understood. Furthermore, the importance of maintaining cerebral perfusion and optimizing systemic physiological and biochemical factors in order to prevent neurological deterioration ('progressing stroke') is increasingly being realized. Numerous antithrombotic and neuroprotective drugs have been evaluated in clinical trials, and while none has shown unequivocal benefits on its own, prospects for successful intervention are still good. This will probably involve different combinations of treatments targeted on different pathophysiological stroke types, so that the management of acute stroke will offer a considerable challenge to the stroke physicians of the future.
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Affiliation(s)
- M Davis
- Stroke Research Team, Queen Elizabeth Hospital, Gateshead, UK
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44
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Venturini G, Colasanti M, Fioravanti E, Bianchini A, Ascenzi P. Direct effect of temperature on the catalytic activity of nitric oxide synthases types I, II, and III. Nitric Oxide 1999; 3:375-82. [PMID: 10534441 DOI: 10.1006/niox.1999.0250] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The effect of temperature (between 5.0 and 45.0 degrees C) on the catalytic activity of nitric oxide synthases types I, II, and III (NOS-I, NOS-II, and NOS-III, respectively) has been investigated, at pH 7.5. The value of V(max) for NOS-I activity increases from 1.8 x 10(1) pmol min(-1) mg(-1), at 5.0 degrees C, to 1.8 x 10(2) pmol min(-1) mg(-1), at 45.0 degrees C; on the other hand, the value of K(m) (=4.0 x 10(-6) M) is temperature independent. Again, the value of V(max) for NOS-II activity increases from 8.0 pmol min(-1) mg(-1), at 7.0 degrees C, to 5.4 x 10(1) pmol min(-1) mg(-1), at 40.0 degrees C, the value of K(m) (=1.8 x 10(-5) M) being unaffected by temperature. Temperature exerts the same effect on NOS-I and NOS-II activity, as shown by the same values of DeltaH(V(max)) (=4.2 x 10(1) kJ mol(-1)), DeltaH(K(m)) (=0 kJ mol(-1)), and DeltaH((V(max))(/K(m))()) (=4.2 x 10(1) kJ mol(-1)). On the contrary, the value of K(m) for NOS-III activity decreases from 3.8 x 10(-5) M, at 10.0 degrees C, to 1.6 x 10(-5) M, at 40.0 degrees C, the value of V(max) (=6.8 x 10(1) pmol min(-1) mg(-1)) being temperature independent. Present results indicate that temperature influences directly NOS-I and NOS-II activity independently of the substrate concentration, the values of K(m) being temperature independent. However, when l-arginine level is higher than 2 x 10(-4) M, as observed under in vivo conditions, NOS-III activity is essentially unaffected by temperature, the substrate concentration exceeding the value of K(m). As a whole, although further studies in vivo are needed, these observations seem to have potential physiopathologic implications.
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Affiliation(s)
- G Venturini
- Department of Biology, University of Rome Tre, Viale Guglielmo Marconi 446, Rome, I-00146, Italy.
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45
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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.
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Affiliation(s)
- R Bryk
- Department of Pharmacology, University of Medicine and Dentistry of New Jersey, Piscataway, New Jersey, 08854, USA
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46
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Lowe JA, Qian W, Volkmann RA, Heck S, Nowakowski J, Nelson R, Nolan C, Liston D, Ward K, Zorn S, Johnson C, Vanase M, Faraci WS, Verdries KA, Baxter J, Doran S, Sanders M, Ashton M, Whittle P, Stefaniak M. A new class of selective and potent inhibitors of neuronal nitric oxide synthase. Bioorg Med Chem Lett 1999; 9:2569-72. [PMID: 10498210 DOI: 10.1016/s0960-894x(99)00432-1] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The synthesis and SAR of a series of 6-(4-(substituted)phenyl)-2-aminopyridines as inhibitors of nitric oxide synthase are described. Compound 3a from this series shows potent and selective inhibition of the human nNOS isoform, with pharmacokinetics sufficient to provide in vivo inhibition of nNOS activity.
