1
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Georgiou K, Konstantinidi A, Hutterer J, Freudenberger K, Kolarov F, Lambrinidis G, Stylianakis I, Stampelou M, Gauglitz G, Kolocouris A. Accurate calculation of affinity changes to the close state of influenza A M2 transmembrane domain in response to subtle structural changes of adamantyl amines using free energy perturbation methods in different lipid bilayers. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184258. [PMID: 37995846 DOI: 10.1016/j.bbamem.2023.184258] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 10/18/2023] [Accepted: 11/15/2023] [Indexed: 11/25/2023]
Abstract
Experimental binding free energies of 27 adamantyl amines against the influenza M2(22-46) WT tetramer, in its closed form at pH 8, were measured by ITC in DPC micelles. The measured Kd's range is ~44 while the antiviral potencies (IC50) range is ~750 with a good correlation between binding free energies computed with Kd and IC50 values (r = 0.76). We explored with MD simulations (ff19sb, CHARMM36m) the binding profile of complexes with strong, moderate and weak binders embedded in DMPC, DPPC, POPC or a viral mimetic membrane and using different experimental starting structures of M2. To predict accurately differences in binding free energy in response to subtle changes in the structure of the ligands, we performed 18 alchemical perturbative single topology FEP/MD NPT simulations (OPLS2005) using the BAR estimator (Desmond software) and 20 dual topology calculations TI/MD NVT simulations (ff19sb) using the MBAR estimator (Amber software) for adamantyl amines in complex with M2(22-46) WT in DMPC, DPPC, POPC. We observed that both methods with all lipids show a very good correlation between the experimental and calculated relative binding free energies (r = 0.77-0.87, mue = 0.36-0.92 kcal mol-1) with the highest performance achieved with TI/MBAR and lowest performance with FEP/BAR in DMPC bilayers. When antiviral potencies are used instead of the Kd values for computing the experimental binding free energies we obtained also good performance with both FEP/BAR (r = 0.83, mue = 0.75 kcal mol-1) and TI/MBAR (r = 0.69, mue = 0.77 kcal mol-1).
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Affiliation(s)
- Kyriakos Georgiou
- Laboratory of Medicinal Chemistry, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis-Zografou, 15771 Athens, Greece
| | - Athina Konstantinidi
- Laboratory of Medicinal Chemistry, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis-Zografou, 15771 Athens, Greece
| | - Johanna Hutterer
- Institut für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Kathrin Freudenberger
- Institut für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Felix Kolarov
- Institut für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany; Roche, Penzberg, Bavaria, Germany
| | - George Lambrinidis
- Laboratory of Medicinal Chemistry, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis-Zografou, 15771 Athens, Greece
| | - Ioannis Stylianakis
- Laboratory of Medicinal Chemistry, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis-Zografou, 15771 Athens, Greece
| | - Margarita Stampelou
- Laboratory of Medicinal Chemistry, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis-Zografou, 15771 Athens, Greece
| | - Günter Gauglitz
- Institut für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Antonios Kolocouris
- Laboratory of Medicinal Chemistry, Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens (NKUA), Panepistimiopolis-Zografou, 15771 Athens, Greece.
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2
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Stampolaki Μ, Hoffmann A, Tekwani K, Georgiou K, Tzitzoglaki C, Ma C, Becker S, Schmerer P, Döring K, Stylianakis I, Turcu AL, Wang J, Vázquez S, Andreas LB, Schmidtke M, Kolocouris A. A Study of the Activity of Adamantyl Amines against Mutant Influenza A M2 Channels Identified a Polycyclic Cage Amine Triple Blocker, Explored by Molecular Dynamics Simulations and Solid-State NMR. ChemMedChem 2023; 18:e202300182. [PMID: 37377066 DOI: 10.1002/cmdc.202300182] [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: 04/03/2023] [Revised: 06/25/2023] [Accepted: 06/26/2023] [Indexed: 06/29/2023]
Abstract
We compared the anti-influenza potencies of 57 adamantyl amines and analogs against influenza A virus with serine-31 M2 proton channel, usually termed as WT M2 channel, which is amantadine sensitive. We also tested a subset of these compounds against viruses with the amantadine-resistant L26F, V27A, A30T, G34E M2 mutant channels. Four compounds inhibited WT M2 virus in vitro with mid-nanomolar potency, with 27 compounds showing sub-micromolar to low micromolar potency. Several compounds inhibited L26F M2 virus in vitro with sub-micromolar to low micromolar potency, but only three compounds blocked L26F M2-mediated proton current as determined by electrophysiology (EP). One compound was found to be a triple blocker of WT, L26F, V27A M2 channels by EP assays, but did not inhibit V27A M2 virus in vitro, and one compound inhibited WT, L26F, V27A M2 in vitro without blocking V27A M2 channel. One compound blocked only L26F M2 channel by EP, but did not inhibit virus replication. The triple blocker compound is as long as rimantadine, but could bind and block V27A M2 channel due to its larger girth as revealed by molecular dynamics simulations, while MAS NMR informed on the interaction of the compound with M2(18-60) WT or L26F or V27A.
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Affiliation(s)
- Μarianna Stampolaki
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou, 15771, Athens, Greece
- Department of NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen, Germany
| | - Anja Hoffmann
- Department of Medical Microbiology, Jena University Hospital, CMB Building, R. 443, Hans Knoell Str. 2, 07745, Jena (Germany), Germany
| | - Kumar Tekwani
- Department of Chemistry and Biochemistry, University of Delaware, Newark, DE 19716, USA
| | - Kyriakos Georgiou
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou, 15771, Athens, Greece
| | - Christina Tzitzoglaki
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou, 15771, Athens, Greece
| | - Chunlong Ma
- Department of Medicinal Chemistry, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ 08854-8020, USA
| | - Stefan Becker
- Department of NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen, Germany
| | - Patrick Schmerer
- Department of Medical Microbiology, Jena University Hospital, CMB Building, R. 443, Hans Knoell Str. 2, 07745, Jena (Germany), Germany
| | - Kristin Döring
- Department of Medical Microbiology, Jena University Hospital, CMB Building, R. 443, Hans Knoell Str. 2, 07745, Jena (Germany), Germany
| | - Ioannis Stylianakis
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou, 15771, Athens, Greece
| | - Andreea L Turcu
- Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona, Av. Joan XXIII, 27-31, Barcelona, 08028, Spain
| | - Jun Wang
- Department of Medicinal Chemistry, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ 08854-8020, USA
| | - Santiago Vázquez
- Facultat de Farmàcia i Ciències de l'Alimentació, and Institute of Biomedicine (IBUB), Universitat de Barcelona, Av. Joan XXIII, 27-31, Barcelona, 08028, Spain
| | - Loren B Andreas
- Department of NMR-Based Structural Biology, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, Göttingen, Germany
| | - Michaela Schmidtke
- Department of Medical Microbiology, Jena University Hospital, CMB Building, R. 443, Hans Knoell Str. 2, 07745, Jena (Germany), Germany
| | - Antonios Kolocouris
- Department of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou, 15771, Athens, Greece
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3
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Fam MS, Sedky CA, Turky NO, Breitinger HG, Breitinger U. Channel activity of SARS-CoV-2 viroporin ORF3a inhibited by adamantanes and phenolic plant metabolites. Sci Rep 2023; 13:5328. [PMID: 37005439 PMCID: PMC10067842 DOI: 10.1038/s41598-023-31764-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2022] [Accepted: 03/16/2023] [Indexed: 04/04/2023] Open
Abstract
SARS-CoV-2 has been responsible for the major worldwide pandemic of COVID-19. Despite the enormous success of vaccination campaigns, virus infections are still prevalent and effective antiviral therapies are urgently needed. Viroporins are essential for virus replication and release, and are thus promising therapeutic targets. Here, we studied the expression and function of recombinant ORF3a viroporin of SARS-CoV-2 using a combination of cell viability assays and patch-clamp electrophysiology. ORF3a was expressed in HEK293 cells and transport to the plasma membrane verified by a dot blot assay. Incorporation of a membrane-directing signal peptide increased plasma membrane expression. Cell viability tests were carried out to measure cell damage associated with ORF3a activity, and voltage-clamp recordings verified its channel activity. The classical viroporin inhibitors amantadine and rimantadine inhibited ORF3a channels. A series of ten flavonoids and polyphenolics were studied. Kaempferol, quercetin, epigallocatechin gallate, nobiletin, resveratrol and curcumin were ORF3a inhibitors, with IC50 values ranging between 1 and 6 µM, while 6-gingerol, apigenin, naringenin and genistein were inactive. For flavonoids, inhibitory activity could be related to the pattern of OH groups on the chromone ring system. Thus, the ORF3a viroporin of SARS-CoV-2 may indeed be a promising target for antiviral drugs.
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Affiliation(s)
- Marina Sherif Fam
- Department of Biochemistry, German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo, New Cairo, 11835, Egypt
| | - Christine Adel Sedky
- Department of Biochemistry, German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo, New Cairo, 11835, Egypt
| | - Nancy Osama Turky
- Department of Biochemistry, German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo, New Cairo, 11835, Egypt
| | - Hans-Georg Breitinger
- Department of Biochemistry, German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo, New Cairo, 11835, Egypt
| | - Ulrike Breitinger
- Department of Biochemistry, German University in Cairo, Main Entrance of Al Tagamoa Al Khames, New Cairo, New Cairo, 11835, Egypt.
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4
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Somberg NH, Wu WW, Medeiros-Silva J, Dregni AJ, Jo H, DeGrado WF, Hong M. SARS-CoV-2 Envelope Protein Forms Clustered Pentamers in Lipid Bilayers. Biochemistry 2022; 61:2280-2294. [PMID: 36219675 PMCID: PMC9583936 DOI: 10.1021/acs.biochem.2c00464] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2022] [Revised: 09/26/2022] [Indexed: 11/30/2022]
Abstract
The SARS-CoV-2 envelope (E) protein is a viroporin associated with the acute respiratory symptoms of COVID-19. E forms cation-selective ion channels that assemble in the lipid membrane of the endoplasmic reticulum Golgi intermediate compartment. The channel activity of E is linked to the inflammatory response of the host cell to the virus. Like many viroporins, E is thought to oligomerize with a well-defined stoichiometry. However, attempts to determine the E stoichiometry have led to inconclusive results and suggested mixtures of oligomers whose exact nature might vary with the detergent used. Here, we employ 19F solid-state nuclear magnetic resonance and the centerband-only detection of exchange (CODEX) technique to determine the oligomeric number of E's transmembrane domain (ETM) in lipid bilayers. The CODEX equilibrium value, which corresponds to the inverse of the oligomeric number, indicates that ETM assembles into pentamers in lipid bilayers, without any detectable fraction of low-molecular-weight oligomers. Unexpectedly, at high peptide concentrations and in the presence of the lipid phosphatidylinositol, the CODEX data indicate that more than five 19F spins are within a detectable distance of about 2 nm, suggesting that the ETM pentamers cluster in the lipid bilayer. Monte Carlo simulations that take into account peptide-peptide and peptide-lipid interactions yielded pentamer clusters that reproduced the CODEX data. This supramolecular organization is likely important for E-mediated virus assembly and budding and for the channel function of the protein.
