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Marchetti C, Vaglietti S, Rizzo F, Di Nardo G, Colnaghi L, Ghirardi M, Fiumara F. Heptad stereotypy, S/Q layering, and remote origin of the SARS-CoV-2 fusion core. Virus Evol 2022; 7:veab097. [PMID: 35039783 PMCID: PMC8754743 DOI: 10.1093/ve/veab097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 10/24/2021] [Accepted: 11/23/2021] [Indexed: 11/13/2022] Open
Abstract
The fusion of the SARS-CoV-2 virus with cells, a key event in the pathogenesis of Covid-19, depends on the assembly of a six-helix fusion core (FC) formed by portions of the spike protein heptad repeats (HRs) 1 and 2. Despite the critical role in regulating infectivity, its distinctive features, origin, and evolution are scarcely understood. Thus, we undertook a structure-guided positional and compositional analysis of the SARS-CoV-2 FC, in comparison with FCs of related viruses, tracing its origin and ongoing evolution. We found that clustered amino acid substitutions within HR1, distinguishing SARS-CoV-2 from SARS-CoV-1, enhance local heptad stereotypy and increase sharply the FC serine-to-glutamine (S/Q) ratio, determining a neat alternate layering of S-rich and Q-rich subdomains along the post-fusion structure. Strikingly, SARS-CoV-2 ranks among viruses with the highest FC S/Q ratio, together with highly syncytiogenic respiratory pathogens (RSV, NDV), whereas MERS-Cov, HIV, and Ebola viruses display low ratios, and this feature reflects onto S/Q segregation and H-bonding patterns. Our evolutionary analyses revealed that the SARS-CoV-2 FC occurs in other SARS-CoV-1-like Sarbecoviruses identified since 2005 in Hong Kong and adjacent regions, tracing its origin to >50 years ago with a recombination-driven spread. Finally, current mutational trends show that the FC is varying especially in the FC1 evolutionary hotspot. These findings establish a novel analytical framework illuminating the sequence/structure evolution of the SARS-CoV-2 FC, tracing its long history within Sarbecoviruses, and may help rationalize the evolution of the fusion machinery in emerging pathogens and the design of novel therapeutic fusion inhibitors.
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Affiliation(s)
- Chiara Marchetti
- Rita Levi Montalcini Department of Neuroscience, University of Torino, Corso Raffaello 30, Torino 10125, Italy
| | - Serena Vaglietti
- Rita Levi Montalcini Department of Neuroscience, University of Torino, Corso Raffaello 30, Torino 10125, Italy
| | - Francesca Rizzo
- Istituto Zooprofilattico Sperimentale (IZS) del Piemonte, Liguria e Valle d'Aosta, Via Bologna 148, Torino 10148, Italy
| | - Giovanna Di Nardo
- Department of Life Sciences and Systems Biology (DBIOS), University of Torino, Via Accademia Albertina 13, Torino 10123, Italy
| | - Luca Colnaghi
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Via Olgettina 60, Milano 20132, Italy
| | - Mirella Ghirardi
- Rita Levi Montalcini Department of Neuroscience, University of Torino, Corso Raffaello 30, Torino 10125, Italy
| | - Ferdinando Fiumara
- Rita Levi Montalcini Department of Neuroscience, University of Torino, Corso Raffaello 30, Torino 10125, Italy
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2
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Extremely Thermostabilizing Core Mutations in Coiled-Coil Mimetic Proteins of HIV-1 gp41 Produce Diverse Effects on Target Binding but Do Not Affect Their Inhibitory Activity. Biomolecules 2021; 11:biom11040566. [PMID: 33921495 PMCID: PMC8069472 DOI: 10.3390/biom11040566] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2021] [Revised: 04/05/2021] [Accepted: 04/09/2021] [Indexed: 11/16/2022] Open
Abstract
A promising strategy to neutralize HIV-1 is to target the gp41 spike subunit to block membrane fusion with the cell. We previously designed a series of single-chain proteins (named covNHR) that mimic the trimeric coiled-coil structure of the gp41 N-terminal heptad repeat (NHR) region and potently inhibit HIV-1 cell infection by avidly binding the complementary C-terminal heptad repeat (CHR) region. These proteins constitute excellent tools to understand the structural and thermodynamic features of this therapeutically important interaction. Gp41, as with many coiled-coil proteins, contains in core positions of the NHR trimer several highly conserved, buried polar residues, the role of which in gp41 structure and function is unclear. Here we produced three covNHR mutants by substituting each triad of polar residues for the canonical isoleucine. The mutants preserve their helical structure and show an extremely increased thermal stability. However, increased hydrophobicity enhances their self-association. Calorimetric analyses show a marked influence of mutations on the binding thermodynamics of CHR-derived peptides. The mutations do not affect however the in vitro HIV-1 inhibitory activity of the proteins. The results support a role of buried core polar residues in maintaining structural uniqueness and promoting an energetic coupling between conformational stability and NHR-CHR binding.
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Kulandaisamy A, Zaucha J, Frishman D, Gromiha MM. MPTherm-pred: Analysis and Prediction of Thermal Stability Changes upon Mutations in Transmembrane Proteins. J Mol Biol 2020; 433:166646. [PMID: 32920050 DOI: 10.1016/j.jmb.2020.09.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2020] [Revised: 09/04/2020] [Accepted: 09/04/2020] [Indexed: 01/06/2023]
Abstract
The stability of membrane proteins differs from globular proteins due to the presence of nonpolar membrane-spanning regions. Using a dataset of 929 membrane protein mutations whose effects on thermal stability (ΔTm) were experimentally determined, we found that the average ΔTm due to 190 stabilizing and 232 destabilizing mutations occurring in membrane-spanning regions are 2.43(3.1) °C and -5.48(5.5) °C, respectively. The ΔTm values for mutations occurring in solvent-exposed regions are 2.56(2.82) and - 6.8(7.2) °C. We have systematically analyzed the factors influencing the stability of mutants and observed that changes in hydrophobicity, number of contacts between Cα atoms and frequency of aliphatic residues are important determinants of the stability change induced by mutations occurring in membrane-spanning regions. We have developed structure- and sequence-based machine learning predictors of ΔTm due to mutations specifically for membrane proteins. They showed a correlation and mean absolute error (MAE) of 0.72 and 2.85 °C, respectively, between experimental and predicted ΔTm for mutations in membrane-spanning regions on 10-fold group-wise cross-validation. The average correlation and MAE for mutations in aqueous regions are 0.73 and 3.7 °C, respectively. These MAE values are about 50% lower than standard deviations from the mean ΔTm values. The reliability of the method was affirmed on a test set of mutations occurring in evolutionary independent protein sequences. The developed MPTherm-pred server for predicting thermal stability changes upon mutations in membrane proteins is available at https://web.iitm.ac.in/bioinfo2/mpthermpred/. Our results provide insights into factors influencing the stability of membrane proteins and can aid in designing mutants that are more resistant to thermal stress.