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Affiliation(s)
- J A Lowe
- Central Research Division, Pfizer Inc. Groton, CT 06340, USA
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47
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Babu BR, Frey C, Griffith OW. L-arginine binding to nitric-oxide synthase. The role of H-bonds to the nonreactive guanidinium nitrogens. J Biol Chem 1999; 274:25218-26. [PMID: 10464242 DOI: 10.1074/jbc.274.36.25218] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [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 the oxidation of L-arginine to nitric oxide and L-citrulline. Because overproduction of nitric oxide causes tissue damage in neurological, inflammatory, and autoimmune disorders, design of NOS inhibitors has received much attention. Most inhibitors described to date include a guanidine-like structural motif and interact with the guanidinium region of the L-arginine-binding site. We report here studies with L-arginine analogs having one or both terminal guanidinium nitrogens replaced by functionalities that preserve some, but not all, of the molecular interactions possible for the -NH(2), =NH, or =NH(2)(+) groups of L-arginine. Replacement groups include -NH-alkyl, -alkyl, =O, and =S. Binding of L-canavanine, an analog unable to form hydrogen bonds involving a N(5)-proton, was also examined. From our results and previous work, we infer the orientation of these compounds in the L-arginine-binding site and use IC(50) or K(i) values and optical difference spectra to quantitate their affinity relative to L-arginine. We find that the non-reactive guanidinium nitrogen of L-arginine binds in a pocket that is relatively intolerant of changes in the size or hydrogen bonding properties of the group bound. The individual H-bonds involved are, however, weaker than expected (<2 versus 3-6 kcal). These findings elucidate substrate binding forces in the NOS active site and identify an important constraint on NOS inhibitor design.
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Affiliation(s)
- B R Babu
- Department of Biochemistry, Medical College of Wisconsin, Milwaukee, Wisconsin 53226, USA
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48
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Li H, Raman CS, Glaser CB, Blasko E, Young TA, Parkinson JF, Whitlow M, Poulos TL. Crystal structures of zinc-free and -bound heme domain of human inducible nitric-oxide synthase. Implications for dimer stability and comparison with endothelial nitric-oxide synthase. J Biol Chem 1999; 274:21276-84. [PMID: 10409685 DOI: 10.1074/jbc.274.30.21276] [Citation(s) in RCA: 152] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The crystal structures of the heme domain of human inducible nitric-oxide synthase (NOS-2) in zinc-free and -bound states have been solved. In the zinc-free structure, two symmetry-related cysteine residues form a disulfide bond. In the zinc-bound state, these same two cysteine residues form part of a zinc-tetrathiolate (ZnS(4)) center indistinguishable from that observed in the endothelial isoform (NOS-3). As in NOS-3, ZnS(4) plays a key role in stabilizing intersubunit contacts and in maintaining the integrity of the cofactor (tetrahydrobiopterin) binding site of NOS-2. A comparison of NOS-2 and NOS-3 structures illustrates the conservation of quaternary structure, tertiary topology, and substrate and cofactor binding sites, in addition to providing insights on isoform-specific inhibitor design. The structural comparison also reveals that pterin binding does not preferentially stabilize the dimer interface of NOS-2 over NOS-3.
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Affiliation(s)
- H Li
- Department of Molecular Biology and Biochemistry, University of California at Irvine, Irvine, California 92697, USA
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49
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Scheele JS, Bruner E, Kharitonov VG, Martásek P, Roman LJ, Masters BS, Sharma VS, Magde D. Kinetics of NO ligation with nitric-oxide synthase by flash photolysis and stopped-flow spectrophotometry. J Biol Chem 1999; 274:13105-10. [PMID: 10224063 DOI: 10.1074/jbc.274.19.13105] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [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 conversion of L-arginine to nitric oxide, which subsequently stimulates a host of physiological processes. Prior work suggests that NOS is inhibited by NO, providing opportunities for autoregulation. This contribution reports that NO reacts rapidly (ka congruent with 2 x 10(7) M-1 s-1) with neuronal NOS in both its ferric and ferrous oxidation states. Association kinetics are almost unaffected by L-arginine or the cofactor tetrahydrobiopterin. There is no evidence for the distinct two phases previously reported for association kinetics of CO. Small amounts of geminate recombination of NO trapped in a protein pocket can be observed over nanoseconds, and a much larger amount is inferred to take place at picosecond time scales. Dissociation rates are also very fast from the ferric form, in the neighborhood of 50 s-1, when measured by extrapolating association rates to the zero NO concentration limit. Scavenging experiments give dissociation rate constants more than an order of magnitude slower: still quite fast. For the ferrous species, extrapolation is not distinguishable from zero, while scavenging experiments give a dissociation rate constant near 10(-4) s-1. Implications of these results for interactions near the heme binding site are discussed.
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Affiliation(s)
- J S Scheele
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, USA
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