1
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Elucidation of the Correlation between Heme Distortion and Tertiary Structure of the Heme-Binding Pocket Using a Convolutional Neural Network. Biomolecules 2022; 12:biom12091172. [PMID: 36139011 PMCID: PMC9496533 DOI: 10.3390/biom12091172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 08/19/2022] [Accepted: 08/22/2022] [Indexed: 11/17/2022] Open
Abstract
Heme proteins serve diverse and pivotal biological functions. Therefore, clarifying the mechanisms of these diverse functions of heme is a crucial scientific topic. Distortion of heme porphyrin is one of the key factors regulating the chemical properties of heme. Here, we constructed convolutional neural network models for predicting heme distortion from the tertiary structure of the heme-binding pocket to examine their correlation. For saddling, ruffling, doming, and waving distortions, the experimental structure and predicted values were closely correlated. Furthermore, we assessed the correlation between the cavity shape and molecular structure of heme and demonstrated that hemes in protein pockets with similar structures exhibit near-identical structures, indicating the regulation of heme distortion through the protein environment. These findings indicate that the tertiary structure of the heme-binding pocket is one of the factors regulating the distortion of heme porphyrin, thereby controlling the chemical properties of heme relevant to the protein function; this implies a structure–function correlation in heme proteins.
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2
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Mittal A, Kakkar R. Nitric Oxide Synthases and Their Inhibitors: A Review. LETT DRUG DES DISCOV 2020. [DOI: 10.2174/1570180816666190222154457] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Nitric Oxide (NO), an important biological mediator, is involved in the regulation of the cardiovascular, nervous and immune systems in mammals. Synthesis of NO is catalyzed by its biosynthetic enzyme, Nitric Oxide Synthase (NOS). There are three main isoforms of the enzyme, neuronal NOS, endothelial NOS and inducible NOS, which have very similar structures but differ in their expression and activities. NO is produced in the active site of the enzyme in two distinct cycles from oxidation of the substrate L-arg (L-arginine) in nicotinamide adenine dinucleotide phosphate (NADPH)-dependent reaction. NOS has gained considerable attention of biochemists due to its complexity and unique catalytic mechanism. The review focuses on NOS structure, its function and catalytic reaction mechanism. In particular, the review is concluded with a discussion on the role of all three isoforms of NOS in physiological and pathological conditions and their inhibitors with a focus on the role of computational techniques in their development.
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Affiliation(s)
- Anshika Mittal
- 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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3
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Cinelli MA, Do HT, Miley GP, Silverman RB. Inducible nitric oxide synthase: Regulation, structure, and inhibition. Med Res Rev 2020; 40:158-189. [PMID: 31192483 PMCID: PMC6908786 DOI: 10.1002/med.21599] [Citation(s) in RCA: 352] [Impact Index Per Article: 88.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2019] [Revised: 04/14/2019] [Accepted: 05/13/2019] [Indexed: 12/11/2022]
Abstract
A considerable number of human diseases have an inflammatory component, and a key mediator of immune activation and inflammation is inducible nitric oxide synthase (iNOS), which produces nitric oxide (NO) from l-arginine. Overexpressed or dysregulated iNOS has been implicated in numerous pathologies including sepsis, cancer, neurodegeneration, and various types of pain. Extensive knowledge has been accumulated about the roles iNOS plays in different tissues and organs. Additionally, X-ray crystal and cryogenic electron microscopy structures have shed new insights on the structure and regulation of this enzyme. Many potent iNOS inhibitors with high selectivity over related NOS isoforms, neuronal NOS, and endothelial NOS, have been discovered, and these drugs have shown promise in animal models of endotoxemia, inflammatory and neuropathic pain, arthritis, and other disorders. A major issue in iNOS inhibitor development is that promising results in animal studies have not translated to humans; there are no iNOS inhibitors approved for human use. In addition to assay limitations, both the dual modalities of iNOS and NO in disease states (ie, protective vs harmful effects) and the different roles and localizations of NOS isoforms create challenges for therapeutic intervention. This review summarizes the structure, function, and regulation of iNOS, with focus on the development of iNOS inhibitors (historical and recent). A better understanding of iNOS' complex functions is necessary before specific drug candidates can be identified for classical indications such as sepsis, heart failure, and pain; however, newer promising indications for iNOS inhibition, such as depression, neurodegenerative disorders, and epilepsy, have been discovered.
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Affiliation(s)
- Maris A. Cinelli
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Center for Developmental Therapeutics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
- Current address: Department of Pharmacology and Toxicology, Michigan State University, East Lansing, MI 48824
| | - Ha T. Do
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Center for Developmental Therapeutics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
- Current address: Mersana Therapeutics, Inc., Cambridge, MA 02139
| | - Galen P. Miley
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Center for Developmental Therapeutics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Richard B. Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Center for Developmental Therapeutics, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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4
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Abstract
Introduction: The development of drug candidates with a defined selectivity profile and a unique molecular structure is of fundamental interest for drug discovery. In contrast to the costly screening of large substance libraries, the targeted de novo design of a drug by using structural information of either the biological target and/or structure-activity relationship data of active modulators offers an efficient and intellectually appealing alternative. Areas covered: This review provides an overview on the different techniques of de novo drug design (ligand-based drug design, structure-based drug design, and fragment-based drug design) and highlights successful examples of this targeted approach toward selective modulators of therapeutically relevant targets. Expert opinion: De novo drug design has established itself as a very efficient method for the development of potent and selective modulators for a variety of different biological target classes. The ever-growing wealth of structural data on therapeutic targets will certainly further enhance the importance of de novo design for the drug discovery process in the future. However, a consistent use of the terminology of de novo drug design in the scientific literature should be sought.
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Affiliation(s)
- Thomas Fischer
- a Center of Organic and Medicinal Chemistry, Institute of Chemistry and Biotechnology , Zurich University of Applied Sciences ZHAW , Wädenswil , Switzerland
| | - Silvia Gazzola
- b Dipartimento di Scienza e Alta Tecnologia , Università degli Studi dell'Insubria , Como , Italy
| | - Rainer Riedl
- a Center of Organic and Medicinal Chemistry, Institute of Chemistry and Biotechnology , Zurich University of Applied Sciences ZHAW , Wädenswil , Switzerland
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5
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Menegatti R, Carvalho FS, Lião LM, Villavicencio B, Verli H, Mourão AA, Xavier CH, Castro CH, Pedrino GR, Franco OL, Oliveira-Silva I, Ashpole NM, Silva ON, Costa EA, Fajemiroye JO. Novel choline analog 2-(4-((1-phenyl-1H-pyrazol-4-yl)methyl)piperazin-1-yl)ethan-1-ol produces sympathoinhibition, hypotension, and antihypertensive effects. Naunyn Schmiedebergs Arch Pharmacol 2019; 392:1071-1083. [DOI: 10.1007/s00210-019-01649-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2019] [Accepted: 03/29/2019] [Indexed: 12/14/2022]
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6
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Olsbu IK, Zoppellaro G, Andersson KK, Boucher JL, Hersleth HP. Importance of Val567 on heme environment and substrate recognition of neuronal nitric oxide synthase. FEBS Open Bio 2018; 8:1553-1566. [PMID: 30186754 PMCID: PMC6120233 DOI: 10.1002/2211-5463.12503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2018] [Revised: 07/22/2018] [Accepted: 08/01/2018] [Indexed: 12/02/2022] Open
Abstract
Nitric oxide (NO) produced by mammalian nitric oxide synthases (mNOSs) is an important mediator in a variety of physiological functions. Crystal structures of mNOSs have shown strong conservation of the active‐site residue Val567 (numbering for rat neuronal NOS, nNOS). NOS‐like proteins have been identified in several bacterial pathogens, and these display striking sequence identity to the oxygenase domain of mNOS (NOSoxy), with the exception of a Val to Ile mutation at the active site. Preliminary studies have highlighted the importance of this Val residue in NO‐binding, substrate recognition, and oxidation in mNOSs. To further elucidate the role of this valine in substrate and substrate analogue recognition, we generated five Val567 mutants of the oxygenase domain of the neuronal NOS (nNOSoxy) and used UV‐visible and EPR spectroscopy to investigate the effects of these mutations on the heme distal environment, the stability of the heme‐FeII‐CO complexes, and the binding of a series of substrate analogues. Our results are consistent with Val567 playing an important role in preserving the integrity of the active site for substrate binding, stability of heme‐bound gaseous ligands, and potential NO production.
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Affiliation(s)
- Inger K Olsbu
- Department of Biosciences Section for Biochemistry and Molecular Biology University of Oslo Norway
| | - Giorgio Zoppellaro
- Regional Centre of Advanced Technologies and Materials Department of Physical Chemistry Faculty of Science Palacky University in Olomouc Czech Republic
| | - K Kristoffer Andersson
- Department of Biosciences Section for Biochemistry and Molecular Biology University of Oslo Norway
| | | | - Hans-Petter Hersleth
- Department of Biosciences Section for Biochemistry and Molecular Biology University of Oslo Norway.,Department of Chemistry Section for Chemical Life Sciences University of Oslo Norway
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7
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Kashfi K. The dichotomous role of H 2S in cancer cell biology? Déjà vu all over again. Biochem Pharmacol 2018; 149:205-223. [PMID: 29397935 PMCID: PMC5866221 DOI: 10.1016/j.bcp.2018.01.042] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2017] [Accepted: 01/17/2018] [Indexed: 02/09/2023]
Abstract
Nitric oxide (NO) a gaseous free radical is one of the ten smallest molecules found in nature, while hydrogen sulfide (H2S) is a gas that bears the pungent smell of rotten eggs. Both are toxic yet they are gasotransmitters of physiological relevance. There appears to be an uncanny resemblance between the general actions of these two gasotransmitters in health and disease. The role of NO and H2S in cancer has been quite perplexing, as both tumor promotion and inflammatory activities as well as anti-tumor and antiinflammatory properties have been described. These paradoxes have been explained for both gasotransmitters in terms of each having a dual or biphasic effect that is dependent on the local flux of each gas. In this review/commentary, I have discussed the major roles of NO and H2S in carcinogenesis, evaluating their dual nature, focusing on the enzymes that contribute to this paradox and evaluate the pros and cons of inhibiting or inducing each of these enzymes.