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Affiliation(s)
- Noah H. Somberg
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - Westley W. Wu
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - João Medeiros-Silva
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - Aurelio J. Dregni
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
| | - Hyunil Jo
- Department of Pharmaceutical Chemistry, 555 Mission Bay Blvd. South, University of California, San Francisco, San Francisco, CA 94158
| | - William F. DeGrado
- Department of Pharmaceutical Chemistry, 555 Mission Bay Blvd. South, University of California, San Francisco, San Francisco, CA 94158
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 170 Albany Street, Cambridge, MA 02139
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5
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Breitinger U, Farag NS, Sticht H, Breitinger HG. Viroporins: Structure, function, and their role in the life cycle of SARS-CoV-2. Int J Biochem Cell Biol 2022; 145:106185. [PMID: 35219876 PMCID: PMC8868010 DOI: 10.1016/j.biocel.2022.106185] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 02/15/2022] [Accepted: 02/21/2022] [Indexed: 12/12/2022]
Abstract
Viroporins are indispensable for viral replication. As intracellular ion channels they disturb pH gradients of organelles and allow Ca2+ flux across ER membranes. Viroporins interact with numerous intracellular proteins and pathways and can trigger inflammatory responses. Thus, they are relevant targets in the search for antiviral drugs. Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) underlies the world-wide pandemic of COVID-19, where an effective therapy is still lacking despite impressive progress in the development of vaccines and vaccination campaigns. Among the 29 proteins of SARS-CoV-2, the E- and ORF3a proteins have been identified as viroporins that contribute to the massive release of inflammatory cytokines observed in COVID-19. Here, we describe structure and function of viroporins and their role in inflammasome activation and cellular processes during the virus replication cycle. Techniques to study viroporin function are presented, with a focus on cellular and electrophysiological assays. Contributions of SARS-CoV-2 viroporins to the viral life cycle are discussed with respect to their structure, channel function, binding partners, and their role in viral infection and virus replication. Viroporin sequences of new variants of concern (α–ο) of SARS-CoV-2 are briefly reviewed as they harbour changes in E and 3a proteins that may affect their function.
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Affiliation(s)
- Ulrike Breitinger
- Department of Biochemistry, German University in Cairo, New Cairo, Egypt
| | - Noha S Farag
- Department of Microbiology and Immunology, German University in Cairo, New Cairo, Egypt
| | - Heinrich Sticht
- Division of Bioinformatics, Institute for Biochemistry, Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany
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6
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Townsend JA, Sanders HM, Rolland AD, Park CK, Horton NC, Prell JS, Wang J, Marty MT. Influenza AM2 Channel Oligomerization Is Sensitive to Its Chemical Environment. Anal Chem 2021; 93:16273-16281. [PMID: 34813702 DOI: 10.1021/acs.analchem.1c04660] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Viroporins are small viral ion channels that play important roles in the viral infection cycle and are proven antiviral drug targets. Matrix protein 2 from influenza A (AM2) is the best-characterized viroporin, and the current paradigm is that AM2 forms monodisperse tetramers. Here, we used native mass spectrometry and other techniques to characterize the oligomeric state of both the full-length and transmembrane (TM) domain of AM2 in a variety of different pH and detergent conditions. Unexpectedly, we discovered that AM2 formed a range of different oligomeric complexes that were strongly influenced by the local chemical environment. Native mass spectrometry of AM2 in nanodiscs with different lipids showed that lipids also affected the oligomeric states of AM2. Finally, nanodiscs uniquely enabled the measurement of amantadine binding stoichiometries to AM2 in the intact lipid bilayer. These unexpected results reveal that AM2 can form a wider range of oligomeric states than previously thought possible, which may provide new potential mechanisms of influenza pathology and pharmacology.
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Affiliation(s)
- Julia A Townsend
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Henry M Sanders
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States
| | - Amber D Rolland
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, United States.,Institute of Molecular Biology, University of Oregon, Eugene, Oregon 97403, United States
| | - Chad K Park
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, United States
| | - Nancy C Horton
- Department of Molecular and Cellular Biology, University of Arizona, Tucson, Arizona 85721, United States
| | - James S Prell
- Department of Chemistry and Biochemistry, University of Oregon, Eugene, Oregon 97403, United States.,Materials Science Institute, University of Oregon, Eugene, Oregon 97403, United States
| | - Jun Wang
- Department of Pharmacology and Toxicology, The University of Arizona, Tucson, Arizona 85721, United States.,Bio5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
| | - Michael T Marty
- Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona 85721, United States.,Bio5 Institute, The University of Arizona, Tucson, Arizona 85721, United States
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7
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Ardalan A, Sowlati-Hashjin S, Oduwoye H, Uwumarenogie SO, Karttunen M, Smith MD, Jelokhani-Niaraki M. Biphasic Proton Transport Mechanism for Uncoupling Proteins. J Phys Chem B 2021; 125:9130-9144. [PMID: 34365794 DOI: 10.1021/acs.jpcb.1c04766] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
It has been suggested that uncoupling proteins (UCPs) transport protons via interconversion between two conformational states: one in the "cytoplasmic state" and the other in the "matrix state". Matrix and cytoplasmic salt-bridge networks are key controllers of these states. This study proposes a mechanism for proton transport in tetrameric UCP2, with focus on the role of the matrix network. Eleven mutants were prepared to disrupt (K → Q or D → N mutations) or alter (K → D and D → K mutations) the salt-bridges in the matrix network. Proteins were recombinantly expressed in Escherichia coli membrane, reconstituted in model lipid membranes, and their structures and functions were analyzed by gel electrophoresis, circular dichroism spectroscopy, fluorescence assays, as well as molecular dynamics simulations. It is shown that the UCP2 matrix network contains five salt-bridges (rather than the previously reported three), and the matrix network can regulate the proton transport by holding the protein's transmembrane helices in close proximity, limiting the movement of the activator fatty acid(s). A biphasic two-state molecular model is proposed for proton transport in tetrameric (a dimer of stable dimers) UCP2, in which all the monomers are functional, and monomers in each dimer are in the same transport mode. Purine nucleotide (e.g., ATP) can occlude the internal pore of the monomeric units of UCP tetramers via interacting with positive residues at or in the proximity of the matrix network (K38, K141, K239, R88, R185, and R279) and prevent switching between cytoplasmic and matrix states, thus inhibiting the proton transport. This study provides new insights into the mechanism of proton transport and regulation in UCPs.
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Affiliation(s)
- Afshan Ardalan
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
| | - Shahin Sowlati-Hashjin
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 3K7, Canada.,The Center for Advanced Materials and Biomaterials Research, The University of Western Ontario, London, Ontario N6K 3K7, Canada
| | - Habib Oduwoye
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
| | - Stephanie O Uwumarenogie
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
| | - Mikko Karttunen
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 3K7, Canada.,The Center for Advanced Materials and Biomaterials Research, The University of Western Ontario, London, Ontario N6K 3K7, Canada.,Department of Physics and Astronomy, The University of Western Ontario, London, Ontario N6A 3K7, Canada
| | - Matthew D Smith
- Department of Biology, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
| | - Masoud Jelokhani-Niaraki
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada
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8
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Li F, Egea PF, Vecchio AJ, Asial I, Gupta M, Paulino J, Bajaj R, Dickinson MS, Ferguson-Miller S, Monk BC, Stroud RM. Highlighting membrane protein structure and function: A celebration of the Protein Data Bank. J Biol Chem 2021; 296:100557. [PMID: 33744283 PMCID: PMC8102919 DOI: 10.1016/j.jbc.2021.100557] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2020] [Revised: 02/10/2021] [Accepted: 03/16/2021] [Indexed: 12/13/2022] Open
Abstract
Biological membranes define the boundaries of cells and compartmentalize the chemical and physical processes required for life. Many biological processes are carried out by proteins embedded in or associated with such membranes. Determination of membrane protein (MP) structures at atomic or near-atomic resolution plays a vital role in elucidating their structural and functional impact in biology. This endeavor has determined 1198 unique MP structures as of early 2021. The value of these structures is expanded greatly by deposition of their three-dimensional (3D) coordinates into the Protein Data Bank (PDB) after the first atomic MP structure was elucidated in 1985. Since then, free access to MP structures facilitates broader and deeper understanding of MPs, which provides crucial new insights into their biological functions. Here we highlight the structural and functional biology of representative MPs and landmarks in the evolution of new technologies, with insights into key developments influenced by the PDB in magnifying their impact.
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Affiliation(s)
- Fei Li
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA; Department of Neurology, University of California San Francisco, San Francisco, California, USA
| | - Pascal F Egea
- Department of Biological Chemistry, School of Medicine, University of California Los Angeles, Los Angeles, California, USA
| | - Alex J Vecchio
- Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | | | - Meghna Gupta
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - Joana Paulino
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - Ruchika Bajaj
- Department of Bioengineering and Therapeutic Sciences, University of California San Francisco, San Francisco, California, USA
| | - Miles Sasha Dickinson
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA
| | - Shelagh Ferguson-Miller
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan, USA
| | - Brian C Monk
- Sir John Walsh Research Institute and Department of Oral Sciences, University of Otago, North Dunedin, Dunedin, New Zealand
| | - Robert M Stroud
- Department of Biochemistry and Biophysics, University of California San Francisco, San Francisco, California, USA.
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9
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Ardalan A, Sowlati-Hashjin S, Uwumarenogie SO, Fish M, Mitchell J, Karttunen M, Smith MD, Jelokhani-Niaraki M. Functional Oligomeric Forms of Uncoupling Protein 2: Strong Evidence for Asymmetry in Protein and Lipid Bilayer Systems. J Phys Chem B 2020; 125:169-183. [PMID: 33373220 DOI: 10.1021/acs.jpcb.0c09422] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Stoichiometry of uncoupling proteins (UCPs) and their coexistence as functional monomeric and associated forms in lipid membranes remain intriguing open questions. In this study, tertiary and quaternary structures of UCP2 were analyzed experimentally and through molecular dynamics (MD) simulations. UCP2 was overexpressed in the inner membrane of Escherichia coli, then purified and reconstituted in lipid vesicles. Structure and proton transport function of UCP2 were characterized by circular dichroism (CD) spectroscopy and fluorescence methods. Findings suggest a tetrameric functional form for UCP2. MD simulations conclude that tetrameric UCP2 is a dimer of dimers, is more stable than its monomeric and dimeric forms, is asymmetrical and induces asymmetry in the membrane's lipid structure, and a biphasic on-off switch between the dimeric units is its possible mode of transport. MD simulations also show that the water density inside the UCP2 monomer is asymmetric, with the cytoplasmic side having a higher water density and a wider radius. In contrast, the structurally comparable adenosine 5'-diphosphate (ADP)/adenosine 5'-triphosphate (ATP) carrier (AAC1) did not form tetramers, implying that tetramerization cannot be generalized to all mitochondrial carriers.
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Affiliation(s)
- Afshan Ardalan
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5
| | - Shahin Sowlati-Hashjin
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 3K7.,Center for Advanced Materials and Biomaterials Research, The University of Western Ontario, London, Ontario, Canada N6K 3K7
| | - Stephanie O Uwumarenogie
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5
| | - Michael Fish
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5.,Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5
| | - Joel Mitchell
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5
| | - Mikko Karttunen
- Department of Chemistry, The University of Western Ontario, London, Ontario, Canada N6A 3K7.,Center for Advanced Materials and Biomaterials Research, The University of Western Ontario, London, Ontario, Canada N6K 3K7.,Department of Applied Mathematics, The University of Western Ontario, London, Ontario, Canada N6A 5B7
| | - Matthew D Smith
- Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5
| | - Masoud Jelokhani-Niaraki
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada N2L 3C5
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10
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Stylianakis I, Shalev A, Scheiner S, Sigalas MP, Arkin IT, Glykos N, Kolocouris A. The balance between side-chain and backbone-driven association in folding of the α-helical influenza A transmembrane peptide. J Comput Chem 2020; 41:2177-2188. [PMID: 32735736 DOI: 10.1002/jcc.26381] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2020] [Revised: 06/17/2020] [Accepted: 06/18/2020] [Indexed: 11/07/2022]
Abstract
The correct balance between attractive, repulsive and peptide hydrogen bonding interactions must be attained for proteins to fold correctly. To investigate these important contributors, we sought a comparison of the folding between two 25-residues peptides, the influenza A M2 protein transmembrane domain (M2TM) and the 25-Ala (Ala25 ). M2TM forms a stable α-helix as is shown by circular dichroism (CD) experiments. Molecular dynamics (MD) simulations with adaptive tempering show that M2TM monomer is more dynamic in nature and quickly interconverts between an ensemble of various α-helical structures, and less frequently turns and coils, compared to one α-helix for Ala25 . DFT calculations suggest that folding from the extended structure to the α-helical structure is favored for M2TM compared with Ala25 . This is due to CH⋯O attractive interactions which favor folding to the M2TM α-helix, and cannot be described accurately with a force field. Using natural bond orbital (NBO) analysis and quantum theory atoms in molecules (QTAIM) calculations, 26 CH⋯O interactions and 22 NH⋯O hydrogen bonds are calculated for M2TM. The calculations show that CH⋯O hydrogen bonds, although individually weaker, have a cumulative effect that cannot be ignored and may contribute as much as half of the total hydrogen bonding energy, when compared to NH⋯O, to the stabilization of the α-helix in M2TM. Further, a strengthening of NH⋯O hydrogen bonding interactions is calculated for M2TM compared to Ala25 . Additionally, these weak CH⋯O interactions can dissociate and associate easily leading to the ensemble of folded structures for M2TM observed in folding MD simulations.
