1
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Serafim MSM, Kronenberger T, Rocha REO, Rosa ADRA, Mello TLG, Poso A, Ferreira RS, Abrahão JS, Kroon EG, Mota BEF, Maltarollo VG. Aminopyrimidine Derivatives as Multiflavivirus Antiviral Compounds Identified from a Consensus Virtual Screening Approach. J Chem Inf Model 2024; 64:393-411. [PMID: 38194508 DOI: 10.1021/acs.jcim.3c01505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Around three billion people are at risk of infection by the dengue virus (DENV) and potentially other flaviviruses. Worldwide outbreaks of DENV, Zika virus (ZIKV), and yellow fever virus (YFV), the lack of antiviral drugs, and limitations on vaccine usage emphasize the need for novel antiviral research. Here, we propose a consensus virtual screening approach to discover potential protease inhibitors (NS3pro) against different flavivirus. We employed an in silico combination of a hologram quantitative structure-activity relationship (HQSAR) model and molecular docking on characterized binding sites followed by molecular dynamics (MD) simulations, which filtered a data set of 7.6 million compounds to 2,775 hits. Lastly, docking and MD simulations selected six final potential NS3pro inhibitors with stable interactions along the simulations. Five compounds had their antiviral activity confirmed against ZIKV, YFV, DENV-2, and DENV-3 (ranging from 4.21 ± 0.14 to 37.51 ± 0.8 μM), displaying aggregator characteristics for enzymatic inhibition against ZIKV NS3pro (ranging from 28 ± 7 to 70 ± 7 μM). Taken together, the compounds identified in this approach may contribute to the design of promising candidates to treat different flavivirus infections.
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Affiliation(s)
- Mateus Sá Magalhães Serafim
- Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG 31270-901, Brazil
| | - Thales Kronenberger
- Institute of Pharmacy, Pharmaceutical/Medicinal Chemistry and Tübingen Center for Academic Drug Discovery (TüCAD2), Eberhard Karls University Tübingen, Auf der Morgenstelle 8, Tübingen 72076, Germany
- Excellence Cluster "Controlling Microbes to Fight Infections" (CMFI), Tübingen 72076, Germany
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Kuopio 70211, Finland
| | - Rafael Eduardo Oliveira Rocha
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG 31270-901, Brazil
| | - Amanda Del Rio Abreu Rosa
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG 31270-901, Brazil
| | - Thaysa Lara Gonçalves Mello
- Departamento de Produtos Farmacêuticos, Faculdade de Farmácia, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG 31270-901, Brazil
| | - Antti Poso
- Institute of Pharmacy, Pharmaceutical/Medicinal Chemistry and Tübingen Center for Academic Drug Discovery (TüCAD2), Eberhard Karls University Tübingen, Auf der Morgenstelle 8, Tübingen 72076, Germany
- School of Pharmacy, Faculty of Health Sciences, University of Eastern Finland, Kuopio 70211, Finland
- Department of Medical Oncology and Pneumology, University Hospital of Tübingen, Tübingen 70211, Germany
| | - Rafaela Salgado Ferreira
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG 31270-901, Brazil
| | - Jonatas Santos Abrahão
- Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG 31270-901, Brazil
| | - Erna Geessien Kroon
- Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG 31270-901, Brazil
| | - Bruno Eduardo Fernandes Mota
- Departamento de Análises Clínicas e Toxicológicas, Faculdade de Farmácia, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG 31270-901, Brazil
| | - Vinícius Gonçalves Maltarollo
- Departamento de Produtos Farmacêuticos, Faculdade de Farmácia, Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG 31270-901, Brazil
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2
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Behnam MAM, Basché T, Klein CDP. 2,2'-Bithiophene as sensor tag for ligand-protein binding assays based on Förster resonance energy transfer. Anal Biochem 2023; 682:115335. [PMID: 37777080 DOI: 10.1016/j.ab.2023.115335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 08/15/2023] [Accepted: 09/27/2023] [Indexed: 10/02/2023]
Abstract
Ligand-protein binding assays based on intrinsic protein fluorescence are straightforward, inexpensive methods to study ligand-protein interactions. However, their applicability is limited to ligands that can interfere with protein emission. In this Note, we describe the applicability of 2,2'-bithiophene as a FRET-based sensor tag, that can be incorporated into high-affinity ligands to generate target-specific compounds able to quench protein fluorescence upon binding. The generated ligands were assessed in different assay designs. Considerations to account for possible sources of interference with the assay readout are addressed, besides interpretation of the obtained results.
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Affiliation(s)
- Mira A M Behnam
- Medicinal Chemistry, Institute of Pharmacy and Molecular Biotechnology IPMB, Heidelberg University, Im Neuenheimer Feld 364, 69120, Heidelberg, Germany
| | - Thomas Basché
- Department of Chemistry, Johannes Gutenberg-University, Mainz, Germany
| | - Christian D P Klein
- Medicinal Chemistry, Institute of Pharmacy and Molecular Biotechnology IPMB, Heidelberg University, Im Neuenheimer Feld 364, 69120, Heidelberg, Germany.
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3
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Voss S, Nitsche C. Targeting the protease of West Nile virus. RSC Med Chem 2021; 12:1262-1272. [PMID: 34458734 PMCID: PMC8372202 DOI: 10.1039/d1md00080b] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 05/17/2021] [Indexed: 01/04/2023] Open
Abstract
West Nile virus infections can cause severe neurological symptoms. During the last 25 years, cases have been reported in Asia, North America, Africa, Europe and Australia (Kunjin). No West Nile virus vaccines or specific antiviral therapies are available to date. Various viral proteins and host-cell factors have been evaluated as potential drug targets. The viral protease NS2B-NS3 is among the most promising viral targets. It releases viral proteins from a non-functional polyprotein precursor, making it a critical factor of viral replication. Despite strong efforts, no protease inhibitors have reached clinical trials yet. Substrate-derived peptidomimetics have facilitated structural elucidations of the active protease state, while alternative compounds with increased drug-likeness have recently expanded drug discovery efforts beyond the active site.
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Affiliation(s)
- Saan Voss
- Research School of Chemistry, Australian National University Canberra ACT 2601 Australia
| | - Christoph Nitsche
- Research School of Chemistry, Australian National University Canberra ACT 2601 Australia
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4
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Mechanisms of Action for Small Molecules Revealed by Structural Biology in Drug Discovery. Int J Mol Sci 2020; 21:ijms21155262. [PMID: 32722222 PMCID: PMC7432558 DOI: 10.3390/ijms21155262] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2020] [Revised: 07/08/2020] [Accepted: 07/20/2020] [Indexed: 12/26/2022] Open
Abstract
Small-molecule drugs are organic compounds affecting molecular pathways by targeting important proteins. These compounds have a low molecular weight, making them penetrate cells easily. Small-molecule drugs can be developed from leads derived from rational drug design or isolated from natural resources. A target-based drug discovery project usually includes target identification, target validation, hit identification, hit to lead and lead optimization. Understanding molecular interactions between small molecules and their targets is critical in drug discovery. Although many biophysical and biochemical methods are able to elucidate molecular interactions of small molecules with their targets, structural biology is the most powerful tool to determine the mechanisms of action for both targets and the developed compounds. Herein, we reviewed the application of structural biology to investigate binding modes of orthosteric and allosteric inhibitors. It is exemplified that structural biology provides a clear view of the binding modes of protease inhibitors and phosphatase inhibitors. We also demonstrate that structural biology provides insights into the function of a target and identifies a druggable site for rational drug design.
