1
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Aisenbrey C, Bechinger B. Multimerization of the heptad repeat regions of the SARS-CoV 2 spike protein. BIOCHIMICA ET BIOPHYSICA ACTA. BIOMEMBRANES 2024; 1866:184259. [PMID: 38061554 DOI: 10.1016/j.bbamem.2023.184259] [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: 07/25/2023] [Revised: 10/30/2023] [Accepted: 11/20/2023] [Indexed: 12/17/2023]
Abstract
The heptad repeat 1 and 2 (HR1, HR2) regions in the spike protein of SARS-CoV 2 play a key role in the fusogenic mechanism of the virus with the host cell. During the fusion process they are thought to rearrange into an interdomain multimer. Functional fragments of the heptad repeat 1 and 2 regions in the spike protein of SARS-CoV 2 were chemically synthesized, labeled with nitrofurazone (NBD) and their interactions investigated by fluorescence spectroscopy. Steady state emission, fluorescence quenching, anisotropy and lifetime measurements in combination with a fluorophore dilution scheme were used to dissect multimer formation of HR1 and HR2 in quantitative detail. In addition, the investigation of the multimers by homo-FRET (via anisotropy) and lifetime measurements reveals new insights into the mechanism of fluorophore-fluorophore interactions in biological samples.
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Affiliation(s)
- Christopher Aisenbrey
- University of Strasbourg/CNRS, UMR7177, Strasbourg Institute of Chemistry, Membrane Biophysics and NMR, 67000 Strasbourg, France.
| | - Burkhard Bechinger
- University of Strasbourg/CNRS, UMR7177, Strasbourg Institute of Chemistry, Membrane Biophysics and NMR, 67000 Strasbourg, France; Institut Universitaire de France, 75231 Paris, France
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2
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Rokonujjaman M, Sahyouni A, Wolfe R, Jia L, Ghosh U, Weliky DP. A large HIV gp41 construct with trimer-of-hairpins structure exhibits V2E mutation-dominant attenuation of vesicle fusion and helicity very similar to V2E attenuation of HIV fusion and infection and supports: (1) hairpin stabilization of membrane apposition with larger distance for V2E; and (2) V2E dominance by an antiparallel β sheet with interleaved fusion peptide strands from two gp41 trimers. Biophys Chem 2023; 293:106933. [PMID: 36508984 PMCID: PMC9879285 DOI: 10.1016/j.bpc.2022.106933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2022] [Revised: 11/13/2022] [Accepted: 11/14/2022] [Indexed: 11/27/2022]
Abstract
There is complete attenuation of fusion and infection mediated by HIV gp160 with gp41 subunit with V2E mutation, and also V2E dominance with WT/V2E mixtures. V2E is at the N-terminus of the ∼25-residue fusion peptide (Fp) which likely binds the target membrane. In this study, large V2E attenuation and dominance were observed for vesicle fusion induced by FP_HM, a large gp41 ectodomain construct with Fp followed by hyperthermostable hairpin with N- and C-helices, and membrane-proximal external region (Mper). FP_HM is a trimer-of-hairpins, the final gp41 structure during fusion. Vesicle fusion and helicity were measured for FP_HM using trimers with different fractions (f's) of WT and V2E proteins. Reductions in FP_HM fusion and helicity vs. fV2E were quantitatively-similar to those for gp160-mediated fusion and infection. Global fitting of all V2E data supports 6 WT gp41 (2 trimers) required for fusion. These data are understood by a model in which the ∼25 kcal/mol free energy for initial membrane apposition is compensated by the thermostable hairpin between the Fp in target membrane and Mper/transmembrane domain in virus membrane. The data support a structural model for V2E dominance with a membrane-bound Fp with antiparallel β sheet and interleaved strands from the two trimers. Relative to fV2E = 0, a longer Fp sheet is stabilized with small fV2E because of salt-bridge and/or hydrogen bonds between E2 on one strand and C-terminal Fp residues on adjacent strands, like R22. A longer Fp sheet results in shorter N- and C-helices, and larger separation during membrane apposition which hinders fusion.
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Affiliation(s)
- Md Rokonujjaman
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Abdulrazak Sahyouni
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Robert Wolfe
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Lihui Jia
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - Ujjayini Ghosh
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
| | - David P Weliky
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA.
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3
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Abstract
This review discusses peptide epitopes used as antigens in the development of vaccines in clinical trials as well as future vaccine candidates. It covers peptides used in potential immunotherapies for infectious diseases including SARS-CoV-2, influenza, hepatitis B and C, HIV, malaria, and others. In addition, peptides for cancer vaccines that target examples of overexpressed proteins are summarized, including human epidermal growth factor receptor 2 (HER-2), mucin 1 (MUC1), folate receptor, and others. The uses of peptides to target cancers caused by infective agents, for example, cervical cancer caused by human papilloma virus (HPV), are also discussed. This review also provides an overview of model peptide epitopes used to stimulate non-specific immune responses, and of self-adjuvanting peptides, as well as the influence of other adjuvants on peptide formulations. As highlighted in this review, several peptide immunotherapies are in advanced clinical trials as vaccines, and there is great potential for future therapies due the specificity of the response that can be achieved using peptide epitopes.