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Affiliation(s)
- Khosrow Kashfi
- Department of Molecular, Cellular and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, NY, USA.
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8
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Hedison TM, Hay S, Scrutton NS. A perspective on conformational control of electron transfer in nitric oxide synthases. Nitric Oxide 2017; 63:61-67. [PMID: 27619338 PMCID: PMC5295631 DOI: 10.1016/j.niox.2016.09.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 09/05/2016] [Accepted: 09/06/2016] [Indexed: 01/20/2023]
Abstract
This perspective reviews single molecule and ensemble fluorescence spectroscopy studies of the three tissue specific nitric oxide synthase (NOS) isoenzymes and the related diflavin oxidoreductase cytochrome P450 reductase. The focus is on the role of protein dynamics and the protein conformational landscape and we discuss how recent fluorescence-based studies have helped in illustrating how the nature of the NOS conformational landscape relates to enzyme turnover and catalysis.
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Affiliation(s)
- Tobias M Hedison
- Manchester Institute of Biotechnology, The University of Manchester, Manchester, United Kingdom
| | - Sam Hay
- Manchester Institute of Biotechnology, The University of Manchester, Manchester, United Kingdom
| | - Nigel S Scrutton
- Manchester Institute of Biotechnology, The University of Manchester, Manchester, United Kingdom.
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9
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Poulos TL, Li H. Nitric oxide synthase and structure-based inhibitor design. Nitric Oxide 2016; 63:68-77. [PMID: 27890696 DOI: 10.1016/j.niox.2016.11.004] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 11/09/2016] [Accepted: 11/21/2016] [Indexed: 11/24/2022]
Abstract
Once it was discovered that the enzyme nitric oxide synthase (NOS) is responsible for the biosynthesis of NO, NOS became a drug target. Particularly important is the over production of NO by neuronal NOS (nNOS) in various neurodegenerative disorders. After the various NOS isoforms were identified, inhibitor development proceeded rapidly. It soon became evident, however, that isoform selectivity presents a major challenge. All 3 human NOS isoforms, nNOS, eNOS (endothelial NOS), and iNOS (inducible NOS) have nearly identical active site structures thus making selective inhibitor design especially difficult. Of particular importance is the avoidance of inhibiting eNOS owing to its vital role in the cardiovascular system. This review summarizes some of the history of NOS inhibitor development and more recent advances in developing isoform selective inhibitors using primarily structure-based approaches.
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Affiliation(s)
- Thomas L Poulos
- Departments of Molecular Biology & Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, Irvine, CA 92697-3900, USA.
| | - Huiying Li
- Departments of Molecular Biology & Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California, Irvine, Irvine, CA 92697-3900, USA
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10
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Hedison TM, Leferink NGH, Hay S, Scrutton NS. Correlating Calmodulin Landscapes with Chemical Catalysis in Neuronal Nitric Oxide Synthase using Time-Resolved FRET and a 5-Deazaflavin Thermodynamic Trap. ACS Catal 2016; 6:5170-5180. [PMID: 27563493 PMCID: PMC4993522 DOI: 10.1021/acscatal.6b01280] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2016] [Revised: 06/23/2016] [Indexed: 11/28/2022]
Abstract
![]()
A major challenge in enzymology is
the need to correlate the dynamic
properties of enzymes with, and understand the impact on, their catalytic
cycles. This is especially the case with large, multicenter enzymes
such as the nitric oxide synthases (NOSs), where the importance of
dynamics has been inferred from a variety of structural, single-molecule,
and ensemble spectroscopic approaches but where motions have not been
correlated experimentally with mechanistic steps in the reaction cycle.
Here we take such an approach. Using time-resolved spectroscopy employing
absorbance and Förster resonance energy transfer (FRET) and
exploiting the properties of a flavin analogue (5-deazaflavin mononucleotide
(5-dFMN)) and isotopically labeled nicotinamide coenzymes, we correlate
the timing of CaM structural changes when bound to neuronal nitric
oxide synthase (nNOS) with the nNOS catalytic cycle. We show that
remodeling of CaM occurs early in the electron transfer sequence (FAD
reduction), not at later points in the reaction cycle (e.g., FMN reduction).
Conformational changes are tightly correlated with FAD reduction kinetics
and reflect a transient “opening” and then “closure”
of the bound CaM molecule. We infer that displacement of the C-terminal
tail on binding NADPH and subsequent FAD reduction are the likely
triggers of conformational change. By combining the use of cofactor/coenzyme
analogues and time-resolved FRET/absorbance spectrophotometry, we
show how the reaction cycles of complex enzymes can be simplified,
enabling a detailed study of the relationship between protein dynamics
and reaction cycle chemistry—an approach that can also be used
with other complex multicenter enzymes.
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Affiliation(s)
- Tobias M. Hedison
- Manchester Synthetic Biology
Research Centre for Fine and Speciality Chemicals (SYNBIOCHEM), Manchester
Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Nicole G. H. Leferink
- Manchester Synthetic Biology
Research Centre for Fine and Speciality Chemicals (SYNBIOCHEM), Manchester
Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Sam Hay
- Manchester Synthetic Biology
Research Centre for Fine and Speciality Chemicals (SYNBIOCHEM), Manchester
Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
| | - Nigel S. Scrutton
- Manchester Synthetic Biology
Research Centre for Fine and Speciality Chemicals (SYNBIOCHEM), Manchester
Institute of Biotechnology, The University of Manchester, Manchester M1 7DN, United Kingdom
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11
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Li H, Wang HY, Kang S, Silverman RB, Poulos TL. Electrostatic Control of Isoform Selective Inhibitor Binding in Nitric Oxide Synthase. Biochemistry 2016; 55:3702-7. [PMID: 27250740 DOI: 10.1021/acs.biochem.6b00261] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Development of potent and isoform selective nitric oxide synthase (NOS) inhibitors is challenging because of the structural similarity in the heme active sites. One amino acid difference between NOS isoforms, Asp597 in rat neuronal NOS (nNOS) versus Asn368 in bovine endothelial NOS (eNOS), has been identified as the structural basis for why some dipeptide amide inhibitors bind more tightly to nNOS than to eNOS. We now have found that the same amino acid variation is responsible for substantially different binding modes and affinity for a new class of aminopyridine-based inhibitors.
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Affiliation(s)
- Huiying Li
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California , Irvine, California 92697-3900, United States
| | - Heng-Yen Wang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Soosung Kang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Richard B Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Thomas L Poulos
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California , Irvine, California 92697-3900, United States
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12
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Miao Z, King SB. Recent advances in the chemical biology of nitroxyl (HNO) detection and generation. Nitric Oxide 2016; 57:1-14. [PMID: 27108951 PMCID: PMC4910183 DOI: 10.1016/j.niox.2016.04.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 04/18/2016] [Indexed: 01/01/2023]
Abstract
Nitroxyl or azanone (HNO) represents the redox-related (one electron reduced and protonated) relative of the well-known biological signaling molecule nitric oxide (NO). Despite the close structural similarity to NO, defined biological roles and endogenous formation of HNO remain unclear due to the high reactivity of HNO with itself, soft nucleophiles and transition metals. While significant work has been accomplished in terms of the physiology, biology and chemistry of HNO, important and clarifying work regarding HNO detection and formation has occurred within the last 10 years. This review summarizes advances in the areas of HNO detection and donation and their application to normal and pathological biology. Such chemical biological tools allow a deeper understanding of biological HNO formation and the role that HNO plays in a variety of physiological systems.
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Affiliation(s)
- Zhengrui Miao
- Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109, USA
| | - S Bruce King
- Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109, USA.
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13
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Parhad SS, Jaiswal D, Ray K, Mazumdar S. The protein inhibitor of nNOS (PIN/DLC1/LC8) binding does not inhibit the NADPH-dependent heme reduction in nNOS, a key step in NO synthesis. Biochem Biophys Res Commun 2016; 472:189-93. [PMID: 26923072 DOI: 10.1016/j.bbrc.2016.02.092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2016] [Accepted: 02/22/2016] [Indexed: 12/01/2022]
Abstract
The neuronal nitric oxide synthase (nNOS) is an essential enzyme involved in the synthesis of nitric oxide (NO), a potent neurotransmitter. Although previous studies have indicated that the dynein light chain 1 (DLC1) binding to nNOS could inhibit the NO synthesis, the claim is challenged by contradicting reports. Thus, the mechanism of nNOS regulation remained unclear. nNOS has a heme-bearing, Cytochrome P450 core, and the functional enzyme is a dimer. The electron flow from NADPH to Flavin, and finally to the heme of the paired nNOS subunit within a dimer, is facilitated upon calmodulin (CaM) binding. Here, we show that DLC1 binding to nNOS-CaM complex does not affect the electron transport from the reductase to the oxygenase domain. Therefore, it cannot inhibit the rate of NADPH-dependent heme reduction in nNOS, which results in l-Arginine oxidation. Also, the NO release activity does not decrease with increasing DLC1 concentration in the reaction mix, which further confirmed that DLC1 does not inhibit nNOS activity. These findings suggest that the DLC1 binding may have other implications for the nNOS function in the cell.
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Affiliation(s)
- Swapnil S Parhad
- Tata Institute of Fundamental Research (TIFR), Homi Bhabha Road, Mumbai 400 005, India
| | - Deepa Jaiswal
- Tata Institute of Fundamental Research (TIFR), Homi Bhabha Road, Mumbai 400 005, India; TIFR Centre for Interdisciplinary Sciences, 21 Brundavan Colony, Narsingi, Hyderabad 500075, India
| | - Krishanu Ray
- Tata Institute of Fundamental Research (TIFR), Homi Bhabha Road, Mumbai 400 005, India.
| | - Shyamalava Mazumdar
- Tata Institute of Fundamental Research (TIFR), Homi Bhabha Road, Mumbai 400 005, India.