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Affiliation(s)
- A Kulandaisamy
- Department of Biotechnology, Bhupat and Jyoti Mehta School of BioSciences, Indian Institute of Technology Madras, Chennai 600 036, Tamilnadu, India
| | - Jan Zaucha
- Department of Bioinformatics, Technische Universität München, Wissenschaftszentrum Weihenstephan, Freising, Germany
| | - Dmitrij Frishman
- Department of Bioinformatics, Technische Universität München, Wissenschaftszentrum Weihenstephan, Freising, Germany; Department of Bioinformatics, Peter the Great St. Petersburg Polytechnic University, St. Petersburg, Russian Federation
| | - M Michael Gromiha
- Department of Biotechnology, Bhupat and Jyoti Mehta School of BioSciences, Indian Institute of Technology Madras, Chennai 600 036, Tamilnadu, India.
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Chu S, Kaur H, Nemati A, Walsh JD, Partida V, Zhang SQ, Gochin M. Swapped-domain constructs of the glycoprotein-41 ectodomain are potent inhibitors of HIV infection. ACS Chem Biol 2015; 10:1247-57. [PMID: 25646644 DOI: 10.1021/cb501021j] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The conformational rearrangement of N- and C-heptad repeats (NHR, CHR) of the HIV-1 glycoprotein-41 (gp41) ectodomain into a trimer of hairpins triggers virus-cell fusion by bringing together membrane-spanning N- and C-terminal domains. Peptides derived from the NHR and CHR inhibit fusion by targeting a prehairpin intermediate state of gp41. Typically, peptides derived from the CHR are low nanomolar inhibitors, whereas peptides derived from the NHR are low micromolar inhibitors. Here, we describe the inhibitory activity of swapped-domain gp41 mimics of the form CHR-loop-NHR, which were designed to form reverse hairpin trimers exposing NHR grooves. We observed low nanomolar inhibition of HIV fusion in constructs that possessed the following properties: an extended NHR C-terminus, an exposed conserved hydrophobic pocket on the NHR, high helical content, and trimer stability. Low nanomolar activity was independent of CHR length. CD studies in membrane mimetic dodecylphosphocholine micelles suggested that bioactivity could be related to the ability of the inhibitors to interact with a membrane-associated prehairpin intermediate. The swapped-domain design resolves the problem of unstable and weakly active NHR peptides and suggests a different mechanism of action from that of CHR peptides in inhibition of HIV-1 fusion.
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Affiliation(s)
- Shidong Chu
- Department
of Basic Sciences, Touro University−California, Vallejo, California 94592, United States
| | - Hardeep Kaur
- Department
of Basic Sciences, Touro University−California, Vallejo, California 94592, United States
| | - Ariana Nemati
- Department
of Basic Sciences, Touro University−California, Vallejo, California 94592, United States
| | - Joseph D. Walsh
- Department
of Basic Sciences, Touro University−California, Vallejo, California 94592, United States
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, United States
| | - Vivian Partida
- Department
of Basic Sciences, Touro University−California, Vallejo, California 94592, United States
| | - Shao-Qing Zhang
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, United States
- Department
of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19014, United States
| | - Miriam Gochin
- Department
of Basic Sciences, Touro University−California, Vallejo, California 94592, United States
- Department
of Pharmaceutical Chemistry, University of California, San Francisco, California 94143, United States
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Hydrophobic mutations in buried polar residues enhance HIV-1 gp41 N-terminal heptad repeat-C-terminal heptad repeat interactions and C-peptides' anti-HIV activity. AIDS 2014; 28:1251-60. [PMID: 24625369 DOI: 10.1097/qad.0000000000000255] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE To investigate the effect of mutations in a highly conserved buried polar area on the function of HIV-1 gp41. DESIGN During HIV-1 entry, a six helical bundle (6-HB) formation between the C-terminal and N-terminal heptad repeat (CHR and NHR) of gp41 provides energy for virus cell membrane fusion. In 6-HB, residues at a and d (a-d) positions of CHR directly interact with NHR and are buried. They are considered critical residues for 6-HB stability and for anti-HIV-1 activity of CHR-derived peptides (C-peptides). Most of a-d residues in CHR are hydrophobic, as buried hydrophobic residues facilitate protein stability. However, HIV-1 gp41 CHR contains a highly conserved polar area with four successive buried a-d polar residues: S649/Q652/N656/E659. We mutated these buried polar residues to hydrophobic residues, either Leu or Ile, and studied its effect on the gp41 NHR-CHR interactions and anti-HIV activities of the C-peptides. METHODS We measured the C-peptide mutants' ability to form 6-HB with NHR, thermal stability of the 6-HBs and C-peptides' inhibitory activity against both T20-sensitive and resistant HIV-1 strains. RESULTS All the mutated C-peptides retained their ability to form stable 6-HB with NHR and strongly inhibited HIV-1 replication. Strikingly, S649L and E659I mutations endow C-peptide with a significantly enhanced activity against T20-resistant HIV-1 strains. CONCLUSION The highly conserved buried a-d polar residues in HIV-1 gp41 CHR can be mutated as a means of developing new fusion inhibitors against drug-resistant HIV-1 strains. The concept can also be utilized to design fusion inhibitors against other viruses with similar mechanisms.