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Affiliation(s)
- Ian W Hamley
- Department of Chemistry, University of Reading, Whiteknights, Reading RG6 6AD, U.K
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4
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Aisenbrey C, Rifi O, Bechinger B. Structure, membrane topology and influence of cholesterol of the membrane proximal region: transmembrane helical anchor sequence of gp41 from HIV. Sci Rep 2020; 10:22278. [PMID: 33335248 PMCID: PMC7746737 DOI: 10.1038/s41598-020-79327-6] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Accepted: 11/30/2020] [Indexed: 11/13/2022] Open
Abstract
During the first steps of HIV infection the Env subunit gp41 is thought to establish contact between the membranes and to be the main driver of fusion. Here we investigated in liquid crystalline membranes the structure and cholesterol recognition of constructs made of a gp41 external region carrying a cholesterol recognition amino acid consensus (CRAC) motif and a hydrophobic membrane anchoring sequence. CD- und ATR-FTIR spectroscopies indicate that the constructs adopt a high degree of helical secondary structure in membrane environments. Furthermore, 15N and 2H solid-state NMR spectra of gp41 polypeptides reconstituted into uniaxially oriented bilayers agree with the CRAC domain being an extension of the transmembrane helix. Upon addition of cholesterol the CRAC NMR spectra remain largely unaffected when being associated with the native gp41 transmembrane sequence but its topology changes when anchored in the membrane by a hydrophobic model sequence. The 2H solid-state NMR spectra of deuterated cholesterol are indicative of a stronger influence of the model sequence on this lipid when compared to the native gp41 sequence. These observations are suggestive of a strong coupling between the transmembrane and the membrane proximal region of gp41 possibly enforced by oligomerization of the transmembrane helical region.
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Affiliation(s)
- Christopher Aisenbrey
- Institut de chimie de Strasbourg, UMR7177, University of Strasbourg/CNRS, 4, Rue Blaise Pascal, 67070, Strasbourg, France
| | - Omar Rifi
- Institut de chimie de Strasbourg, UMR7177, University of Strasbourg/CNRS, 4, Rue Blaise Pascal, 67070, Strasbourg, France
| | - Burkhard Bechinger
- Institut de chimie de Strasbourg, UMR7177, University of Strasbourg/CNRS, 4, Rue Blaise Pascal, 67070, Strasbourg, France.
- Institut Universitaire de France, Paris, France.
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5
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Parajuli B, Acharya K, Nangarlia A, Zhang S, Parajuli B, Dick A, Ngo B, Abrams CF, Chaiken I. Identification of a glycan cluster in gp120 essential for irreversible HIV-1 lytic inactivation by a lectin-based recombinantly engineered protein conjugate. Biochem J 2020; 477:4263-4280. [PMID: 33057580 DOI: 10.1042/bcj20200495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 10/13/2020] [Accepted: 10/15/2020] [Indexed: 11/17/2022]
Abstract
We previously discovered a class of recombinant lectin conjugates, denoted lectin DLIs ('dual-acting lytic inhibitors') that bind to the HIV-1 envelope (Env) protein trimer and cause both lytic inactivation of HIV-1 virions and cytotoxicity of Env-expressing cells. To facilitate mechanistic investigation of DLI function, we derived the simplified prototype microvirin (MVN)-DLI, containing an MVN domain that binds high-mannose glycans in Env, connected to a DKWASLWNW sequence (denoted 'Trp3') derived from the membrane-associated region of gp41. The relatively much stronger affinity of the lectin component than Trp3 argues that the lectin functions to capture Env to enable Trp3 engagement and consequent Env membrane disruption and virolysis. The relatively simplified engagement pattern of MVN with Env opened up the opportunity, pursued here, to use recombinant glycan knockout gp120 variants to identify the precise Env binding site for MVN that drives DLI engagement and lysis. Using mutagenesis combined with a series of biophysical and virological experiments, we identified a restricted set of residues, N262, N332 and N448, all localized in a cluster on the outer domain of gp120, as the essential epitope for MVN binding. By generating these mutations in the corresponding HIV-1 virus, we established that the engagement of this glycan cluster with the lectin domain of MVN*-DLI is the trigger for DLI-derived virus and cell inactivation. Beyond defining the initial encounter step for lytic inactivation, this study provides a guide to further elucidate DLI mechanism, including the stoichiometry of Env trimer required for function, and downstream DLI optimization.
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Affiliation(s)
- Bibek Parajuli
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A
| | - Kriti Acharya
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A
| | - Aakansha Nangarlia
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A
| | - Shiyu Zhang
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A
| | - Bijay Parajuli
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A
| | - Alexej Dick
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A
| | - Brendon Ngo
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A
| | - Cameron F Abrams
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A
- Department of Chemical and Biological Engineering, Drexel University, Philadelphia, PA 19104, U.S.A
| | - Irwin Chaiken
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA 19102, U.S.A
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6
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Structure, interactions and membrane topology of HIV gp41 ectodomain sequences. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2020; 1862:183274. [DOI: 10.1016/j.bbamem.2020.183274] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/16/2020] [Revised: 03/06/2020] [Accepted: 03/10/2020] [Indexed: 11/21/2022]
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7
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Murphy RE, Saad JS. The Interplay between HIV-1 Gag Binding to the Plasma Membrane and Env Incorporation. Viruses 2020; 12:E548. [PMID: 32429351 PMCID: PMC7291237 DOI: 10.3390/v12050548] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2020] [Revised: 05/14/2020] [Accepted: 05/14/2020] [Indexed: 12/21/2022] Open
Abstract
Advancement in drug therapies and patient care have drastically improved the mortality rates of HIV-1 infected individuals. Many of these therapies were developed or improved upon by using structure-based techniques, which underscore the importance of understanding essential mechanisms in the replication cycle of HIV-1 at the structural level. One such process which remains poorly understood is the incorporation of the envelope glycoprotein (Env) into budding virus particles. Assembly of HIV particles is initiated by targeting of the Gag polyproteins to the inner leaflet of the plasma membrane (PM), a process mediated by the N-terminally myristoylated matrix (MA) domain and phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). There is strong evidence that formation of the Gag lattice on the PM is a prerequisite for the incorporation of Env into budding particles. It is also suggested that Env incorporation is mediated by an interaction between its cytoplasmic tail (gp41CT) and the MA domain of Gag. In this review, we highlight the latest developments and current efforts to understand the interplay between gp41CT, MA, and the membrane during assembly. Elucidation of the molecular determinants of Gag-Env-membrane interactions may help in the development of new antiviral therapeutic agents that inhibit particle assembly, Env incorporation and ultimately virus production.
