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Updated: May 15, 2026

Proton Transfer and Protein Conformation Dynamics in Photosensitive Proteins by Time-resolved Step-scan Fourier-transform Infrared Spectroscopy
Published on: June 27, 2014
Proton-Coupled Gate Closing Mechanism in Guillardia theta Anion Channelrhodopsin 1
Miu Sudo1, Sayo Inoko2, Yuma Ito3
1Division of Soft Matter, Graduate School of Life Science, Hokkaido University, Sapporo 060-0810, Japan.
None:
Light-gated anion channelrhodopsins are widely used as optogenetic silencers, yet the molecular events underlying gate opening and closing remain unclear. Here we show that gate closure in Guillardia theta anion channelrhodopsin 1 (GtACR1) is tightly coupled to coordinated proton-transfer reactions. Time-resolved spectroscopic and electrochemical analyses reveal that formation of the M-intermediate, which governs gate closure, involves not only deprotonation of the retinal Schiff base but also proton release from Asp234 to the extracellular side. We further demonstrate that residues Tyr207 and Cys237 participate in a hydrogen-bond network that modulates retinal Schiff base deprotonation, with Cys237 undergoing deprotonation during M-intermediate formation. In addition, analyses of the dark state provide new experimental evidence regarding the protonation states of functionally important residues in GtACR1, while characterization of the L-intermediate reveals hydrogen-bond rearrangements associated with channel activation. Together, these findings support a mechanistic model in which proton transfer reactions involving Asp234, Tyr207, and Cys237 coordinate retinal Schiff base deprotonation, thereby driving gate closure in GtACR1.
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