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Affiliation(s)
- Ioannis Stylianakis
- Section of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
| | - Ariella Shalev
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus Givat-Ram, Jerusalem, Israel
| | - Steve Scheiner
- Department of Chemistry and Biochemistry, Utah State University, Logan, Utah, USA
| | - Michael P Sigalas
- Department of Chemistry, Laboratory of Applied Quantum Chemistry, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Isaiah T Arkin
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, The Hebrew University of Jerusalem, Edmond J. Safra Campus Givat-Ram, Jerusalem, Israel
| | - Nikolas Glykos
- Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece
| | - Antonios Kolocouris
- Section of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
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11
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Site-directed M2 proton channel inhibitors enable synergistic combination therapy for rimantadine-resistant pandemic influenza. PLoS Pathog 2020; 16:e1008716. [PMID: 32780760 PMCID: PMC7418971 DOI: 10.1371/journal.ppat.1008716] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2019] [Accepted: 06/19/2020] [Indexed: 12/05/2022] Open
Abstract
Pandemic influenza A virus (IAV) remains a significant threat to global health. Preparedness relies primarily upon a single class of neuraminidase (NA) targeted antivirals, against which resistance is steadily growing. The M2 proton channel is an alternative clinically proven antiviral target, yet a near-ubiquitous S31N polymorphism in M2 evokes resistance to licensed adamantane drugs. Hence, inhibitors capable of targeting N31 containing M2 (M2-N31) are highly desirable. Rational in silico design and in vitro screens delineated compounds favouring either lumenal or peripheral M2 binding, yielding effective M2-N31 inhibitors in both cases. Hits included adamantanes as well as novel compounds, with some showing low micromolar potency versus pandemic “swine” H1N1 influenza (Eng195) in culture. Interestingly, a published adamantane-based M2-N31 inhibitor rapidly selected a resistant V27A polymorphism (M2-A27/N31), whereas this was not the case for non-adamantane compounds. Nevertheless, combinations of adamantanes and novel compounds achieved synergistic antiviral effects, and the latter synergised with the neuraminidase inhibitor (NAi), Zanamivir. Thus, site-directed drug combinations show potential to rejuvenate M2 as an antiviral target whilst reducing the risk of drug resistance. "Swine flu" illustrated that the spread of influenza pandemics in the modern era is rapid, making antiviral drugs the best way of limiting disease. One proven influenza drug target is the M2 proton channel, which plays an essential role during virus entry. However, resistance against licensed drugs targeting this protein is now ubiquitous, largely due to an S31N change in the M2 sequence. Understandably, considerable effort has focused on developing M2-N31 inhibitors, yet this has been hampered by controversy surrounding two potential drug binding sites. Here, we show that both sites can in fact be targeted by new M2-N31 inhibitors, generating synergistic antiviral effects. Developing such drug combinations should improve patient outcomes and minimise the emergence of future drug resistance.
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12
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Abstract
H-bonding is the predominant geometrical determinant of biomolecular structure and interactions. As such, considerable analyses have been undertaken to study its detailed energetics. The focus, however, has been mostly reserved for H-bonds comprising a single donor and a single acceptor. Herein, we measure the prevalence and energetics of multiplex H-bonds that are formed between three or more groups. We show that 92% of all transmembrane helices have at least one non-canonical H-bond formed by a serine or threonine residue whose hydroxyl side chain H-bonds to an over-coordinated carbonyl oxygen at position i-4, i-3, or i in the sequence. Isotope-edited FTIR spectroscopy, coupled with DFT calculations, enables us to determine the bond enthalpies, pointing to values that are up to 127% higher than that of a single canonical H-bond. We propose that these strong H-bonds serve to stabilize serine and threonine residues in hydrophobic environments while concomitantly providing them flexibility between different configurations, which may be necessary for function.
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Affiliation(s)
- Esther S Brielle
- The Alexander Grass Center for Bioengineering, Benin School of Computer Science and Engineering, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem 9190400, Israel
| | - Isaiah T Arkin
- The Alexander Silberman Institute of Life Sciences. Department of Biological Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem 9190400, Israel
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13
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Konstantinidi A, Chountoulesi M, Naziris N, Sartori B, Amenitsch H, Mali G, Čendak T, Plakantonaki M, Triantafyllakou I, Tselios T, Demetzos C, Busath DD, Mavromoustakos T, Kolocouris A. The boundary lipid around DMPC-spanning influenza A M2 transmembrane domain channels: Its structure and potential for drug accommodation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1862:183156. [PMID: 31846647 DOI: 10.1016/j.bbamem.2019.183156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2019] [Revised: 12/11/2019] [Accepted: 12/12/2019] [Indexed: 10/25/2022]
Abstract
We have investigated the perturbation of influenza A M2TM in DMPC bilayers. We have shown that (a) DSC and SAXS detect changes in membrane organization caused by small changes (micromolar) in M2TM or aminoadamantane concentration and aminoadamantane structure, by comparison of amantadine and spiro[pyrrolidine-2,2'-adamantane] (AK13), (b) that WAXS and MD can suggest details of ligand topology. DSC and SAXS show that at a low M2TM micromolar concentration in DPMC bilayers, two lipid domains are observed, which likely correspond to M2TM boundary lipids and bulk-like lipids. At higher M2TM concentrations, one domain only is identified, which constitutes essentially all of the lipid molecules behaving as boundary lipids. According to SAXS, WAXS, and DSC in the absence of M2TM, both aminoadamantane drugs exert a similar perturbing effect on the bilayer at low concentrations. At the same concentrations of the drug when M2TM is present, amantadine and, to a lesser extent, AK13 cause, according to WAXS, a significant disordering of chain-stacking, which also leads to the formation of two lipid domains. This effect is likely due, according to MD simulations, to the preference of the more lipophilic AK13 to locate closer to the lateral surfaces of M2TM when compared to amantadine, which forms stronger ionic interactions with phosphate groups. The preference of AK13 to concentrate inside the lipid bilayer close to the exterior of the hydrophobic M2TM helices may contribute to its higher binding affinity compared to amantadine.
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Affiliation(s)
- Athina Konstantinidi
- Section of Pharmaceutical Chemistry, Department of Pharmacy, School of Health Sciences, National and Kapodistrian University of Athens, Athens 15771, Greece
| | - Maria Chountoulesi
- Section of Pharmaceutical Technology, Department of Pharmacy, School of Health Sciences, National and Kapodistrian University of Athens, Athens 15771, Greece
| | - Nikolaos Naziris
- Section of Pharmaceutical Technology, Department of Pharmacy, School of Health Sciences, National and Kapodistrian University of Athens, Athens 15771, Greece
| | - Barbara Sartori
- Institute of Inorganic Chemistry, Graz University of Technology, Stremayrgasse 9/IV, A-8010 Graz, Austria
| | - Heinz Amenitsch
- Institute of Inorganic Chemistry, Graz University of Technology, Stremayrgasse 9/IV, A-8010 Graz, Austria
| | - Gregor Mali
- Department of Inorganic Chemistry and Technology, National Institute of Chemistry, Ljubljana SI-1001, Slovenia
| | - Tomaž Čendak
- Department of Inorganic Chemistry and Technology, National Institute of Chemistry, Ljubljana SI-1001, Slovenia
| | - Maria Plakantonaki
- Department of Chemistry, School of Natural Sciences, University of Patras, Rion, Patras 26500, Greece
| | - Iro Triantafyllakou
- Department of Chemistry, School of Natural Sciences, University of Patras, Rion, Patras 26500, Greece
| | - Theodore Tselios
- Department of Chemistry, School of Natural Sciences, University of Patras, Rion, Patras 26500, Greece
| | - Costas Demetzos
- Section of Pharmaceutical Technology, Department of Pharmacy, School of Health Sciences, National and Kapodistrian University of Athens, Athens 15771, Greece
| | - David D Busath
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, UT 84602, USA
| | - Thomas Mavromoustakos
- Section of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Athens 15771, Greece.
| | - Antonios Kolocouris
- Section of Pharmaceutical Chemistry, Department of Pharmacy, School of Health Sciences, National and Kapodistrian University of Athens, Athens 15771, Greece.
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14
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Thomaston JL, Wu Y, Polizzi N, Liu L, Wang J, DeGrado WF. X-ray Crystal Structure of the Influenza A M2 Proton Channel S31N Mutant in Two Conformational States: An Open and Shut Case. J Am Chem Soc 2019; 141:11481-11488. [PMID: 31184871 DOI: 10.1021/jacs.9b02196] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The amantadine-resistant S31N mutant of the influenza A M2 proton channel has become prevalent in currently circulating viruses. Here, we have solved an X-ray crystal structure of M2(22-46) S31N that contains two distinct conformational states within its asymmetric unit. This structure reveals the mechanism of adamantane resistance in both conformational states of the M2 channel. In the Inwardopen conformation, the mutant Asn31 side chain faces the channel pore and sterically blocks the adamantane binding site. In the Inwardclosed conformation, Asn31 forms hydrogen bonds with carbonyls at the monomer-monomer interface, which twists the monomer helices and constricts the channel pore at the drug binding site. We also examine M2(19-49) WT and S31N using solution NMR spectroscopy and show that distribution of the two conformational states is dependent on both detergent choice and experimental pH.
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Affiliation(s)
- Jessica L Thomaston
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
| | - Yibing Wu
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
| | - Nicholas Polizzi
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
| | - Lijun Liu
- State Key Laboratory of Chemical Oncogenomics , Peking University Shenzhen Graduate School , Shenzhen 518055 , China.,DLX Scientific , Lawrence , Kansas 66049 , United States
| | - Jun Wang
- Department of Pharmacology and Toxicology, College of Pharmacy , University of Arizona , Tucson , Arizona 85721 , United States
| | - William F DeGrado
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
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15
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Fernández A. Protein structural defects enable pharmaceutical targeting while functionalizing the M2 proton channel. Biochem Biophys Res Commun 2019; 514:86-91. [PMID: 31023526 DOI: 10.1016/j.bbrc.2019.04.094] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2019] [Accepted: 04/12/2019] [Indexed: 11/28/2022]
Abstract
The influenza M2 (22-46) proton channel is therapeutically targetable and a prototype for proton transport across membranes. Conduction initiation, requiring a hydronium formed with exceptionally high pKa, remains nebulous. We tackle the problem by focusing on the dynamic interplay between protein structure and solvent interface. We identify two packing defects in the protein subunits that predict exactly the low and high-affinity drug-binding sites. The latter defect frustrates water coordination, enhancing water basicity and stabilizing the nearby hydronium that forms upon proton penetration in the channel. Thus, the trigger of proton conduction is directly related to the high-affinity binding site. The findings, in quantitative agreement with affinity measurements, are consistent with the targetable functional nature of protein packing defects. These findings enable the design of proton-conducting biomimetic materials, where the epistructure may be engineered to tune the basicity of interfacial water.