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Affiliation(s)
| | - Jamil S. Saad
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA;
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8
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Abstract
Vaccines have had a profound impact on the management and prevention of infectious disease. In addition, the development of vaccines against chronic diseases has attracted considerable interest as an approach to prevent, rather than treat, conditions such as cancer, Alzheimer's disease, and others. Subunit vaccines consist of nongenetic components of the infectious agent or disease-related epitope. In this Review, we discuss peptide-based vaccines and their potential in three therapeutic areas: infectious disease, Alzheimer's disease, and cancer. We discuss factors that contribute to vaccine efficacy and how these parameters may potentially be modulated by design. We examine both clinically tested vaccines as well as nascent approaches and explore current challenges and potential remedies. While peptide vaccines hold substantial promise in the prevention of human disease, many obstacles remain that have hampered their clinical use; thus, continued research efforts to address these challenges are warranted.
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Affiliation(s)
- Ryan J. Malonis
- Department of Biochemistry, Albert Einstein College of Medicine, Michael F. Price Center for Translational Research, 1301 Morris Park Avenue, Bronx, NY 10461
| | - Jonathan R. Lai
- Department of Biochemistry, Albert Einstein College of Medicine, Michael F. Price Center for Translational Research, 1301 Morris Park Avenue, Bronx, NY 10461
| | - Olivia Vergnolle
- Department of Biochemistry, Albert Einstein College of Medicine, Michael F. Price Center for Translational Research, 1301 Morris Park Avenue, Bronx, NY 10461
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9
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Liu N, Girvin ME, Brenowitz M, Lai JR. Conformational and lipid bilayer-perturbing properties of Marburg virus GP2 segments containing the fusion loop and membrane-proximal external region/transmembrane domain. Heliyon 2019; 5:e03018. [PMID: 31890962 PMCID: PMC6926192 DOI: 10.1016/j.heliyon.2019.e03018] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Revised: 11/04/2019] [Accepted: 12/06/2019] [Indexed: 12/13/2022] Open
Abstract
Fusion of host and viral membranes is a crucial step during infection by enveloped viruses. In the structurally-defined "class I″ viral glycoproteins, the formation of a highly stable α-helical bundle by the ectodomain of the fusion subunit (e.g., GP2 for Marburg virus, MARV) is postulated to provide the energetic driving force to overcome barriers associated with membrane fusion. Upon cell binding, the fusion subunit is proposed to form an extended intermediate that bridges both the viral and host membranes, and collapse of this extended intermediate brings the two membranes into proximity. While there is much high-resolution structural data available for prefusion and post-fusion structures of viral glycoproteins, little information is available about intermediate conformations especially in the context of the fusion loop/peptide (FL or FP) and membrane-proximal external region (MPER)/transmembrane (TM) segments. We present structural and functional studies on segments of MARV GP2 that encompass the FL and MPER/TM in detergent micelles and lipid bicelles. A protein that contains most elements of GP2 ("MGP2-full") is α-helical in membrane-mimicking environments and has pH-dependent membrane lytic activity. MGP2-full is monomeric under such conditions, contrasting with the trimeric species that has been described previously for MARV GP2 ectodomain in aqueous buffer. Variants of MARV GP2 containing the N- and C-terminal halves ("MGP2-FNL" and "MGP2-CMT", respectively) have similar properties. This work provides novel insight into conformational and membrane-perturbing properties of the MARV fusion subunit and how they may relate to viral membrane fusion.
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Affiliation(s)
- Nina Liu
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Mark E Girvin
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Michael Brenowitz
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.,Department of Molecular Pharmacology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Jonathan R Lai
- Department of Biochemistry, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
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10
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Lee M, Morgan CA, Hong M. Fully hydrophobic HIV gp41 adopts a hemifusion-like conformation in phospholipid bilayers. J Biol Chem 2019; 294:14732-14744. [PMID: 31409642 DOI: 10.1074/jbc.ra119.009542] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 08/04/2019] [Indexed: 11/06/2022] Open
Abstract
The HIV envelope glycoprotein mediates virus entry into target cells by fusing the virus lipid envelope with the cell membrane. This process requires large-scale conformational changes of the fusion protein gp41. Current understanding of the mechanisms with which gp41 induces membrane merger is limited by the fact that the hydrophobic N-terminal fusion peptide (FP) and C-terminal transmembrane domain (TMD) of the protein are challenging to characterize structurally in the lipid bilayer. Here we have expressed a gp41 construct that contains both termini, including the FP, the fusion peptide-proximal region (FPPR), the membrane-proximal external region (MPER), and the TMD. These hydrophobic domains are linked together by a shortened water-soluble ectodomain. We reconstituted this "short NC" gp41 into a virus-mimetic lipid membrane and conducted solid-state NMR experiments to probe the membrane-bound conformation and topology of the protein. 13C chemical shifts indicate that the C-terminal MPER-TMD is predominantly α-helical, whereas the N-terminal FP-FPPR exhibits β-sheet character. Water and lipid 1H polarization transfer to the protein revealed that the TMD is well-inserted into the lipid bilayer, whereas the FPPR and MPER are exposed to the membrane surface. Importantly, correlation signals between the FP-FPPR and the MPER are observed, providing evidence that the ectodomain is sufficiently collapsed to bring the N- and C-terminal hydrophobic domains into close proximity. These results support a hemifusion-like model of the short NC gp41 in which the ectodomain forms a partially folded hairpin that places the FPPR and MPER on the opposing surfaces of two lipid membranes.
