Abstract
Channelrhodopsins (ChRs) are a member of microbial rhodopsin and consist of the chromophore retinal
and a seven-transmembrane helix (TM7) protein (opsin) with a function of photoreceptor. Retinal forms
a protonated Schiff base with a conserved lysine residue located on TM7. Upon light stimulation, ChRs
function as cation channels accompanying with the conformational changes of retinal and opsin.
Optogenetics is a powerful new tool, which allows the control of neuronal activity by light. ChRs which
are now used in optogenetics are ChR1 and CHR2, and they are the most sensitive to green to blue light.
However, short-wavelength light such as blue-green light cannot deeply penetrate into the neural tissues due
to scattering or absorption of the light by the tissue. Therefore, the development of red-shifted ChRs, which
are sensitive to long-wavelength light such as yellow-red light, are eagerly desired.
To develop a novel red-shifted ChR, the research group including me prepared retinal derivatives which
have longer conjugated polyene systems than retinal as the chromophore and evaluated their interactions
with opsin proteins.