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Aiamkitsumrit B, Dampier W, Antell G, Rivera N, Martin-Garcia J, Pirrone V, Nonnemacher MR, Wigdahl B. Bioinformatic analysis of HIV-1 entry and pathogenesis. Curr HIV Res 2014; 12:132-61. [PMID: 24862329 PMCID: PMC4382797 DOI: 10.2174/1570162x12666140526121746] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Revised: 03/18/2014] [Accepted: 05/06/2014] [Indexed: 02/07/2023]
Abstract
The evolution of human immunodeficiency virus type 1 (HIV-1) with respect to co-receptor utilization has been shown to be relevant to HIV-1 pathogenesis and disease. The CCR5-utilizing (R5) virus has been shown to be important in the very early stages of transmission and highly prevalent during asymptomatic infection and chronic disease. In addition, the R5 virus has been proposed to be involved in neuroinvasion and central nervous system (CNS) disease. In contrast, the CXCR4-utilizing (X4) virus is more prevalent during the course of disease progression and concurrent with the loss of CD4(+) T cells. The dual-tropic virus is able to utilize both co-receptors (CXCR4 and CCR5) and has been thought to represent an intermediate transitional virus that possesses properties of both X4 and R5 viruses that can be encountered at many stages of disease. The use of computational tools and bioinformatic approaches in the prediction of HIV-1 co-receptor usage has been growing in importance with respect to understanding HIV-1 pathogenesis and disease, developing diagnostic tools, and improving the efficacy of therapeutic strategies focused on blocking viral entry. Current strategies have enhanced the sensitivity, specificity, and reproducibility relative to the prediction of co-receptor use; however, these technologies need to be improved with respect to their efficient and accurate use across the HIV-1 subtypes. The most effective approach may center on the combined use of different algorithms involving sequences within and outside of the env-V3 loop. This review focuses on the HIV-1 entry process and on co-receptor utilization, including bioinformatic tools utilized in the prediction of co-receptor usage. It also provides novel preliminary analyses for enabling identification of linkages between amino acids in V3 with other components of the HIV-1 genome and demonstrates that these linkages are different between X4 and R5 viruses.
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Affiliation(s)
| | | | | | | | | | | | | | - Brian Wigdahl
- Department of Microbiology and Immunology, Drexel University College of Medicine, 245 N. 15th Street, Philadelphia, PA 19102.
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7
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Chong H, Yao X, Qiu Z, Qin B, Han R, Waltersperger S, Wang M, Cui S, He Y. Discovery of critical residues for viral entry and inhibition through structural Insight of HIV-1 fusion inhibitor CP621-652. J Biol Chem 2012; 287:20281-9. [PMID: 22511760 DOI: 10.1074/jbc.m112.354126] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The core structure of HIV-1 gp41 is a stable six-helix bundle (6-HB) folded by its trimeric N- and C-terminal heptad repeats (NHR and CHR). We previously identified that the (621)QIWNNMT(627) motif located at the upstream region of gp41 CHR plays critical roles for the stabilization of the 6-HB core and peptide CP621-652 containing this motif is a potent HIV-1 fusion inhibitor, however, the molecular determinants underlying the stability and anti-HIV activity remained elusive. In this study, we determined the high-resolution crystal structure of CP621-652 complexed by T21. We find that the (621)QIWNNMT(627) motif does not maintain the α-helical conformation. Instead, residues Met(626) and Thr(627) form a unique hook-like structure (denoted as M-T hook), in which Thr(627) redirects the peptide chain to position Met(626) above the left side of the hydrophobic pocket on the NHR trimer. The side chain of Met(626) caps the hydrophobic pocket, stabilizing the interaction between the pocket and the pocket-binding domain. Our mutagenesis studies demonstrate that mutations of the M-T hook residues could completely abolish HIV-1 Env-mediated cell fusion and virus entry, and significantly destabilize the interaction of NHR and CHR peptides and reduce the anti-HIV activity of CP621-652. Our results identify an unusual structural feature that stabilizes the six-helix bundle, providing novel insights into the mechanisms of HIV-1 fusion and inhibition.
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Affiliation(s)
- Huihui Chong
- MOH Key Laboratory of Systems Biology of Pathogens, Institute of Pathogen Biology, Chinese Academy of Medical Sciences & Peking Union Medical College, 9 Dong Dan San Tiao, Beijing 100730, China
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8
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Chang CC, Cheng SF, Lin CH, Chen SSL, Chang DK. Stability of gp41 hairpin and helix bundle assembly probed by combined stacking and circular dichroic approaches. J Struct Biol 2011; 175:406-14. [DOI: 10.1016/j.jsb.2011.06.007] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Revised: 05/17/2011] [Accepted: 06/16/2011] [Indexed: 10/18/2022]
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9
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Teixeira C, Gomes JRB, Gomes P, Maurel F, Barbault F. Viral surface glycoproteins, gp120 and gp41, as potential drug targets against HIV-1: brief overview one quarter of a century past the approval of zidovudine, the first anti-retroviral drug. Eur J Med Chem 2011; 46:979-92. [PMID: 21345545 DOI: 10.1016/j.ejmech.2011.01.046] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2010] [Revised: 01/15/2011] [Accepted: 01/25/2011] [Indexed: 12/15/2022]
Abstract
The first anti-HIV drug, zidovudine (AZT), was approved by the FDA a quarter of a century ago, in 1985. Currently, anti-HIV drug-combination therapies only target HIV-1 protease and reverse transcriptase. Unfortunately, most of these molecules present numerous shortcomings such as viral resistances and adverse effects. In addition, these drugs are involved in later stages of infection. Thus, it is necessary to develop new drugs that are able to block the first steps of viral life cycle. Entry of HIV-1 is mediated by its two envelope glycoproteins: gp120 and gp41. Upon gp120 binding to cellular receptors, gp41 undergoes a series of conformational changes from a non-fusogenic to a fusogenic conformation. The fusogenic core of gp41 is a trimer-of-hairpins structure in which three C-terminal helices pack against a central trimeric-coiled coil formed by three N-terminal helices. The formation of this fusogenic structure brings the viral and cellular membranes close together, a necessary condition for membrane fusion to occur. As gp120 and gp41 are attractive targets, the development of entry inhibitors represents an important avenue of anti-HIV drug therapy. The present review will focus on some general considerations about HIV, the main characteristics of gp120, gp41 and their inhibitors, with special emphasis on the advances of computational approaches employed in the development of bioactive compounds against HIV-1 entry process.