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5
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Pach S, Sarter TM, Yousef R, Schaller D, Bergemann S, Arkona C, Rademann J, Nitsche C, Wolber G. Catching a Moving Target: Comparative Modeling of Flaviviral NS2B-NS3 Reveals Small Molecule Zika Protease Inhibitors. ACS Med Chem Lett 2020; 11:514-520. [PMID: 32292558 DOI: 10.1021/acsmedchemlett.9b00629] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Accepted: 03/03/2020] [Indexed: 02/06/2023] Open
Abstract
The pivotal role of viral proteases in virus replication has already been successfully exploited in several antiviral drug design campaigns. However, no efficient antivirals are currently available against flaviviral infections. In this study, we present lead-like small molecule inhibitors of the Zika Virus (ZIKV) NS2B-NS3 protease. Since only few nonpeptide competitive ligands are known, we take advantage of the high structural similarity with the West Nile Virus (WNV) NS2B-NS3 protease. A comparative modeling approach involving our in-house software PyRod was employed to systematically analyze the binding sites and develop molecular dynamics-based 3D pharmacophores for virtual screening. The identified compounds were biochemically characterized revealing low micromolar affinity for both ZIKV and WNV proteases. Their lead-like properties together with rationalized binding modes represent valuable starting points for future lead optimization. Since the NS2B-NS3 protease is highly conserved among flaviviruses, these compounds may also drive the development of pan-flaviviral antiviral drugs.
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Affiliation(s)
- Szymon Pach
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Straße 2+4, Berlin 14195, Germany
| | - Tim M. Sarter
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Rafe Yousef
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Straße 2+4, Berlin 14195, Germany
| | - David Schaller
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Straße 2+4, Berlin 14195, Germany
| | - Silke Bergemann
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Straße 2+4, Berlin 14195, Germany
| | - Christoph Arkona
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Straße 2+4, Berlin 14195, Germany
| | - Jörg Rademann
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Straße 2+4, Berlin 14195, Germany
| | - Christoph Nitsche
- Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia
| | - Gerhard Wolber
- Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Straße 2+4, Berlin 14195, Germany
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6
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Insights into Structures and Dynamics of Flavivirus Proteases from NMR Studies. Int J Mol Sci 2020; 21:ijms21072527. [PMID: 32260545 PMCID: PMC7177695 DOI: 10.3390/ijms21072527] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2020] [Revised: 03/29/2020] [Accepted: 03/31/2020] [Indexed: 12/29/2022] Open
Abstract
Nuclear magnetic resonance (NMR) spectroscopy plays important roles in structural biology and drug discovery, as it is a powerful tool to understand protein structures, dynamics, and ligand binding under physiological conditions. The protease of flaviviruses is an attractive target for developing antivirals because it is essential for the maturation of viral proteins. High-resolution structures of the proteases in the absence and presence of ligands/inhibitors were determined using X-ray crystallography, providing structural information for rational drug design. Structural studies suggest that proteases from Dengue virus (DENV), West Nile virus (WNV), and Zika virus (ZIKV) exist in open and closed conformations. Solution NMR studies showed that the closed conformation is predominant in solution and should be utilized in structure-based drug design. Here, we reviewed solution NMR studies of the proteases from these viruses. The accumulated studies demonstrated that NMR spectroscopy provides additional information to understand conformational changes of these proteases in the absence and presence of substrates/inhibitors. In addition, NMR spectroscopy can be used for identifying fragment hits that can be further developed into potent protease inhibitors.
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7
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Marchand JR, Caflisch A. In silico fragment-based drug design with SEED. Eur J Med Chem 2018; 156:907-917. [PMID: 30064119 DOI: 10.1016/j.ejmech.2018.07.042] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 07/11/2018] [Accepted: 07/15/2018] [Indexed: 12/13/2022]
Abstract
We report on two fragment-based drug design protocols, SEED2XR and ALTA, which start by high-throughput docking. SEED2XR is a two-stage protocol for fragment-based drug design. The first stage is in silico and consists of the automatic docking of 103-104 fragments using SEED, which requires about 1 s per fragment. SEED is a docking software developed specifically for fragment docking and binding energy evaluation by a force field with implicit solvent. In the second stage of SEED2XR, the 10-102 fragments with the most favorable predicted binding energies are validated by protein X-ray crystallography. The recent applications of SEED2XR to bromodomains demonstrate that the whole SEED2XR protocol can be carried out in about a week of working time, with hit rates ranging from 10% to 40%. Information on fragment-target interactions generated by the SEED2XR protocol or directly from SEED docking has been used for the discovery of hundreds of hits. ALTA is a computational protocol for screening which identifies candidate ligands that preserve the interactions between the optimal SEED fragments and the protein target. Medicinal chemistry optimization of ligands predicted by ALTA has resulted in pre-clinical candidates for protein kinases and bromodomains. The high-throughput, very low cost, sustainability, and high hit rate of the SEED-based protocols, unreachable by purely experimental techniques, make them perfectly suitable for both academic and industrial drug discovery research.
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Affiliation(s)
- Jean-Rémy Marchand
- Department of Biochemistry, University of Zürich, CH-8057, Zürich, Switzerland
| | - Amedeo Caflisch
- Department of Biochemistry, University of Zürich, CH-8057, Zürich, Switzerland.
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8
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Abstract
The persistence of West Nile virus (WNV) infections throughout the USA since its inception in 1999 and its continuous spread throughout the globe calls for an urgent need of effective treatments and prevention measures. Although the licensing of several WNV vaccines for veterinary use provides a proof of concept, similar efforts on the development of an effective vaccine for humans remain still unsuccessful. Increased understanding of biology and pathogenesis of WNV together with recent technological advancements have raised hope that an effective WNV vaccine may be available in the near future. In addition, rapid progress in the structural and functional characterization of WNV and other flaviviral proteins have provided a solid base for the design and development of several classes of inhibitors as potential WNV therapeutics. Moreover, the therapeutic monoclonal antibodies demonstrate an excellent efficacy against WNV in animal models and represent a promising class of WNV therapeutics. However, there are some challenges as to the design and development of a safe and efficient WNV vaccine or therapeutic. In this chapter, we discuss the current approaches, progress, and challenges toward the development of WNV vaccines, therapeutic antibodies, and antiviral drugs.
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9
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STD-NMR experiments identify a structural motif with novel second-site activity against West Nile virus NS2B-NS3 protease. Antiviral Res 2017; 146:174-183. [PMID: 28927677 DOI: 10.1016/j.antiviral.2017.09.008] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2017] [Revised: 09/09/2017] [Accepted: 09/14/2017] [Indexed: 11/22/2022]
Abstract
West Nile virus (WNV) belongs to the genus Flavivirus of the family Flaviviridae. This mosquito-borne virus that is highly pathogenic to humans has been evolving into a global threat during the past two decades. Despite many efforts, neither antiviral drugs nor vaccines are available. The viral protease NS2B-NS3pro is essential for viral replication, and therefore it is considered a prime drug target. However, success in the development of specific NS2B-NS3pro inhibitors had been moderate so far. In the search for new structural motifs with binding affinity for NS2B-NS3pro, we have screened a fragment library, the Maybridge Ro5 library, employing saturation transfer difference (STD) NMR experiments as readout. About 30% of 429 fragments showed binding to NS2B-NS3pro. Subsequent STD-NMR competition experiments using the known active site fragment A as reporter ligand yielded 14 competitively binding fragments, and 22 fragments not competing with A. In a fluorophore-based protease assay, all of these fragments showed inhibition in the micromolar range. Interestingly, 10 of these 22 fragments showed a notable increase of STD intensities in the presence of compound A suggesting cooperative binding. The most promising non-competitive inhibitors 1 and 2 (IC50 ∼ 500 μM) share a structural motif that may guide the development of novel second-site (potentially allosteric) inhibitors of NS2B-NS3pro. To identify the matching protein binding site, chemical shift perturbation studies employing 1H,15N-TROSY-HSQC experiments with uniformly 2H,15N-labeled protease were performed in the presence of 1, and in the concomitant absence or presence of A. The data suggest that 1 interacts with Met 52* of NS2B, identifying a secondary site adjacent to the binding site of A. Therefore, our study paves the way for the synthesis of novel bidentate NS2B-NS3pro inhibitors.
