Crystal structure of a natural light-gated anion channelrhodopsin
- University of Texas Health Science Center at Houston, McGovern Medical School, United States
- Swiss Light Source, Paul Scherrer Institute, Switzerland
Abstract
The anion channelrhodopsin GtACR1 from the alga Guillardia theta is a potent neuron-inhibiting optogenetics tool. Presented here, its X-ray structure at 2.9 Å reveals a tunnel traversing the protein from its extracellular surface to a large cytoplasmic cavity. The tunnel is lined primarily by small polar and aliphatic residues essential for anion conductance. A disulfide-immobilized extracellular cap facilitates channel closing and the ion path is blocked mid-membrane by its photoactive retinylidene chromophore and further by a cytoplasmic side constriction. The structure also reveals a novel photoactive site configuration that maintains the retinylidene Schiff base protonated when the channel is open. These findings suggest a new channelrhodopsin mechanism, in which the Schiff base not only controls gating, but also serves as a direct mediator for anion flux.
Data availability
Diffraction data have been deposited in PDB under the accession code 6EDQ.
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Crystal Structure of the Light-Gated Anion Channelrhodopsin GtACR1Protein Data Bank, 6EDQ.
Article and author information
Author details
Funding
National Institutes of Health (R01GM027750)
- John L Spudich
National Institutes of Health (U01MH109146)
- John L Spudich
Welch Foundation (AU-0009)
- John L Spudich
American Heart Association (18TPA34230046)
- Lei Zheng
Hermann Eye Fund
- John L Spudich
Marie-Skłodowska-Curie (701647)
- Chia-Ying Huang
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Li 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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Crystal structure of a natural light-gated anion channelrhodopsin
eLife 8:e41741.
https://doi.org/10.7554/eLife.41741
Further reading
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