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bioRxiv · 10.1101/405308

Crystal Structure of a Natural Light-Gated Anion Channelrhodopsin

Li, H.·Huang, C.-Y.·Govorunova, E.·Schafer, C.·Sineshchekov, O.·Wang, M.·Zheng, L.·Spudich, J.
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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 [A] 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.

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Li, H., Huang, C.-Y., Govorunova, E., Schafer, C., Sineshchekov, O., Wang, M., Zheng, L., Spudich, J.. 2018-08-31. Crystal Structure of a Natural Light-Gated Anion Channelrhodopsin. https://doi.org/10.1101/405308

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