Molecular mechanisms of gating in the calcium-activated chloride channel bestrophin
- Memorial Sloan Kettering Cancer Center, United States
Abstract
Bestrophin (BEST1-4) ligand-gated chloride (Cl-) channels are activated by calcium (Ca2+). Mutation of BEST1 causes retinal disease. Partly because bestrophin channels have no sequence or structural similarity to other ion channels, the molecular mechanisms underlying gating are unknown. Here, we present a series of cryo-electron microscopy structures of chicken BEST1, determined at 3.1 Å resolution or better, that represent the channel's principal gating states. Unlike other channels, opening of the pore is due to the repositioning of tethered pore-lining helices within a surrounding protein shell that dramatically widens a neck of the pore through a concertina of amino acid rearrangements. The neck serves as both the activation and the inactivation gate. Ca2+ binding instigates opening of the neck through allosteric means whereas inactivation peptide binding induces closing. An aperture within the otherwise wide pore controls anion permeability. The studies define a new molecular paradigm for gating among ligand-gated ion channels.
Data availability
Atomic coordinates and cryo-EM density maps of have been deposited with the PDB and Electron Microscopy Data Bank with the accession numbers: 6N23 (BEST1405, inactivated; EMD-9321), 6N24 (BEST1345 W287F mutant, Ca2+-free; EMD-9322), 6N25 (BEST1345 W287F mutant, Ca2+-bound; EMD-9323), 6N26 ( BEST1345 Ca2+-free closed state; EMD-9324), 6N27 (BEST1345 Ca2+-bound closed state; EMD-9325), and 6N28 ( BEST1345 Ca2+-bound open state; EMD-9326).
-
BEST1 in a calcium-bound inactivated stateProtein Databank, 6N23.
-
BEST1 open state W287F mutant, calcium-freeProtein Databank, 6N24.
-
BEST1 open state W287F mutant, calcium-boundProtein Databank, 6N25.
-
BEST1 calcium-free closed state (deactivated)Protein Databank, 6N26.
-
BEST1 in a calcium-bound inactivated stateElectron Microscopy Data Bank, EMD-9321.
-
BEST1 open state W287F mutant, calcium-freeElectron Microscopy Data Bank, EMD-9322.
-
BEST1 open state W287F mutant, calcium-boundElectron Microscopy Data Bank, EMD-9323.
-
BEST1 calcium-free closed state (deactivated)Electron Microscopy Data Bank, EMD-9324.
-
BEST1 calcium-bound closed stateElectron Microscopy Data Bank, EMD-9325.
-
BEST1 calcium-bound open stateElectron Microscopy Data Bank, EMD-9326.
Article and author information
Author details
Stephen Barstow Long
Funding
National Institutes of Health (R01-GM110396)
- Stephen Barstow Long
National Cancer Institute (P30 CA008748)
- Stephen Barstow Long
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Miller 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.
Metrics
-
- 5,226
- views
-
- 738
- downloads
-
- 45
- citations
Views, downloads and citations are aggregated across all versions of this paper published by eLife.
Download links
A two-part list of links to download the article, or parts of the article, in various formats.
Downloads (link to download the article as PDF)
Open citations (links to open the citations from this article in various online reference manager services)
Cite this article (links to download the citations from this article in formats compatible with various reference manager tools)
Molecular mechanisms of gating in the calcium-activated chloride channel bestrophin
eLife 8:e43231.
https://doi.org/10.7554/eLife.43231