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Affiliation(s)
- Ariel Fernández
- National Research Council (CONICET), Rivadavia 1917, Buenos Aires, 1033, Argentina; INQUISUR/UNS/CONICET, Avenida Alem 1253, Bahía Blanca, 8000, Argentina; AF Innovation Pharma Consultancy GmbH, Buenos Aires, 1112, Argentina; Collegium Basilea, Institute for Advanced Study, Hochstrasse 51, 4053, Basel, Switzerland.
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16
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Thomaston JL, Polizzi NF, Konstantinidi A, Wang J, Kolocouris A, DeGrado WF. Inhibitors of the M2 Proton Channel Engage and Disrupt Transmembrane Networks of Hydrogen-Bonded Waters. J Am Chem Soc 2018; 140:15219-15226. [PMID: 30165017 DOI: 10.1021/jacs.8b06741] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Water-mediated interactions play key roles in drug binding. In protein sites with sparse polar functionality, a small-molecule approach is often viewed as insufficient to achieve high affinity and specificity. Here we show that small molecules can enable potent inhibition by targeting key waters. The M2 proton channel of influenza A is the target of the antiviral drugs amantadine and rimantadine. Structural studies of drug binding to the channel using X-ray crystallography have been limited because of the challenging nature of the target, with the one previously solved crystal structure limited to 3.5 Å resolution. Here we describe crystal structures of amantadine bound to M2 in the Inwardclosed conformation (2.00 Å), rimantadine bound to M2 in both the Inwardclosed (2.00 Å) and Inwardopen (2.25 Å) conformations, and a spiro-adamantyl amine inhibitor bound to M2 in the Inwardclosed conformation (2.63 Å). These X-ray crystal structures of the M2 proton channel with bound inhibitors reveal that ammonium groups bind to water-lined sites that are hypothesized to stabilize transient hydronium ions formed in the proton-conduction mechanism. Furthermore, the ammonium and adamantyl groups of the adamantyl-amine class of drugs are free to rotate in the channel, minimizing the entropic cost of binding. These drug-bound complexes provide the first high-resolution structures of drugs that interact with and disrupt networks of hydrogen-bonded waters that are widely utilized throughout nature to facilitate proton diffusion within proteins.
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Affiliation(s)
- Jessica L Thomaston
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
| | - Nicholas F Polizzi
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
| | - Athina Konstantinidi
- Department of Pharmaceutical Chemistry , National and Kapodistrian University of Athens , 15771 Athens , Greece
| | - Jun Wang
- Department of Pharmacology and Toxicology, College of Pharmacy , University of Arizona , Tucson , Arizona 85721 , United States
| | - Antonios Kolocouris
- Department of Pharmaceutical Chemistry , National and Kapodistrian University of Athens , 15771 Athens , Greece
| | - William F DeGrado
- Department of Pharmaceutical Chemistry , University of California , San Francisco , California 94158 , United States
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17
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Membrane-associated human tyrosinase is an enzymatically active monomeric glycoprotein. PLoS One 2018; 13:e0198247. [PMID: 29870551 PMCID: PMC5988326 DOI: 10.1371/journal.pone.0198247] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 05/16/2018] [Indexed: 11/19/2022] Open
Abstract
Human tyrosinase (hTyr) is a Type 1 membrane bound glycoenzyme that catalyzes the initial and rate-limiting steps of melanin production in the melanosome. Mutations in the Tyr gene are linked to oculocutaneous albinism type 1 (OCA1), an autosomal recessive disorder. Currently, the application of enzyme replacement therapy for a treatment of OCA1 is hampered by the absence of pure hTyr. Here, full-length hTyr (residues 1-529) was overexpressed in Trichoplusia ni larvae infected with a baculovirus, solubilized with detergent and purified using chromatography. Michaelis-Menten kinetics, enzymatic specific activity, and analytical ultracentrifugation were used to compare the hTyr in detergent with the soluble recombinant intra-melanosomal domain, hTyrCtr (residues 19-469). Active hTyr is monomeric in detergent micelles suggesting no stable interactions between protein molecules. Both, hTyr and hTyrCtr, exhibited similar enzymatic activity and ligand affinity in L-DOPA and L-Tyrosine reactions. In addition, expression in larvae is a scalable process that will allow high yield protein production. Thus, larval production of enzymatically active human tyrosinase potentially could be a useful tool in developing a cure for OCA1.
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18
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Drakopoulos A, Tzitzoglaki C, McGuire K, Hoffmann A, Konstantinidi A, Kolokouris D, Ma C, Freudenberger K, Hutterer J, Gauglitz G, Wang J, Schmidtke M, Busath DD, Kolocouris A. Unraveling the Binding, Proton Blockage, and Inhibition of Influenza M2 WT and S31N by Rimantadine Variants. ACS Med Chem Lett 2018. [PMID: 29541360 DOI: 10.1021/acsmedchemlett.7b00458] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Recently, the binding kinetics of a ligand-target interaction, such as the residence time of a small molecule on its protein target, are seen as increasingly important for drug efficacy. Here, we investigate these concepts to explain binding and proton blockage of rimantadine variants bearing progressively larger alkyl groups to influenza A virus M2 wild type (WT) and M2 S31N protein proton channel. We showed that resistance of M2 S31N to rimantadine analogues compared to M2 WT resulted from their higher koff rates compared to the kon rates according to electrophysiology (EP) measurements. This is due to the fact that, in M2 S31N, the loss of the V27 pocket for the adamantyl cage resulted in low residence time inside the M2 pore. Both rimantadine enantiomers have similar channel blockage and binding kon and koff against M2 WT. To compare the potency between the rimantadine variants against M2, we applied approaches using different mimicry of M2, i.e., isothermal titration calorimetry and molecular dynamics simulation, EP, and antiviral assays. It was also shown that a small change in an amino acid at site 28 of M2 WT, which does not line the pore, seriously affects M2 WT blockage kinetics.
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Affiliation(s)
- Antonios Drakopoulos
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou 15771, Greece
| | - Christina Tzitzoglaki
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou 15771, Greece
| | - Kelly McGuire
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah 84602, United States
| | - Anja Hoffmann
- Department of Medicinal Microbiology, Section Experimental Virology, Jena University Hospital, Hans Knoell Str. 2, D-07745 Jena, Germany
| | - Athina Konstantinidi
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou 15771, Greece
| | - Dimitrios Kolokouris
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou 15771, Greece
| | - Chunlong Ma
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, United States
| | - Kathrin Freudenberger
- Institut für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität Tübingen, 72074 Tübingen, Germany
| | - Johanna Hutterer
- Institut für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität Tübingen, 72074 Tübingen, Germany
| | - Günter Gauglitz
- Institut für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität Tübingen, 72074 Tübingen, Germany
| | - Jun Wang
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, United States
| | - Michaela Schmidtke
- Department of Medicinal Microbiology, Section Experimental Virology, Jena University Hospital, Hans Knoell Str. 2, D-07745 Jena, Germany
| | - David D. Busath
- Department of Physiology and Developmental Biology, Brigham Young University, Provo, Utah 84602, United States
| | - Antonios Kolocouris
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Panepistimiopolis-Zografou 15771, Greece
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19
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Schroeder S, Kaufman JD, Grunwald M, Walla PJ, Lakomek NA, Wingfield PT. HIV-1 gp41 transmembrane oligomerization monitored by FRET and FCS. FEBS Lett 2018; 592:939-948. [PMID: 29453892 DOI: 10.1002/1873-3468.13010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 01/21/2018] [Accepted: 02/11/2018] [Indexed: 11/08/2022]
Abstract
The HIV-1 envelope gp120/gp41 trimer mediates viral membrane fusion. After cluster of differentiation-4 recognition, gp120 detaches from the virus, exposing gp41 which triggers fusion. During the fusion process, gp41 may not remain trimeric, which could have functional importance. Here, we probe the reversible association of full length gp41 (minus the cytoplasmic domain) in detergent micelles (with probes attached to transmembrane domain) by fluorescence resonance energy transfer (FRET) with a μm dissociation constant. This is compared with other methods. A gp41-targeted fusion inhibitor must interfere with this transition, and monomeric, partially monomeric or trimeric states all present potential binding epitopes. The gp41 self-association is a valid drug target model and FRET, a potential high-throughput assay system, could be used to screen drug libraries.
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Affiliation(s)
| | - Joshua D Kaufman
- Protein Expression Laboratory, NIAMS, National Institutes of Health, Bethesda, MD, USA
| | | | - Peter J Walla
- Institute for Physical and Theoretical Chemistry, Technical University Braunschweig, Germany
| | - Nils-Alexander Lakomek
- Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Laboratory of Physical Chemistry, Department of Chemistry and Applied Biosciences (D-CHAB), ETH Zurich, Switzerland
| | - Paul T Wingfield
- Protein Expression Laboratory, NIAMS, National Institutes of Health, Bethesda, MD, USA
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20
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Influenza A Virus M2 Protein: Roles from Ingress to Egress. Int J Mol Sci 2017; 18:ijms18122649. [PMID: 29215568 PMCID: PMC5751251 DOI: 10.3390/ijms18122649] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2017] [Revised: 12/04/2017] [Accepted: 12/05/2017] [Indexed: 11/17/2022] Open
Abstract
Influenza A virus (IAV) matrix protein 2 (M2) is among the smallest bona fide, hence extensively studied, ion channel proteins. The M2 ion channel activity is not only essential for virus replication, but also involved in modulation of cellular homeostasis in a variety of ways. It is also the target for ion channel inhibitors, i.e., anti-influenza drugs. Thus far, several studies have been conducted to elucidate its biophysical characteristics, structure-function relationships of the ion channel, and the M2-host interactome. In this review, we discuss M2 protein synthesis and assembly into an ion channel, its roles in IAV replication, and the pathophysiological impact on the host cell.
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21
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XFEL structures of the influenza M2 proton channel: Room temperature water networks and insights into proton conduction. Proc Natl Acad Sci U S A 2017; 114:13357-13362. [PMID: 28835537 DOI: 10.1073/pnas.1705624114] [Citation(s) in RCA: 53] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The M2 proton channel of influenza A is a drug target that is essential for the reproduction of the flu virus. It is also a model system for the study of selective, unidirectional proton transport across a membrane. Ordered water molecules arranged in "wires" inside the channel pore have been proposed to play a role in both the conduction of protons to the four gating His37 residues and the stabilization of multiple positive charges within the channel. To visualize the solvent in the pore of the channel at room temperature while minimizing the effects of radiation damage, data were collected to a resolution of 1.4 Å using an X-ray free-electron laser (XFEL) at three different pH conditions: pH 5.5, pH 6.5, and pH 8.0. Data were collected on the Inwardopen state, which is an intermediate that accumulates at high protonation of the His37 tetrad. At pH 5.5, a continuous hydrogen-bonded network of water molecules spans the vertical length of the channel, consistent with a Grotthuss mechanism model for proton transport to the His37 tetrad. This ordered solvent at pH 5.5 could act to stabilize the positive charges that build up on the gating His37 tetrad during the proton conduction cycle. The number of ordered pore waters decreases at pH 6.5 and 8.0, where the Inwardopen state is less stable. These studies provide a graphical view of the response of water to a change in charge within a restricted channel environment.
