Biochemical analysis of low thermal isomerization mechanism of rod visual pigment.

2015 Fiscal Year Final Research Report

• Project/Area Number: 26650119
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Animal physiology/Animal behavior
• Research Institution: Kyoto University
• Principal Investigator: Shichida Yoshinori 京都大学, 理学(系)研究科(研究院), 教授 (60127090)
• Project Period (FY): 2014-04-01 – 2016-03-31
• Keywords: 視物質 / 視細胞 / 暗ノイズ / 生化学的方法 / 分子進化

Outline of Final Research Achievements

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 isomerization rate of the chromophore in visual pigments. Using an isomerization locked chromophore, we confirmed that thermal isomerization rate of the chromophore in rhodopsin is about 1/1000 of that of cone visual pigment and identified two critical residues (E122 and I189) in the chromophore binding pocket which account for the extremely low thermal activation rate of rhodopsin. Furthermore, we found that anura blue-sensitive cone visual pigment expressed in green rods acquired the low thermal isomerization rate of the chromophore by the specific mutation during the molecular evolution, which led to optimization for scotopic vision.

Free Research Field

分子生理学