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14
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Basavaprabhu H, Prabhu G, Krishnamurthy M, Rao PN, Sureshbabu VV. “Thioureidopeptide”: Novel Synthon for the Synthesis of N, N′, N″-Trisubstituted Guanidinopeptide Mimics. Int J Pept Res Ther 2015. [DOI: 10.1007/s10989-015-9496-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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15
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Cinelli MA, Li H, Pensa AV, Kang S, Roman LJ, Martásek P, Poulos TL, Silverman RB. Phenyl Ether- and Aniline-Containing 2-Aminoquinolines as Potent and Selective Inhibitors of Neuronal Nitric Oxide Synthase. J Med Chem 2015; 58:8694-712. [PMID: 26469213 DOI: 10.1021/acs.jmedchem.5b01330] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Excess nitric oxide (NO) produced by neuronal nitric oxide synthase (nNOS) is implicated in neurodegenerative disorders. As a result, inhibition of nNOS and reduction of NO levels is desirable therapeutically, but many nNOS inhibitors are poorly bioavailable. Promising members of our previously reported 2-aminoquinoline class of nNOS inhibitors, although orally bioavailable and brain-penetrant, suffer from unfavorable off-target binding to other CNS receptors, and they resemble known promiscuous binders. Rearranged phenyl ether- and aniline-linked 2-aminoquinoline derivatives were therefore designed to (a) disrupt the promiscuous binding pharmacophore and diminish off-target interactions and (b) preserve potency, isoform selectivity, and cell permeability. A series of these compounds was synthesized and tested against purified nNOS, endothelial NOS (eNOS), and inducible NOS (iNOS) enzymes. One compound, 20, displayed high potency, selectivity, and good human nNOS inhibition, and retained some permeability in a Caco-2 assay. Most promisingly, CNS receptor counterscreening revealed that this rearranged scaffold significantly reduces off-target binding.
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Affiliation(s)
- Maris A Cinelli
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Huiying Li
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California , Irvine, California 92697-3900, United States
| | - Anthony V Pensa
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Soosung Kang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Linda J Roman
- Department of Biochemistry, University of Texas Health Science Center , San Antonio, Texas 78384-7760, United States
| | - Pavel Martásek
- Department of Biochemistry, University of Texas Health Science Center , San Antonio, Texas 78384-7760, United States.,Department of Pediatrics, First Faculty of Medicine, Charles University , Prague, Czech Republic.,BIOCEV , Prague, Czech Republic
| | - Thomas L Poulos
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California , Irvine, California 92697-3900, United States
| | - Richard B Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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16
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Hollingsworth SA, Holden JK, Li H, Poulos TL. Elucidating nitric oxide synthase domain interactions by molecular dynamics. Protein Sci 2015; 25:374-82. [PMID: 26448477 PMCID: PMC4815339 DOI: 10.1002/pro.2824] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Revised: 09/25/2015] [Accepted: 10/04/2015] [Indexed: 12/19/2022]
Abstract
Nitric oxide synthase (NOS) is a multidomain enzyme that catalyzes the production of nitric oxide (NO) by oxidizing L-Arg to NO and L-citrulline. NO production requires multiple interdomain electron transfer steps between the flavin mononucleotide (FMN) and heme domain. Specifically, NADPH-derived electrons are transferred to the heme-containing oxygenase domain via the flavin adenine dinucleotide (FAD) and FMN containing reductase domains. While crystal structures are available for both the reductase and oxygenase domains of NOS, to date there is no atomic level structural information on domain interactions required for the final FMN-to-heme electron transfer step. Here, we evaluate a model of this final electron transfer step for the heme-FMN-calmodulin NOS complex based on the recent biophysical studies using a 105-ns molecular dynamics trajectory. The resulting equilibrated complex structure is very stable and provides a detailed prediction of interdomain contacts required for stabilizing the NOS output state. The resulting equilibrated complex model agrees well with previous experimental work and provides a detailed working model of the final NOS electron transfer step required for NO biosynthesis.
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Affiliation(s)
- Scott A Hollingsworth
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697.,Department of Chemistry, University of California, Irvine, California, 92697.,Department of Pharmaceutical Sciences, University of California, Irvine, California, 92697
| | - Jeffrey K Holden
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697.,Department of Chemistry, University of California, Irvine, California, 92697.,Department of Pharmaceutical Sciences, University of California, Irvine, California, 92697
| | - Huiying Li
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697.,Department of Chemistry, University of California, Irvine, California, 92697.,Department of Pharmaceutical Sciences, University of California, Irvine, California, 92697
| | - Thomas L Poulos
- Department of Molecular Biology and Biochemistry, University of California, Irvine, California, 92697.,Department of Chemistry, University of California, Irvine, California, 92697.,Department of Pharmaceutical Sciences, University of California, Irvine, California, 92697
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17
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Tang W, Li H, Doud EH, Chen Y, Choing S, Plaza C, Kelleher NL, Poulos TL, Silverman RB. Mechanism of Inactivation of Neuronal Nitric Oxide Synthase by (S)-2-Amino-5-(2-(methylthio)acetimidamido)pentanoic Acid. J Am Chem Soc 2015; 137:5980-9. [PMID: 25874809 PMCID: PMC4431946 DOI: 10.1021/jacs.5b01202] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Nitric oxide synthase (NOS) catalyzes the conversion of l-arginine to l-citrulline and the second messenger nitric oxide. Three mechanistic pathways are proposed for the inactivation of neuronal NOS (nNOS) by (S)-2-amino-5-(2-(methylthio)acetimidamido)pentanoic acid (1): sulfide oxidation, oxidative dethiolation, and oxidative demethylation. Four possible intermediates were synthesized. All compounds were assayed with nNOS, their IC50, KI, and kinact values were obtained, and their crystal structures were determined. The identification and characterization of the products formed during inactivation provide evidence for the details of the inactivation mechanism. On the basis of these studies, the most probable mechanism for the inactivation of nNOS involves oxidative demethylation with the resulting thiol coordinating to the cofactor heme iron. Although nNOS is a heme-containing enzyme, this is the first example of a NOS that catalyzes an S-demethylation reaction; the novel mechanism of inactivation described here could be applied to the design of inactivators of other heme-dependent enzymes.
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Affiliation(s)
- Wei Tang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Huiying Li
- Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Emma H. Doud
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Proteomics Center of Excellence, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Yunqiu Chen
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Proteomics Center of Excellence, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Stephanie Choing
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Carla Plaza
- Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Neil L. Kelleher
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Proteomics Center of Excellence, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Thomas L. Poulos
- Departments of Molecular Biology and Biochemistry, Chemistry, and Pharmaceutical Sciences, University of California, Irvine, California 92697-3900, United States
| | - Richard B. Silverman
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, and Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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18
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Leferink NGH, Hay S, Rigby SEJ, Scrutton NS. Towards the free energy landscape for catalysis in mammalian nitric oxide synthases. FEBS J 2014; 282:3016-29. [PMID: 25491181 DOI: 10.1111/febs.13171] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2014] [Revised: 12/05/2014] [Accepted: 12/05/2014] [Indexed: 01/30/2023]
Abstract
The general requirement for conformational sampling in biological electron transfer reactions catalysed by multi-domain redox systems has been emphasized in recent years. Crucially, we lack insight into the extent of the conformational space explored and the nature of the energy landscapes associated with these reactions. The nitric oxide synthases (NOS) produce the signalling molecule NO through a series of complex electron transfer reactions. There is accumulating evidence that protein domain dynamics and calmodulin binding are implicated in regulating electron flow from NADPH, through the FAD and FMN cofactors, to the haem oxygenase domain, where NO is generated. Simple models based on static crystal structures of the isolated reductase domain have suggested a role for large-scale motions of the FMN-binding domain in shuttling electrons from the reductase domain to the oxygenase domain. However, detailed insight into the higher-order domain architecture and dynamic structural transitions in NOS enzymes during enzyme turnover is lacking. In this review, we discuss the recent advances made towards mapping the catalytic free energy landscapes of NOS enzymes through integration of both structural techniques (e.g. cryo-electron microscopy) and biophysical techniques (e.g. pulsed-electron paramagnetic resonance). The general picture that emerges from these experiments is that NOS enzymes exist in an equilibrium of conformations, comprising a 'rugged' or 'frustrated' energy landscape, with a key regulatory role for calmodulin in driving vectorial electron transfer by altering the conformational equilibrium. A detailed understanding of these landscapes may provide new opportunities for discovery of isoform-specific inhibitors that bind at the dynamic interfaces of these multi-dimensional energy landscapes.
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Affiliation(s)
- Nicole G H Leferink
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, UK
| | - Sam Hay
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, UK
| | - Stephen E J Rigby
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, UK
| | - Nigel S Scrutton
- Manchester Institute of Biotechnology and Faculty of Life Sciences, The University of Manchester, UK
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19
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Mukherjee P, Cinelli MA, Kang S, Silverman RB. Development of nitric oxide synthase inhibitors for neurodegeneration and neuropathic pain. Chem Soc Rev 2014; 43:6814-38. [PMID: 24549364 PMCID: PMC4138306 DOI: 10.1039/c3cs60467e] [Citation(s) in RCA: 105] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Nitric oxide (NO) is an important signaling molecule in the human body, playing a crucial role in cell and neuronal communication, regulation of blood pressure, and in immune activation. However, overproduction of NO by the neuronal isoform of nitric oxide synthase (nNOS) is one of the fundamental causes underlying neurodegenerative disorders and neuropathic pain. Therefore, developing small molecules for selective inhibition of nNOS over related isoforms (eNOS and iNOS) is therapeutically desirable. The aims of this review focus on the regulation and dysregulation of NO signaling, the role of NO in neurodegeneration and pain, the structure and mechanism of nNOS, and the use of this information to design selective inhibitors of this enzyme. Structure-based drug design, the bioavailability and pharmacokinetics of these inhibitors, and extensive target validation through animal studies are addressed.
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Affiliation(s)
- Paramita Mukherjee
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA.