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22
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Jeong BS, Dyer RB. Proton Transport Mechanism of M2 Proton Channel Studied by Laser-Induced pH Jump. J Am Chem Soc 2017; 139:6621-6628. [PMID: 28467842 DOI: 10.1021/jacs.7b00617] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The M2 proton transport channel of the influenza virus A is an important model system because it conducts protons with high selectivity and unidirectionally when activated at low pH, despite the relative simplicity of its structure. Although it has been studied extensively, the molecular details of the pH-dependent gating and proton conductance mechanisms are incompletely understood. We report direct observation of the M2 proton channel activation process using a laser-induced pH jump coupled with tryptophan fluorescence as a probe. Biphasic kinetics is observed, with the fast phase corresponding to the His37 protonation, and the slow phase associated with the subsequent conformation change. Unusually fast His37 protonation was observed (2.0 × 1010 M-1 s-1), implying the existence of proton collecting antennae for expedited proton transport. The conformation change (4 × 103 s-1) was about 2 orders of magnitude slower than protonation at endosomal pH, suggesting that a transporter model is likely not feasible.
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Affiliation(s)
- Ban-Seok Jeong
- Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States
| | - R Brian Dyer
- Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States
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23
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Tzitzoglaki C, Wright A, Freudenberger K, Hoffmann A, Tietjen I, Stylianakis I, Kolarov F, Fedida D, Schmidtke M, Gauglitz G, Cross TA, Kolocouris A. Binding and Proton Blockage by Amantadine Variants of the Influenza M2WT and M2S31N Explained. J Med Chem 2017; 60:1716-1733. [DOI: 10.1021/acs.jmedchem.6b01115] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Christina Tzitzoglaki
- Section
of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece
| | - Anna Wright
- Institute
of Molecular Biophysics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, United States
| | - Kathrin Freudenberger
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls Universität, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - Anja Hoffmann
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Strasse 2, D-07745 Jena, Germany
| | - Ian Tietjen
- Department
of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Ioannis Stylianakis
- Section
of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece
| | - Felix Kolarov
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls Universität, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - David Fedida
- Department
of Anesthesiology, Pharmacology and Therapeutics, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada
| | - Michaela Schmidtke
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Strasse 2, D-07745 Jena, Germany
| | - Günter Gauglitz
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls Universität, Auf der Morgenstelle 18, D-72076 Tübingen, Germany
| | - Timothy A. Cross
- Institute
of Molecular Biophysics and National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32306, United States
- Department
of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Antonios Kolocouris
- Section
of Pharmaceutical Chemistry, Department of Pharmacy, National and Kapodistrian University of Athens, Athens 157 71, Greece
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24
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Drakopoulos A, Tzitzoglaki C, Ma C, Freudenberger K, Hoffmann A, Hu Y, Gauglitz G, Schmidtke M, Wang J, Kolocouris A. Affinity of Rimantadine Enantiomers against Influenza A/M2 Protein Revisited. ACS Med Chem Lett 2017; 8:145-150. [PMID: 28217261 DOI: 10.1021/acsmedchemlett.6b00311] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 01/13/2017] [Indexed: 12/28/2022] Open
Abstract
Recent findings from solid state NMR (ssNMR) studies suggested that the (R)-enantiomer of rimantadine binds to the full M2 protein with higher affinity than the (S)-enantiomer. Intrigued by these findings, we applied functional assays, such as antiviral assay and electrophysiology (EP), to evaluate the binding affinity of rimantadine enantiomers to the M2 protein channel. Unexpectedly, no significant difference was found between the two enantiomers. Our experimental data based on the full M2 protein function were further supported by alchemical free energy calculations and isothermal titration calorimetry (ITC) allowing an evaluation of the binding affinity of rimantadine enantiomers to the M2TM pore. Both enantiomers have similar channel blockage, affinity, and antiviral potency.
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Affiliation(s)
- Antonios Drakopoulos
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
| | - Christina Tzitzoglaki
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
| | - Chulong Ma
- Department
of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, United States
| | - Kathrin Freudenberger
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Anja Hoffmann
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Str. 2, D-07745 Jena, Germany
| | - Yanmei Hu
- Department
of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, United States
| | - Günter Gauglitz
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Michaela Schmidtke
- Department
of Virology and Antiviral Therapy, Jena University Hospital, Hans Knoell Str. 2, D-07745 Jena, Germany
| | - Jun Wang
- Department
of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, United States
| | - Antonios Kolocouris
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, Athens, Greece
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25
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Liang R, Swanson JMJ, Madsen JJ, Hong M, DeGrado WF, Voth GA. Acid activation mechanism of the influenza A M2 proton channel. Proc Natl Acad Sci U S A 2016; 113:E6955-E6964. [PMID: 27791184 PMCID: PMC5111692 DOI: 10.1073/pnas.1615471113] [Citation(s) in RCA: 70] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The homotetrameric influenza A M2 channel (AM2) is an acid-activated proton channel responsible for the acidification of the influenza virus interior, an important step in the viral lifecycle. Four histidine residues (His37) in the center of the channel act as a pH sensor and proton selectivity filter. Despite intense study, the pH-dependent activation mechanism of the AM2 channel has to date not been completely understood at a molecular level. Herein we have used multiscale computer simulations to characterize (with explicit proton transport free energy profiles and their associated calculated conductances) the activation mechanism of AM2. All proton transfer steps involved in proton diffusion through the channel, including the protonation/deprotonation of His37, are explicitly considered using classical, quantum, and reactive molecular dynamics methods. The asymmetry of the proton transport free energy profile under high-pH conditions qualitatively explains the rectification behavior of AM2 (i.e., why the inward proton flux is allowed when the pH is low in viral exterior and high in viral interior, but outward proton flux is prohibited when the pH gradient is reversed). Also, in agreement with electrophysiological results, our simulations indicate that the C-terminal amphipathic helix does not significantly change the proton conduction mechanism in the AM2 transmembrane domain; the four transmembrane helices flanking the channel lumen alone seem to determine the proton conduction mechanism.
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Affiliation(s)
- Ruibin Liang
- Department of Chemistry, The University of Chicago, Chicago, IL 60637
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637
- James Franck Institute, The University of Chicago, Chicago, IL 60637
| | - Jessica M J Swanson
- Department of Chemistry, The University of Chicago, Chicago, IL 60637
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637
- James Franck Institute, The University of Chicago, Chicago, IL 60637
| | - Jesper J Madsen
- Department of Chemistry, The University of Chicago, Chicago, IL 60637
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637
- James Franck Institute, The University of Chicago, Chicago, IL 60637
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of San Francisco, San Francisco, CA 94158
| | - Gregory A Voth
- Department of Chemistry, The University of Chicago, Chicago, IL 60637;
- Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637
- James Franck Institute, The University of Chicago, Chicago, IL 60637
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26
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Ng DP, Deber CM. Modulating Transmembrane α-Helix Interactions through pH-Sensitive Boundary Residues. Biochemistry 2016; 55:4306-15. [DOI: 10.1021/acs.biochem.6b00380] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Derek P. Ng
- Department
of Biology, University of Toronto Mississauga, Mississauga, Ontario, Canada L5L 1C6
- Institute
of Medical Science, University of Toronto, Toronto, Ontario, Canada M5S 1A8
| | - Charles M. Deber
- Division of Molecular Structure & Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada M5G 1X8
- Department
of Biochemistry, University of Toronto, Toronto, Ontario, Canada M5S 1A8
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27
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Georgieva ER, Borbat PP, Grushin K, Stoilova-McPhie S, Kulkarni NJ, Liang Z, Freed JH. Conformational Response of Influenza A M2 Transmembrane Domain to Amantadine Drug Binding at Low pH (pH 5.5). Front Physiol 2016; 7:317. [PMID: 27524969 PMCID: PMC4965473 DOI: 10.3389/fphys.2016.00317] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 07/13/2016] [Indexed: 12/27/2022] Open
Abstract
The M2 protein from influenza A plays important roles in its viral cycle. It contains a single transmembrane helix, which oligomerizes into a homotetrameric proton channel that conducts in the low-pH environment of the host-cell endosome and Golgi apparatus, leading to virion uncoating at an early stage of infection. We studied conformational rearrangements that occur in the M2 core transmembrane domain residing on the lipid bilayer, flanked by juxtamembrane residues (M2TMD21-49 fragment), upon its interaction with amantadine drug at pH 5.5 when M2 is conductive. We also tested the role of specific mutation and lipid chain length. Electron spin resonance (ESR) spectroscopy and electron microscopy were applied to M2TMD21-49, labeled at the residue L46C with either nitroxide spin-label or Nanogold® reagent, respectively. Electron microscopy confirmed that M2TMD21-49 reconstituted into DOPC/POPS at 1:10,000 peptide-to-lipid molar ratio (P/L) either with or without amantadine, is an admixture of monomers, dimers, and tetramers, confirming our model based on a dimer intermediate in the assembly of M2TMD21-49. As reported by double electron-electron resonance (DEER), in DOPC/POPS membranes amantadine shifts oligomer equilibrium to favor tetramers, as evidenced by an increase in DEER modulation depth for P/L's ranging from 1:18,000 to 1:160. Furthermore, amantadine binding shortens the inter-spin distances (for nitroxide labels) by 5-8 Å, indicating drug induced channel closure on the C-terminal side. No such effect was observed for the thinner membrane of DLPC/DLPS, emphasizing the role of bilayer thickness. The analysis of continuous wave (cw) ESR spectra of spin-labeled L46C residue provides additional support to a more compact helix bundle in amantadine-bound M2TMD 21-49 through increased motional ordering. In contrast to wild-type M2TMD21-49, the amantadine-bound form does not exhibit noticeable conformational changes in the case of G34A mutation found in certain drug-resistant influenza strains. Thus, the inhibited M2TMD21-49 channel is a stable tetramer with a closed C-terminal exit pore. This work is aimed at contributing to the development of structure-based anti-influenza pharmaceuticals.
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Affiliation(s)
- Elka R Georgieva
- Department of Chemistry and Chemical Biology, Cornell UniversityIthaca, NY, USA; National Biomedical Center for Advanced ESR TechnologyIthaca, NY, USA
| | - Peter P Borbat
- Department of Chemistry and Chemical Biology, Cornell UniversityIthaca, NY, USA; National Biomedical Center for Advanced ESR TechnologyIthaca, NY, USA
| | - Kirill Grushin
- Department of Neuroscience and Cell Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston Galveston, TX, USA
| | - Svetla Stoilova-McPhie
- Department of Neuroscience and Cell Biology, Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch at Galveston Galveston, TX, USA
| | | | - Zhichun Liang
- Department of Chemistry and Chemical Biology, Cornell UniversityIthaca, NY, USA; National Biomedical Center for Advanced ESR TechnologyIthaca, NY, USA
| | - Jack H Freed
- Department of Chemistry and Chemical Biology, Cornell UniversityIthaca, NY, USA; National Biomedical Center for Advanced ESR TechnologyIthaca, NY, USA
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28
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Ioannidis H, Drakopoulos A, Tzitzoglaki C, Homeyer N, Kolarov F, Gkeka P, Freudenberger K, Liolios C, Gauglitz G, Cournia Z, Gohlke H, Kolocouris A. Alchemical Free Energy Calculations and Isothermal Titration Calorimetry Measurements of Aminoadamantanes Bound to the Closed State of Influenza A/M2TM. J Chem Inf Model 2016; 56:862-76. [DOI: 10.1021/acs.jcim.6b00079] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Harris Ioannidis
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece
| | - Antonios Drakopoulos
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece
| | - Christina Tzitzoglaki
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece
| | - Nadine Homeyer
- Mathematisch-Naturwissenschaftliche
Fakultät, Institut für Pharmazeutische und Medizinische
Chemie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Felix Kolarov
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Paraskevi Gkeka
- Biomedical
Research Foundation, Academy of Athens, 11527 Athens, Greece
| | - Kathrin Freudenberger
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Christos Liolios
- Demokritos, National Center for Scientific Research, 15310 Athens, Greece
| | - Günter Gauglitz
- Institut
für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität, D-72076 Tübingen, Germany
| | - Zoe Cournia
- Biomedical
Research Foundation, Academy of Athens, 11527 Athens, Greece
| | - Holger Gohlke
- Mathematisch-Naturwissenschaftliche
Fakultät, Institut für Pharmazeutische und Medizinische
Chemie, Heinrich-Heine-Universität Düsseldorf, 40225 Düsseldorf, Germany
| | - Antonios Kolocouris
- Department
of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens, 15771 Athens, Greece
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29
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Goparaju G, Fry BA, Chobot SE, Wiedman G, Moser CC, Leslie Dutton P, Discher BM. First principles design of a core bioenergetic transmembrane electron-transfer protein. BIOCHIMICA ET BIOPHYSICA ACTA 2016; 1857:503-512. [PMID: 26672896 PMCID: PMC4846532 DOI: 10.1016/j.bbabio.2015.12.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 11/14/2015] [Accepted: 12/01/2015] [Indexed: 12/26/2022]
Abstract
Here we describe the design, Escherichia coli expression and characterization of a simplified, adaptable and functionally transparent single chain 4-α-helix transmembrane protein frame that binds multiple heme and light activatable porphyrins. Such man-made cofactor-binding oxidoreductases, designed from first principles with minimal reference to natural protein sequences, are known as maquettes. This design is an adaptable frame aiming to uncover core engineering principles governing bioenergetic transmembrane electron-transfer function and recapitulate protein archetypes proposed to represent the origins of photosynthesis. This article is part of a Special Issue entitled Biodesign for Bioenergetics--the design and engineering of electronic transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson.