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Affiliation(s)
- Myungwoon Lee
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Chloe A Morgan
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
| | - Mei Hong
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
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11
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Ranaweera A, Ratnayake PU, Weliky DP. The Stabilities of the Soluble Ectodomain and Fusion Peptide Hairpins of the Influenza Virus Hemagglutinin Subunit II Protein Are Positively Correlated with Membrane Fusion. Biochemistry 2018; 57:5480-5493. [PMID: 30141905 DOI: 10.1021/acs.biochem.8b00764] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Cellular entry of influenza virus is mediated by the viral protein hemagglutinin (HA), which forms an initial complex of three HA1 and three HA2 subunits. Each HA2 includes a fusion peptide (FP), a soluble ectodomain (SE), and a transmembrane domain. HA1 binds to cellular sialic acids, followed by virus endocytosis, pH reduction, dissociation of HA1, and structural rearrangement of HA2 into a final trimer-of-SE hairpins. A decrease in pH also triggers HA2-mediated virus/endosome membrane fusion. SE hairpins have an interior parallel helical bundle and C-terminal strands in the grooves of the exterior of the bundle. FPs are separate helical hairpins. This study compares wild-type HA2 (WT-HA2) with G1E(FP) and I173E(SE strand) mutants. WT-HA2 induces vesicle fusion at pH 5.0, whereas the extent of fusion is greatly reduced for both mutants. Circular dichroism for HA2 and FHA2≡FP+SE constructs shows dramatic losses of stability for the mutants, including a Tm reduced by 40 °C for I173E-FHA2. This is evidence of destabilization of SE hairpins via dissociation of strands from the helical bundle, which is also supported by larger monomer fractions for mutant versus WT proteins. The G1E mutant may have disrupted FP hairpins, with consequent non-native FP binding to dissociated SE strands. It is commonly proposed that free energy released by the HA2 structural rearrangement catalyzes HA-mediated fusion. This study supports an alternate mechanistic model in which fusion is preceded by FP insertion in the target membrane and formation of the final SE hairpin. Less fusion by the mutants is due to the loss of hairpin stability and consequent reduced level of membrane apposition of the virus and target membranes.
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Affiliation(s)
- Ahinsa Ranaweera
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| | - Punsisi U Ratnayake
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
| | - David P Weliky
- Department of Chemistry , Michigan State University , East Lansing , Michigan 48824 , United States
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12
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Kwon B, Lee M, Waring AJ, Hong M. Oligomeric Structure and Three-Dimensional Fold of the HIV gp41 Membrane-Proximal External Region and Transmembrane Domain in Phospholipid Bilayers. J Am Chem Soc 2018; 140:8246-8259. [PMID: 29888593 DOI: 10.1021/jacs.8b04010] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The HIV-1 glycoprotein, gp41, mediates fusion of the virus lipid envelope with the target cell membrane during virus entry into cells. Despite extensive studies of this protein, inconsistent and contradictory structural information abounds in the literature about the C-terminal membrane-interacting region of gp41. This C-terminal region contains the membrane-proximal external region (MPER), which harbors the epitopes for four broadly neutralizing antibodies, and the transmembrane domain (TMD), which anchors the protein to the virus lipid envelope. Due to the difficulty of crystallizing and solubilizing the MPER-TMD, most structural studies of this functionally important domain were carried out using truncated peptides either in the absence of membrane-mimetic solvents or bound to detergents and lipid bicelles. To determine the structural architecture of the MPER-TMD in the native environment of lipid membranes, we have now carried out a solid-state NMR study of the full MPER-TMD segment bound to cholesterol-containing phospholipid bilayers. 13C chemical shifts indicate that the majority of the peptide is α-helical, except for the C-terminus of the TMD, which has moderate β-sheet character. Intermolecular 19F-19F distance measurements of singly fluorinated peptides indicate that the MPER-TMD is trimerized in the virus-envelope mimetic lipid membrane. Intramolecular 13C-19F distance measurements indicate the presence of a turn between the MPER helix and the TMD helix. This is supported by lipid-peptide and water-peptide 2D 1H-13C correlation spectra, which indicate that the MPER binds to the membrane surface whereas the TMD spans the bilayer. Together, these data indicate that full-length MPER-TMD assembles into a trimeric helix-turn-helix structure in lipid membranes. We propose that the turn between the MPER and TMD may be important for inducing membrane defects in concert with negative-curvature lipid components such as cholesterol and phosphatidylethanolamine, while the surface-bound MPER helix may interact with N-terminal segments of the protein during late stages of membrane fusion.