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10
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Li Y, Kang C. Solution NMR Spectroscopy in Target-Based Drug Discovery. Molecules 2017; 22:E1399. [PMID: 28832542 PMCID: PMC6151424 DOI: 10.3390/molecules22091399] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Revised: 08/18/2017] [Accepted: 08/18/2017] [Indexed: 12/14/2022] Open
Abstract
Solution NMR spectroscopy is a powerful tool to study protein structures and dynamics under physiological conditions. This technique is particularly useful in target-based drug discovery projects as it provides protein-ligand binding information in solution. Accumulated studies have shown that NMR will play more and more important roles in multiple steps of the drug discovery process. In a fragment-based drug discovery process, ligand-observed and protein-observed NMR spectroscopy can be applied to screen fragments with low binding affinities. The screened fragments can be further optimized into drug-like molecules. In combination with other biophysical techniques, NMR will guide structure-based drug discovery. In this review, we describe the possible roles of NMR spectroscopy in drug discovery. We also illustrate the challenges encountered in the drug discovery process. We include several examples demonstrating the roles of NMR in target-based drug discoveries such as hit identification, ranking ligand binding affinities, and mapping the ligand binding site. We also speculate the possible roles of NMR in target engagement based on recent processes in in-cell NMR spectroscopy.
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Affiliation(s)
- Yan Li
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), 31 Biopolis Way, Nanos, #03-01, Singapore 138669, Singapore.
| | - Congbao Kang
- Experimental Therapeutics Centre, Agency for Science, Technology and Research (A*STAR), 31 Biopolis Way, Nanos, #03-01, Singapore 138669, Singapore.
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11
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Li Y, Phoo WW, Loh YR, Zhang Z, Ng EY, Wang W, Keller TH, Luo D, Kang C. Structural characterization of the linked NS2B-NS3 protease of Zika virus. FEBS Lett 2017; 591:2338-2347. [PMID: 28675775 DOI: 10.1002/1873-3468.12741] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 06/16/2017] [Accepted: 06/29/2017] [Indexed: 01/23/2023]
Abstract
The Zika virus (ZIKV) NS2B-NS3 protease is an important drug target. The conventional flaviviral protease constructs used for structural studies contain the NS2B cofactor region linked to the NS3 protease domain via a glycine-rich flexible linker. Here, we examined the structural dynamics of this conventional Zika protease (gZiPro) using NMR spectroscopy. Although the glycine-rich linker in gZiPro does not alter the overall folding of the protease in solution, gZiPro is not homogenous in ion exchange chromatography. Compared to the unlinked protease construct, the artificial linker affects the chemical environment of many residues including H51 in the catalytic triad. Our study provides a direct comparison of ZIKV protease constructs with and without an artificial linker.
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Affiliation(s)
- Yan Li
- Experimental Therapeutics Centre Agency for Science Technology and Research (A*STAR), Singapore, Singapore
| | - Wint Wint Phoo
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore.,School of Biological Sciences, Nanyang Technological University, Singapore, Singapore
| | - Ying Ru Loh
- Experimental Therapeutics Centre Agency for Science Technology and Research (A*STAR), Singapore, Singapore
| | - Zhenzhen Zhang
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore
| | - Elizabeth Yihui Ng
- Experimental Therapeutics Centre Agency for Science Technology and Research (A*STAR), Singapore, Singapore
| | - Weiling Wang
- Experimental Therapeutics Centre Agency for Science Technology and Research (A*STAR), Singapore, Singapore
| | - Thomas H Keller
- Experimental Therapeutics Centre Agency for Science Technology and Research (A*STAR), Singapore, Singapore
| | - Dahai Luo
- Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore.,NTU Institute of Structural Biology, Nanyang Technological University, Singapore, Singapore
| | - CongBao Kang
- Experimental Therapeutics Centre Agency for Science Technology and Research (A*STAR), Singapore, Singapore
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12
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Marasini BP, Rahim F, Perveen S, Karim A, Mohammed Khan K, Atta-ur-Rahman, Choudhary MI. Synthesis, structure-activity relationships studies of benzoxazinone derivatives as α -chymotrypsin inhibitors. Bioorg Chem 2017; 70:210-221. [DOI: 10.1016/j.bioorg.2017.01.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Revised: 12/20/2016] [Accepted: 01/03/2017] [Indexed: 01/29/2023]
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13
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Li Y, Li Q, Wong YL, Liew LSY, Kang C. Membrane topology of NS2B of dengue virus revealed by NMR spectroscopy. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:2244-52. [DOI: 10.1016/j.bbamem.2015.06.010] [Citation(s) in RCA: 50] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 05/20/2015] [Accepted: 06/09/2015] [Indexed: 12/27/2022]
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14
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Yotmanee P, Rungrotmongkol T, Wichapong K, Choi SB, Wahab HA, Kungwan N, Hannongbua S. Binding specificity of polypeptide substrates in NS2B/NS3pro serine protease of dengue virus type 2: A molecular dynamics Study. J Mol Graph Model 2015; 60:24-33. [PMID: 26086900 DOI: 10.1016/j.jmgm.2015.05.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 05/14/2015] [Accepted: 05/15/2015] [Indexed: 02/05/2023]
Abstract
The pathogenic dengue virus (DV) is a growing global threat, particularly in South East Asia, for which there is no specific treatment available. The virus possesses a two-component (NS2B/NS3) serine protease that cleaves the viral precursor proteins. Here, we performed molecular dynamics simulations of the NS2B/NS3 protease complexes with six peptide substrates (capsid, intNS3, 2A/2B, 4B/5, 3/4A and 2B/3 containing the proteolytic site between P(1) and P(1)' subsites) of DV type 2 to compare the specificity of the protein-substrate binding recognition. Although all substrates were in the active conformation for cleavage reaction by NS2B/NS3 protease, their binding strength was somewhat different. The simulated results of intermolecular hydrogen bonds and decomposition energies suggested that among the ten substrate residues (P(5)-P(5)') the P(1) and P(2) subsites play a major role in the binding with the focused protease. The arginine residue at these two subsites was found to be specific preferential binding at the active site with a stabilization energy of <-10 kcal mol(-1). Besides, the P(3), P(1)', P(2)' and P(4)' subsites showed a less contribution in binding interaction (<-2 kcal mol(-1)). The catalytic water was detected nearby the carbonyl oxygen of the P(1) reacting center of the capsid, intNS3, 2A/2B and 4B/5 peptides. These results led to the order of absolute binding free energy (ΔGbind) between these substrates and the NS2B/NS3 protease ranked as capsid>intNS3>2A/2B>4B/5>3/4A>2B/3 in a relative correspondence with previous experimentally derived values.
