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Kyaw A, Roepke K, Arthur T, Howard KP. Conformation of influenza AM2 membrane protein in nanodiscs and liposomes. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2023; 1865:184152. [PMID: 36948480 PMCID: PMC10175228 DOI: 10.1016/j.bbamem.2023.184152] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2022] [Revised: 02/15/2023] [Accepted: 03/14/2023] [Indexed: 03/24/2023]
Abstract
The influenza A M2 protein (AM2) is a multifunctional membrane-associated homotetramer that orchestrates several essential events in the viral infection cycle including viral assembly and budding. An atomic-level conformational understanding of this key player in the influenza life cycle could inform new antiviral strategies. For conformational studies of complex systems like the AM2 membrane protein, a multipronged approach using different biophysical methods and different model membranes is a powerful way to incorporate complementary data and achieve a fuller, more robust understanding of the system. However, one must be aware of how the sample composition required for a particular method impacts the data collected and how conclusions are drawn. In that spirit, we systematically compared the properties of AM2 in two different model membranes: nanodiscs and liposomes. Electron paramagnetic spectroscopy of spin-labeled AM2 showed that the conformation and dynamics were strikingly similar in both AM2-nanodiscs and AM2-liposomes consistent with similar conformations in both model membranes. Analysis of spin labeled lipids embedded in both model membranes revealed that the bilayer in AM2-liposomes was more fluid and permeable to oxygen than AM2-nanodiscs with the same lipid composition. Once the difference in the partitioning of the paramagnetic oxygen relaxation agent was taken into account, the membrane topology of AM2 appeared to be the same in both liposomes and nanodiscs. Finally, functionally relevant AM2 conformational shifts previously seen in liposomes due to the addition of cholesterol were also observed in nanodiscs.
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Affiliation(s)
- Aye Kyaw
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Kyra Roepke
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Tyrique Arthur
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Kathleen P Howard
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America.
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2
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Dregni AJ, McKay MJ, Surya W, Queralt-Martin M, Medeiros-Silva J, Wang HK, Aguilella V, Torres J, Hong M. The Cytoplasmic Domain of the SARS-CoV-2 Envelope Protein Assembles into a β-Sheet Bundle in Lipid Bilayers. J Mol Biol 2023; 435:167966. [PMID: 36682677 PMCID: PMC9851921 DOI: 10.1016/j.jmb.2023.167966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Revised: 12/23/2022] [Accepted: 01/11/2023] [Indexed: 01/21/2023]
Abstract
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) envelope (E) protein forms a pentameric ion channel in the lipid membrane of the endoplasmic reticulum Golgi intermediate compartment (ERGIC) of the infected cell. The cytoplasmic domain of E interacts with host proteins to cause virus pathogenicity and may also mediate virus assembly and budding. To understand the structural basis of these functions, here we investigate the conformation and dynamics of an E protein construct (residues 8-65) that encompasses the transmembrane domain and the majority of the cytoplasmic domain using solid-state NMR. 13C and 15N chemical shifts indicate that the cytoplasmic domain adopts a β-sheet-rich conformation that contains three β-strands separated by turns. The five subunits associate into an umbrella-shaped bundle that is attached to the transmembrane helices by a disordered loop. Water-edited NMR spectra indicate that the third β-strand at the C terminus of the protein is well hydrated, indicating that it is at the surface of the β-bundle. The structure of the cytoplasmic domain cannot be uniquely determined from the inter-residue correlations obtained here due to ambiguities in distinguishing intermolecular and intramolecular contacts for a compact pentameric assembly of this small domain. Instead, we present four structural topologies that are consistent with the measured inter-residue contacts. These data indicate that the cytoplasmic domain of the SARS-CoV-2 E protein has a strong propensity to adopt β-sheet conformations when the protein is present at high concentrations in lipid bilayers. The equilibrium between the β-strand conformation and the previously reported α-helical conformation may underlie the multiple functions of E in the host cell and in the virion.
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Affiliation(s)
- Aurelio J Dregni
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States
| | - Matthew J McKay
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States
| | - Wahyu Surya
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Maria Queralt-Martin
- Laboratory of Molecular Biophysics. Department of Physics. Universitat Jaume I. 12080 Castellón, Spain
| | - João Medeiros-Silva
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States
| | - Harrison K Wang
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States
| | - Vicente Aguilella
- Laboratory of Molecular Biophysics. Department of Physics. Universitat Jaume I. 12080 Castellón, Spain
| | - Jaume Torres
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, United States.
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3
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Salnikov E, Bechinger B. Effect of lipid saturation on the topology and oligomeric state of helical membrane polypeptides. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2022; 1864:184001. [PMID: 35817122 DOI: 10.1016/j.bbamem.2022.184001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2022] [Revised: 06/27/2022] [Accepted: 06/28/2022] [Indexed: 06/15/2023]
Abstract
Natural liquid crystalline membranes are made up of many different lipids carrying a mixture of saturated and unsaturated fatty acyl chains. Whereas in the past considerable attention has been paid to cholesterol content, the phospholipid head groups and the membrane surface charge the detailed fatty acyl composition was often considered less important. However, recent investigations indicate that the detailed fatty acyl chain composition has pronounced effects on the oligomerization of the transmembrane helical anchoring domains of the MHC II receptor or the membrane alignment of the cationic antimicrobial peptide PGLa. In contrast the antimicrobial peptides magainin 2 and alamethicin are less susceptible to lipid saturation. Using histidine-rich LAH4 designer peptides the high energetic contributions of lipid saturation in stabilizing transmembrane helical alignments are quantitatively evaluated. These observations can have important implications for the biological regulation of membrane proteins and should be taken into considerations during biophysical or structural experiments.