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20
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Li H, Jamal J, Plaza C, Pineda SH, Chreifi G, Jing Q, Cinelli MA, Silverman RB, Poulos TL. Structures of human constitutive nitric oxide synthases. ACTA CRYSTALLOGRAPHICA. SECTION D, BIOLOGICAL CRYSTALLOGRAPHY 2014; 70:2667-74. [PMID: 25286850 PMCID: PMC4188008 DOI: 10.1107/s1399004714017064] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 07/23/2014] [Indexed: 11/10/2022]
Abstract
Mammals produce three isoforms of nitric oxide synthase (NOS): neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS). The overproduction of NO by nNOS is associated with a number of neurodegenerative disorders; therefore, a desirable therapeutic goal is the design of drugs that target nNOS but not the other isoforms. Crystallography, coupled with computational approaches and medicinal chemistry, has played a critical role in developing highly selective nNOS inhibitors that exhibit exceptional neuroprotective properties. For historic reasons, crystallography has focused on rat nNOS and bovine eNOS because these were available in high quality; thus, their structures have been used in structure-activity-relationship studies. Although these constitutive NOSs share more than 90% sequence identity across mammalian species for each NOS isoform, inhibitor-binding studies revealed that subtle differences near the heme active site in the same NOS isoform across species still impact enzyme-inhibitor interactions. Therefore, structures of the human constitutive NOSs are indispensible. Here, the first structure of human neuronal NOS at 2.03 Å resolution is reported and a different crystal form of human endothelial NOS is reported at 1.73 Å resolution.
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Affiliation(s)
- Huiying Li
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences and Chemistry, University of California, Irvine, 517 Bison Avenue, Irvine, CA 92697-3900, USA
| | - Joumana Jamal
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences and Chemistry, University of California, Irvine, 517 Bison Avenue, Irvine, CA 92697-3900, USA
| | - Carla Plaza
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences and Chemistry, University of California, Irvine, 517 Bison Avenue, Irvine, CA 92697-3900, USA
| | - Stephanie Hai Pineda
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences and Chemistry, University of California, Irvine, 517 Bison Avenue, Irvine, CA 92697-3900, USA
| | - Georges Chreifi
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences and Chemistry, University of California, Irvine, 517 Bison Avenue, Irvine, CA 92697-3900, USA
| | - Qing Jing
- Department of Chemistry and Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
| | - Maris A. Cinelli
- Department of Chemistry and Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
| | - Richard B. Silverman
- Department of Chemistry and Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
| | - Thomas L. Poulos
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences and Chemistry, University of California, Irvine, 517 Bison Avenue, Irvine, CA 92697-3900, USA
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21
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Li H, Jamal J, Delker S, Plaza C, Ji H, Jing Q, Huang H, Kang S, Silverman RB, Poulos TL. The mobility of a conserved tyrosine residue controls isoform-dependent enzyme-inhibitor interactions in nitric oxide synthases. Biochemistry 2014; 53:5272-9. [PMID: 25089924 PMCID: PMC4139154 DOI: 10.1021/bi500561h] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
![]()
Many pyrrolidine-based inhibitors
highly selective for neuronal
nitric oxide synthase (nNOS) over endothelial NOS (eNOS) exhibit dramatically
different binding modes. In some cases, the inhibitor binds in a 180°
flipped orientation in nNOS relative to eNOS. From the several crystal
structures we have determined, we know that isoform selectivity correlates
with the rotamer position of a conserved tyrosine residue that H-bonds
with a heme propionate. In nNOS, this Tyr more readily adopts the
out-rotamer conformation, while in eNOS, the Tyr tends to remain fixed
in the original in-rotamer conformation. In the out-rotamer conformation,
inhibitors are able to form better H-bonds with the protein and heme,
thus increasing inhibitor potency. A segment of polypeptide that runs
along the surface near the conserved Tyr has long been thought to
be the reason for the difference in Tyr mobility. Although this segment
is usually disordered in both eNOS and nNOS, sequence comparisons
and modeling from a few structures show that this segment is structured
quite differently in eNOS and nNOS. In this study, we have probed
the importance of this surface segment near the Tyr by making a few
mutants in the region followed by crystal structure determinations.
In addition, because the segment near the conserved Tyr is highly
ordered in iNOS, we also determined the structure of an iNOS–inhibitor
complex. This new structure provides further insight into the critical
role that mobility plays in isoform selectivity.
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Affiliation(s)
- Huiying Li
- Departments of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and Chemistry, University of California , Irvine, California 92697-3900, United States
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22
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Astashkin AV, Chen L, Zhou X, Li H, Poulos TL, Liu KJ, Guillemette JG, Feng C. Pulsed electron paramagnetic resonance study of domain docking in neuronal nitric oxide synthase: the calmodulin and output state perspective. J Phys Chem A 2014; 118:6864-72. [PMID: 25046446 PMCID: PMC4148148 DOI: 10.1021/jp503547w] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The binding of calmodulin (CaM) to neuronal nitric oxide synthase (nNOS) enables formation of the output state of nNOS for nitric oxide production. Essential to NOS function is the geometry and dynamics of CaM docking to the NOS oxygenase domain, but little is known about these details. In the present work, the domain docking in a CaM-bound oxygenase/FMN (oxyFMN) construct of nNOS was investigated using the relaxation-induced dipolar modulation enhancement (RIDME) technique, which is a pulsed electron paramagnetic resonance technique sensitive to the magnetic dipole interaction between the electron spins. A cysteine was introduced at position 110 of CaM, after which a nitroxide spin label was attached at the position. The RIDME study of the magnetic dipole interaction between the spin label and the ferric heme centers in the oxygenase domain of nNOS revealed that, with increasing [Ca(2+)], the concentration of nNOS·CaM complexes increases and reaches a maximum at [Ca(2+)]/[CaM] ≥ 4. The RIDME kinetics of CaM-bound nNOS represented monotonous decays without well-defined oscillations. The analysis of these kinetics based on the structural models for the open and docked states has shown that only about 15 ± 3% of the CaM-bound nNOS is in the docked state at any given time, while the remaining 85 ± 3% of the protein is in the open conformations characterized by a wide distribution of distances between the bound CaM and the oxygenase domain. The results of this investigation are consistent with a model that the Ca(2+)-CaM interaction causes CaM docking with the oxygenase domain. The low population of the docked state indicates that the CaM-controlled docking between the FMN and heme domains is highly dynamic.
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Affiliation(s)
- Andrei V Astashkin
- Department of Chemistry and Biochemistry, University of Arizona , Tucson, Arizona 85721, United States
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23
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Huang H, Li H, Yang S, Chreifi G, Martásek P, Roman L, Meyskens FL, Poulos TL, Silverman RB. Potent and selective double-headed thiophene-2-carboximidamide inhibitors of neuronal nitric oxide synthase for the treatment of melanoma. J Med Chem 2014; 57:686-700. [PMID: 24447275 PMCID: PMC3983353 DOI: 10.1021/jm401252e] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2013] [Indexed: 01/10/2023]
Abstract
Selective inhibitors of neuronal nitric oxide synthase (nNOS) are regarded as valuable and powerful agents with therapeutic potential for the treatment of chronic neurodegenerative pathologies and human melanoma. Here, we describe a novel hybrid strategy that combines the pharmacokinetically promising thiophene-2-carboximidamide fragment and structural features of our previously reported potent and selective aminopyridine inhibitors. Two inhibitors, 13 and 14, show low nanomolar inhibitory potency (Ki = 5 nM for nNOS) and good isoform selectivities (nNOS over eNOS [440- and 540-fold, respectively] and over iNOS [260- and 340-fold, respectively]). The crystal structures of these nNOS-inhibitor complexes reveal a new hot spot that explains the selectivity of 14 and why converting the secondary to tertiary amine leads to enhanced selectivity. More importantly, these compounds are the first highly potent and selective nNOS inhibitory agents that exhibit excellent in vitro efficacy in melanoma cell lines.
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Affiliation(s)
- He Huang
- Department
of Chemistry, Department of Molecular Biosciences, Chemistry of Life
Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
| | - Huiying Li
- Departments
of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and
Chemistry, University of California, Irvine, California 92697-3900, United States
| | - Sun Yang
- Chao
Family Comprehensive Cancer Center, University
of California, Irvine, California 92697-3900, United States
| | - Georges Chreifi
- Departments
of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and
Chemistry, University of California, Irvine, California 92697-3900, United States
| | - Pavel Martásek
- Department
of Biochemistry, University of Texas Health
Science Center, San Antonio, Texas 78384-7760, United States
- Department
of Pediatrics and Center for Applied Genomics, First School of Medicine, Charles University, Prague, Czech Republic
| | - Linda
J. Roman
- Department
of Biochemistry, University of Texas Health
Science Center, San Antonio, Texas 78384-7760, United States
| | - Frank L. Meyskens
- Chao
Family Comprehensive Cancer Center, University
of California, Irvine, California 92697-3900, United States
| | - Thomas L. Poulos
- Departments
of Molecular Biology and Biochemistry, Pharmaceutical Sciences, and
Chemistry, University of California, Irvine, California 92697-3900, United States
| | - Richard B. Silverman
- Department
of Chemistry, Department of Molecular Biosciences, Chemistry of Life
Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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24
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Cinelli MA, Li H, Chreifi G, Martásek P, Roman LJ, Poulos TL, Silverman RB. Simplified 2-aminoquinoline-based scaffold for potent and selective neuronal nitric oxide synthase inhibition. J Med Chem 2014; 57:1513-30. [PMID: 24472039 PMCID: PMC3954451 DOI: 10.1021/jm401838x] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
![]()
Since high levels of nitric oxide
(NO) are implicated in neurodegenerative
disorders, inhibition of the neuronal isoform of nitric oxide synthase
(nNOS) and reduction of NO levels are therapeutically desirable. Nonetheless,
many nNOS inhibitors mimic l-arginine and are poorly bioavailable.
2-Aminoquinoline-based scaffolds were designed with the hope that
they could (a) mimic aminopyridines as potent, isoform-selective arginine
isosteres and (b) possess chemical properties more conducive to oral
bioavailability and CNS penetration. A series of these compounds was
synthesized and assayed against purified nNOS enzymes, endothelial
NOS (eNOS), and inducible NOS (iNOS). Several compounds built on a
7-substituted 2-aminoquinoline core are potent and isoform-selective;
X-ray crystallography indicates that aminoquinolines exert inhibitory
effects by mimicking substrate interactions with the conserved active
site glutamate residue. The most potent and selective compounds, 7 and 15, were tested in a Caco-2 assay and showed
good permeability and low efflux, suggesting high potential for oral
bioavailability.