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Affiliation(s)
- Byungsu Kwon
- Department of Chemistry , Massachusetts Institute of Technology , 170 Albany Street , Cambridge , Massachusetts 02139 , United States
| | - Myungwoon Lee
- Department of Chemistry , Massachusetts Institute of Technology , 170 Albany Street , Cambridge , Massachusetts 02139 , United States
| | - Alan J Waring
- Department of Medicine , Harbor-UCLA Medical Center , 1000 West Carson Street, Building RB2 , Torrance , California 90502 , United States
| | - Mei Hong
- Department of Chemistry , Massachusetts Institute of Technology , 170 Albany Street , Cambridge , Massachusetts 02139 , United States
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13
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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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14
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Liang S, Ratnayake PU, Keinath C, Jia L, Wolfe R, Ranaweera A, Weliky DP. Efficient Fusion at Neutral pH by Human Immunodeficiency Virus gp41 Trimers Containing the Fusion Peptide and Transmembrane Domains. Biochemistry 2018; 57:1219-1235. [PMID: 29345922 DOI: 10.1021/acs.biochem.7b00753] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Human immunodeficiency virus (HIV) is membrane-enveloped, and an initial infection step is joining/fusion of viral and cell membranes. This step is catalyzed by gp41, which is a single-pass integral viral membrane protein. The protein contains an ∼170-residue ectodomain located outside the virus that is important for fusion and includes the fusion peptide (FP), N-helix, loop, C-helix, and viral membrane-proximal external region (MPER). The virion initially has noncovalent complexes between three gp41 ectodomains and three gp120 proteins. A gp120 contains ∼500 residues and functions to identify target T-cells and macrophages via binding to specific protein receptors of the target cell membrane. gp120 moves away from the gp41 ectodomain, and the ectodomain is thought to bind to the target cell membrane and mediate membrane fusion. The secondary and tertiary structures of the ectodomain are different in the initial complex with gp120 and the final state without gp120. There is not yet imaging of gp41 during fusion, so the temporal relationship between the gp41 and membrane structures is not known. This study describes biophysical and functional characterization of large gp41 constructs that include the ectodomain and transmembrane domain (TM). Significant fusion is observed of both neutral and anionic vesicles at neutral pH, which reflects the expected conditions of HIV/cell fusion. Fusion is enhanced by the FP, which in HIV/cell fusion likely contacts the host membrane, and the MPER and TM, which respectively interfacially contact and traverse the HIV membrane. Initial contact with vesicles is made by protein trimers that are in a native oligomeric state that reflects the initial complex with gp120 and also is commonly observed for the ectodomain without gp120. Circular dichroism data support helical structure for the N-helix, C-helix, and MPER and nonhelical structure for the FP and loop. Distributions of monomer, trimer, and hexamer states are observed by size-exclusion chromatography (SEC), with dependences on solubilizing detergent and construct. These SEC and other data are integrated into a refined working model of HIV/cell fusion that includes dissociation of the ectodomain into gp41 monomers followed by folding into hairpins that appose the two membranes, and subsequent fusion catalysis by trimers and hexamers of hairpins. The monomer and oligomer gp41 states may therefore satisfy dual requirements for HIV entry of membrane apposition and fusion.
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Affiliation(s)
- S Liang
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - P U Ratnayake
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - C Keinath
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - L Jia
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - R Wolfe
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - A Ranaweera
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
| | - D P Weliky
- Department of Chemistry, Michigan State University , East Lansing, Michigan 48824, United States
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15
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Chiliveri SC, Louis JM, Ghirlando R, Baber JL, Bax A. Tilted, Uninterrupted, Monomeric HIV-1 gp41 Transmembrane Helix from Residual Dipolar Couplings. J Am Chem Soc 2017; 140:34-37. [PMID: 29277995 DOI: 10.1021/jacs.7b10245] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Cryo-electron microscopy and X-ray crystallography have shown that the pre- and postfusion states of the HIV-1 gp41 viral coat protein, although very different from one another, each adopt C3 symmetric structures. A stable homotrimeric structure for the transmembrane domain (TM) also was modeled and supported by experimental data. For a C3 symmetric structure, alignment in an anisotropic medium must be axially symmetric, with the unique axis of the alignment tensor coinciding with the C3 axis. However, NMR residual dipolar couplings (RDCs) measured under three different alignment conditions were found to be incompatible with C3 symmetry. Subsequent measurements by paramagnetic relaxation enhancement, analytical ultracentrifugation, and DEER EPR, indicate that the transmembrane domain is monomeric. 15N NMR relaxation data and RDCs show that TM is highly ordered and uninterrupted for a total length of 32 residues, extending well into the membrane proximal external region.