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Affiliation(s)
- Geetha Goparaju
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Bryan A Fry
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Sarah E Chobot
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Gregory Wiedman
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Christopher C Moser
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - P Leslie Dutton
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Bohdana M Discher
- Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA 19104, USA.
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30
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Gosavi PM, Moroz YS, Korendovych IV. β-(1-Azulenyl)-L-alanine--a functional probe for determination of pKa of histidine residues. Chem Commun (Camb) 2016; 51:5347-50. [PMID: 25645241 DOI: 10.1039/c4cc08720h] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
β-(1-Azulenyl)-L-alanine (AzAla) can be incorporated into the influenza A virus M2 proton channel. AzAla's sensitivity to the protonation state of the nearby histidines and the lack of environmental fluorescence dependence allow for direct and straightforward determination of histidine pKa values in ion channels.
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Affiliation(s)
- Pallavi M Gosavi
- Department of Chemistry, Syracuse University, 111 College Place, Syracuse, NY 13244, USA.
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31
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Homeyer N, Ioannidis H, Kolarov F, Gauglitz G, Zikos C, Kolocouris A, Gohlke H. Interpreting Thermodynamic Profiles of Aminoadamantane Compounds Inhibiting the M2 Proton Channel of Influenza A by Free Energy Calculations. J Chem Inf Model 2016; 56:110-26. [PMID: 26690735 DOI: 10.1021/acs.jcim.5b00467] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The development of novel anti-influenza drugs is of great importance because of the capability of influenza viruses to occasionally cross interspecies barriers and to rapidly mutate. One class of anti-influenza agents, aminoadamantanes, including the drugs amantadine and rimantadine now widely abandoned due to virus resistance, bind to and block the pore of the transmembrane domain of the M2 proton channel (M2TM) of influenza A. Here, we present one of the still rare studies that interprets thermodynamic profiles from isothermal titration calorimetry (ITC) experiments in terms of individual energy contributions to binding, calculated by the computationally inexpensive implicit solvent/implicit membrane molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approach, for aminoadamantane compounds binding to M2TM of the avian "Weybridge" strain. For all eight pairs of aminoadamantane compounds considered, the trend of the predicted relative binding free energies and their individual components, effective binding energies and changes in the configurational entropy, agrees with experimental measures (ΔΔG, ΔΔH, TΔΔS) in 88, 88, and 50% of the cases. In addition, information yielded by the MM-PBSA approach about determinants of binding goes beyond that available in component quantities (ΔH, ΔS) from ITC measurements. We demonstrate how one can make use of such information to link thermodynamic profiles from ITC with structural causes on the ligand side and, ultimately, to guide decision making in lead optimization in a prospective manner, which results in an aminoadamantane derivative with improved binding affinity against M2TM(Weybridge).
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Affiliation(s)
- Nadine Homeyer
- Mathematisch-Naturwissenschaftliche Fakultät, Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf , 40225 Düsseldorf, Germany
| | - Harris Ioannidis
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens , 15771 Athens, Greece
| | - Felix Kolarov
- Institut für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität Tübingen , 72076 Tübingen, Germany
| | - Günter Gauglitz
- Institut für Physikalische und Theoretische Chemie, Eberhard-Karls-Universität Tübingen , 72076 Tübingen, Germany
| | - Christos Zikos
- Demokritos, National Center for Scientific Research , 15310 Athens, Greece
| | - Antonios Kolocouris
- Department of Pharmaceutical Chemistry, Faculty of Pharmacy, National and Kapodistrian University of Athens , 15771 Athens, Greece
| | - Holger Gohlke
- Mathematisch-Naturwissenschaftliche Fakultät, Institut für Pharmazeutische und Medizinische Chemie, Heinrich-Heine-Universität Düsseldorf , 40225 Düsseldorf, Germany
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32
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Mechanism of influenza A M2 transmembrane domain assembly in lipid membranes. Sci Rep 2015; 5:11757. [PMID: 26190831 PMCID: PMC4507135 DOI: 10.1038/srep11757] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2015] [Accepted: 06/04/2015] [Indexed: 12/20/2022] Open
Abstract
M2 from influenza A virus functions as an oligomeric proton channel essential for the viral cycle, hence it is a high-priority pharmacological target whose structure and functions require better understanding. We studied the mechanism of M2 transmembrane domain (M2TMD) assembly in lipid membranes by the powerful biophysical technique of double electron-electron resonance (DEER) spectroscopy. By varying the M2TMD-to-lipid molar ratio over a wide range from 1:18,800 to 1:160, we found that M2TMD exists as monomers, dimers, and tetramers whose relative populations shift to tetramers with the increase of peptide-to-lipid (P/L) molar ratio. Our results strongly support the tandem mechanism of M2 assembly that is monomers-to-dimer then dimers-to-tetramer, since tight dimers are abundant at small P/L’s, and thereafter they assemble as dimers of dimers in weaker tetramers. The stepwise mechanism found for a single-pass membrane protein oligomeric assembly should contribute to the knowledge of the association steps in membrane protein folding.
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33
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Hoang T, Kuljanin M, Smith MD, Jelokhani-Niaraki M. A biophysical study on molecular physiology of the uncoupling proteins of the central nervous system. Biosci Rep 2015; 35:e00226. [PMID: 26182433 PMCID: PMC4613710 DOI: 10.1042/bsr20150130] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2015] [Accepted: 06/04/2015] [Indexed: 01/16/2023] Open
Abstract
Mitochondrial inner membrane uncoupling proteins (UCPs) facilitate transmembrane (TM) proton flux and consequently reduce the membrane potential and ATP production. It has been proposed that the three neuronal human UCPs (UCP2, UCP4 and UCP5) in the central nervous system (CNS) play significant roles in reducing cellular oxidative stress. However, the structure and ion transport mechanism of these proteins remain relatively unexplored. Recently, we reported a novel expression system for obtaining functionally folded UCP1 in bacterial membranes and applied this system to obtain highly pure neuronal UCPs in high yields. In the present study, we report on the structure and function of the three neuronal UCP homologues. Reconstituted neuronal UCPs were dominantly helical in lipid membranes and transported protons in the presence of physiologically-relevant fatty acid (FA) activators. Under similar conditions, all neuronal UCPs also exhibited chloride transport activities that were partially inhibited by FAs. CD, fluorescence and MS measurements and semi-native gel electrophoresis collectively suggest that the reconstituted proteins self-associate in the lipid membranes. Based on SDS titration experiments and other evidence, a general molecular model for the monomeric, dimeric and tetrameric functional forms of UCPs in lipid membranes is proposed. In addition to their shared structural and ion transport features, neuronal UCPs differ in their conformations and proton transport activities (and possibly mechanism) in the presence of different FA activators. The differences in FA-activated UCP-mediated proton transport could serve as an essential factor in understanding and differentiating the physiological roles of UCP homologues in the CNS.
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Affiliation(s)
- Tuan Hoang
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5 Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Miljan Kuljanin
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5
| | - Matthew D Smith
- Department of Biology, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5 Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
| | - Masoud Jelokhani-Niaraki
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, Waterloo, Ontario, Canada, N2L 3C5 Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
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34
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Hoang T, Matovic T, Parker J, Smith MD, Jelokhani-Niaraki M. Role of positively charged residues of the second transmembrane domain in the ion transport activity and conformation of human uncoupling protein-2. Biochemistry 2015; 54:2303-13. [PMID: 25789405 DOI: 10.1021/acs.biochem.5b00177] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Residing at the inner mitochondrial membrane, uncoupling protein-2 (UCP2) mediates proton transport from the intermembrane space (IMS) to the mitochondrial matrix and consequently reduces the rate of ATP synthesis in the mitochondria. The ubiquitous expression of UCP2 in humans can be attributed to the protein's multiple physiological roles in tissues, including its involvement in protective mechanisms against oxidative stress, as well as glucose and lipid metabolisms. Currently, the structural properties and ion transport mechanism of UCP2 and other UCP homologues remain poorly understood. UCP2-mediated proton transport is activated by fatty acids and inhibited by di- and triphosphate purine nucleotides. UCP2 also transports chloride and some other small anions. Identification of key amino acid residues of UCP2 in its ion transport pathway can shed light on the protein's ion transport function. On the basis of our previous studies, the second transmembrane helix segment (TM2) of UCP2 exhibited chloride channel activity. In addition, it was suggested that the positively charged residues on TM2 domains of UCPs 1 and 2 were important for their chloride transport activity. On this basis, to further understand the role of these positively charged residues on the ion transport activity of UCP2, we recombinantly expressed four TM2 mutants: R76Q, R88Q, R96Q, and K104Q. The wild type UCP2 and its mutants were purified and reconstituted into liposomes, and their conformation and ion (proton and chloride) transport activity were studied. TM2 Arg residues at the matrix interface of UCP2 proved to be crucial for the protein's anion transport function, and their absence resulted in highly diminished Cl(-) transport rates. On the other hand, the two other positively charged residues of TM2, located at the UCP2-IMS interface, could participate in the salt-bridge formation in the protein and promote the interhelical tight packing in the UCP2. Absence of these residues did not influence Cl(-) transport rates, but disturbed the dense packing in UCP2 and resulted in higher UCP2-mediated proton transport rates in the presence of long chain fatty acids. Overall, the outcome of this study provides a deeper and more detailed molecular image of UCP2's ion transport mechanism.
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Affiliation(s)
- Tuan Hoang
- §Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | | | | | - Matthew D Smith
- §Biophysics Interdepartmental Group, University of Guelph, Guelph, Ontario N1G 2W1, Canada
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35
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Gu R, Liu LA, Wei D. Drug inhibition and proton conduction mechanisms of the influenza a M2 proton channel. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015; 827:205-26. [PMID: 25387967 DOI: 10.1007/978-94-017-9245-5_13] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The influenza A virus matrix protein 2 (M2 protein) is a pH-regulated proton channel embedded in the viral membrane. Inhibition of the M2 proton channel has been used to treat influenza infections for decades due to the crucial role of this protein in viral infection and replication. However, the widely-used M2 inhibitors, amantadine and rimantadine, have gradually lost their efficiencies because of naturally-occurring drug resistant mutations. Therefore, investigation of the structure and function of the M2 proton channel will not only increase our understanding of this important biological system, but also lead to the design of novel and effective anti-influenza drugs. Despite the simplicity of the M2 molecular structure, the M2 channel is highly flexible and there have been controversies and arguments regarding the channel inhibition mechanism and the proton conduction mechanism. In this book chapter, we will first carefully review the experimental and computational studies of the two possible drug binding sites on the M2 protein and explain the mechanisms regarding how inhibitors prevent proton conduction. Then, we will summarize our recent molecular dynamics simulations of the drug-resistant mutant channels and propose mechanisms for drug resistance. Finally, we will discuss two existing proton conduction mechanisms and talk about the remaining questions regarding the proton-relay process through the channel. The studies reviewed here demonstrate how molecular modeling and simulations have complemented experimental work and helped us understand the M2 channel structure and function.