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Affiliation(s)
- Maris A Cinelli
- Departments of Chemistry and Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University , 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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25
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Padayachee ER, Arowolo A, Whiteley CG. Nanomedicine: Action of Metal Nanoparticles on Neuronal Nitric Oxide Synthase—Fluorimetric Analysis on the Mechanism for Fibrillogenesis. Neurochem Res 2013; 39:194-201. [DOI: 10.1007/s11064-013-1206-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Revised: 09/16/2013] [Accepted: 11/20/2013] [Indexed: 12/23/2022]
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26
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Structural and biological studies on bacterial nitric oxide synthase inhibitors. Proc Natl Acad Sci U S A 2013; 110:18127-31. [PMID: 24145412 DOI: 10.1073/pnas.1314080110] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Nitric oxide (NO) produced by bacterial NOS functions as a cytoprotective agent against oxidative stress in Staphylococcus aureus, Bacillus anthracis, and Bacillus subtilis. The screening of several NOS-selective inhibitors uncovered two inhibitors with potential antimicrobial properties. These two compounds impede the growth of B. subtilis under oxidative stress, and crystal structures show that each compound exhibits a unique binding mode. Both compounds serve as excellent leads for the future development of antimicrobials against bacterial NOS-containing bacteria.
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27
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Padayachee ER, Whiteley CG. Etiology of Alzheimer's disease: kinetic, thermodynamic and fluorimetric analyses of interactions of pseudo Aβ-peptides with neuronal nitric oxide synthase. Neuropeptides 2013; 47:321-7. [PMID: 24034554 DOI: 10.1016/j.npep.2013.08.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 07/09/2013] [Accepted: 08/09/2013] [Indexed: 10/26/2022]
Abstract
Aggregated β-amyloid deposit is a hallmark in the neuropathology of Alzheimer's disease but their mechanism of formation still remains unresolved. Previously we reported that a normal pentapeptide Aβ(17-21) and glycine zipper peptide Aβ(29-33) strongly inhibited nitric oxide synthase and rapidly initiated fibrillogenesis. Critical amino acids within these fragments were not identified. We now report on the interaction of four pseudo-peptides with nNOS - two peptides with a reversed amino acid sequence [Aβ(17-21r); Aβ(29-33r)] and two peptides with Phe19, Phe20 and Ile31, Ile32 substituted with polar glutamic acid [Aβ(17-21p); Aβ(29-33p)]. It was shown that while the inhibitor constants (Ki) increased 2-3 fold for each of the pseudo-peptides when compared with the normal peptides the dissociation constant Kd increased between 20 and 50 fold. Stern-Volmer fluorescence quenching constants (K(SV)) for Aβ(17-21p) and Aβ(29-33p) were 7.2×10(-3) and 6.1×10(-3) μM(-1) respectively at 298 K some 2-3 fold lower than the corresponding Aβ(17-21r); Aβ(29-33r). With temperature increase there was an increase in K(SV) and Kd, suggesting a dynamic quenching mechanism. Thermodynamic parameters, ΔH, ΔS and ΔG were all positive indicating endothermic, non-spontaneous, hydrophobic-hydrophobic associations of the pseudo-peptides with the enzyme. By FRET analysis the efficiency of fluorescence transfer between enzyme tryptophans and the pseudo-peptides was 90% (compared to 97% for the natural substrate). The distance the tryptophans moved after interaction with Aβ(17-21r) and Aβ(17-21p) was 10% greater, while for Aβ(29-33r) and Aβ(29-33p) it was 20-25% greater, than with the normal peptides; the fluorescence intensity was 20-75% higher. This increase in distance, fluorescent intensity and transfer efficiency illustrate an increase in interaction energy for the pseudo-peptides with nNOS lending support for the strategic position of the Phe19, Phe20, Ile31 and Ile32 in the original peptides not only for inhibition of the nNOS but for initiation of fibrillogenesis.
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Affiliation(s)
- E R Padayachee
- Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown, South Africa
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28
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Feng C, Chen L, Li W, Elmore BO, Fan W, Sun X. Dissecting regulation mechanism of the FMN to heme interdomain electron transfer in nitric oxide synthases. J Inorg Biochem 2013; 130:130-40. [PMID: 24084585 DOI: 10.1016/j.jinorgbio.2013.09.005] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 08/12/2013] [Accepted: 09/05/2013] [Indexed: 11/25/2022]
Abstract
Nitric oxide synthase (NOS), a flavo-hemoprotein, is responsible for biosynthesis of nitric oxide (NO) in mammals. Three NOS isoforms, iNOS, eNOS and nNOS (inducible, endothelial, and neuronal NOS), achieve their biological functions by tight control of interdomain electron transfer (IET) process through interdomain interactions. In particular, the FMN-heme IET is essential in coupling electron transfer in the reductase domain with NO synthesis in the heme domain by delivery of electrons required for O2 activation at the catalytic heme site. Emerging evidence indicates that calmodulin (CaM) activates NO synthesis in eNOS and nNOS by a conformational change of the FMN domain from its shielded electron-accepting (input) state to a new electron-donating (output) state, and that CaM is also required for proper alignment of the FMN and heme domains in the three NOS isoforms. In the absence of a structure of full-length NOS, an integrated approach of spectroscopic, rapid kinetic and mutagenesis methods is required to unravel regulation mechanism of the FMN-heme IET process. This is to investigate the roles of the FMN domain motions and the docking between the primary functional FMN and heme domains in regulating NOS activity. The recent developments in this area that are driven by the combined approach are the focuses of this review. A better understanding of the roles of interdomain FMN/heme interactions and CaM binding may serve as a basis for the rational design of new selective modulators of the NOS enzymes.
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Affiliation(s)
- Changjian Feng
- Department of Pharmaceutical Sciences, University of New Mexico, Albuquerque, NM 87131, USA.
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29
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Han YT, Yang SM, Wang XY, Li FN. Design, synthesis and biological evaluation of B-region modified diarylalkyl amide analogues as novel TRPV1 antagonists. Arch Pharm Res 2013; 37:440-51. [PMID: 23943439 DOI: 10.1007/s12272-013-0228-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Accepted: 07/26/2013] [Indexed: 11/29/2022]
Abstract
Design, synthesis and biological evaluation of B-region, known to be a dipolar interacting pharmacophore, modified diarylalkyl amide analogues for novel TRPV1 (transient receptor potential channel, vanilloid subfamily member 1) antagonists was described. A variety of moieties including guanidines, heterocyclic rings, cinnamides, and α-substituted acetamides were introduced at the B-region. TRPV1 antagonistic activities of these analogues were evaluated by (45)Ca(2+) uptake assay in rat DRG neuron. In particular, α,α-difluoroamide 53 exhibited 3-fold more potent TRPV1 antagonistic activity (IC50 = 0.058 μM) than the parent amide analogue 6.
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Affiliation(s)
- Young Taek Han
- College of Pharmacy, Woosuk University, Wanju, 565-701, Republic of Korea
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30
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In search of potent and selective inhibitors of neuronal nitric oxide synthase with more simple structures. Bioorg Med Chem 2013; 21:5323-31. [PMID: 23867386 DOI: 10.1016/j.bmc.2013.06.014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2013] [Revised: 05/30/2013] [Accepted: 06/06/2013] [Indexed: 11/24/2022]
Abstract
In certain neurodegenerative diseases damaging levels of nitric oxide (NO) are produced by neuronal nitric oxide synthase (nNOS). It, therefore, is important to develop inhibitors selective for nNOS that do not interfere with other NOS isoforms, especially endothelial NOS (eNOS), which is critical for proper functioning of the cardiovascular system. While we have been successful in developing potent and isoform-selective inhibitors, such as lead compounds 1 and 2, the ease of synthesis and bioavailability have been problematic. Here we describe a new series of compounds including crystal structures of NOS-inhibitor complexes that integrate the advantages of easy synthesis and good biological properties compared to the lead compounds. These results provide the basis for additional structure-activity relationship (SAR) studies to guide further improvement of isozyme selective inhibitors.
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Padayachee ER, Whiteley CG. Interaction of glycine zipper fragments of Aβ-peptides with neuronal nitric oxide synthase: kinetic, thermodynamic and spectrofluorimetric analysis. Neuropeptides 2013; 47:171-8. [PMID: 23375441 DOI: 10.1016/j.npep.2012.12.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 11/13/2012] [Accepted: 12/24/2012] [Indexed: 01/05/2023]
Abstract
Five peptide fragments [Aβ(17-21); Aβ(25-29); Aβ(29-33); Aβ(33-37); Aβ(25-37)] of the toxic Aβ(1-40(42)) amyloid peptide were shown to bind with neuronal nitric oxide synthase by means of hydrophobic-hydrophobic forces. The enzyme has a single site for the amyloid peptide binding, which resulted in a quenching of the intrinsic fluorescence of the enzyme. Binding constants determined from Stern-Volmer analysis were between 9×10(-3) and 1.8×10(-2) μM(-1). As temperature increased these binding constants increased reflecting that the interaction of the amyloid peptides with nNOS was endothermic and the quenching was dynamic. Kinetic analysis revealed a non-competitive interaction of the amyloid peptides to the enzyme with inhibitor constants of 5.1 μM for Aβ(17-21) to about 8-12 μM for the other peptides. According to the van't Hoff relationship the thermodynamic parameters, ΔH, ΔS and ΔG for the interaction of the amyloid peptides were all positive and between 41.28 and 77.86 kJ mol(-1)K(-1), 104.92 and 220.82 J mol(-1)K(-1) and 9.92 and 13.13 kJ mol(-1)K(-1), respectively. This suggested that the transition state, created by the amyloid peptide-nNOS complex and generated during the initial stages of Aβ aggregation had to, initially, overcome an activation barrier. Since the ΔG values decreased as temperature increased it not only implied a non-spontaneous interaction but that hydrophobic forces were operative during the binding. By FRET analysis the distance between the donor enzyme and the acceptor amyloid peptide was between 2.7 and 2.8 nm. As the temperature increased from 298 K through 313 K (and higher) the fraction of these tryptophan residues that became exposed increased, to approach a value of 1. There was strong support for the initial interaction being through the glycine zipper regions of Aβ(25-37).