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Affiliation(s)
- Cátia Teixeira
- ITODYS, Université Paris Diderot, CNRS - UMR7086, 15 Rue Jean Antoine de Baif, 75205 Paris Cedex 13, France
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Conserved salt bridge between the N- and C-terminal heptad repeat regions of the human immunodeficiency virus type 1 gp41 core structure is critical for virus entry and inhibition. J Virol 2008; 82:11129-39. [PMID: 18768964 DOI: 10.1128/jvi.01060-08] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The fusogenic human immunodeficiency virus type 1 (HIV-1) gp41 core structure is a stable six-helix bundle formed by its N- and C-terminal heptad repeat sequences. Notably, the negatively charged residue Asp(632) located at the pocket-binding motif in the C-terminal heptad repeat interacts with the positively charged residue Lys(574) in the pocket formation region of the N-terminal heptad repeat to form a salt bridge. We previously demonstrated that the residue Lys(574) plays an essential role in six-helix bundle formation and virus infectivity and is a key determinant of the target for anti-HIV fusion inhibitors. In this study, the functionality of residue Asp(632) has been specifically characterized by mutational analysis and biophysical approaches. We show that Asp(632) substitutions with positively charged residues (D632K and D632R) or a hydrophobic residue (D632V) could completely abolish Env-mediated viral entry, while a protein with a conserved substitution (D632E) retained its activity. Similar to the Lys(574) mutations, nonconserved substitutions of Asp(632) also severely impaired the alpha-helicity, stability, and conformation of six-helix bundles as shown by N36 and C34 peptides as a model system. Furthermore, nonconserved substitutions of Asp(632) significantly reduced the potency of C34 to sequestrate six-helix bundle formation and to inhibit HIV-1-mediated cell-cell fusion and infection, suggesting its importance for designing antiviral fusion inhibitors. Taken together, these data suggest that the salt bridge between the N- and C-terminal heptad repeat regions of the fusion-active HIV-1 gp41 core structure is critical for viral entry and inhibition.
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11
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Peng X, Pan J, Gong R, Liu Y, Kang S, Feng H, Qiu G, Guo D, Tien P, Xiao G. Functional Characterization of Syncytin-A, a Newly Murine Endogenous Virus Envelope Protein. J Biol Chem 2007; 282:381-9. [PMID: 17105734 DOI: 10.1074/jbc.m606353200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Trophoblast fusion in placenta is an important event for preservation of a healthy pregnancy. This process takes place throughout the pregnancy and is crucial for the formation of syncytiotrophoblast layer. Syncytin-1 and syncytin-2 are strong candidate regulators of fusion from retroviral origin. Syncytin-A and syncytin-B are other candidates from retroviral origin in Muridae. The active role of syncytin in driving fusion of trophoblast has been identified, but its fusion mechanism is still unclear. As an intact retroviral envelope protein, syncytin-A shares similar structure profiling with other viral envelope fusion proteins, especially in the regions of N- and C-terminal heptad repeats (NHR and CHR, respectively). In this paper, we showed that SynA 1 + 2 of syncytin-A (residues 445-536, including predicted NHR, CHR, and a natural linker) could form trimer and exhibited significant alpha-helix structure and high thermo-stability. Limited proteolysis result identified a stable protease-resistant core of SynA 1 + 2, which was in good agreement with computational modeling data. NHR and CHR could interact with each other in vitro, too. Different from the previous studies, the disulfide-bonded linker was apparently vital to the stability of fusion core structure. By biological assays, NHR was shown to be inhibitive to cell-cell fusion, with IC(50) value about 5.4 microm, but CHR seemed to have no inhibitory activity even at 50 microm. From both biochemical and functional data, we first gave an explanation how syncytin-A mediated cell fusion. The insight into the mechanism of syncytin-A-mediated cell-cell fusion may provide a crucial clue to placental cytotrophoblast morphogenesis.
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Affiliation(s)
- Xiaoxue Peng
- State Key Laboratory of Virology and Modern Virology Research Centre, College of Life Sciences, Wuhan University, Wuhan, Hubei 430072, China
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12
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Veazey RS, Klasse PJ, Schader SM, Hu Q, Ketas TJ, Lu M, Marx PA, Dufour J, Colonno RJ, Shattock RJ, Springer MS, Moore JP. Protection of macaques from vaginal SHIV challenge by vaginally delivered inhibitors of virus-cell fusion. Nature 2005; 438:99-102. [PMID: 16258536 DOI: 10.1038/nature04055] [Citation(s) in RCA: 257] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Accepted: 07/21/2005] [Indexed: 02/07/2023]
Abstract
Human immunodeficiency virus type 1 (HIV-1) continues to spread, principally by heterosexual sex, but no vaccine is available. Hence, alternative prevention methods are needed to supplement educational and behavioural-modification programmes. One such approach is a vaginal microbicide: the application of inhibitory compounds before intercourse. Here, we have evaluated the microbicide concept using the rhesus macaque 'high dose' vaginal transmission model with a CCR5-receptor-using simian-human immunodeficiency virus (SHIV-162P3) and three compounds that inhibit different stages of the virus-cell attachment and entry process. These compounds are BMS-378806, a small molecule that binds the viral gp120 glycoprotein and prevents its attachment to the CD4 and CCR5 receptors, CMPD167, a small molecule that binds to CCR5 to inhibit gp120 association, and C52L, a bacterially expressed peptide inhibitor of gp41-mediated fusion. In vitro, all three compounds inhibit infection of T cells and cervical tissue explants, and C52L acts synergistically with CMPD167 or BMS-378806 to inhibit infection of cell lines. In vivo, significant protection was achieved using each compound alone and in combinations. CMPD167 and BMS-378806 were protective even when applied 6 h before challenge.
