Alternative Formation of Red-Shifted Channelrhodopsins: Noncovalent Incorporation with Retinal-Based Enamine-Type Schiff Bases and Mutated Channelopsin.

Red-shifted channelrhodopsins (ChRs) are attractive for optogenetic tools. We developed a new type of red-shifted ChRs that utilized noncovalent incorporation of retinal and 3,4-dehydroretinal-based enamine-type Schiff bases and mutated channelopsin, C1C2-K296G. These ChRs exhibited absorption maxima that were shifted 10-30 nm toward longer wavelengths than that of C1C2-ChR regenerated with all-trans-retinal.