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Affiliation(s)
- E R Padayachee
- Department of Biochemistry, Microbiology and Biotechnology, Rhodes University, Grahamstown, South Africa
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Jansen Labby K, Li H, Roman LJ, Martásek P, Poulos TL, Silverman RB. Methylated N(ω)-hydroxy-L-arginine analogues as mechanistic probes for the second step of the nitric oxide synthase-catalyzed reaction. Biochemistry 2013; 52:3062-73. [PMID: 23586781 DOI: 10.1021/bi301571v] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Nitric oxide synthase (NOS) catalyzes the conversion of L-arginine to L-citrulline through the intermediate N(ω)-hydroxy-L-arginine (NHA), producing nitric oxide, an important mammalian signaling molecule. Several disease states are associated with improper regulation of nitric oxide production, making NOS a therapeutic target. The first step of the NOS reaction has been well-characterized and is presumed to proceed through a compound I heme species, analogous to the cytochrome P450 mechanism. The second step, however, is enzymatically unprecedented and is thought to occur via a ferric peroxo heme species. To gain insight into the details of this unique second step, we report here the synthesis of NHA analogues bearing guanidinium methyl or ethyl substitutions and their investigation as either inhibitors of or alternate substrates for NOS. Radiolabeling studies reveal that N(ω)-methoxy-L-arginine, an alternative NOS substrate, produces citrulline, nitric oxide, and methanol. On the basis of these results, we propose a mechanism for the second step of NOS catalysis in which a methylated nitric oxide species is released and is further metabolized by NOS. Crystal structures of our NHA analogues bound to nNOS have been determined, revealing the presence of an active site water molecule only in the presence of singly methylated analogues. Bulkier analogues displace this active site water molecule; a different mechanism is proposed in the absence of the water molecule. Our results provide new insights into the steric and stereochemical tolerance of the NOS active site and substrate capabilities of NOS.
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Affiliation(s)
- Kristin Jansen Labby
- Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
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Li W, Chen L, Lu C, Elmore BO, Astashkin AV, Rousseau DL, Yeh SR, Feng C. Regulatory role of Glu546 in flavin mononucleotide-heme electron transfer in human inducible nitric oxide synthase. Inorg Chem 2013; 52:4795-801. [PMID: 23570607 DOI: 10.1021/ic3020892] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Nitric oxide (NO) production by mammalian NO synthase (NOS) is believed to be regulated by the docking of the flavin mononucleotide (FMN) domain in one subunit of the dimer onto the heme domain of the adjacent subunit. Glu546, a conserved charged surface residue of the FMN domain in human inducible NOS (iNOS), is proposed to participate in the interdomain FMN/heme interactions [Sempombe et al. Inorg. Chem.2011, 50, 6869-6861]. In the present work, we further investigated the role of the E546 residue in the FMN-heme interdomain electron transfer (IET), a catalytically essential step in the NOS enzymes. Laser flash photolysis was employed to directly measure the FMN-heme IET kinetics for the E546N mutant of human iNOS oxygenase/FMN (oxyFMN) construct. The temperature dependence of the IET kinetics was also measured over the temperature range of 283-304 K to determine changes in the IET activation parameters. The E546N mutation was found to retard the IET by significantly raising the activation entropic barrier. Moreover, pulsed electron paramagnetic resonance data showed that the geometry of the docked FMN/heme complex in the mutant is basically the same as in the wild type construct, whereas the probability of formation of such a complex is about twice lower. These results indicate that the retarded IET in the E546N mutant is not caused by an altered conformation of the docked FMN/heme complex, but by a lower population of the IET-active conformation. In addition, the negative activation entropy of the mutant is still substantially lower than that of the holoenzyme. This supports a mechanism by which the FMN domain can modify the IET through altering probability of the docked state formation.
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Affiliation(s)
- Wenbing Li
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, New Mexico 87131, United States
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Huang H, Li H, Martásek P, Roman LJ, Poulos TL, Silverman RB. Structure-guided design of selective inhibitors of neuronal nitric oxide synthase. J Med Chem 2013; 56:3024-32. [PMID: 23451760 DOI: 10.1021/jm4000984] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Nitric oxide synthases (NOSs) comprise three closely related isoforms that catalyze the oxidation of L-arginine to L-citrulline and the important second messenger nitric oxide (NO). Pharmacological selective inhibition of neuronal NOS (nNOS) has the potential to be therapeutically beneficial in various neurodegenerative diseases. Here, we present a structure-guided, selective nNOS inhibitor design based on the crystal structure of lead compound 1 in nNOS. The best inhibitor, 7, exhibited low nanomolar inhibitory potency and good isoform selectivities (nNOS over eNOS and iNOS are 472-fold and 239-fold, respectively). Consistent with the good selectivity, 7 binds to nNOS and eNOS with different binding modes. The distinctly different binding modes of 7, driven by the critical residue Asp597 in nNOS, offers compelling insight to explain its isozyme selectivity, which should guide future drug design programs.
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Affiliation(s)
- He Huang
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, United States
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Santo RDDE, Simas RC, Magalhães A, Santos VGD, Regiani T, Isler AC, Martins NG, Eberlin MN, González ERP. Experimental NMR and MS study of benzoylguanidines. Investigation ofE/Zisomerism. J PHYS ORG CHEM 2013. [DOI: 10.1002/poc.3088] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Affiliation(s)
| | - Rosineide Costa Simas
- Laboratório ThoMSon de Espectrometria de Massas; Instituto de Química, Universidade de Campinas (UNICAMP); Campinas; 13083-970; São Paulo; Brazil
| | | | - Vanessa Gonçalves dos Santos
- Laboratório ThoMSon de Espectrometria de Massas; Instituto de Química, Universidade de Campinas (UNICAMP); Campinas; 13083-970; São Paulo; Brazil
| | - Thais Regiani
- Laboratório ThoMSon de Espectrometria de Massas; Instituto de Química, Universidade de Campinas (UNICAMP); Campinas; 13083-970; São Paulo; Brazil
| | | | - Natiza Graziele Martins
- Laboratório de Química Orgânica Fina, Departamento de Física, Química e Biologia, Faculdade de Ciências e Tecnologia; Universidade Estadual Paulista (UNESP), Campus de Presidente Prudente; 19060-900; São Paulo; Brazil
| | - Marcos Nogueira Eberlin
- Laboratório ThoMSon de Espectrometria de Massas; Instituto de Química, Universidade de Campinas (UNICAMP); Campinas; 13083-970; São Paulo; Brazil
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Bruce King S. Potential biological chemistry of hydrogen sulfide (H2S) with the nitrogen oxides. Free Radic Biol Med 2013; 55:1-7. [PMID: 23165065 PMCID: PMC3798156 DOI: 10.1016/j.freeradbiomed.2012.11.005] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Revised: 10/24/2012] [Accepted: 11/08/2012] [Indexed: 12/14/2022]
Abstract
Hydrogen sulfide, an important gaseous signaling agent generated in numerous biological tissues, influences many physiological processes. This biological profile seems reminiscent of nitric oxide, another important endogenously synthesized gaseous signaling molecule. Hydrogen sulfide reacts with nitric oxide or oxidized forms of nitric oxide and nitric oxide donors in vitro to form species that display distinct biology compared to both hydrogen sulfide and NO. The products of these interesting reactions may include small-molecule S-nitrosothiols or nitroxyl, the one-electron-reduced form of nitric oxide. In addition, thionitrous acid or thionitrite, compounds structurally analogous to nitrous acid and nitrite, may constitute a portion of the reaction products. Both the chemistry and the biology of thionitrous acid and thionitrite, compared to nitric oxide or hydrogen sulfide, remain poorly defined. General mechanisms for the formation of S-nitrosothiols, nitroxyl, and thionitrous acid based upon the ability of hydrogen sulfide to act as a nucleophile and a reducing agent with reactive nitric oxide-based intermediates are proposed. Hydrogen sulfide reactivity seems extensive and could have an impact on numerous areas of redox-controlled biology and chemistry, warranting more work in this exciting and developing area.
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Affiliation(s)
- S Bruce King
- Department of Chemistry, Wake Forest University, Winston-Salem, NC 27109, USA.
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37
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Kaplánek R, Martásek P, Grüner B, Panda S, Rak J, Masters BSS, Král V, Roman LJ. Nitric oxide synthases activation and inhibition by metallacarborane-cluster-based isoform-specific affectors. J Med Chem 2012; 55:9541-8. [PMID: 23075390 DOI: 10.1021/jm300805x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A small library of boron-cluster- and metallacarborane-cluster-based ligands was designed, prepared, and tested for isoform-selective activation or inhibition of the three nitric oxide synthase isoforms. On the basis of the concept of creating a hydrophobic analogue of a natural substrate, a stable and nontoxic basic boron cluster system, previously used for boron neutron capture therapy, was modified by the addition of positively charged moieties to its periphery, providing hydrophobic and nonclassical hydrogen bonding interactions with the protein. Several of these compounds show efficacy for inhibition of NO synthesis with differential effects on the various nitric oxide synthase isoforms.
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Affiliation(s)
- Robert Kaplánek
- Department of Analytical Chemistry, Institute of Chemical Technology in Prague, Technická 5, 166 28 Prague 6, Czech Republic
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38
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Huang H, Ji H, Li H, Jing Q, Labby KJ, Martásek P, Roman LJ, Poulos TL, Silverman RB. Selective monocationic inhibitors of neuronal nitric oxide synthase. Binding mode insights from molecular dynamics simulations. J Am Chem Soc 2012; 134:11559-72. [PMID: 22731813 DOI: 10.1021/ja302269r] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
The reduction of pathophysiologic levels of nitric oxide through inhibition of neuronal nitric oxide synthase (nNOS) has the potential to be therapeutically beneficial in various neurodegenerative diseases. We have developed a series of pyrrolidine-based nNOS inhibitors that exhibit excellent potencies and isoform selectivities (J. Am. Chem. Soc. 2010, 132, 5437). However, there are still important challenges, such as how to decrease the multiple positive charges derived from basic amino groups, which contribute to poor bioavailability, without losing potency and/or selectivity. Here we present an interdisciplinary study combining molecular docking, crystallography, molecular dynamics simulations, synthesis, and enzymology to explore potential pharmacophoric features of nNOS inhibitors and to design potent and selective monocationic nNOS inhibitors. The simulation results indicate that different hydrogen bond patterns, electrostatic interactions, hydrophobic interactions, and a water molecule bridge are key factors for stabilizing ligands and controlling ligand orientation. We find that a heteroatom in the aromatic head or linker chain of the ligand provides additional stability and blocks the substrate binding pocket. Finally, the computational insights are experimentally validated with double-headed pyridine analogues. The compounds reported here are among the most potent and selective monocationic pyrrolidine-based nNOS inhibitors reported to date, and 10 shows improved membrane permeability.