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Affiliation(s)
- Sai Chaitanya Chiliveri
- Laboratory of Chemical Physics and ‡Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - John M Louis
- Laboratory of Chemical Physics and ‡Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - Rodolfo Ghirlando
- Laboratory of Chemical Physics and ‡Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - James L Baber
- Laboratory of Chemical Physics and ‡Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892, United States
| | - Ad Bax
- Laboratory of Chemical Physics and ‡Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892, United States
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16
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Pérez Y, Gómara MJ, Yuste E, Gómez-Gutierrez P, Pérez JJ, Haro I. Structural Study of a New HIV-1 Entry Inhibitor and Interaction with the HIV-1 Fusion Peptide in Dodecylphosphocholine Micelles. Chemistry 2017; 23:11703-11713. [DOI: 10.1002/chem.201702531] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Indexed: 11/07/2022]
Affiliation(s)
- Yolanda Pérez
- Nuclear Magnetic Resonance Facility; IQAC-CSIC; Jordi Girona, 18-26 08034 Barcelona Spain
| | - Maria José Gómara
- Unit of Synthesis and Biomedical Applications of Peptides; IQAC-CSIC; Jordi Girona, 18-26 08034 Barcelona Spain
| | - Eloísa Yuste
- Department of Chemical Engineering (ETSEIB); Universitat Politecnica de Catalunya; 08034 Barcelona Spain
- Present address: AIDS Immunopathology Unit; Centro Nacional Microbiología; Instituto de Salud Carlos III; 28029 Madrid Spain
| | | | | | - Isabel Haro
- Unit of Synthesis and Biomedical Applications of Peptides; IQAC-CSIC; Jordi Girona, 18-26 08034 Barcelona Spain
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17
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Parajuli B, Acharya K, Yu R, Ngo B, Rashad AA, Abrams CF, Chaiken IM. Lytic Inactivation of Human Immunodeficiency Virus by Dual Engagement of gp120 and gp41 Domains in the Virus Env Protein Trimer. Biochemistry 2016; 55:6100-6114. [PMID: 27731975 DOI: 10.1021/acs.biochem.6b00570] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We recently reported the discovery of a recombinant chimera, denoted DAVEI (dual-acting virucidal entry inhibitor), which is able to selectively cause specific and potent lytic inactivation of both pseudotyped and fully infectious human immunodeficiency virus (HIV-1) virions. The chimera is composed of the lectin cyanovirin-N (CVN) fused to the 20-residue membrane-proximal external region (MPER) of HIV-1 gp41. Because the Env gp120-binding CVN domain on its own is not lytic, we sought here to determine how the MPER(DAVEI) domain is able to endow the chimera with virolytic activity. We used a protein engineering strategy to identify molecular determinants of MPER(DAVEI) that are important for function. Recombinant mutagenesis and truncation demonstrated that the MPER(DAVEI) domain could be significantly minimized without loss of function. The dependence of lysis on specific MPER sequences of DAVEI, determination of minimal linker length, and competition by a simplified MPER surrogate peptide suggested that the MPER domain of DAVEI interacts with the Env spike trimer, likely with the gp41 region. This conclusion was further supported by observations from binding of the biotinylated MPER surrogate peptide to Env protein expressed on cells, monoclonal antibody competition, a direct binding enzyme-linked immunosorbent assay on viruses with varying numbers of trimeric spikes on their surfaces, and comparison of maximal interdomain spacing in DAVEI to that in high-resolution structures of Env. The finding that MPER(DAVEI) in CVN-MPER linker sequences can be minimized without loss of virolytic function provides an improved experimental path for constructing size-minimized DAVEI chimeras and molecular tools for determining how simultaneous engagement of gp120 and gp41 by these chimeras can disrupt the metastable virus Env spike.
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Affiliation(s)
- Bibek Parajuli
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine , Philadelphia, Pennsylvania 19102, United States
| | - Kriti Acharya
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine , Philadelphia, Pennsylvania 19102, United States
| | - Reina Yu
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine , Philadelphia, Pennsylvania 19102, United States
| | - Brendon Ngo
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine , Philadelphia, Pennsylvania 19102, United States
| | - Adel A Rashad
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine , Philadelphia, Pennsylvania 19102, United States
| | - Cameron F Abrams
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine , Philadelphia, Pennsylvania 19102, United States.,Department of Chemical and Biological Engineering, Drexel University , Philadelphia, Pennsylvania 19104, United States
| | - Irwin M Chaiken
- Department of Biochemistry and Molecular Biology, Drexel University College of Medicine , Philadelphia, Pennsylvania 19102, United States
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18
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Lin X, Noel JK, Wang Q, Ma J, Onuchic JN. Lowered pH Leads to Fusion Peptide Release and a Highly Dynamic Intermediate of Influenza Hemagglutinin. J Phys Chem B 2016; 120:9654-60. [PMID: 27541202 DOI: 10.1021/acs.jpcb.6b06775] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hemagglutinin (HA), the membrane-bound fusion protein of the influenza virus, enables the entry of virus into host cells via a structural rearrangement. There is strong evidence that the primary trigger for this rearrangement is the low pH environment of a late endosome. To understand the structural basis and the dynamic consequences of the pH trigger, we employed explicit-solvent molecular dynamics simulations to investigate the initial stages of the HA transition. Our results indicate that lowered pH destabilizes HA and speeds up the dissociation of the fusion peptides (FPs). A buried salt bridge between the N-terminus and Asp1122 of HA stem domain locks the FPs and may act as one of the pH sensors. In line with recent observations from simplified protein models, we find that, after the dissociation of FPs, a structural order-disorder transition in a loop connecting the central coiled-coil to the C-terminal domains produces a highly mobile HA. This motion suggests the existence of a long-lived asymmetric or "symmetry-broken" intermediate during the HA conformational change. This intermediate conformation is consistent with models of hemifusion, and its early formation during the conformational change has implications for the aggregation seen in HA activity.
