1. Biochemistry and Chemical Biology
  2. Structural Biology and Molecular Biophysics
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Cryo-EM structure of the calcium release-activated calcium channel Orai in an open conformation

  1. Xiaowei Hou
  2. Ian R Outhwaite
  3. Leanne Pedi
  4. Stephen Barstow Long  Is a corresponding author
  1. Memorial Sloan Kettering Cancer Center, United States
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Cite this article as: eLife 2020;9:e62772 doi: 10.7554/eLife.62772

Abstract

The calcium release-activated calcium channel Orai regulates Ca2+ entry into non-excitable cells and is required for proper immune function. While the channel typically opens following Ca2+ release from the endoplasmic reticulum, certain pathologic mutations render the channel constitutively open. Previously, using one such mutation (H206A), we obtained low (6.7 Å) resolution X-ray structural information on Drosophila melanogaster Orai in an open conformation (Hou, Burstein, & Long, 2018). Here, we present a structure of this open conformation at 3.3 Å resolution using fiducial-assisted cryo-EM. The improved structure reveals the conformations of amino acids in the open pore, which dilates by outward movements of subunits. A ring of phenylalanine residues repositions to expose previously shielded glycine residues to the pore without significant rotational movement of the associated helices. Together with other hydrophobic amino acids, the phenylalanines act as the channel's gate. Structured M1-M2 turrets, not evident previously, form the channel's extracellular entrance.

Data availability

The cryo-EM map and the atomic model have been deposited in the Electron Microscopy Data Bank (EMDB) and in the Protein Data Bank (PDB) with accession numbers EMD-23002 and 7KR5, respectively.

Article and author information

Author details

  1. Xiaowei Hou

    Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  2. Ian R Outhwaite

    Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0003-2037-3261
  3. Leanne Pedi

    Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
    Competing interests
    The authors declare that no competing interests exist.
  4. Stephen Barstow Long

    Structural Biology Program, Memorial Sloan Kettering Cancer Center, New York, United States
    For correspondence
    longs@mskcc.org
    Competing interests
    The authors declare that no competing interests exist.
    ORCID icon "This ORCID iD identifies the author of this article:" 0000-0002-8144-1398

Funding

National Institute of General Medical Sciences (R01GM094273)

  • Stephen Barstow Long

National Institute of General Medical Sciences (R35GM131921)

  • Stephen Barstow Long

National Cancer Institute (P30CA008748)

  • Stephen Barstow Long

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Reviewing Editor

  1. Randy B Stockbridge, University of Michigan, United States

Publication history

  1. Received: September 4, 2020
  2. Accepted: November 26, 2020
  3. Accepted Manuscript published: November 30, 2020 (version 1)
  4. Version of Record published: December 8, 2020 (version 2)

Copyright

© 2020, Hou 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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