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Affiliation(s)
- Pathumwadee Yotmanee
- Department of Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok 10240, Thailand; Computational Chemistry Unit Cell, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Thanyada Rungrotmongkol
- Ph.D. Program in Bioinformatics and Computational Biology, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand; Department of Biochemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Kanin Wichapong
- Computational Chemistry Unit Cell, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Sy Bing Choi
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, Gelugor 11800, Pulau Pinang, Malaysia; Natural Product and Drug Discovery Centre, Malaysian Institutes of Pharmaceuticals and Nutraceuticals, National Institutes of Biotechnology Malaysia, Ministry of Science, Technology and Innovation, Block 5-A, Halaman Bukit Gambir, 11700, Penang, Malaysia
| | - Habibah A Wahab
- School of Pharmaceutical Sciences, Universiti Sains Malaysia, Gelugor 11800, Pulau Pinang, Malaysia; Natural Product and Drug Discovery Centre, Malaysian Institutes of Pharmaceuticals and Nutraceuticals, National Institutes of Biotechnology Malaysia, Ministry of Science, Technology and Innovation, Block 5-A, Halaman Bukit Gambir, 11700, Penang, Malaysia.
| | - Nawee Kungwan
- Department of Chemistry, Faculty of Science, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Supot Hannongbua
- Computational Chemistry Unit Cell, Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.
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15
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Zhao H, Caflisch A. Molecular dynamics in drug design. Eur J Med Chem 2015; 91:4-14. [DOI: 10.1016/j.ejmech.2014.08.004] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Revised: 07/31/2014] [Accepted: 08/03/2014] [Indexed: 11/30/2022]
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16
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Bhakat S, Karubiu W, Jayaprakash V, Soliman ME. A perspective on targeting non-structural proteins to combat neglected tropical diseases: Dengue, West Nile and Chikungunya viruses. Eur J Med Chem 2014; 87:677-702. [DOI: 10.1016/j.ejmech.2014.10.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2014] [Revised: 09/29/2014] [Accepted: 10/04/2014] [Indexed: 01/07/2023]
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17
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Elseginy SA, Massarotti A, Nawwar GAM, Amin KM, Brancale A. Small Molecule Inhibitors of West Nile Virus. ACTA ACUST UNITED AC 2014; 23:179-87. [DOI: 10.3851/imp2581] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/09/2013] [Indexed: 10/26/2022]
Abstract
West Nile virus (WNV) is a human pathogen which is rapidly expanding worldwide. It is a member of the Flavivirus genus and it is transmitted by mosquitos between its avian hosts and occasionally in mammalian hosts. In humans the infection is often asymptomatic, however, the most severe cases result in encephalitis or meningitis. Approximately 10% of cases of neuroinvasive disease are fatal. To date there is no effective human vaccine or effective antiviral therapy available to treat WNV infections. For this reason, research in this field is rapidly growing. In this article we will review the latest efforts in the design and development of novel WNV inhibitors from a medicinal chemistry point of view, highlighting challenges and opportunities for the researchers working in this field.
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Affiliation(s)
- Samia A Elseginy
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, UK
| | - Alberto Massarotti
- Dipartimento di Scienze del Farmaco, Università degli Studi del Piemonte Orientale ‘A Avogadro’, Novara, Italy
| | - Galal AM Nawwar
- Department of Chemical Industries, National Research Centre, Giza, Egypt
| | - Kamilia M Amin
- Department of Therapeutic Chemistry, Faculty of Pharmacy, Cairo University, Cairo, Egypt
| | - Andrea Brancale
- School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Cardiff, UK
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18
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Coutard B, Decroly E, Li C, Sharff A, Lescar J, Bricogne G, Barral K. Assessment of Dengue virus helicase and methyltransferase as targets for fragment-based drug discovery. Antiviral Res 2014; 106:61-70. [DOI: 10.1016/j.antiviral.2014.03.013] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 03/14/2014] [Accepted: 03/18/2014] [Indexed: 12/18/2022]
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19
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Ghoorchian A, Chilkoti A, López GP. Simple assay for proteases based on aggregation of stimulus-responsive polypeptides. Anal Chem 2014; 86:6103-10. [PMID: 24832919 DOI: 10.1021/ac5012574] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Unregulated changes in protease activity are linked to many diseases including cancer. Fast, accurate, and low-cost assays for detection of these changes are being explored for early diagnosis and monitoring of these diseases and can also be used as platforms for the discovery of new drugs. We report a new methodology for the simple detection and quantification of protease activity in buffer and human serum. The assay is based on recombinant diblock polypeptides that undergo temperature- or salt-triggered micellization in water. The coronae of the micelles are linked to the water-insoluble cores by a peptide substrate that is cleaved in the presence of the target protease. Protease cleavage of the diblock polypeptide triggers the aggregation of the core-forming segment, leading to a change in solution optical density, which can be used to detect the presence of, and to quantify the concentration of, protease. We used matrix metalloproteinase-1 (MMP-1) as a model protease and found peptide aggregation time to be proportional to enzyme concentration over a range from endogenous MMP-1 level in human serum (∼3 ng/mL) to 100 ng/mL (0.15-5 nM) in 40% human serum and 1-100 ng/mL in buffer. The assay does not require any intermediate steps or sophisticated data analysis, and the modular design of the assay system is amenable to straightforward adaptation for the detection of a wide range of proteases.
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Affiliation(s)
- Ali Ghoorchian
- NSF Research Triangle Materials Research Science and Engineering Center, Duke University , Durham, North Carolina 27708, United States
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20
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de la Cruz L, Chen WN, Graham B, Otting G. Binding mode of the activity-modulating C-terminal segment of NS2B to NS3 in the dengue virus NS2B-NS3 protease. FEBS J 2014; 281:1517-33. [PMID: 24472363 DOI: 10.1111/febs.12729] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2013] [Revised: 01/21/2014] [Accepted: 01/24/2014] [Indexed: 12/16/2022]
Abstract
The two-component dengue virus NS2B-NS3 protease (NS2B-NS3pro) is an established drug target but inhibitor design is hampered by uncertainties about its 3D structure in solution. Crystal structures reported very different conformations for the functionally important C-terminal segment of the NS2B cofactor (NS2Bc), indicating open and closed conformations in the absence and presence of inhibitors, respectively. An earlier NMR study in solution indicated that a closed state is the preferred conformation in the absence of an artificial linker engineered between NS2B and NS3pro. To obtain direct structural information on the fold of unlinked NS2B-NS3pro in solution, we tagged NS3pro with paramagnetic tags and measured pseudocontact shifts by NMR to position NS2Bc relative to NS3pro. NS2Bc was found to bind to NS3pro in the same way as reported in a previously published model and crystal structure of the closed state. The structure is destabilized, however, by high ionic strength and basic pH, showing the importance of electrostatic forces to tie NS2Bc to NS3pro. Narrow NMR signals previously thought to represent the open state are associated with protein degradation. In conclusion, the closed conformation of the NS2B-NS3 protease is the best model for structure-guided drug design.
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Affiliation(s)
- Laura de la Cruz
- Research School of Chemistry, Australian National University, Canberra, Australia
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21
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Recent Advances in Targeting Dengue and West Nile Virus Proteases Using Small Molecule Inhibitors. TOPICS IN MEDICINAL CHEMISTRY 2014. [DOI: 10.1007/7355_2014_46] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Abstract
Computer-aided drug discovery/design methods have played a major role in the development of therapeutically important small molecules for over three decades. These methods are broadly classified as either structure-based or ligand-based methods. Structure-based methods are in principle analogous to high-throughput screening in that both target and ligand structure information is imperative. Structure-based approaches include ligand docking, pharmacophore, and ligand design methods. The article discusses theory behind the most important methods and recent successful applications. Ligand-based methods use only ligand information for predicting activity depending on its similarity/dissimilarity to previously known active ligands. We review widely used ligand-based methods such as ligand-based pharmacophores, molecular descriptors, and quantitative structure-activity relationships. In addition, important tools such as target/ligand data bases, homology modeling, ligand fingerprint methods, etc., necessary for successful implementation of various computer-aided drug discovery/design methods in a drug discovery campaign are discussed. Finally, computational methods for toxicity prediction and optimization for favorable physiologic properties are discussed with successful examples from literature.