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Affiliation(s)
- Xingcheng Lin
- Center for Theoretical Biological Physics, Rice University , Houston, Texas 77030, United States.,Department of Physics and Astronomy, Rice University , Houston, Texas 77005, United States
| | - Jeffrey K Noel
- Max Delbrück Center for Molecular Medicine , Berlin 13125, Germany.,Fritz Haber Institute of the Max Planck Society , Berlin 14195, Germany
| | - Qinghua Wang
- Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine , Houston 77030, Texas, United States
| | - Jianpeng Ma
- Center for Theoretical Biological Physics, Rice University , Houston, Texas 77030, United States.,Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine , Houston 77030, Texas, United States.,Department of Bioengineering, Rice University , Houston, Texas 77005, United States
| | - José N Onuchic
- Center for Theoretical Biological Physics, Rice University , Houston, Texas 77030, United States.,Department of Physics and Astronomy, Rice University , Houston, Texas 77005, United States.,Departments of Chemistry and Biosciences, Rice University , Houston, Texas 77005, United States
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19
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Louis JM, Baber JL, Ghirlando R, Aniana A, Bax A, Roche J. Insights into the Conformation of the Membrane Proximal Regions Critical to the Trimerization of the HIV-1 gp41 Ectodomain Bound to Dodecyl Phosphocholine Micelles. PLoS One 2016; 11:e0160597. [PMID: 27513582 PMCID: PMC4981318 DOI: 10.1371/journal.pone.0160597] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 07/21/2016] [Indexed: 01/06/2023] Open
Abstract
The transitioning of the ectodomain of gp41 from a pre-hairpin to a six-helix bundle conformation is a crucial aspect of virus-cell fusion. To gain insight into the intermediary steps of the fusion process we have studied the pH and dodecyl phosphocholine (DPC) micelle dependent trimer association of gp41 by systematic deletion analysis of an optimized construct termed 17-172 (residues 528 to 683 of Env) that spans the fusion peptide proximal region (FPPR) to the membrane proximal external region (MPER) of gp41, by sedimentation velocity and double electron-electron resonance (DEER) EPR spectroscopy. Trimerization at pH 7 requires the presence of both the FPPR and MPER regions. However, at pH 4, the protein completely dissociates to monomers. DEER measurements reveal a partial fraying of the C-terminal MPER residues in the 17-172 trimer while the other regions, including the FPPR, remain compact. In accordance, truncating nine C-terminal MPER residues (675-683) in the 17-172 construct does not shift the trimer-monomer equilibrium significantly. Thus, in the context of the gp41 ectodomain spanning residues 17-172, trimerization is clearly dependent on FPPR and MPER regions even when the terminal residues of MPER unravel. The antibody Z13e1, which spans both the 2F5 and 4E10 epitopes in MPER, binds to 17-172 with a Kd of 1 ± 0.12 μM. Accordingly, individual antibodies 2F5 and 4E10 also recognize the 17-172 trimer/DPC complex. We propose that binding of the C-terminal residues of MPER to the surface of the DPC micelles models a correct positioning of the trimeric transmembrane domain anchored in the viral membrane.
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Affiliation(s)
- John M. Louis
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (JL)); (JR)
| | - James L. Baber
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Rodolfo Ghirlando
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Annie Aniana
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Ad Bax
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Julien Roche
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- Roy J. Carver Department of Biochemistry, Biophysics and Molecular Biology, Iowa State University, Ames, Iowa, United States of America
- * E-mail: (JL)); (JR)
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20
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Reichart TM, Baksh MM, Rhee JK, Fiedler JD, Sligar SG, Finn MG, Zwick MB, Dawson PE. Trimerization of the HIV Transmembrane Domain in Lipid Bilayers Modulates Broadly Neutralizing Antibody Binding. Angew Chem Int Ed Engl 2016. [DOI: 10.1002/ange.201508421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Timothy M. Reichart
- Department of Chemistry; The Scripps Research Institute; 10550 North Torrey Pines Road La Jolla CA 92037 USA
| | - Michael M. Baksh
- Department of Chemistry; The Scripps Research Institute; 10550 North Torrey Pines Road La Jolla CA 92037 USA
- School of Chemistry & Biochemistry; Georgia Institute of Technology; 901 Atlantic Drive Atlanta GA 30332 USA
| | - Jin-Kyu Rhee
- Department of Food Science and Engineering; Ewha Womans University; Seoul 03760 Korea
| | - Jason D. Fiedler
- Department of Chemistry; The Scripps Research Institute; 10550 North Torrey Pines Road La Jolla CA 92037 USA
| | - Stephen G. Sligar
- Department of Biochemistry; University of Illinois; Urbana IL 61801 USA
| | - M. G. Finn
- Department of Chemistry; The Scripps Research Institute; 10550 North Torrey Pines Road La Jolla CA 92037 USA
- School of Chemistry & Biochemistry; Georgia Institute of Technology; 901 Atlantic Drive Atlanta GA 30332 USA
| | - Michael B. Zwick
- Department of Immunology and Microbial Science; The Scripps Research Institute; 10550 North Torrey Pines Road La Jolla CA USA
| | - Philip E. Dawson
- Department of Chemistry; The Scripps Research Institute; 10550 North Torrey Pines Road La Jolla CA 92037 USA
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21
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Reichart TM, Baksh MM, Rhee JK, Fiedler JD, Sligar SG, Finn MG, Zwick MB, Dawson PE. Trimerization of the HIV Transmembrane Domain in Lipid Bilayers Modulates Broadly Neutralizing Antibody Binding. Angew Chem Int Ed Engl 2016; 55:2688-92. [PMID: 26799917 PMCID: PMC5405556 DOI: 10.1002/anie.201508421] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Revised: 11/04/2015] [Indexed: 12/18/2022]
Abstract
The membrane-proximal external region (MPER) of HIV gp41 is an established target of antibodies that neutralize a broad range of HIV isolates. To evaluate the role of the transmembrane (TM) domain, synthetic MPER-derived peptides were incorporated into lipid nanoparticles using natural and designed TM domains, and antibody affinity was measured using immobilized and solution-based techniques. Peptides incorporating the native HIV TM domain exhibit significantly stronger interactions with neutralizing antibodies than peptides with a monomeric TM domain. Furthermore, a peptide with a trimeric, three-helix bundle TM domain recapitulates the binding profile of the native sequence. These studies suggest that neutralizing antibodies can bind the MPER when the TM domain is a three-helix bundle and this presentation could influence the binding of neutralizing antibodies to the virus. Lipid-bilayer presentation of viral antigens in Nanodiscs is a new platform for evaluating neutralizing antibodies.
