National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
5T32DK007680
United States
National Institutes of Health/National Institute of Neurological Disorders and Stroke (NIH/NINDS)
5F31NS096782
United States
National Institutes of Health/National Institute of Neurological Disorders and Stroke (NIH/NINDS)
5R01NS038631
United States
Citation
Journal: Nature / Year: 2018 Title: Gating mechanisms of acid-sensing ion channels. Authors: Nate Yoder / Craig Yoshioka / Eric Gouaux / Abstract: Acid-sensing ion channels (ASICs) are trimeric, proton-gated and sodium-selective members of the epithelial sodium channel/degenerin (ENaC/DEG) superfamily of ion channels and are expressed ...Acid-sensing ion channels (ASICs) are trimeric, proton-gated and sodium-selective members of the epithelial sodium channel/degenerin (ENaC/DEG) superfamily of ion channels and are expressed throughout vertebrate central and peripheral nervous systems. Gating of ASICs occurs on a millisecond time scale and the mechanism involves three conformational states: high pH resting, low pH open and low pH desensitized. Existing X-ray structures of ASIC1a describe the conformations of the open and desensitized states, but the structure of the high pH resting state and detailed mechanisms of the activation and desensitization of the channel have remained elusive. Here we present structures of the high pH resting state of homotrimeric chicken (Gallus gallus) ASIC1a, determined by X-ray crystallography and single particle cryo-electron microscopy, and present a comprehensive molecular mechanism for proton-dependent gating in ASICs. In the resting state, the position of the thumb domain is further from the three-fold molecular axis, thereby expanding the 'acidic pocket' in comparison to the open and desensitized states. Activation therefore involves 'closure' of the thumb into the acidic pocket, expansion of the lower palm domain and an iris-like opening of the channel gate. Furthermore, we demonstrate how the β11-β12 linkers that demarcate the upper and lower palm domains serve as a molecular 'clutch', and undergo a simple rearrangement to permit rapid desensitization.
History
Deposition
Sep 2, 2017
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Header (metadata) release
Dec 20, 2017
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Map release
Mar 21, 2018
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Update
Jul 29, 2020
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Current status
Jul 29, 2020
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Cryogen name: ETHANE / Chamber humidity: 100 % / Chamber temperature: 291.15 K / Instrument: FEI VITROBOT MARK IV
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Electron microscopy
Microscope
FEI TITAN KRIOS
Image recording
Film or detector model: GATAN K2 SUMMIT (4k x 4k) / Detector mode: SUPER-RESOLUTION / Number grids imaged: 1 / Average exposure time: 10.0 sec. / Average electron dose: 45.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron optics
Illumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
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Image processing
CTF correction
Software - Name: Gctf
Final reconstruction
Number classes used: 1 / Applied symmetry - Point group: C3 (3 fold cyclic) / Resolution.type: BY AUTHOR / Resolution: 3.7 Å / Resolution method: FSC 0.143 CUT-OFF / Software - Name: cisTEM / Number images used: 26117
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