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Affiliation(s)
- Ruoxu Gu
- State Key Laboratory of Microbial Metabolism, College of Life Sciences and Biotechnology, Shanghai Jiao Tong University, Shanghai, China
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36
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Stockdale TP, Williams CM. Pharmaceuticals that contain polycyclic hydrocarbon scaffolds. Chem Soc Rev 2015; 44:7737-63. [DOI: 10.1039/c4cs00477a] [Citation(s) in RCA: 137] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
This review comprehensively explores approved pharmaceutical compounds that contain polycyclic scaffolds and the properties that these skeletons convey.
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Affiliation(s)
- Tegan P. Stockdale
- School of Chemistry and Molecular Biosciences
- University of Queensland
- St Lucia
- Australia
| | - Craig M. Williams
- School of Chemistry and Molecular Biosciences
- University of Queensland
- St Lucia
- Australia
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37
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Campbell JH, Hoang T, Jelokhani-Niaraki M, Smith MD. Folding and self-association of atTic20 in lipid membranes: implications for understanding protein transport across the inner envelope membrane of chloroplasts. BMC BIOCHEMISTRY 2014; 15:29. [PMID: 25551276 PMCID: PMC4307631 DOI: 10.1186/s12858-014-0029-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 12/12/2014] [Indexed: 11/24/2022]
Abstract
Background The Arabidopsis thaliana protein atTic20 is a key component of the protein import machinery at the inner envelope membrane of chloroplasts. As a component of the TIC complex, it is believed to form a preprotein-conducting channel across the inner membrane. Results We report a method for producing large amounts of recombinant atTic20 using a codon-optimized strain of E. coli coupled with an autoinduction method of protein expression. This method resulted in the recombinant protein being directed to the bacterial membrane without the addition of a bacterial targeting sequence. Using biochemical and biophysical approaches, we were able to demonstrate that atTic20 homo-oligomerizes in vitro when solubilized in detergents or reconstituted into liposomes. Furthermore, we present evidence that the extramembranous N-terminus of the mature protein displays characteristics that are consistent with it being an intrinsically disordered protein domain. Conclusion Our work strengthens the hypothesis that atTic20 functions similarly to other small α-helical integral membrane proteins, such as Tim23, that are involved in protein transport across membranes. Electronic supplementary material The online version of this article (doi:10.1186/s12858-014-0029-y) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- James H Campbell
- Department of Biology, Wilfrid Laurier University, 75 University Avenue West, Waterloo, ON, N2L 3C5, Canada. .,Current address: Department of Biology, University of Waterloo, Waterloo, ON, Canada.
| | - Tuan Hoang
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, Canada. .,Biophysics Interdepartmental Group, University of Guelph, Guelph, ON, Canada.
| | - Masoud Jelokhani-Niaraki
- Department of Chemistry & Biochemistry, Wilfrid Laurier University, Waterloo, ON, Canada. .,Biophysics Interdepartmental Group, University of Guelph, Guelph, ON, Canada.
| | - Matthew D Smith
- Department of Biology, Wilfrid Laurier University, 75 University Avenue West, Waterloo, ON, N2L 3C5, Canada. .,Biophysics Interdepartmental Group, University of Guelph, Guelph, ON, Canada.
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38
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Gleed ML, Busath DD. Why bound amantadine fails to inhibit proton conductance according to simulations of the drug-resistant influenza A M2 (S31N). J Phys Chem B 2014; 119:1225-31. [PMID: 25426702 PMCID: PMC4306489 DOI: 10.1021/jp508545d] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The mechanisms responsible for drug resistance in the Asn31 variant of the M2 protein of influenza A are not well understood. Molecular dynamics simulations were performed on wild-type (Ser31) and S31N influenza A M2 in the homotetramer configuration. After evaluation of 13 published M2 structures, a solid-state NMR structure with amantadine bound was selected for simulations, an S31N mutant structure was developed and equilibrated, and the native and mutant structures were used to determine the binding behavior of amantadine and the dynamics of water in the two channels. Amantadine is stable in the plugging region of wild-type M2, with the adamantane in contact with the Val27 side chains, while amantadine in S31N M2 has more variable movement and orientation, and spontaneously moves lower into the central cavity of the channel. Free energy profiles from umbrella sampling support this observation. In this configuration, water surrounds the drug and can easily transport protons past it, so the drug binds without blocking proton transport in the S31N M2 channel.
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Affiliation(s)
- Mitchell L Gleed
- Department of Physiology and Developmental Biology, Brigham Young University , Provo, Utah 84602, United States
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39
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Colvin MT, Andreas LB, Chou JJ, Griffin RG. Proton association constants of His 37 in the Influenza-A M218-60 dimer-of-dimers. Biochemistry 2014; 53:5987-94. [PMID: 25184631 PMCID: PMC4179598 DOI: 10.1021/bi5005393] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
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The membrane protein M2 from influenza-A
forms a single-pass transmembrane
helix that assembles in lipid membrane as homotetramers whose primary
function is to act as a proton transporter for viral acidification.
A single residue, histidine 37 (His 37), is known to be responsible
for selectivity and plays an integral role in the protein’s
function. We report pH-dependent 15N MAS NMR spectra of
His 37 within the influenza-A proton conduction domain of M2, M218–60, which has been previously shown to be a fully
functional construct and was recently determined to adopt a dimer-of-dimers
structure in lipids. By extracting the ratio of [His]/[HisH+] as a function of pH, we obtained two doubly degenerate proton disassociation
constants, 7.63 ± 0.15 and 4.52 ± 0.15, despite a possible
maximum of four. We also report the 1HNε chemical shifts at pH 6.5 recorded at 60 kHz MAS in a CP-based 1H–15N spectrum. We were unable to detect
resonances indicative of direct proton sharing among His 37 side chains
when the tetramer is in the +2 state. In the neutral state, His 37
is exclusively in the τ tautomer, indicating that the δ
nitrogen is protonated solely as a function of pH. We also found that
the plot of [HisH+]/[His] as a function of pH is qualitatively
similar to previously reported proton conduction rates, indicating
that proton conduction rate is proportional to the level of histidine
protonation within the channel. Two-dimensional 13C–13C and 13C–15N correlations suggest
that at low pH multiple conformations are populated as the spectra
broaden and eventually disappear as the acidity is increased. A second
highly resolved state at low pH was not observed.
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Affiliation(s)
- Michael T Colvin
- Department of Chemistry and Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
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40
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Ghosh A, Wang J, Moroz YS, Korendovych IV, Zanni M, DeGrado WF, Gai F, Hochstrasser RM. 2D IR spectroscopy reveals the role of water in the binding of channel-blocking drugs to the influenza M2 channel. J Chem Phys 2014; 140:235105. [PMID: 24952572 PMCID: PMC4098053 DOI: 10.1063/1.4881188] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2013] [Accepted: 05/21/2014] [Indexed: 12/21/2022] Open
Abstract
Water is an integral part of the homotetrameric M2 proton channel of the influenza A virus, which not only assists proton conduction but could also play an important role in stabilizing channel-blocking drugs. Herein, we employ two dimensional infrared (2D IR) spectroscopy and site-specific IR probes, i.e., the amide I bands arising from isotopically labeled Ala30 and Gly34 residues, to probe how binding of either rimantadine or 7,7-spiran amine affects the water dynamics inside the M2 channel. Our results show, at neutral pH where the channel is non-conducting, that drug binding leads to a significant increase in the mobility of the channel water. A similar trend is also observed at pH 5.0 although the difference becomes smaller. Taken together, these results indicate that the channel water facilitates drug binding by increasing its entropy. Furthermore, the 2D IR spectral signatures obtained for both probes under different conditions collectively support a binding mechanism whereby amantadine-like drugs dock in the channel with their ammonium moiety pointing toward the histidine residues and interacting with a nearby water cluster, as predicted by molecular dynamics simulations. We believe these findings have important implications for designing new anti-influenza drugs.
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Affiliation(s)
- Ayanjeet Ghosh
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Jun Wang
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143, USA
| | - Yurii S Moroz
- Department of Chemistry, Syracuse University, Syracuse, New York 13244, USA
| | - Ivan V Korendovych
- Department of Chemistry, Syracuse University, Syracuse, New York 13244, USA
| | - Martin Zanni
- Department of Chemistry, University of Wisconsin, Madison, Wisconsin 53706, USA
| | - William F DeGrado
- Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California 94143, USA
| | - Feng Gai
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Robin M Hochstrasser
- Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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41
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Wei C, Pohorille A. Activation and proton transport mechanism in influenza A M2 channel. Biophys J 2014; 105:2036-45. [PMID: 24209848 DOI: 10.1016/j.bpj.2013.08.030] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Revised: 07/09/2013] [Accepted: 08/08/2013] [Indexed: 12/23/2022] Open
Abstract
Molecular dynamics trajectories 2 μs in length have been generated for the pH-activated, tetrameric M2 proton channel of the influenza A virus in all protonation states of the pH sensor located at the His(37) tetrad. All simulated structures are in very good agreement with high-resolution structures. Changes in the channel caused by progressive protonation of His(37) provide insight into the mechanism of proton transport. The channel is closed at both His(37) and Trp(41) sites in the singly and doubly protonated states, but it opens at Trp(41) upon further protonation. Anions access the charged His(37) and by doing so stabilize the protonated states of the channel. The narrow opening at the His(37) site, further blocked by anions, is inconsistent with the water-wire mechanism of proton transport. Instead, conformational interconversions of His(37) correlated with hydrogen bonding to water molecules indicate that these residues shuttle protons in high-protonation states. Hydrogen bonds between charged and uncharged histidines are rare. The valve at Val(27) remains on average quite narrow in all protonation states but fluctuates sufficiently to support water and proton transport. A proton transport mechanism in which the channel, depending on pH, opens at either the histidine or valine gate is only partially supported by the simulations.
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Affiliation(s)
- Chenyu Wei
- NASA Ames Research Center, Moffett Field, California; Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, California.
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42
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Kawano K, Yano Y, Matsuzaki K. A dimer is the minimal proton-conducting unit of the influenza a virus M2 channel. J Mol Biol 2014; 426:2679-91. [PMID: 24816000 DOI: 10.1016/j.jmb.2014.05.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2013] [Revised: 04/30/2014] [Accepted: 05/01/2014] [Indexed: 12/16/2022]
Abstract
When influenza A virus infects host cells, its integral matrix protein M2 forms a proton-selective channel in the viral envelope. Although X-ray crystallography and NMR studies using fragment peptides have suggested that M2 stably forms a tetrameric channel irrespective of pH, the oligomeric states of the full-length protein in the living cells have not yet been assessed directly. In the present study, we utilized recently developed stoichiometric analytical methods based on fluorescence resonance energy transfer using coiled-coil labeling technique and spectral imaging, and we examined the relationship between the oligomeric states of full-length M2 and its channel activities in living cells. In contrast to previous models, M2 formed proton-conducting dimers at neutral pH and these dimers were converted to tetramers at acidic pH. The antiviral drug amantadine hydrochloride inhibited both tetramerization and channel activity. The removal of cholesterol resulted in a significant decrease in the activity of the dimer. These results indicate that the minimum functional unit of the M2 protein is a dimer, which forms a complex with cholesterol for its function.