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Affiliation(s)
- Evgeniy Salnikov
- University of Strasbourg/CNRS, UMR7177 Chemistry Institute, Membrane Biophysics and NMR, Strasbourg, France
| | - Burkhard Bechinger
- University of Strasbourg/CNRS, UMR7177 Chemistry Institute, Membrane Biophysics and NMR, Strasbourg, France; Institut Universitaire de France, France.
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4
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de la Arada I, Torralba J, Tascón I, Colom A, Ubarretxena-Belandia I, Arrondo JLR, Apellániz B, Nieva JL. Conformational plasticity underlies membrane fusion induced by an HIV sequence juxtaposed to the lipid envelope. Sci Rep 2021; 11:1278. [PMID: 33446748 PMCID: PMC7809034 DOI: 10.1038/s41598-020-80156-w] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2020] [Accepted: 12/13/2020] [Indexed: 01/05/2023] Open
Abstract
Envelope glycoproteins from genetically-divergent virus families comprise fusion peptides (FPs) that have been posited to insert and perturb the membranes of target cells upon activation of the virus-cell fusion reaction. Conserved sequences rich in aromatic residues juxtaposed to the external leaflet of the virion-wrapping membranes are also frequently found in viral fusion glycoproteins. These membrane-proximal external regions (MPERs) have been implicated in the promotion of the viral membrane restructuring event required for fusion to proceed, hence, proposed to comprise supplementary FPs. However, it remains unknown whether the structure–function relationships governing canonical FPs also operate in the mirroring MPER sequences. Here, we combine infrared spectroscopy-based approaches with cryo-electron microscopy to analyze the alternating conformations adopted, and perturbations generated in membranes by CpreTM, a peptide derived from the MPER of the HIV-1 Env glycoprotein. Altogether, our structural and morphological data support a cholesterol-dependent conformational plasticity for this HIV-1 sequence, which could assist cell-virus fusion by destabilizing the viral membrane at the initial stages of the process.
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Affiliation(s)
- Igor de la Arada
- Instituto Biofisika (CSIC-UPV/EHU), University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain
| | - Johana Torralba
- Instituto Biofisika (CSIC-UPV/EHU), University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain.,Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain
| | - Igor Tascón
- Instituto Biofisika (CSIC-UPV/EHU), University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain.,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - Adai Colom
- Instituto Biofisika (CSIC-UPV/EHU), University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain.,Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain.,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - Iban Ubarretxena-Belandia
- Instituto Biofisika (CSIC-UPV/EHU), University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain.,Ikerbasque, Basque Foundation for Science, 48013, Bilbao, Spain
| | - José L R Arrondo
- Instituto Biofisika (CSIC-UPV/EHU), University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain.,Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain
| | - Beatriz Apellániz
- Department of Physiology, Faculty of Pharmacy, University of the Basque Country (UPV/EHU), Paseo de la Universidad, 7, 01006, Vitoria-Gasteiz, Spain
| | - José L Nieva
- Instituto Biofisika (CSIC-UPV/EHU), University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain. .,Department of Biochemistry and Molecular Biology, University of the Basque Country (UPV/EHU), PO Box 644, 48080, Bilbao, Spain.
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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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6
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Kim G, Raymond HE, Herneisen AL, Wong-Rolle A, Howard KP. The distal cytoplasmic tail of the influenza A M2 protein dynamically extends from the membrane. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:1421-1427. [PMID: 31153909 DOI: 10.1016/j.bbamem.2019.05.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 05/24/2019] [Accepted: 05/28/2019] [Indexed: 12/19/2022]
Abstract
The influenza A M2 protein is a multifunctional membrane-associated homotetramer that orchestrates several essential events in the viral infection cycle. The monomeric subunits of the M2 homotetramer consist of an N-terminal ectodomain, a transmembrane domain, and a C-terminal cytoplasmic domain. The transmembrane domain forms a four-helix proton channel that promotes uncoating of virions upon host cell entry. The membrane-proximal region of the C-terminal domain forms a surface-associated amphipathic helix necessary for viral budding. The structure of the remaining ~34 residues of the distal cytoplasmic tail has yet to be fully characterized despite the functional significance of this region for influenza infectivity. Here, we extend structural and dynamic studies of the poorly characterized M2 cytoplasmic tail. We used SDSL-EPR to collect site-specific information on the mobility, solvent accessibility, and conformational properties of residues 61-70 of the full-length, cell-expressed M2 protein reconstituted into liposomes. Our analysis is consistent with the predominant population of the C-terminal tail dynamically extending away from the membranes surface into the aqueous medium. These findings provide insight into the hypothesis that the C-terminal domain serves as a sensor that regulates how M2 protein participates in critical events in the viral infection cycle.
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Affiliation(s)
- Grace Kim
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Hayley E Raymond
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Alice L Herneisen
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Abigail Wong-Rolle
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America
| | - Kathleen P Howard
- Department of Chemistry and Biochemistry, Swarthmore College, Swarthmore, PA 19081, United States of America.
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Affiliation(s)
- Xiaolin Cheng
- Division of Medicinal Chemistry and Pharmacognosy, Biophysics Graduate Program, Translational Data Analytics Institute, The Ohio State University, Columbus, Ohio 43210, United States
| | - Jeremy C. Smith
- UT/ORNL Center for Molecular Biophysics, Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6309, United States
- Department of Biochemistry and Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, United States
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