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Affiliation(s)
- Gregory Sliwoski
- Jr., Center for Structural Biology, 465 21st Ave South, BIOSCI/MRBIII, Room 5144A, Nashville, TN 37232-8725.
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23
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Lim SP, Shi PY. West Nile virus drug discovery. Viruses 2013; 5:2977-3006. [PMID: 24300672 PMCID: PMC3967157 DOI: 10.3390/v5122977] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 11/25/2013] [Accepted: 11/25/2013] [Indexed: 02/08/2023] Open
Abstract
The outbreak of West Nile virus (WNV) in 1999 in the USA, and its continued spread throughout the Americas, parts of Europe, the Middle East and Africa, underscored the need for WNV antiviral development. Here, we review the current status of WNV drug discovery. A number of approaches have been used to search for inhibitors of WNV, including viral infection-based screening, enzyme-based screening, structure-based virtual screening, structure-based rationale design, and antibody-based therapy. These efforts have yielded inhibitors of viral or cellular factors that are critical for viral replication. For small molecule inhibitors, no promising preclinical candidate has been developed; most of the inhibitors could not even be advanced to the stage of hit-to-lead optimization due to their poor drug-like properties. However, several inhibitors developed for related members of the family Flaviviridae, such as dengue virus and hepatitis C virus, exhibited cross-inhibition of WNV, suggesting the possibility to re-purpose these antivirals for WNV treatment. Most promisingly, therapeutic antibodies have shown excellent efficacy in mouse model; one of such antibodies has been advanced into clinical trial. The knowledge accumulated during the past fifteen years has provided better rationale for the ongoing WNV and other flavivirus antiviral development.
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Affiliation(s)
- Siew Pheng Lim
- Novartis Institute for Tropical Diseases, 10 Biopolis Road, Chromos 05-01, Singapore 138670, Singapore.
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Junaid M, Angsuthanasombat C, Wikberg JES, Ali N, Katzenmeier G. A straightforward experimental approach to expression, purification, refolding, and enzymatic analysis of recombinant dengue virus NS2B(H)-NS3pro protease. BIOCHEMISTRY. BIOKHIMIIA 2013; 78:920-4. [PMID: 24228881 DOI: 10.1134/s0006297913080099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Dengue virus threatens around 2.5 billion people worldwide; about 50 million become infected every year, and yet no vaccine or drug is available for prevention and/or treatment. The flaviviral NS2B-NS3pro complex is indispensable for flaviviral replication and is considered to be an important drug target. The aim of this study was to develop a simple and generally applicable experimental strategy to construct, purify, and assay a highly active recombinant NS2B(H)-NS3pro complex that would be useful for high-throughput screening of potential inhibitors. The sequence of NS2B(H)-NS3pro was generated by overlap extension PCR (SOE-PCR) and cloned into the pTrcHisA vector. Hexahistidine-tagged NS2B(H)-NS3pro complex was expressed in E. coli predominantly as insoluble protein and purified to >95% purity by single-step immobilized metal affinity chromatography. SDS-PAGE followed by immunoblotting of the purified enzyme demonstrated the presence of the NS2B(H)-NS3pro precursor and its autocleavage products, NS3pro and NS2B(H), as 37, 21, and 10 kDa bands, respectively. Kinetic parameters, Km, kcat, and kcat/Km for the fluorophore-linked protease model substrate Ac-nKRR-amc were obtained using inner-filter effect correction. The kinetic parameters Km, kcat, and kcat/Km for Ac-nKRR-amc substrate were 100 µM, 0.112 s(-1), and 1120 M(-1)·s(-1), respectively. A simplified procedure for the cloning, overexpression, and purification of the NS2B(H)-NS3pro complex was applied, and a highly active recombinant NS2B(H)-NS3pro complex was obtained that could be useful for the design of high-throughput assays aimed at flaviviral inhibitor discovery.
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Affiliation(s)
- M Junaid
- Department of Pharmacy, University of Malakand, Chakdara, 18550 Pakistan.
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25
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The flavivirus protease as a target for drug discovery. Virol Sin 2013; 28:326-36. [PMID: 24242363 DOI: 10.1007/s12250-013-3390-x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2013] [Accepted: 11/01/2013] [Indexed: 01/27/2023] Open
Abstract
Many flaviviruses are significant human pathogens causing considerable disease burdens, including encephalitis and hemorrhagic fever, in the regions in which they are endemic. A paucity of treatments for flaviviral infections has driven interest in drug development targeting proteins essential to flavivirus replication, such as the viral protease. During viral replication, the flavivirus genome is translated as a single polyprotein precursor, which must be cleaved into individual proteins by a complex of the viral protease, NS3, and its cofactor, NS2B. Because this cleavage is an obligate step of the viral life-cycle, the flavivirus protease is an attractive target for antiviral drug development. In this review, we will survey recent drug development studies targeting the NS3 active site, as well as studies targeting an NS2B/NS3 interaction site determined from flavivirus protease crystal structures.
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26
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Lyso-myristoyl phosphatidylcholine micelles sustain the activity of Dengue non-structural (NS) protein 3 protease domain fused with the full-length NS2B. Protein Expr Purif 2013; 92:156-62. [PMID: 24084007 DOI: 10.1016/j.pep.2013.09.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Revised: 09/03/2013] [Accepted: 09/17/2013] [Indexed: 12/16/2022]
Abstract
Dengue virus (DENV), a member of the flavivirus genus, affects 50-100 million people in tropical and sub-tropical regions. The DENV protease domain is located at the N-terminus of the NS3 protease and requires for its enzymatic activity a hydrophilic segment of the NS2B that acts as a cofactor. The protease is an important antiviral drug target because it plays a crucial role in virus replication by cleaving the genome-coded polypeptide into mature functional proteins. Currently, there are no drugs to inhibit DENV protease activity. Most structural and functional studies have been conducted using protein constructs containing the NS3 protease domain connected to a soluble segment of the NS2B membrane protein via a nine-residue linker. For in vitro structural and functional studies, it would be useful to produce a natural form of the DENV protease containing the NS3 protease domain and the full-length NS2B protein. Herein, we describe the expression and purification of a natural form of DENV protease (NS2BFL-NS3pro) containing the full-length NS2B protein and the protease domain of NS3 (NS3pro). The protease was expressed and purified in detergent micelles necessary for its folding. Our results show that this purified protein was active in detergent micelles such as lyso-myristoyl phosphatidylcholine (LMPC). These findings should facilitate further structural and functional studies of the protease and will facilitate drug discovery targeting DENV.