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Affiliation(s)
- Timothy M Reichart
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA, 92037, USA
| | - Michael M Baksh
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA, 92037, USA
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, GA, 30332, USA
| | - Jin-Kyu Rhee
- Department of Food Science and Engineering, Ewha Womans University, Seoul, 03760, Korea
| | - Jason D Fiedler
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA, 92037, USA
| | - Stephen G Sligar
- Department of Biochemistry, University of Illinois, Urbana, IL, 61801, USA
| | - M G Finn
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA, 92037, USA
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, GA, 30332, USA
| | - Michael B Zwick
- Department of Immunology and Microbial Science, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA, USA
| | - Philip E Dawson
- Department of Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA, 92037, USA
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22
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Louis JM, Baber JL, Clore GM. The C34 Peptide Fusion Inhibitor Binds to the Six-Helix Bundle Core Domain of HIV-1 gp41 by Displacement of the C-Terminal Helical Repeat Region. Biochemistry 2015; 54:6796-805. [PMID: 26506247 DOI: 10.1021/acs.biochem.5b01021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The conformational transition of the core domain of HIV-1 gp41 from a prehairpin intermediate to a six-helix bundle is responsible for virus-cell fusion. Several inhibitors which target the N-heptad repeat helical coiled-coil trimer that is fully accessible in the prehairpin intermediate have been designed. One such inhibitor is the peptide C34 derived from the C-heptad repeat of gp41 that forms the exterior of the six-helix bundle. Here, using a variety of biophysical techniques, including dye tagging, size-exclusion chromatography combined with multiangle light scattering, double electron-electron resonance EPR spectroscopy, and circular dichroism, we investigate the binding of C34 to two six-helix bundle mimetics comprising N- and C-heptad repeats either without (core(SP)) or with (core(S)) a short spacer connecting the two. In the case of core(SP), C34 directly exchanges with the C-heptad repeat. For core(S), up to two molecules of C34 bind the six-helix bundle via displacement of the C-heptad repeat. These results suggest that fusion inhibitors such as C34 can target a continuum of transitioning conformational states from the prehairpin intermediate to the six-helix bundle prior to the occurrence of irreversible fusion of viral and target cell membranes.
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Affiliation(s)
- John M Louis
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0520, United States
| | - James L Baber
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0520, United States
| | - G Marius Clore
- Laboratory of Chemical Physics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health , Bethesda, Maryland 20892-0520, United States
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23
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Ratnayake PU, Prabodha Ekanayaka EA, Komanduru SS, Weliky DP. Full-length trimeric influenza virus hemagglutinin II membrane fusion protein and shorter constructs lacking the fusion peptide or transmembrane domain: Hyperthermostability of the full-length protein and the soluble ectodomain and fusion peptide make significant contributions to fusion of membrane vesicles. Protein Expr Purif 2015; 117:6-16. [PMID: 26297995 DOI: 10.1016/j.pep.2015.08.021] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2015] [Revised: 08/17/2015] [Accepted: 08/18/2015] [Indexed: 10/23/2022]
Abstract
Influenza virus is a class I enveloped virus which is initially endocytosed into a host respiratory epithelial cell. Subsequent reduction of the pH to the 5-6 range triggers a structural change of the viral hemagglutinin II (HA2) protein, fusion of the viral and endosomal membranes, and release of the viral nucleocapsid into the cytoplasm. HA2 contains fusion peptide (FP), soluble ectodomain (SE), transmembrane (TM), and intraviral domains with respective lengths of ∼ 25, ∼ 160, ∼ 25, and ∼ 10 residues. The present work provides a straightforward protocol for producing and purifying mg quantities of full-length HA2 from expression in bacteria. Biophysical and structural comparisons are made between full-length HA2 and shorter constructs including SHA2 ≡ SE, FHA2 ≡ FP+SE, and SHA2-TM ≡ SE+TM constructs. The constructs are helical in detergent at pH 7.4 and the dominant trimer species. The proteins are highly thermostable in decylmaltoside detergent with Tm>90 °C for HA2 with stabilization provided by the SE, FP, and TM domains. The proteins are likely in a trimer-of-hairpins structure, the final protein state during fusion. All constructs induce fusion of negatively-charged vesicles at pH 5.0 with much less fusion at pH 7.4. Attractive protein/vesicle electrostatics play a role in fusion, as the proteins are positively-charged at pH 5.0 and negatively-charged at pH 7.4 and the pH-dependence of fusion is reversed for positively-charged vesicles. Comparison of fusion between constructs supports significant contributions to fusion from the SE and the FP with little effect from the TM.
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Affiliation(s)
- Punsisi U Ratnayake
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States
| | - E A Prabodha Ekanayaka
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States
| | - Sweta S Komanduru
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States
| | - David P Weliky
- Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States.
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