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Affiliation(s)
- Ronald S Veazey
- Tulane National Primate Research Center, Covington, Louisiana 70433, USA
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13
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York J, Agnihothram SS, Romanowski V, Nunberg JH. Genetic analysis of heptad-repeat regions in the G2 fusion subunit of the Junín arenavirus envelope glycoprotein. Virology 2005; 343:267-74. [PMID: 16169032 PMCID: PMC7173107 DOI: 10.1016/j.virol.2005.08.030] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2005] [Revised: 08/10/2005] [Accepted: 08/22/2005] [Indexed: 11/03/2022]
Abstract
The G2 fusion subunit of the Junín virus envelope glycoprotein GP-C contains two hydrophobic heptad-repeat regions that are postulated to form a six-helix bundle structure required for the membrane fusion activity of Class I viral fusion proteins. We have investigated the role of these heptad-repeat regions and, specifically, the importance of the putative interhelical a and d position sidechains by using alanine-scanning mutagenesis. All the mutant glycoproteins were expressed and transported to the cell surface. Proteolytic maturation at the subtilisin kexin isozyme-1/site-1-protease (SKI-1/S1P) cleavage site was observed in all but two of the mutants. Among the adequately cleaved mutant glycoproteins, four positions in the N-terminal region (I333, L336, L347 and L350) and two positions in the C-terminal region (R392 and W395) were shown to be important determinants of cell–cell fusion. Taken together, our results indicate that α-helical coiled-coil structures are likely critical in promoting arenavirus membrane fusion. These findings support the inclusion of the arenavirus GP-C among the Class I viral fusion proteins and suggest pharmacologic and immunologic strategies for targeting arenavirus infection and hemorrhagic fever.
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Affiliation(s)
- Joanne York
- Montana Biotechnology Center, The University of Montana, Science Complex Room 221, Missoula, MT 59812, USA
| | - Sudhakar S. Agnihothram
- Montana Biotechnology Center, The University of Montana, Science Complex Room 221, Missoula, MT 59812, USA
| | - Victor Romanowski
- Instituto de Bioquímica y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, La Plata, Argentina
- Departmento de Ciencia y Tecnología, Universidad Nacional de Quilmes, Bernal, Argentina
| | - Jack H. Nunberg
- Montana Biotechnology Center, The University of Montana, Science Complex Room 221, Missoula, MT 59812, USA
- Corresponding author. Fax: +1 406 243 6425.
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14
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Abstract
In this study we examine the distribution of hydrophobic residues in a nonredundant set of monomeric globular single-domain proteins. We find that the total fraction of hydrophobic residues is roughly constant and has no discernible dependence on protein size. This results in a decrease of the hydrophobicity of the core as the size of proteins increases. Using a normalized measure, and by comparing with sets of randomly reshuffled sequences, we show that this change in the composition of the core is statistically significant and robust with respect to which amino acids are considered hydrophobic and to how buried residues are defined. Comparison with model sequences optimized for stability, while still required to retain their native state as a unique minimum energy conformation, suggests that the size-independence of the total fraction of hydrophobic residues could be a result of requiring proteins to be conformationally specific.
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Affiliation(s)
- Erik Sandelin
- Stockholm Bioinformatics Center, AlbaNova, Stockholms Universitet, Stockholm, Sweden.
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15
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Glenn AA, Novembre FJ. A single amino acid change in gp41 is linked to the macrophage-only replication phenotype of a molecular clone of simian immunodeficiency virus derived from the brain of a macaque with neuropathogenic infection. Virology 2004; 325:297-307. [PMID: 15246269 DOI: 10.1016/j.virol.2004.04.048] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2004] [Revised: 04/27/2004] [Accepted: 04/30/2004] [Indexed: 10/26/2022]
Abstract
Simian immunodeficiency virus (SIV)-related neuropathogenesis has been observed in 90% of pig-tailed macaques infected with strain SIVsmmFGb, making it an excellent system for studying human immunodeficiency virus (HIV)-associated neurological disease. To investigate the genetics of SIV neurovirulence, infectious molecular clones were generated from the brain of a SIVsmmFGb-infected pig-tailed macaque. One clone, BPZm.12, displayed a macrophage-restricted phenotype not previously described; this clone replicated to high levels in macrophages, but did not replicate in peripheral blood mononuclear cells (PBMC) until at least 21 days postinfection. Sequence analysis of the env gene of BPZm.12 revealed the substitution of a serine residue for a highly conserved proline residue at position 629 in gp41. A mutant clone, which contained the conserved proline to serine (BPZm.12-629P), was able to replicate in both macrophages and PBMC without delay. A mutant of an unrelated dual tropic molecular clone PBj6.6, substituting proline for serine (PBj6.6-629S), replicated to high levels in macrophages, but did not replicate in PBMC at any time point. These data indicated that a single determinant in gp41 of an SIV clone changed its phenotype from macrophage tropic to dual tropic.
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Affiliation(s)
- Amanda A Glenn
- Division of Microbiology and Immunology, Yerkes National Primate Research Center, Department of Microbiology and Immunology, Emory University, Atlanta, GA 30329, USA
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16
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Krell T, Greco F, Engel O, Dubayle J, Dubayle J, Kennel A, Charloteaux B, Brasseur R, Chevalier M, Sodoyer R, El Habib R. HIV-1 gp41 and gp160 are hyperthermostable proteins in a mesophilic environment. Characterization of gp41 mutants. ACTA ACUST UNITED AC 2004; 271:1566-79. [PMID: 15066182 DOI: 10.1111/j.1432-1033.2004.04068.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
HIV gp41(24-157) unfolds cooperatively over the pH range of 1.0-4.0 with T(m) values of > 100 degrees C. At pH 2.8, protein unfolding was 80% reversible and the DeltaH(vH)/DeltaH(cal) ratio of 3.7 is indicative of gp41 being trimeric. No evidence for a monomer-trimer equilibrium in the concentration range of 0.3-36 micro m was obtained by DSC and tryptophan fluorescence. Glycosylation of gp41 was found to have only a marginal impact on the thermal stability. Reduction of the disulfide bond or mutation of both cysteine residues had only a marginal impact on protein stability. There was no cooperative unfolding event in the DSC thermogram of gp160 in NaCl/P(i), pH 7.4, over a temperature range of 8-129 degrees C. When the pH was lowered to 5.5-3.4, a single unfolding event at around 120 degrees C was noted, and three unfolding events at 93.3, 106.4 and 111.8 degrees C were observed at pH 2.8. Differences between gp41 and gp160, and hyperthermostable proteins from thermophile organisms are discussed. A series of gp41 mutants containing single, double, triple or quadruple point mutations were analysed by DSC and CD. The impact of mutations on the protein structure, in the context of generating a gp41 based vaccine antigen that resembles a fusion intermediate state, is discussed. A gp41 mutant, in which three hydrophobic amino acids in the gp41 loop were replaced with charged residues, showed an increased solubility at neutral pH.