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27
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Garces AP, Watowich SJ. Intrinsic Flexibility of West Nile Virus Protease in Solution Characterized Using Small-Angle X-ray Scattering. Biochemistry 2013; 52:6856-65. [DOI: 10.1021/bi400782w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Andrea P. Garces
- Department of Biochemistry
and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Stanley J. Watowich
- Department of Biochemistry
and Molecular Biology, University of Texas Medical Branch, Galveston, Texas 77555, United States
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28
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Honarparvar B, Govender T, Maguire GEM, Soliman MES, Kruger HG. Integrated Approach to Structure-Based Enzymatic Drug Design: Molecular Modeling, Spectroscopy, and Experimental Bioactivity. Chem Rev 2013; 114:493-537. [DOI: 10.1021/cr300314q] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- Bahareh Honarparvar
- Catalysis
and Peptide Research Unit and ‡School of Health Sciences, University of KwaZulu Natal, Durban 4001, South Africa
| | - Thavendran Govender
- Catalysis
and Peptide Research Unit and ‡School of Health Sciences, University of KwaZulu Natal, Durban 4001, South Africa
| | - Glenn E. M. Maguire
- Catalysis
and Peptide Research Unit and ‡School of Health Sciences, University of KwaZulu Natal, Durban 4001, South Africa
| | - Mahmoud E. S. Soliman
- Catalysis
and Peptide Research Unit and ‡School of Health Sciences, University of KwaZulu Natal, Durban 4001, South Africa
| | - Hendrik G. Kruger
- Catalysis
and Peptide Research Unit and ‡School of Health Sciences, University of KwaZulu Natal, Durban 4001, South Africa
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29
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Adamek RN, Maniquis RV, Khakoo S, Bridges MD, Salzameda NT. A FRET-based assay for the discovery of West Nile Virus NS2B-NS3 protease inhibitors. Bioorg Med Chem Lett 2013; 23:4848-50. [DOI: 10.1016/j.bmcl.2013.06.081] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 06/17/2013] [Accepted: 06/27/2013] [Indexed: 10/26/2022]
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30
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de Almeida H, Bastos IMD, Ribeiro BM, Maigret B, Santana JM. New binding site conformations of the dengue virus NS3 protease accessed by molecular dynamics simulation. PLoS One 2013; 8:e72402. [PMID: 23991109 PMCID: PMC3749139 DOI: 10.1371/journal.pone.0072402] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Accepted: 07/10/2013] [Indexed: 12/21/2022] Open
Abstract
Dengue fever is caused by four distinct serotypes of the dengue virus (DENV1-4), and is estimated to affect over 500 million people every year. Presently, there are no vaccines or antiviral treatments for this disease. Among the possible targets to fight dengue fever is the viral NS3 protease (NS3PRO), which is in part responsible for viral processing and replication. It is now widely recognized that virtual screening campaigns should consider the flexibility of target protein by using multiple active conformational states. The flexibility of the DENV NS3PRO could explain the relatively low success of previous virtual screening studies. In this first work, we explore the DENV NS3PRO conformational states obtained from molecular dynamics (MD) simulations to take into account protease flexibility during the virtual screening/docking process. To do so, we built a full NS3PRO model by multiple template homology modeling. The model comprised the NS2B cofactor (essential to the NS3PRO activation), a glycine flexible link and the proteolytic domain. MD simulations had the purpose to sample, as closely as possible, the ligand binding site conformational landscape prior to inhibitor binding. The obtained conformational MD sample was clustered into four families that, together with principal component analysis of the trajectory, demonstrated protein flexibility. These results allowed the description of multiple binding modes for the Bz-Nle-Lys–Arg–Arg-H inhibitor, as verified by binding plots and pair interaction analysis. This study allowed us to tackle protein flexibility in our virtual screening campaign against the dengue virus NS3 protease.
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Affiliation(s)
- Hugo de Almeida
- Laboratório de Interação Patógeno-Hospedeiro, Departamento de Biologia Celular, Universidade de Brasília, Brasília, Brasília, Brazil
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31
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Gao Y, Samanta S, Cui T, Lam Y. Synthesis and in vitro evaluation of West Nile virus protease inhibitors based on the 1,3,4,5-tetrasubstituted 1H-pyrrol-2(5H)-one scaffold. ChemMedChem 2013; 8:1554-60. [PMID: 23868614 DOI: 10.1002/cmdc.201300244] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Indexed: 11/07/2022]
Abstract
West Nile virus (WNV), a member of the Flaviviridae family, is a mosquito-borne pathogen that causes a large number of human infections each year. There are currently no vaccines or antiviral therapies available for human use against WNV. Therefore, efforts to develop new chemotherapeutics against this virus are highly desired. In this study, a WNV NS2B-NS3 protease inhibitor with a 1,3,4,5-tetrasubstituted 1H-pyrrol-2(5H)-one scaffold was identified by screening a small library of nonpeptidic compounds. Optimization of this initial hit by the synthesis and screening of a focused library of compounds with this scaffold led to the identification of a novel uncompetitive inhibitor ((-)-1a16, IC₅₀ =2.2±0.7 μM) of the WNV NS2B-NS3 protease. Molecular docking of the chiral compound onto the WNV protease indicates that the R enantiomer of 1a16 interferes with the productive interactions between the NS2B cofactor and the NS3 protease domain and is thus the preferred isomer for inhibition of the WNV NS2B-NS3 protease.
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Affiliation(s)
- Yaojun Gao
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543
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32
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Samanta S, Lim TL, Lam Y. Synthesis and in vitro evaluation of West Nile virus protease inhibitors based on the 2-{6-[2-(5-phenyl-4H-{1,2,4]triazol-3-ylsulfanyl)acetylamino]benzothiazol-2-ylsulfanyl}acetamide scaffold. ChemMedChem 2013; 8:994-1001. [PMID: 23619931 DOI: 10.1002/cmdc.201300114] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Indexed: 11/06/2022]
Abstract
In recent years, clinical symptoms resulting from West Nile virus (WNV) infection have worsened in severity, with an increased frequency in neuroinvasive diseases among the elderly. As there are presently no successful therapies against WNV for use in humans, continual efforts to develop new chemotherapeutics against this virus are highly desired. The viral NS2B-NS3 protease is a promising target for viral inhibition due to its importance in viral replication and its unique substrate preference. In this study, a WNV NS2B-NS3 protease inhibitor with a 2-{6-[2-(5-phenyl-4H-[1,2,4]triazol-3-ylsulfanyl)acetylamino]benzothiazol-2-ylsulfanyl}acetamide scaffold was identified during screening. Optimization of this initial hit by synthesis and screening of a focused compound library with this scaffold led to the identification of a novel uncompetitive inhibitor (1 a24, IC50 =3.4±0.2 μM) of the WNV NS2B-NS3 protease. Molecular docking of 1 a24 into the WNV protease showed that the compound interferes with productive interactions of the NS2B cofactor with the NS3 protease and is an allosteric inhibitor of the WNV NS3 protease.
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Affiliation(s)
- Sanjay Samanta
- Department of Chemistry, National University of Singapore, Singapore
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33
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Shen M, Yu H, Li Y, Li P, Pan P, Zhou S, Zhang L, Li S, Lee SMY, Hou T. Discovery of Rho-kinase inhibitors by docking-based virtual screening. MOLECULAR BIOSYSTEMS 2013; 9:1511-21. [DOI: 10.1039/c3mb00016h] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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West Nile Virus (WNV) protease and membrane interactions revealed by NMR spectroscopy. Biochem Biophys Res Commun 2012; 423:799-804. [PMID: 22713461 DOI: 10.1016/j.bbrc.2012.06.043] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Accepted: 06/09/2012] [Indexed: 01/04/2023]
Abstract
West Nile Virus (WNV) protease is a two-component protease, important for the maturation of virus by cleaving the viral ploypeptide into functional proteins. WNV protease contains a Nonstructural (NS) protein 3 possessing the protease active sites and is regulated by a cofactor region containing approximately 40 amino acids from an integral membrane protein, NS2B. Although NS2B was demonstrated to be important for the location of the protease on the membrane, there was no direct evidence to show the interaction between protease (NS3) and membrane. Herein, we investigated the interaction between WNV protease and dodecylphosphocoline (DPC) micelles using NMR spectroscopy. The results showed that amino acids (31-33) from NS3 were important for the interaction with detergent micelles, which was similar to the finding in the study of protease from Dengue virus. This region may serve as an anchoring site to stabilized NS3 protease domain on the membrane.