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Affiliation(s)
- Kenichi Kawano
- Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-Shimoadachicho, Sakyo-ku, Kyoto 606-8501, Japan.
| | - Yoshiaki Yano
- Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-Shimoadachicho, Sakyo-ku, Kyoto 606-8501, Japan.
| | - Katsumi Matsuzaki
- Graduate School of Pharmaceutical Sciences, Kyoto University, 46-29 Yoshida-Shimoadachicho, Sakyo-ku, Kyoto 606-8501, Japan.
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43
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Polishchuk AL, Cristian L, Pinto LH, Lear JD, DeGrado WF. Mechanistic insights from functional characterization of an unnatural His37 mutant of the influenza A/M2 protein. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2013; 1838:1082-7. [PMID: 24269540 DOI: 10.1016/j.bbamem.2013.11.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 10/02/2013] [Accepted: 11/12/2013] [Indexed: 11/25/2022]
Abstract
The influenza A/M2 protein is a homotetrameric single-pass integral membrane protein encoded by the influenza A viral genome. Its transmembrane domain represents both a crucial drug target and a minimalistic model system for transmembrane proton transport and charge stabilization. Recent structural and functional studies of M2 have suggested that the proton transport mechanism involves sequential extraviral protonation and intraviral deprotonation of a highly conserved His37 side chain by the transported proton, consistent with a pH-activated proton shuttle mechanism. Multiple tautomeric forms of His can be formed, and it is not known whether they contribute to the mechanism of proton shuttling. Here we present the thermodynamic and functional characterization of an unnatural amino acid mutant at His37, where the imidazole side chain is substituted with a 4-thiazolyl group that is unable to undergo tautomerization and has a significantly lower solution pKa. The mutant construct has a similar stability to the wild-type protein at pH8 in bilayers and is virtually inactive at external pH7.4 in a semiquantitative liposome flux assay as expected from its lower sidechain pKa. However when the external buffer pH is lowered to 4.9 and 2.4, the mutant shows increasing amantadine sensitive flux of a similar magnitude to that of the wild type construct at pH7.4 and 4.9 respectively. These findings are in line with mechanistic hypotheses suggesting that proton flux through M2 is mediated by proton exchange from adjacent water molecules with the His37 sidechain, and that tautomerization is not required for proton translocation. This article is part of a Special Issue entitled: Viral Membrane Proteins - Channels for Cellular Networking.
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Affiliation(s)
- Alexei L Polishchuk
- Department of Biochemistry and Biophysics, The Robert Wood Johnson Foundation, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Lidia Cristian
- Department of Biochemistry and Biophysics, The Robert Wood Johnson Foundation, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Lawrence H Pinto
- Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208, USA
| | - James D Lear
- Department of Biochemistry and Biophysics, The Robert Wood Johnson Foundation, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - William F DeGrado
- Department of Biochemistry and Biophysics, The Robert Wood Johnson Foundation, University of Pennsylvania, Perelman School of Medicine, Philadelphia, PA 19104, USA.
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44
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Tarasenko IV, Taranov AI, Firsov AP, Dolgov SV. Expression of the nucleotide sequence for the M2e peptide of avian influenza virus in transgenic tobacco plants. APPL BIOCHEM MICRO+ 2013. [DOI: 10.1134/s0003683813080061] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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45
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Hoang T, Smith MD, Jelokhani-Niaraki M. Expression, folding, and proton transport activity of human uncoupling protein-1 (UCP1) in lipid membranes: evidence for associated functional forms. J Biol Chem 2013; 288:36244-58. [PMID: 24196960 DOI: 10.1074/jbc.m113.509935] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Uncoupling protein-1 (UCP1) is abundantly expressed in the mitochondrial inner membrane of brown adipose tissues and has an important role in heat generation, mediated by its proton transport function. The structure and function of UCP1 are not fully understood, partially due to the difficulty in obtaining native-like folded proteins in vitro. In this study, using the auto-induction method, we have successfully expressed UCP1 in Escherichia coli membranes in high yield. Overexpressed UCP1 in bacterial membranes was extracted using mild detergents and reconstituted into phospholipid bilayers for biochemical studies. UCP1 was folded in octyl glucoside, as indicated by its high helical content and binding to ATP, a known UCP1 proton transport inhibitor. Reconstituted UCP1 in phospholipid vesicles also exhibited highly helical structures and proton transport that is activated by fatty acids and inhibited by purine nucleotides. Self-associated functional forms of UCP1 in lipid membranes were observed for the first time. The self-assembly of UCP1 into tetramers was unambiguously characterized by circular dichroism and fluorescence spectroscopy, analytical ultracentrifugation, and semi-native gel electrophoresis. In addition, the mitochondrial lipid cardiolipin stabilized the structure of associated UCP1 and enhanced the proton transport activity of the protein. The existence of the functional oligomeric states of UCP1 in the lipid membranes has important implications for understanding the structure and proton transport mechanism of this protein in brown adipose tissues as well as structure-function relationships of other mammalian UCPs in other tissues.
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46
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Schmidt NW, Mishra A, Wang J, DeGrado WF, Wong GCL. Influenza virus A M2 protein generates negative Gaussian membrane curvature necessary for budding and scission. J Am Chem Soc 2013; 135:13710-9. [PMID: 23962302 DOI: 10.1021/ja400146z] [Citation(s) in RCA: 93] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The M2 protein is a multifunctional protein, which plays several roles in the replication cycle of the influenza A virus. Here we focus on its ability to promote budding of the mature virus from the cell surface. Using high-resolution small-angle X-ray scattering we show that M2 can restructure lipid membranes into bicontinuous cubic phases which are rich in negative Gaussian curvature (NGC). The active generation of negative Gaussian membrane curvature by M2 is essential to influenza virus budding. M2 has been observed to colocalize with the region of high NGC at the neck of a bud. The structural requirements for scission are even more stringent than those for budding, as the neck must be considerably smaller than the virus during 'pinch off'. Consistent with this, the amount of NGC in the induced cubic phases suggests that M2 proteins can generate high curvatures comparable to those on a neck with size 10× smaller than a spherical influenza virus. Similar experiments on variant proteins containing different M2 domains show that the cytoplasmic amphipathic helix is necessary and sufficient for NGC generation. Mutations to the helix which reduce its amphiphilicity and are known to diminish budding attenuated NGC generation. An M2 construct comprising the membrane interactive domains, the transmembrane helix and the cytoplasmic helix, displayed enhanced ability to generate NGC, suggesting that other domains cooperatively promote membrane curvature. These studies establish the importance of M2-induced NGC during budding and suggest that antagonizing this curvature is a viable anti-influenza strategy.
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Affiliation(s)
- Nathan W Schmidt
- Department of Bioengineering, University of California, Los Angeles , Los Angeles, California 90095, United States
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47
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Nanda V, Cristian L, Toptygin D, Brand L, Degrado WF. Nanosecond Dynamics of InfluenzaA/M2TM and an Amantadine Resistant Mutant Probed by Time-Dependent Red Shifts of a Native Tryptophan. Chem Phys 2013; 422:10.1016/j.chemphys.2012.12.018. [PMID: 24273370 PMCID: PMC3833813 DOI: 10.1016/j.chemphys.2012.12.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Proteins involved in functions such as electron transfer or ion transport must be capable of stabilizing transient charged species on time scales ranging from picoseconds to microseconds. We study the influenza A M2 proton channel, containing a tryptophan residue that serves as an essential part of the proton conduction pathway. We induce a transition dipole in tryptophan by photoexcitation, and then probe the dielectric stabilization of its excited state. The magnitude of the stabilization over this time regime was larger than that generally found for tryptophan in membrane or protein environments. M2 achieves a water-like stabilization over a 25 nanosecond time scale, slower than that of bulk water, but sufficiently rapid to contribute to stabilization of charge as protons diffuse through the channel. These measurements should stimulate future MD studies to clarify the role of sidechain versus non-bulk water in defining the process of relaxation.
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Affiliation(s)
- Vikas Nanda
- Center for Advanced Biotechnology and Medicine, Robert Wood Johnson Medical School - UMDNJ, Piscataway, New Jersey 08854 ; Department of Biochemistry, Robert Wood Johnson Medical School - UMDNJ, Piscataway, New Jersey 08854
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48
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Gu RX, Liu LA, Wang YH, Xu Q, Wei DQ. Structural Comparison of the Wild-Type and Drug-Resistant Mutants of the Influenza A M2 Proton Channel by Molecular Dynamics Simulations. J Phys Chem B 2013; 117:6042-51. [DOI: 10.1021/jp312396q] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Affiliation(s)
- Ruo-Xu Gu
- State Key Laboratory of Microbial
Metabolism and Shanghai Jiao Tong University, Shanghai Minhang District,
200240, China
| | - Limin Angela Liu
- Fred Hutchinson
Cancer Research
Center, Seattle Washington 98109, United States
| | - Yong-Hua Wang
- College of Light Industry and
Food Sciences, South China University of Technology, Guangzhou, 510640,
China
| | - Qin Xu
- State Key Laboratory of Microbial
Metabolism and Shanghai Jiao Tong University, Shanghai Minhang District,
200240, China
| | - Dong-Qing Wei
- State Key Laboratory of Microbial
Metabolism and Shanghai Jiao Tong University, Shanghai Minhang District,
200240, China
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49
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Wanka L, Iqbal K, Schreiner PR. The lipophilic bullet hits the targets: medicinal chemistry of adamantane derivatives. Chem Rev 2013; 113:3516-604. [PMID: 23432396 PMCID: PMC3650105 DOI: 10.1021/cr100264t] [Citation(s) in RCA: 433] [Impact Index Per Article: 39.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- Lukas Wanka
- Institute of Organic Chemistry, Justus-Liebig University Giessen, Heinrich-Buff-Ring 58, 35392 Giessen, Germany; Fax +49(641)9934309
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314-6399, USA
| | - Khalid Iqbal
- Department of Neurochemistry, New York State Institute for Basic Research in Developmental Disabilities, 1050 Forest Hill Road, Staten Island, NY 10314-6399, USA
| | - Peter R. Schreiner
- Institute of Organic Chemistry, Justus-Liebig University Giessen, Heinrich-Buff-Ring 58, 35392 Giessen, Germany; Fax +49(641)9934309
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50
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Zhou HX, Cross TA. Modeling the membrane environment has implications for membrane protein structure and function: influenza A M2 protein. Protein Sci 2013; 22:381-94. [PMID: 23389890 DOI: 10.1002/pro.2232] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 01/29/2013] [Accepted: 01/30/2013] [Indexed: 12/13/2022]
Abstract
The M2 protein, a proton channel, from Influenza A has been structurally characterized by X-ray diffraction and by solution and solid-state NMR spectroscopy in a variety of membrane mimetic environments. These structures show substantial backbone differences even though they all present a left-handed tetrameric helical bundle for the transmembrane domain. Variations in the helix tilt influence drug binding and the chemistry of the histidine tetrad responsible for acid activation, proton selectivity and transport. Some of the major structural differences do not arise from the lack of precision, but instead can be traced to the influences of the membrane mimetic environments. The structure in lipid bilayers displays unique chemistry for the histidine tetrad, which binds two protons cooperatively to form a pair of imidazole-imidazolium dimers. The resulting interhistidine hydrogen bonds contribute to a three orders of magnitude enhancement in tetramer stability. Integration with computation has provided detailed understanding of the functional mechanism for proton selectivity, conductance and gating of this important drug target.
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Affiliation(s)
- Huan-Xiang Zhou
- Department of Physics, Florida State University, Tallahassee, Florida 32306, USA
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