National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
GM128263
United States
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
GM123496
United States
Citation
Journal: bioRxiv / Year: 2021 Title: Cryo-EM structure of the SARS-CoV-2 3a ion channel in lipid nanodiscs. Authors: David M Kern / Ben Sorum / Sonali S Mali / Christopher M Hoel / Savitha Sridharan / Jonathan P Remis / Daniel B Toso / Abhay Kotecha / Diana M Bautista / Stephen G Brohawn / Abstract: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes the coronavirus disease 2019 (COVID-19). SARS-CoV-2 encodes three putative ion channels: E, 8a, and 3a. 3a is ...Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus that causes the coronavirus disease 2019 (COVID-19). SARS-CoV-2 encodes three putative ion channels: E, 8a, and 3a. 3a is expressed in SARS patient tissue and anti-3a antibodies are observed in patient plasma. 3a has been implicated in viral release, inhibition of autophagy, inflammasome activation, and cell death and its deletion reduces viral titer and morbidity in mice, raising the possibility that 3a could be an effective vaccine or therapeutic target. Here, we present the first cryo-EM structures of SARS-CoV-2 3a to 2.1 Å resolution and demonstrate 3a forms an ion channel in reconstituted liposomes. The structures in lipid nanodiscs reveal 3a dimers and tetramers adopt a novel fold with a large polar cavity that spans halfway across the membrane and is accessible to the cytosol and the surrounding bilayer through separate water- and lipid-filled openings. Electrophysiology and fluorescent ion imaging experiments show 3a forms Ca-permeable non-selective cation channels. We identify point mutations that alter ion permeability and discover polycationic inhibitors of 3a channel activity. We find 3a-like proteins in multiple and lineages that infect bats and humans. These data show 3a forms a functional ion channel that may promote COVID-19 pathogenesis and suggest targeting 3a could broadly treat coronavirus diseases.
History
Deposition
Jun 11, 2020
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Header (metadata) release
Jun 17, 2020
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Map release
Jun 17, 2020
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Update
Aug 31, 2022
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Current status
Aug 31, 2022
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
EMPIAR-10441 (Title: Tetrameric SARS-CoV-2 ORF3a in a lipid nanodisc / Data size: 4.8 TB Data #1: Unaligned multi-frame movies of Tetrameric SARS-CoV-2 ORF3a in a lipid nanodisc [micrographs - multiframe])
Model: Quantifoil / Material: GOLD / Mesh: 300 / Support film - Material: CARBON / Support film - topology: HOLEY / Support film - Film thickness: 120.0 nm / Pretreatment - Type: GLOW DISCHARGE
Vitrification
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 277 K / Instrument: FEI VITROBOT MARK IV Details: 1 blot force, 5 second wait time, 3 second blot time.
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Electron microscopy
Microscope
FEI TALOS ARCTICA
Image recording
Film or detector model: GATAN K3 (6k x 4k) / Digitization - Dimensions - Width: 11520 pixel / Digitization - Dimensions - Height: 8184 pixel / Number grids imaged: 1 / Number real images: 7092 / Average exposure time: 5.65 sec. / Average electron dose: 49.95 e/Å2 / Details: 50 frames per image, 113 ms per frame
Electron beam
Acceleration voltage: 200 kV / Electron source: FIELD EMISSION GUN
Electron optics
C2 aperture diameter: 50.0 µm / Illumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD / Cs: 2.7 mm
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