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35
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Samanta S, Cui T, Lam Y. Discovery, synthesis, and in vitro evaluation of West Nile virus protease inhibitors based on the 9,10-dihydro-3H,4aH-1,3,9,10a-tetraazaphenanthren-4-one scaffold. ChemMedChem 2012; 7:1210-6. [PMID: 22550001 DOI: 10.1002/cmdc.201200136] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Revised: 04/05/2012] [Indexed: 11/07/2022]
Abstract
West Nile virus (WNV), a member of the Flaviviridae family, is a mosquito-borne pathogen that causes a great number of human infections each year. Neither vaccines nor antiviral therapies are currently available for human use. In this study, a WNV NS2B-NS3 protease inhibitor with a 9,10-dihydro-3H,4aH-1,3,9,10a-tetraazaphenanthren-4-one scaffold was identified by screening a small library of non-peptidic compounds. This initial hit was optimized by solution-phase synthesis and screening of a focused library of compounds bearing this scaffold. This led to the identification of a novel, uncompetitive inhibitor (1a40, IC(50) = 5.41±0.45 μM) of WNV NS2B-NS3 protease. Molecular docking of this chiral compound onto the WNV protease indicates that the S enantiomer of 1a40 appears to interfere with the productive interactions between the NS2B cofactor and the NS3 protease domain; (S)-1a40 is a preferred isomer for inhibition of WNV NS3 protease.
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Affiliation(s)
- Sanjay Samanta
- Department of Chemistry, National University of Singapore, 3 Science Drive 3, 117543, Singapore
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36
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High-throughput virtual screening lead to discovery of non-peptidic inhibitors of West Nile virus NS3 protease. Methods Mol Biol 2012; 819:615-23. [PMID: 22183561 DOI: 10.1007/978-1-61779-465-0_36] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
The non-structural 3 protease is an essential flaviviral enzyme and therefore one of the most promising targets for drug development against West Nile virus infections. In this chapter, we discuss in detail the computational methods used in the previous two docking campaigns which lead to the discovery of non-peptidic low micromolar inhibitors. Not only an X-ray structure but also an alternative conformation generated from molecular dynamic simulations is used in the in silico screening. Moreover, unique scoring schemes are developed based on the properties of the binding site of the protein.
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37
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Jia X, Yagi H, Su XC, Stanton-Cook M, Huber T, Otting G. Engineering [Ln(DPA)3] 3- binding sites in proteins: a widely applicable method for tagging proteins with lanthanide ions. JOURNAL OF BIOMOLECULAR NMR 2011; 50:411-420. [PMID: 21786031 DOI: 10.1007/s10858-011-9529-x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Accepted: 06/20/2011] [Indexed: 05/31/2023]
Abstract
Paramagnetic relaxation enhancements from unpaired electrons observed in nuclear magnetic resonance (NMR) spectra present powerful long-range distance restraints. The most frequently used paramagnetic tags, however, are tethered to the protein via disulfide bonds, requiring proteins with single cysteine residues for covalent attachment. Here we present a straightforward strategy to tag proteins site-specifically with paramagnetic lanthanides without a tether and independent of cysteine residues. It relies on preferential binding of the complex between three dipicolinic acid molecules (DPA) and a lanthanide ion (Ln(3+)), [Ln(DPA)(3)](3-), to a pair of positively charged amino acids whose charges are not compensated by negatively charged residues nearby. This situation rarely occurs in wild-type proteins, allowing the creation of specific binding sites simply by introduction of positively charged residues that are positioned far from glutamate or aspartate residues. The concept is demonstrated with the hnRNPLL RRM1 domain. In addition, we show that histidine- and arginine-tags present binding sites for [Ln(DPA)(3)](3-).
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Affiliation(s)
- Xinying Jia
- Research School of Chemistry, Australian National University, Canberra, ACT, 0200, Australia
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38
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Huang D, Caflisch A. Fragment-Based Approaches in Virtual Screening. METHODS AND PRINCIPLES IN MEDICINAL CHEMISTRY 2011. [DOI: 10.1002/9783527633326.ch17] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
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Zoete V, Cuendet MA, Grosdidier A, Michielin O. SwissParam: A fast force field generation tool for small organic molecules. J Comput Chem 2011; 32:2359-68. [DOI: 10.1002/jcc.21816] [Citation(s) in RCA: 1090] [Impact Index Per Article: 83.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 02/10/2011] [Accepted: 03/20/2011] [Indexed: 11/08/2022]
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40
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Knehans T, Schüller A, Doan DN, Nacro K, Hill J, Güntert P, Madhusudhan MS, Weil T, Vasudevan SG. Structure-guided fragment-based in silico drug design of dengue protease inhibitors. J Comput Aided Mol Des 2011; 25:263-74. [DOI: 10.1007/s10822-011-9418-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Accepted: 02/07/2011] [Indexed: 11/24/2022]
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Wichapong K, Lawson M, Pianwanit S, Kokpol S, Sippl W. Postprocessing of protein-ligand docking poses using linear response MM-PB/SA: application to Wee1 kinase inhibitors. J Chem Inf Model 2011; 50:1574-88. [PMID: 20712342 DOI: 10.1021/ci1002153] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Prediction of the binding strength of untested ligands is a central issue in structure-based drug design. In order to rapidly screen large compound databases, simple scoring schemes are often used in target-based virtual screening. The resulting scores often correlate poorly with biological affinities. More rigorous scoring methods, such as MM-PB/SA, correlate better with biological data by considering solvation effects and protein flexibility in the calculation of the binding free energy of a ligand. Here we describe the performance of a modified MM-PB/SA method on 222 Wee1 kinase inhibitors (48 pyridopyrimidine and 174 pyrrolocarbazole derivatives). Docking of these inhibitors into the available Wee1 kinase crystal structure yielded a consistent binding mode, and the derived MM-PB/SA models showed a significant correlation between calculated and experimental data (r(2) values between 0.64 and 0.67). Further study of these models on external test sets of Wee1 kinase inhibitors and structurally related decoys showed that a model based on a single kinase-inhibitor conformation can discriminate the active inhibitors from decoys. We also tested whether the linear interaction energy method with continuum electrostatics (LIECE) yields comparable results to MM-PB/SA and whether the LIECE and MM-PB/SA models can be applied for virtual screening of compound libraries.
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Affiliation(s)
- Kanin Wichapong
- Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok, 10330, Thailand
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Ugwumba IN, Ozawa K, de la Cruz L, Xu ZQ, Herlt AJ, Hadler KS, Coppin C, Brown SE, Schenk G, Oakeshott JG, Otting G. Using a genetically encoded fluorescent amino acid as a site-specific probe to detect binding of low-molecular-weight compounds. Assay Drug Dev Technol 2010; 9:50-7. [PMID: 21050031 DOI: 10.1089/adt.2010.0306] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Development of enzyme inhibitors requires an activity assay for the identification of hits and lead compounds. To determine dissociation constants in a straightforward manner, we explored the use of a genetically encoded fluorescent amino acid for site-specific tagging of the target protein. The unnatural amino acid 7-(hydroxy-coumarin-4-yl) ethylglycine (Hco) was site-specifically incorporated in the target protein by cell-free protein synthesis using an orthogonal amber suppressor tRNA/aminoacyl-tRNA synthetase pair. Using the West Nile virus nonstructural protein 2B-nonstructural protein 3 protease as the target protein, the fluorescence of Hco-tagged samples proved to be exquisitely sensitive to the presence of inhibitors and small ligand molecules if they bind in the vicinity of the Hco residue. No significant change in fluorescence was observed when the ligand-binding site was far from the Hco residue. Hco-tagged proteins thus combine outstanding sensitivity with accurate information on the site of binding, making Hco labeling an attractive tool in drug discovery.
