Origin of the low thermal isomerization rate of rhodopsin chromophore

Masataka Yanagawa, Keiichi Kojima, Takahiro Yamashita, Yasushi Imamoto, Take Matsuyama, Koji Nakanishi, Yumiko Yamano, Akimori Wada, Yasushi Sako, Yoshinori Shichida

Research output: Contribution to journalArticlepeer-review

36 Citations (Scopus)


Low dark noise is a prerequisite for rod cells, which mediate our dim-light vision. The low dark noise is achieved by the extremely stable character of the rod visual pigment, rhodopsin, which evolved from less stable cone visual pigments. We have developed a biochemical method to quickly evaluate the thermal activation rate of visual pigments. Using an isomerization locked chromophore, we confirmed that thermal isomerization of the chromophore is the sole cause of thermal activation. Interestingly, we revealed an unexpected correlation between the thermal stability of the dark state and that of the active intermediate MetaII. Furthermore, we assessed key residues in rhodopsin and cone visual pigments by mutation analysis and identified two critical residues (E122 and I189) in the retinal binding pocket which account for the extremely low thermal activation rate of rhodopsin.

Original languageEnglish
Article number11081
JournalScientific reports
Publication statusPublished - Jun 10 2015
Externally publishedYes

ASJC Scopus subject areas

  • General


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