1. Structural Biology and Molecular Biophysics

Sequential conformational rearrangements in flavivirus membrane fusion

  1. Luke H Chao
  2. Daryl E Klein
  3. Aaron G Schmidt
  4. Jennifer M Peña
  5. Stephen C Harrison  Is a corresponding author
  1. Harvard Medical School, United States
https://doi.org/10.7554/eLife.04389
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  1. Luke H Chao
  2. Daryl E Klein
  3. Aaron G Schmidt
  4. Jennifer M Peña
  5. Stephen C Harrison
(2014)
Sequential conformational rearrangements in flavivirus membrane fusion
eLife 3:e04389.
https://doi.org/10.7554/eLife.04389
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Abstract

The West Nile Virus (WNV) envelope protein, E, promotes membrane fusion during viral cell entry by undergoing a low-pH triggered conformational reorganization. We have examined the mechanism of WNV fusion and sought evidence for potential intermediates during the conformational transition by following hemifusion of WNV virus-like particles (VLPs) in a single particle format. We have introduced specific mutations into E, to relate their influence on fusion kinetics to structural features of the protein. At the level of individual E subunits, trimer formation and membrane engagement of the threefold clustered fusion loops are rate-limiting. Hemifusion requires at least two adjacent trimers. Simulation of the kinetics indicates that availability of competent monomers within the contact zone between virus and target membrane makes trimerization a bottleneck in hemifusion. We discuss the implications of the model we have derived for mechanisms of membrane fusion in other contexts.

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Author details

  1. Luke H Chao

    Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States
    Competing interests
    No competing interests declared.

  2. Daryl E Klein

    Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States
    Competing interests
    No competing interests declared.

  3. Aaron G Schmidt

    Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States
    Competing interests
    No competing interests declared.

  4. Jennifer M Peña

    Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States
    Competing interests
    No competing interests declared.

  5. Stephen C Harrison

    Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, United States
    For correspondence
    harrison@crystal.harvard.edu
    Competing interests
    Stephen C Harrison, Reviewing editor, eLife.

Copyright

© 2014, Chao et al.

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.

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  1. Luke H Chao
  2. Daryl E Klein
  3. Aaron G Schmidt
  4. Jennifer M Peña
  5. Stephen C Harrison
(2014)
Sequential conformational rearrangements in flavivirus membrane fusion
eLife 3:e04389.
https://doi.org/10.7554/eLife.04389

Share this article

https://doi.org/10.7554/eLife.04389

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Further reading

    1. Structural Biology and Molecular Biophysics

    How small-molecule inhibitors of dengue-virus infection interfere with viral membrane fusion

    Luke H Chao, Jaebong Jang ... Stephen C Harrison
    Research Advance Updated

    Dengue virus (DV) is a compact, icosahedrally symmetric, enveloped particle, covered by 90 dimers of envelope protein (E), which mediates viral attachment and membrane fusion. Fusion requires a dimer-to-trimer transition and membrane engagement of hydrophobic ‘fusion loops’. We previously characterized the steps in membrane fusion for the related West Nile virus (WNV), using recombinant, WNV virus-like particles (VLPs) for single-particle experiments (Chao et al., 2014). Trimerization and membrane engagement are rate-limiting; fusion requires at least two adjacent trimers; availability of competent monomers within the contact zone between virus and target membrane creates a trimerization bottleneck. We now report an extension of that work to dengue VLPs, from all four serotypes, finding an essentially similar mechanism. Small-molecule inhibitors of dengue virus infection that target E block its fusion-inducing conformational change. We show that ~12–14 bound molecules per particle (~20–25% occupancy) completely prevent fusion, consistent with the proposed mechanism.

    1. Structural Biology and Molecular Biophysics

    The Arthropoda-specific Tramtrack group BTB protein domains use previously unknown interface to form hexamers

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    BTB (bric-a-brack, Tramtrack, and broad complex) is a diverse group of protein-protein interaction domains found within metazoan proteins. Transcription factors contain a dimerizing BTB subtype with a characteristic N-terminal extension. The Tramtrack group (TTK) is a distinct type of BTB domain, which can multimerize. Single-particle cryo-EM microscopy revealed that the TTK-type BTB domains assemble into a hexameric structure consisting of three canonical BTB dimers connected through a previously uncharacterized interface. We demonstrated that the TTK-type BTB domains are found only in Arthropods and have undergone lineage-specific expansion in modern insects. The Drosophila genome encodes 24 transcription factors with TTK-type BTB domains, whereas only four have non-TTK-type BTB domains. Yeast two-hybrid analysis revealed that the TTK-type BTB domains have an unusually broad potential for heteromeric associations presumably through a dimer-dimer interaction interface. Thus, the TTK-type BTB domains are a structurally and functionally distinct group of protein domains specific to Arthropodan transcription factors.