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Affiliation(s)
- Tino Krell
- Aventis Pasteur, 1541 avenue Marcel Meriueux, 69280 Marcy l'Etoile, France.
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17
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Soler-Lopez M, Petosa C, Fukuzawa M, Ravelli R, Williams JG, Müller CW. Structure of an activated Dictyostelium STAT in its DNA-unbound form. Mol Cell 2004; 13:791-804. [PMID: 15053873 DOI: 10.1016/s1097-2765(04)00130-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2003] [Revised: 01/28/2004] [Accepted: 02/02/2004] [Indexed: 11/19/2022]
Abstract
Dd-STATa is a STAT protein which transcriptionally regulates cellular differentiation in Dictyostelium discoideum, the only non-metazoan known to employ SH2 domain signaling. The 2.7 A crystal structure of a tyrosine phosphorylated Dd-STATa homodimer reveals a four-domain architecture similar to that of mammalian STATs 1 and 3, but with an inverted orientation for the coiled-coil domain. Dimerization is mediated by SH2 domain:phosphopeptide interactions and by a direct interaction between SH2 domains. The unliganded Dd-STATa dimer adopts a fully extended conformation remarkably different from that of the DNA-bound mammalian STATs, implying a large conformational change upon target site recognition. Buried hydrophilic residues predicted to destabilize the coiled-coil domain suggest how hydrophobic residues may become exposed and mediate nuclear export. Functional and evolutionary implications for metazoan STAT proteins are discussed.
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Affiliation(s)
- Montserrat Soler-Lopez
- European Molecular Biology Laboratory, Grenoble Outstation, B.P. 181, 38042 Grenoble Cedex 9, France
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18
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Peisajovich SG, Blank L, Epand RF, Epand RM, Shai Y. On the interaction between gp41 and membranes: the immunodominant loop stabilizes gp41 helical hairpin conformation. J Mol Biol 2003; 326:1489-501. [PMID: 12595260 DOI: 10.1016/s0022-2836(03)00040-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
gp41 is the protein responsible for the process of membrane fusion that allows primate lentiviruses (HIV and SIV) to enter into their host cells. gp41 ectodomain contains an N-terminal and a C-terminal heptad repeat region (NHR and CHR) connected by an immunodominant loop. In the absence of membranes, the NHR and CHR segments fold into a protease-resistant core with a trimeric helical hairpin structure. However, when the immunodominant loop is not present (either in a complex formed by HIV-1 gp41-derived NHR and CHR peptides or by mild treatment with protease of recombinant constructs of HIV-1 gp41 ectodomain, which also lack the N-terminal fusion peptide and the C-terminal Trp-rich region) membrane binding induces a conformational change in the gp41 core structure. Here, we further investigated whether covalently linking the NHR and CHR segments by the immunodominant loop affects this conformational change. Specifically, we analyzed a construct corresponding to a fragment of SIVmac239 gp41ectodomain (residues 27-149, named e-gp41) by means of surface plasmon resonance, Trp and rhodamine fluorescence, ATR-FTIR spectroscopy, and differential scanning calorimetry. Our results suggest that the presence of the loop stabilizes the trimeric helical hairpin both when e-gp41 is in aqueous solution and when it is bound to the membrane surface. Bearing in mind possible differences between HIV-1 and SIV gp41, and considering that the gp41 ectodomain constructs analyzed to date lack the N-terminal fusion peptide and the C-terminal Trp-rich region, we discuss our observations in relation to the mechanism of virus-induced membrane fusion.
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Affiliation(s)
- Sergio G Peisajovich
- Department of Biological Chemistry, Weizmann Institute of Science, 76100, Rehovot, Israel
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19
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Sanders RW, Vesanen M, Schuelke N, Master A, Schiffner L, Kalyanaraman R, Paluch M, Berkhout B, Maddon PJ, Olson WC, Lu M, Moore JP. Stabilization of the soluble, cleaved, trimeric form of the envelope glycoprotein complex of human immunodeficiency virus type 1. J Virol 2002; 76:8875-89. [PMID: 12163607 PMCID: PMC136973 DOI: 10.1128/jvi.76.17.8875-8889.2002] [Citation(s) in RCA: 361] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The envelope glycoprotein (Env) complex of human immunodeficiency virus type 1 has evolved a structure that is minimally immunogenic while retaining its natural function of receptor-mediated virus-cell fusion. The Env complex is trimeric; its six individual subunits (three gp120 and three gp41 subunits) are associated by relatively weak, noncovalent interactions. The induction of neutralizing antibodies after vaccination with individual Env subunits has proven very difficult, probably because they are inadequate mimics of the native complex. Our hypothesis is that a stable form of the Env complex, perhaps with additional modifications to rationally alter its antigenic structure, may be a better immunogen than the individual subunits. A soluble form of Env, SOS gp140, can be made that has gp120 stably linked to the gp41 ectodomain by an intermolecular disulfide bond. This protein is fully cleaved at the proteolysis site between gp120 and gp41. However, the gp41-gp41 interactions in SOS gp140 are too weak to maintain the protein in a trimeric configuration. Consequently, purified SOS gp140 is a monomer (N. Schülke, M. S. Vesanen, R. W. Sanders, P. Zhu, D. J. Anselma, A. R. Villa, P. W. H. I. Parren, J. M. Binley, K. H. Roux, P. J. Maddon, J. P. Moore, and W. C. Olson, J. Virol. 76:7760-7776, 2002). Here we describe modifications of SOS gp140 that increase its trimer stability. A variant SOS gp140, designated SOSIP gp140, contains an isoleucine-to-proline substitution at position 559 in the N-terminal heptad repeat region of gp41. This protein is fully cleaved, has favorable antigenic properties, and is predominantly trimeric. SOSIP gp140 trimers are noncovalently associated and can be partially purified by gel filtration chromatography. These gp140 trimers are dissociated into monomers by anionic detergents or heat but are relatively resistant to nonionic detergents, high salt concentrations, or exposure to a mildly acidic pH. SOSIP gp140 should be a useful reagent for structural and immunogenicity studies.