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Affiliation(s)
- Isaac N Ugwumba
- Commonwealth Scientific and Industrial Research Organization, Black Mountain Laboratories, Canberra, ACT 0200, Australia
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Shiryaev SA, Cheltsov AV, Gawlik K, Ratnikov BI, Strongin AY. Virtual ligand screening of the National Cancer Institute (NCI) compound library leads to the allosteric inhibitory scaffolds of the West Nile Virus NS3 proteinase. Assay Drug Dev Technol 2010; 9:69-78. [PMID: 21050032 DOI: 10.1089/adt.2010.0309] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Viruses of the genus Flavivirus are responsible for significant human disease and mortality. The N-terminal domain of the flaviviral nonstructural (NS)3 protein codes for the serine, chymotrypsin-fold proteinase (NS3pro). The presence of the nonstructural (NS)2B cofactor, which is encoded by the upstream gene in the flaviviral genome, is necessary for NS3pro to exhibit its proteolytic activity. The two-component NS2B-NS3pro functional activity is essential for the viral polyprotein processing and replication. Both the structure and the function of NS2B-NS3pro are conserved in the Flavivirus family. Because of its essential function in the posttranslational processing of the viral polyprotein precursor, NS2B-NS3pro is a promising target for anti-flavivirus drugs. To identify selective inhibitors with the reduced cross-reactivity and off-target effects, we focused our strategy on the allosteric inhibitors capable of targeting the NS2B-NS3pro interface rather than the NS3pro active site. Using virtual ligand screening of the diverse, ∼275,000-compound library and the catalytic domain of the two-component West Nile virus (WNV) NS2B-NS3pro as a receptor, we identified a limited subset of the novel inhibitory scaffolds. Several of the discovered compounds performed as allosteric inhibitors and exhibited a nanomolar range potency in the in vitro cleavage assays. The inhibitors were also potent in cell-based assays employing the sub-genomic, luciferase-tagged WNV and Dengue viral replicons. The selectivity of the inhibitors was confirmed using the in vitro cleavage assays with furin, a human serine proteinase, the substrate preferences of which are similar to those of WNV NS2B-NS3pro. Conceptually, the similar in silico drug discovery strategy may be readily employed for the identification of inhibitors of other flaviviruses.
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Affiliation(s)
- Sergey A Shiryaev
- Inflammatory and Infectious Disease Center, Sanford-Burnham Medical Research Institute, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA
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Yuriev E, Agostino M, Ramsland PA. Challenges and advances in computational docking: 2009 in review. J Mol Recognit 2010; 24:149-64. [DOI: 10.1002/jmr.1077] [Citation(s) in RCA: 223] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2010] [Revised: 07/20/2010] [Accepted: 07/21/2010] [Indexed: 12/12/2022]
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Dou D, Viwanathan P, Li Y, He G, Alliston KR, Lushington GH, Brown-Clay JD, Padmanabhan R, Groutas WC. Design, synthesis, and in vitro evaluation of potential West Nile virus protease inhibitors based on the 1-oxo-1,2,3,4-tetrahydroisoquinoline and 1-oxo-1,2-dihydroisoquinoline scaffolds. ACTA ACUST UNITED AC 2010; 12:836-43. [PMID: 20882963 DOI: 10.1021/cc100091h] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The 1-oxo-1, 2, 3, 4-tetrahydroisoquinoline and 1-Oxo-1, 2-dihydroisoquinoline scaffolds were utilized in the design and solution phase synthesis of focused libraries of compounds for screening against West Nile Virus (WNV) protease. Exploratory studies have led to the identification of a WNV protease inhibitor (a 1-oxo-1, 2-dihydroisoquinoline-based derivative, 12j) which could potentially serve as a launching pad for a hit-to-lead optimization campaign. The identified hit was devoid of any inhibitory activity toward a panel of mammalian serine proteases.
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Affiliation(s)
- Dengfeng Dou
- Department of Chemistry, Wichita State University, Wichita, Kansas 67260, USA
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Shiryaev SA, Strongin AY. Structural and functional parameters of the flaviviral protease: a promising antiviral drug target. Future Virol 2010; 5:593-606. [PMID: 21076642 DOI: 10.2217/fvl.10.39] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Flaviviruses have a single-strand, positive-polarity RNA genome that encodes a single polyprotein. The polyprotein is comprised of seven nonstructural (NS) and three structural proteins. The N- and C-terminal parts of NS3 represent the serine protease and the RNA helicase, respectively. The cleavage of the polyprotein by the protease is required to produce the individual viral proteins, which assemble a new viral progeny. Conversely, inactivation of the protease blocks viral infection. Both the protease and the helicase are conserved among flaviviruses. As a result, NS3 is a promising drug target in flaviviral infections. This article examines the West Nile virus NS3 with an emphasis on the structural and functional parameters of the protease, the helicase and their cofactors.
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Affiliation(s)
- Sergey A Shiryaev
- Inflammatory & Infectious Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
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Small molecule drug discovery for Dengue and West Nile viruses: applying experience from hepatitis C virus. Future Med Chem 2010; 2:1181-203. [DOI: 10.4155/fmc.10.195] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
There are currently no specific treatments for infection with Dengue virus (DENV) and West Nile Virus (WNV). Drug-discovery programs are underway for both viruses, but as yet no small molecules have advanced to clinical trials. Hepatitis C virus (HCV) is a related flavivirus that has been the focus of intense drug discovery efforts for the last two decades. Many approaches currently being pursued for DENV and WNV have been previously attempted for HCV with varying degrees of success. The experience with HCV may direct DENV and WNV efforts towards approaches with the best chance of success. Based on experience with HCV, the viral polymerase and protease are attractive targets to focus on since these have been most successful to date. Cell-based phenotypic screening may also yield attractive inhibitors. The helicase and methyltransferase enzymes are likely to prove difficult targets and host target approaches are fraught with safety concerns.
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48
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Identification of palmatine as an inhibitor of West Nile virus. Arch Virol 2010; 155:1325-9. [DOI: 10.1007/s00705-010-0702-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2010] [Accepted: 05/12/2010] [Indexed: 12/15/2022]
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49
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Isolation and characterization of selective and potent human Fab inhibitors directed to the active-site region of the two-component NS2B-NS3 proteinase of West Nile virus. Biochem J 2010; 427:369-76. [PMID: 20156198 DOI: 10.1042/bj20100074] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
There is a need to develop inhibitors of mosquito-borne flaviviruses, including WNV (West Nile virus). In the present paper, we describe a novel and efficient recombinant-antibody technology that led us to the isolation of inhibitory high-affinity human antibodies to the active-site region of a viral proteinase. As a proof-of-principal, we have successfully used this technology and the synthetic naive human combinatorial antibody library HuCAL GOLD(R) to isolate selective and potent function-blocking active-site-targeting antibodies to the two-component WNV NS (non-structural protein) 2B-NS3 serine proteinase, the only proteinase encoded by the flaviviral genome. First, we used the wild-type enzyme in antibody screens. Next, the positive antibody clones were counter-screened using an NS2B-NS3 mutant with a single mutation of the catalytically essential active-site histidine residue. The specificity of the antibodies to the active site was confirmed by substrate-cleavage reactions and also by using proteinase mutants with additional single amino-acid substitutions in the active-site region. The selected WNV antibodies did not recognize the structurally similar viral proteinases from Dengue virus type 2 and hepatitis C virus, and human serine proteinases. Because of their high selectivity and affinity, the identified human antibodies are attractive reagents for both further mutagenesis and structure-based optimization and, in addition, for studies of NS2B-NS3 activity. Conceptually, it is likely that the generic technology reported in the present paper will be useful for the generation of active-site-specific antibody probes for multiple enzymes.
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Design, structure-based focusing and in silico screening of combinatorial library of peptidomimetic inhibitors of Dengue virus NS2B-NS3 protease. J Comput Aided Mol Des 2010; 24:195-212. [DOI: 10.1007/s10822-010-9326-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Accepted: 03/08/2010] [Indexed: 10/19/2022]
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