Journal Article Opn5L1 is a retinal receptor that behaves as a reverse and self-regenerating photoreceptor

Sato, Keita  ,  Yamashita, Takahiro  ,  Ohuchi, Hideyo  ,  Takeuchi, Atsuko  ,  Gotoh, Hitoshi  ,  Ono, Katsuhiko  ,  Mizuno, Misao  ,  Mizutani, Yasuhisa  ,  Tomonari, Sayuri  ,  Sakai, Kazumi  ,  Imamoto, Yasushi  ,  Wada, Akimori  ,  Shichida, Yoshinori

92018-03-28 , Springer Nature
光を受けるとオフになる動物のユニークな光センサーを発見 --ニワトリの脳内で機能するOpn5L1の性質を解明--. 京都大学プレスリリース. 2018-04-02.
Most opsins are G protein-coupled receptors that utilize retinal both as a ligand and as a chromophore. Opsins’ main established mechanism is light-triggered activation through retinal 11-cis-to-all-trans photoisomerization. Here we report a vertebrate non-visual opsin that functions as a Gi-coupled retinal receptor that is deactivated by light and can thermally self-regenerate. This opsin, Opn5L1, binds exclusively to all-trans-retinal. More interestingly, the light-induced deactivation through retinal trans-to-cis isomerization is followed by formation of a covalent adduct between retinal and a nearby cysteine, which breaks the retinal-conjugated double bond system, probably at the C11 position, resulting in thermal re-isomerization to all-trans-retinal. Thus, Opn5L1 acts as a reverse photoreceptor. We conclude that, like vertebrate rhodopsin, Opn5L1 is a unidirectional optical switch optimized from an ancestral bidirectional optical switch, such as invertebrate rhodopsin, to increase the S/N ratio of the signal transduction, although the direction of optimization is opposite to that of vertebrate rhodopsin.

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