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Affiliation(s)
- Rogier W Sanders
- Department of Microbiology and Immunology, Weill Medical College, Cornell University, New York, New York 10021, USA
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20
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Follis KE, Larson SJ, Lu M, Nunberg JH. Genetic evidence that interhelical packing interactions in the gp41 core are critical for transition of the human immunodeficiency virus type 1 envelope glycoprotein to the fusion-active state. J Virol 2002; 76:7356-62. [PMID: 12072535 PMCID: PMC136323 DOI: 10.1128/jvi.76.14.7356-7362.2002] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2002] [Accepted: 04/23/2002] [Indexed: 11/20/2022] Open
Abstract
The envelope glycoprotein complex (gp120-gp41) of human immunodeficiency virus type 1 (HIV-1) promotes the fusion of viral and cellular membranes through formation of the fusion-active six-helix bundle in the gp41 ectodomain. This gp41 core structure consists of three C-terminal helices packed in an antiparallel manner into hydrophobic grooves on the surface of the N-terminal trimeric coiled coil. Alanine mutations that destabilize the N- and C-terminal interhelical packing interactions also reduce viral infectivity. Here we show that viruses bearing these mutations exhibit a marked potentiation of inhibition by peptides that make up the gp41 core. By contrast, these viruses are unchanged in their sensitivities to soluble CD4, the CXCR4 coreceptor ligand SDF-1alpha, and human anti-HIV immunoglobulin, reagents that impact the initial, receptor-induced conformational changes in the envelope glycoprotein. Our results support the notion that these alanine mutations specifically affect the conformational transition to the fusion-active gp41 structure. The mutations also increase viral sensitivity to the gp41-directed monoclonal antibody 2F5, suggesting that this broadly neutralizing antibody may also interfere with this transition. The conformational activation of the HIV-1 envelope glycoprotein likely represents a viable target for vaccine and antiviral drug development.
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Affiliation(s)
- Kathryn E Follis
- Montana Biotechnology Center, The University of Montana, Missoula, Montana 59812, USA
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21
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Liu J, Wang S, Hoxie JA, LaBranche CC, Lu M. Mutations that destabilize the gp41 core are determinants for stabilizing the simian immunodeficiency virus-CPmac envelope glycoprotein complex. J Biol Chem 2002; 277:12891-900. [PMID: 11830586 DOI: 10.1074/jbc.m110315200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The human and simian immunodeficiency viruses (HIV and SIV) envelope glycoprotein consists of a trimer of two noncovalently and weakly associated subunits, gp120 and gp41. Upon binding of gp120 to cellular receptors, this labile native envelope complex undergoes conformational changes, resulting in a stable trimer-of-hairpins structure in gp41. Formation of the hairpin structure is thought to mediate membrane fusion by placing the viral and cellular membranes in close proximity. An in vitro-derived variant of SIVmac251, denoted CPmac, has acquired an unusually stable virion-associated gp120-gp41 complex. This unique phenotype is conferred by five amino acid substitutions in the gp41 ectodomain. Here we characterize the structural and physicochemical properties of the N40(L6)C38 model of the CPmac gp41 core. The 1.7-A resolution crystal structure of N40(L6)C38 is very similar to the six-helix bundle structure present in the parent SIVmac251 gp41. In both structures, three N40 peptides form a central three-stranded coiled coil, and three C38 peptides pack in an antiparallel orientation into hydrophobic grooves on the coiled-coil surface. Thermal unfolding studies show that the CPmac mutations destabilize the SIVmac251 six-helix bundle by 15 kJ/mol. Our results suggest that the formation of the gp41 trimer-of-hairpins structure is thermodynamically coupled to the conformational stability of the native envelope glycoprotein and raise the intriguing possibility that introduction of mutations to destabilize the six-helix bundle may lead to the stabilization of the trimeric gp120-gp41 complex. This study suggests a potential strategy for the production of stably folded envelope protein immunogens for HIV vaccine development.
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Affiliation(s)
- Jie Liu
- Department of Biochemistry, Weill Medical College of Cornell University, 1300 York Avenue, New York, NY 10021, USA
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22
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Lu M, Stoller MO, Wang S, Liu J, Fagan MB, Nunberg JH. Structural and functional analysis of interhelical interactions in the human immunodeficiency virus type 1 gp41 envelope glycoprotein by alanine-scanning mutagenesis. J Virol 2001; 75:11146-56. [PMID: 11602754 PMCID: PMC114694 DOI: 10.1128/jvi.75.22.11146-11156.2001] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2001] [Accepted: 08/08/2001] [Indexed: 11/20/2022] Open
Abstract
Membrane fusion by human immunodeficiency virus type 1 (HIV-1) is promoted by the refolding of the viral envelope glycoprotein into a fusion-active conformation. The structure of the gp41 ectodomain core in its fusion-active state is a trimer of hairpins in which three antiparallel carboxyl-terminal helices pack into hydrophobic grooves on the surface of an amino-terminal trimeric coiled coil. In an effort to identify amino acid residues in these grooves that are critical for gp41 activation, we have used alanine-scanning mutagenesis to investigate the importance of individual side chains in determining the biophysical properties of the gp41 core and the membrane fusion activity of the gp120-gp41 complex. Alanine substitutions at Leu-556, Leu-565, Val-570, Gly-572, and Arg-579 positions severely impaired membrane fusion activity in envelope glycoproteins that were for the most part normally expressed. Whereas alanine mutations at Leu-565 and Val-570 destabilized the trimer-of-hairpins structure, mutations at Gly-572 and Arg-579 led to the formation of a stable gp41 core. Our results suggest that the Leu-565 and Val-570 residues are important determinants of conserved packing interactions between the amino- and carboxyl-terminal helices of gp41. We propose that the high degree of sequence conservation at Gly-572 and Arg-579 may result from selective pressures imposed by prefusogenic conformations of the HIV-1 envelope glycoprotein. Further analysis of the gp41 activation process may elucidate targets for antiviral intervention.