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Affiliation(s)
- He Huang
- Department of Chemistry, Chemistry of Life Processes Institute, amd Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208-3113, USA
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Astashkin AV, Elmore BO, Chen L, Fan W, Guillemette JG, Feng C. Pulsed ENDOR determination of the arginine location in the ferrous-NO form of neuronal NOS. J Phys Chem A 2012; 116:6731-9. [PMID: 22667467 DOI: 10.1021/jp302319c] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Mammalian nitric oxide synthases (NOSs) are enzymes responsible for oxidation of L-arginine (L-Arg) to nitric oxide (NO). Mechanisms of reactions at the catalytic heme site are not well understood, and it is of current interest to study structures of the heme species that activates O(2) and transforms the substrate. The NOS ferrous-NO complex is a close mimic of the obligatory ferric (hydro)peroxo intermediate in NOS catalysis. In this work, pulsed electron-nuclear double resonance (ENDOR) was used to probe the position of the l-Arg substrate at the NO(•)-coordinated ferrous heme center(s) in the oxygenase domain of rat neuronal NOS (nNOS). The analysis of (2)H and (15)N ENDOR spectra of samples containing d(7)- or guanidino-(15)N(2) labeled L-Arg has resulted in distance estimates for the nearby guanidino nitrogen and the nearby proton (deuteron) at C(δ). The L-Arg position was found to be noticeably different from that in the X-ray crystal structure of nNOS ferrous-NO complex [Li et al. J. Biol. Inorg. Chem.2006, 11, 753-768], with the nearby guanidino nitrogen being ~0.5 Å closer to, and the nearby H(δ) about 1 Å further from, the NO ligand than in the X-ray structure. The difference might be related to the structural constraints imposed on the protein by the crystal. Importantly, in spite of its closer position, the guanidino nitrogen does not form a hydrogen bond with the NO ligand, as evidenced by the absence of significant isotropic hfi constant for N(g1). This is consistent with the previous reports that it is not the L-Arg substrate itself that would most likely serve as a direct proton donor to the diatomic ligands (NO and O(2)) bound to the heme.
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Affiliation(s)
- Andrei V Astashkin
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, USA
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Oxygen activation in neuronal NO synthase: resolving the consecutive mono-oxygenation steps. Biochem J 2012; 443:505-14. [PMID: 22300432 DOI: 10.1042/bj20111644] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The vital signalling molecule NO is produced by mammalian NOS (nitric oxide synthase) enzymes in two steps. L-arginine is converted into NOHA (Nω-hydroxy-L-arginine), which is converted into NO and citrulline. Both steps are thought to proceed via similar mechanisms in which the cofactor BH4 (tetrahydrobiopterin) activates dioxygen at the haem site by electron transfer. The subsequent events are poorly understood due to the lack of stable intermediates. By analogy with cytochrome P450, a haem-iron oxo species may be formed, or direct reaction between a haem-peroxy intermediate and substrate may occur. The two steps may also occur via different mechanisms. In the present paper we analyse the two reaction steps using the G586S mutant of nNOS (neuronal NOS), which introduces an additional hydrogen bond in the active site and provides an additional proton source. In the mutant enzyme, BH4 activates dioxygen as in the wild-type enzyme, but an interesting intermediate haem species is then observed. This may be a stabilized form of the active oxygenating species. The mutant is able to perform step 2 (reaction with NOHA), but not step 1 (with L-arginine) indicating that the extra hydrogen bond enables it to discriminate between the two mono-oxygenation steps. This implies that the two steps follow different chemical mechanisms.
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41
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Sheng C, Zhang W. Fragment Informatics and Computational Fragment-Based Drug Design: An Overview and Update. Med Res Rev 2012; 33:554-98. [DOI: 10.1002/med.21255] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Affiliation(s)
- Chunquan Sheng
- Department of Medicinal Chemistry; School of Pharmacy; Second Military Medical University; 325 Guohe Road Shanghai 200433 People's Republic of China
| | - Wannian Zhang
- Department of Medicinal Chemistry; School of Pharmacy; Second Military Medical University; 325 Guohe Road Shanghai 200433 People's Republic of China
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Li W, Fan W, Chen L, Elmore BO, Piazza M, Guillemette JG, Feng C. Role of an isoform-specific serine residue in FMN-heme electron transfer in inducible nitric oxide synthase. J Biol Inorg Chem 2012; 17:675-85. [PMID: 22407542 DOI: 10.1007/s00775-012-0887-y] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 02/26/2012] [Indexed: 01/30/2023]
Abstract
In the crystal structure of a calmodulin (CaM)-bound FMN domain of human inducible nitric oxide synthase (NOS), the CaM-binding region together with CaM forms a hinge, and pivots on an R536(NOS)/E47(CaM) pair (Xia et al. J Biol Chem 284:30708-30717, 2009). Notably, isoform-specific human inducible NOS S562 and C563 residues form hydrogen bonds with the R536 residue through their backbone oxygens. In this study, we investigated the roles of the S562 and C563 residues in the NOS FMN-heme interdomain electron transfer (IET), the rates of which can be used to probe the interdomain FMN/heme alignment. Human inducible NOS S562K and C563R mutants of an oxygenase/FMN (oxyFMN) construct were made by introducing charged residues at these sites as found in human neuronal NOS and endothelial NOS isoforms, respectively. The IET rate constant of the S562K mutant is notably decreased by one third, and its flavin fluorescence intensity per micromole per liter is diminished by approximately 24 %. These results suggest that a positive charge at position 562 destabilizes the hydrogen-bond-mediated NOS/CaM alignment, resulting in slower FMN-heme IET in the mutant. On the other hand, the IET rate constant of the C563R mutant is similar to that of the wild-type, indicating that the mutational effect is site-specific. Moreover, the human inducible NOS oxyFMN R536E mutant was constructed to disrupt the bridging CaM/NOS interaction, and its FMN-heme IET rate was decreased by 96 %. These results demonstrated a new role of the isoform-specific serine residue of the key CaM/FMN(NOS) bridging site in regulating the FMN-heme IET (possibly by tuning the alignment of the FMN and heme domains).
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Affiliation(s)
- Wenbing Li
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM 87131, USA
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43
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Labby KJ, Xue F, Kraus JM, Ji H, Mataka J, Li H, Martásek P, Roman LJ, Poulos TL, Silverman RB. Intramolecular hydrogen bonding: a potential strategy for more bioavailable inhibitors of neuronal nitric oxide synthase. Bioorg Med Chem 2012; 20:2435-43. [PMID: 22370337 DOI: 10.1016/j.bmc.2012.01.037] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Revised: 01/18/2012] [Accepted: 01/22/2012] [Indexed: 11/15/2022]
Abstract
Selective neuronal nitric oxide synthase (nNOS) inhibitors have therapeutic applications in the treatment of numerous neurodegenerative diseases. Here we report the synthesis and evaluation of a series of inhibitors designed to have increased cell membrane permeability via intramolecular hydrogen bonding. Their potencies were examined in both purified enzyme and cell-based assays; a comparison of these results demonstrates that two of the new inhibitors display significantly increased membrane permeability over previous analogs. NMR spectroscopy provides evidence of intramolecular hydrogen bonding under physiological conditions in two of the inhibitors. Crystal structures of the inhibitors in the nNOS active site confirm the predicted non-intramolecular hydrogen bonded binding mode. Intramolecular hydrogen bonding may be an effective approach for increasing cell membrane permeability without affecting target protein binding.
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Affiliation(s)
- Kristin Jansen Labby
- Department of Chemistry, Department of Molecular Biosciences, Chemistry of Life Processes Institute, Center for Molecular Innovation and Drug Discovery, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208-3113, USA
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Feng C. Mechanism of Nitric Oxide Synthase Regulation: Electron Transfer and Interdomain Interactions. Coord Chem Rev 2012; 256:393-411. [PMID: 22523434 PMCID: PMC3328867 DOI: 10.1016/j.ccr.2011.10.011] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Nitric oxide synthase (NOS), a flavo-hemoprotein, tightly regulates nitric oxide (NO) synthesis and thereby its dual biological activities as a key signaling molecule for vasodilatation and neurotransmission at low concentrations, and also as a defensive cytotoxin at higher concentrations. Three NOS isoforms, iNOS, eNOS and nNOS (inducible, endothelial, and neuronal NOS), achieve their key biological functions by tight regulation of interdomain electron transfer (IET) process via interdomain interactions. In particular, the FMN-heme IET is essential in coupling electron transfer in the reductase domain with NO synthesis in the heme domain by delivery of electrons required for O(2) activation at the catalytic heme site. Compelling evidence indicates that calmodulin (CaM) activates NO synthesis in eNOS and nNOS through a conformational change of the FMN domain from its shielded electron-accepting (input) state to a new electron-donating (output) state, and that CaM is also required for proper alignment of the domains. Another exciting recent development in NOS enzymology is the discovery of importance of the the FMN domain motions in modulating reactivity and structure of the catalytic heme active site (in addition to the primary role of controlling the IET processes). In the absence of a structure of full-length NOS, an integrated approach of spectroscopic (e.g. pulsed EPR, MCD, resonance Raman), rapid kinetics (laser flash photolysis and stopped flow) and mutagenesis methods is critical to unravel the molecular details of the interdomain FMN/heme interactions. This is to investigate the roles of dynamic conformational changes of the FMN domain and the docking between the primary functional FMN and heme domains in regulating NOS activity. The recent developments in understanding of mechanisms of the NOS regulation that are driven by the combined approach are the focuses of this review. An improved understanding of the role of interdomain FMN/heme interaction and CaM binding may serve as the basis for the design of new selective inhibitors of NOS isoforms.