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Affiliation(s)
- M Lu
- Department of Biochemistry, Weill Medical College of Cornell University, New York, New York 10021, USA.
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23
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Jelesarov I, Lu M. Thermodynamics of trimer-of-hairpins formation by the SIV gp41 envelope protein. J Mol Biol 2001; 307:637-56. [PMID: 11254387 DOI: 10.1006/jmbi.2001.4469] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The gp41 envelope protein mediates the entry of primate immunodeficiency viruses into target cells by promoting the fusion of viral and cellular membranes. The structure of the gp41 ectodomain core represents a trimer of identical helical hairpins in which a central trimeric coiled-coil made up of three amino-terminal helices is wrapped in an outer layer of three antiparallel carboxyl-terminal helices. Triggering formation of this fusion-active gp41 conformation appears to cause close membrane apposition and thus overcome the activation energy barrier for lipid bilayer fusion. We present a detailed description of the folding thermodynamics of the simian immunodeficiency virus (SIV) gp41 core by using a recombinant trimeric N34(L6)C28 model. Differential scanning calorimetry and spectroscopic experiments on denaturant-induced and thermal unfolding indicate that the free energy of association of three 68 residue N34(L6)C28 peptides to a trimer-of-hairpins is 76 kJ mol(-1) at pH 7.0 and 25 degrees C in physiological buffer. The associated enthalpy change, Delta H(unf), is 177 kJ mol(-1), while the entropy of unfolding, Delta S(unf), is 0.32 kJ K(-1) mol(-1). The temperature of maximal stability is close to 20 degrees C. The unfolding heat capacity increment is approximately 9 kJ K(-1) mol(-1) (approximately 45 J K(-1) mol residue(-1)), which is lower than expected for unfolding of the trimer to an extended and fully hydrated polypeptide chain. Replacement by isoleucine of the polar residues Thr582 or Thr586 buried in the N-terminal trimeric coiled-coil interface leads to very strong stabilization of the trimer-of-hairpins, 30-35 kJ mol(-1). Single-point mutations in the central coiled-coil thus strongly stabilize the gp41 core structure. These thermodynamic characteristics may be important for the refolding of the gp41 envelope protein into its fusion-active conformation during membrane fusion.
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Affiliation(s)
- I Jelesarov
- Biochemisches Institut der Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
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24
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Gratkowski H, Lear JD, DeGrado WF. Polar side chains drive the association of model transmembrane peptides. Proc Natl Acad Sci U S A 2001; 98:880-5. [PMID: 11158564 PMCID: PMC14678 DOI: 10.1073/pnas.98.3.880] [Citation(s) in RCA: 273] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The forces stabilizing the three-dimensional structures of membrane proteins are currently not well understood. Previously, it was shown that a single Asn side chain in a transmembrane segment can mediate the dimerization and trimerization of a variety of hydrophobic helices. Here, we examine the tendencies of a representative set of amino acids (Asn, Gln, Asp, Glu, Lys, Ala, Val, Leu, Ser, Thr) to direct the oligomerization of a model transmembrane helix. The model peptide is entirely hydrophobic throughout a 20-residue segment and contains a single central site for the introduction of various amino acid "guests." Analytical ultracentrifugation and gel electrophoresis were used to determine the stoichiometry and free energy of association of the entire set of peptides within micelles. Variants with two polar atoms at the guest site-Asn, Gln, Asp, and Glu-formed stable trimers, whereas residues with one or fewer polar atoms showed a much weaker tendency to associate. The data are examined in light of the frequencies of occurrence of various amino acid side chains in membrane proteins and provide insight into the role of polar interactions in directing transmembrane helix association. These data also suggest an approach to the design of variants of natural single-span transmembrane proteins with various potentials to associate in the bilayer.
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Affiliation(s)
- H Gratkowski
- The Johnson Research Foundation, Department of Biochemistry and Biophysics, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6059, USA
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25
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Dong XN, Xiao Y, Dierich MP, Chen YH. N- and C-domains of HIV-1 gp41: mutation, structure and functions. Immunol Lett 2001; 75:215-20. [PMID: 11166378 DOI: 10.1016/s0165-2478(00)00302-3] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Recent studies demonstrated that the N- and C-domains of HIV-1 gp41 is involved in virus-mediated membrane fusion resulting in HIV-entry into the target cells. Up to now, viral mutation baffled many scientists to develop effective vaccines and drugs against HIV-1. To acquire more information of mutation of gp41 and to reveal the relationship of structure and function of the N- and C-domains, we compared and analyzed amino acid sequences of the gp41 ectodomain (aa 512-681) of 862 isolates from most HIV-1 clades (including A, B, C, D, E, F, G, H, I, J and O clades). A consensus sequence of the ectodomain with the highest frequency emerging on each position is constituted. The fusion domain and the N-domain belong to the most conserved regions in gp41, and most variable residues assemble partial to the C terminal of gp41. The hydrophobicity of each position is also calculated. The a and d positions in the N-domain for maintaining stabilization of the trimeric coiled coil interactions are highly conservative, and the e and g positions in the C-domain to retain the interaction show also highly conservative. The strange high conservation of the c residues may have an implication in the coiled coil structure. The highly conserved residues form the lining of the hydrophobic cavity and the deep cavity is an ideal target for small molecular inhibitors. On the C-terminal of the C-domain there is a highly conserved segment GIVQQQ. They are intimately involved in forming the three interfaces between neighboring helices. The function of the N- and C-domains, such as binding to the potential cellular receptor and inducing protective activities, are also discussed. These studies on the mutation, structure and functions of the N- and C-domains suggested that both domains become a new focus to develop effective vaccine and antiviral drugs in the new strategies.
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Affiliation(s)
- X N Dong
- Laboratory of Immunology, Department of Biological Science and Technology, Research Centre for Medical Science, Tsinghua University, 100084, Beijing, People's Republic of China
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