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Affiliation(s)
- Changjian Feng
- Department of Pharmaceutical Sciences, University of New Mexico, Albuquerque, NM 87131 (USA) , Tel: 505-925-4326
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45
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Mansuy D, Mathieu D, Battioni P, Boucher JL. Reactions between iron porphyrins and tetrahydropterins. J PORPHYR PHTHALOCYA 2012. [DOI: 10.1142/s1088424604000258] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Data from the last few years have revealed a novel biological role of the tetrahydrobiopterin ( H 4 B ) cofactor, in one-electron transfers to the heme of the active site of NO-synthases (NOSs) with intermediate formation of a H 4 B -derived radical. These electron transfers play a key role in the catalytic cycles of the two steps catalyzed by NOS, the N ω-hydroxylation of L-arginine, and the three-electron oxidation of N ω-hydroxyarginine to L-citrulline and NO. Recent experiments performed between various tetrahydropterins and iron porphyrins have shown that the one-electron transfer from tetrahydropterins, such as the natural cofactors H 4 B and tetrahydrofolate or the synthetic 6,7-dimethyltetrahydropterin (diMeH4P), to Fe(III) porphyrins of sufficiently high redox potentials (> about -100 mV versus NHE for the Fe(III)/Fe(II) couple) is a very general reaction that occurs with formation of a tetrahydropterin-derived radical. Reaction of diMeH4P with a stable porphyrin Fe(II)-O 2 complex leads to a diMeH4P-derived radical and a transient Fe(III)-OOH complex, mimicking the reaction between H 4 B and heme Fe(II)-O 2 in the NOS catalytic cycle. Tetrahydropterins such as diMeH4P also reduce hemeproteins Fe(III) of sufficiently high redox potentials, such as cytochromes c and b5 or metmyoglobin, to the corresponding hemeproteins Fe(II) .
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Affiliation(s)
- Daniel Mansuy
- Université Paris 5, UMR 8601, 45 rue des Saints-Pères, 75270 Paris Cedex 06, France
| | - Delphine Mathieu
- Université Paris 5, UMR 8601, 45 rue des Saints-Pères, 75270 Paris Cedex 06, France
| | - Pierrette Battioni
- Université Paris 5, UMR 8601, 45 rue des Saints-Pères, 75270 Paris Cedex 06, France
| | - Jean-Luc Boucher
- Université Paris 5, UMR 8601, 45 rue des Saints-Pères, 75270 Paris Cedex 06, France
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Salard-Arnaud I, Stuehr D, Boucher JL, Mansuy D. Spectroscopic, catalytic and binding properties of Bacillus subtilis NO synthase-like protein: comparison with other bacterial and mammalian NO synthases. J Inorg Biochem 2012; 106:164-71. [PMID: 22119809 DOI: 10.1016/j.jinorgbio.2011.10.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2011] [Revised: 09/08/2011] [Accepted: 10/03/2011] [Indexed: 11/28/2022]
Abstract
Genome sequencing has shown the presence of genes coding for NO-synthase (NOS)-like proteins in bacteria. The roles and properties of these proteins remain unclear. UV-visible spectroscopy was used to characterize the recombinant NOS-like protein from Bacillus subtilis (bsNOS) in its ferric and ferrous states in the presence of various Fe(III)- and Fe(II)-heme-ligands and of a series of L-arginine (L-arg) analogs. BsNOS exhibited several spectroscopic and binding properties in common with Bacillus anthracis NOS (baNOS) that were clearly different from those of tetrahydrobiopterin (H4B)-free mammalian NOS oxygenase domains (mNOS(oxys)) and of Staphylococcus aureus NOS (saNOS). Interestingly, bsNOS and baNOS that do not contain H4B exhibited properties much closer to those of H4B-containing mNOS(oxys). Moreover, bsNOS was found to efficiently catalyze the oxidation of L-arginine into L-citrulline by H(2)O(2), whereas H4B-free mNOS(oxys) exhibited low activities for this reaction.
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Affiliation(s)
- Isabelle Salard-Arnaud
- Laboratoire de Chimie et Biochimie Pharmacologiques et Toxicologiques, Université Paris Descartes, UMR 8601 CNRS, Paris, France
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Maddaford SP. A medicinal chemistry perspective on structure-based drug design and development. Methods Mol Biol 2012; 841:351-381. [PMID: 22222460 DOI: 10.1007/978-1-61779-520-6_15] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The application of X-ray crystallography and molecular modeling can provide valuable insight into the optimization of the molecular interactions of a drug-protein complex to achieve potency and selectivity of a drug candidate. For the successful application of SBDD in a drug development program, the impact of these structural modifications required to improve potency and selectivity must be considered in the context of balancing of a multitude of drug properties and other considerations that include solubility, bioavailability, metabolism, distribution, toxicology, chemical stability, and intellectual property space. The utility of structure-based design from the medicinal chemist's perspective is described in this chapter.
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Watanabe M, Yamaguchi K, Tang W, Yoshida K, Silverman RB, Arisawa M, Shuto S. Synthesis of a series of 3,4-methanoarginines as side-chain conformationally restricted analogues of arginine. Bioorg Med Chem 2011; 19:5984-8. [DOI: 10.1016/j.bmc.2011.08.049] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Revised: 08/20/2011] [Accepted: 08/22/2011] [Indexed: 12/21/2022]
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Astashkin AV, Fan W, Elmore BO, Guillemette JG, Feng C. Pulsed ENDOR determination of relative orientation of g-frame and molecular frame of imidazole-coordinated heme center of iNOS. J Phys Chem A 2011; 115:10345-52. [PMID: 21834532 PMCID: PMC3174316 DOI: 10.1021/jp204969d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mammalian nitric oxide synthase (NOS) is a flavo-hemoprotein that catalyzes the oxidation of L-arginine to nitric oxide. Information about the relative alignment of the heme and FMN domains of NOS is important for understanding the electron transfer between the heme and FMN centers, but no crystal structure data for NOS holoenzyme are available. In our previous work [Astashkin, A. V.; Elmore, B. O.; Fan, W.; Guillemette, J. G.; Feng, C. J. Am. Chem. Soc. 2010, 132, 12059-12067], the distance between the imidazole-coordinated low-spin Fe(III) heme and FMN semiquinone in a human inducible NOS (iNOS) oxygenase/FMN construct has been determined by pulsed electron paramagnetic resonance (EPR). The orientation of the Fe-FMN radius vector, R(Fe-FMN), with respect to the heme g-frame was also determined. In the present study, pulsed electron-nuclear double resonance (ENDOR) investigation of the deuterons at carbons C2 and C5 in the deuterated coordinated imidazole was used to determine the relative orientation of the heme g-frame and molecular frame, from which R(Fe-FMN) can be referenced to the heme molecular frame. Numerical simulations of the ENDOR spectra showed that the g-factor axis corresponding to the low-field EPR turning point is perpendicular to the heme plane, whereas the axis corresponding to the high-field turning point is in the heme plane and makes an angle of about 80° with the coordinated imidazole plane. The FMN-heme domain docking model obtained in the previous work was found to be in qualitative agreement with the combined experimental results of the two pulsed EPR works.
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Affiliation(s)
- Andrei V. Astashkin
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ 85721, USA
| | - Weihong Fan
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM 87131, USA
| | - Bradley O. Elmore
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM 87131, USA
| | - J. Guy Guillemette
- Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
| | - Changjian Feng
- Department of Pharmaceutical Sciences, College of Pharmacy, University of New Mexico, Albuquerque, NM 87131, USA
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Maddaford S, Renton P, Speed J, Annedi SC, Ramnauth J, Rakhit S, Andrews J, Mladenova G, Majuta L, Porreca F. 1,6-Disubstituted indole derivatives as selective human neuronal nitric oxide synthase inhibitors. Bioorg Med Chem Lett 2011; 21:5234-8. [PMID: 21824773 PMCID: PMC5699210 DOI: 10.1016/j.bmcl.2011.07.042] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 07/08/2011] [Accepted: 07/11/2011] [Indexed: 10/17/2022]
Abstract
A series of 1,6-disubstituted indole derivatives was designed, synthesized and evaluated as inhibitors of human nitric oxide synthase (NOS). By varying the basic amine side chain at the 1-position of the indole ring, several potent and selective inhibitors of human neuronal NOS were identified. In general compounds with bulkier side chains displayed increased selectivity for nNOS over eNOS and iNOS isoforms. One of the compounds, (R)-8 was shown to reduce tactile hyperesthesia (allodynia) after oral administration (30 mg/kg) in an in vivo rat model of dural inflammation relevant to migraine pain.
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Affiliation(s)
- Shawn Maddaford
- NeurAxon Inc., 2395 Speakman Drive, Suite #1001, Mississauga, ON, Canada L5K 1B3
| | - Paul Renton
- NeurAxon Inc., 2395 Speakman Drive, Suite #1001, Mississauga, ON, Canada L5K 1B3
| | - Joanne Speed
- NeurAxon Inc., 2395 Speakman Drive, Suite #1001, Mississauga, ON, Canada L5K 1B3
| | - Subhash C. Annedi
- NeurAxon Inc., 2395 Speakman Drive, Suite #1001, Mississauga, ON, Canada L5K 1B3
| | - Jailall Ramnauth
- NeurAxon Inc., 2395 Speakman Drive, Suite #1001, Mississauga, ON, Canada L5K 1B3
| | - Suman Rakhit
- NeurAxon Inc., 2395 Speakman Drive, Suite #1001, Mississauga, ON, Canada L5K 1B3
| | - John Andrews
- NeurAxon Inc., 2395 Speakman Drive, Suite #1001, Mississauga, ON, Canada L5K 1B3
| | - Gabriela Mladenova
- NeurAxon Inc., 2395 Speakman Drive, Suite #1001, Mississauga, ON, Canada L5K 1B3
| | - Lisa Majuta
- Department of Pharmacology, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ, USA
| | - Frank Porreca
- Department of Pharmacology, University of Arizona, 1501 N. Campbell Ave., Tucson, AZ, USA
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