High resolution X-ray crystallographic structural study of blue sensitive cone pigment

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K14662
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 43040:Biophysics-related
• Research Institution: Nagoya Institute of Technology
• Principal Investigator: Katayama Kota 名古屋工業大学, 工学(系)研究科(研究院), 助教 (00799182)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Keywords: 色覚視物質 / X線結晶構造解析 / 赤外分光解析 / 人工合成レチナール / 波長制御 / 水分子

Outline of Final Research Achievements

Humans have two kinds of vision: twilight vision mediated by rhodopsin (Rh) and color vision achieved by three cone pigments. A common chromophore, 11-cis-retinal, is used to distinguish different colors in vision. While X-ray structure of Rh was determined, structural studies of cone pigments lag far behind those of Rh.
Here, I attempted to determine the 3D structure of cone pigments. To develop light-stable cone pigments, I introduced analogue retinal that is restricted cis-trans isomerization. Successfully obtained blue pigment regenerated with analogue retinal exhibited high thermal stability. Furthermore, by using a novel crystallization procedure, blue pigment analogue resulted in an appropriate phase separation in the crystal drops, which gave the possibility for discovering the suitable condition to obtain crystals. I also found the unique photochromic property of blue pigment upon illumination by using spectroscopic studies, which indicated the specific photoreaction.

Free Research Field

生物物理

Academic Significance and Societal Importance of the Research Achievements

色認識は生物学者、物理学者から哲学者まで多くの研究者の関心を集める一方、色覚視物質の発現試料に対する構造生物学的解析は過去に全く行われていなかった。本研究では、構造解析のための結晶取得に向けた実験条件の確立に差し迫っており、今後の結晶化・構造決定が大いに期待できる。そして光耐性を有する青視物質アナログの構造基盤に立脚した色盲患者の治療に向けた新薬開発への研究発展が期待される。さらに、分光法による青視物質の中間体の同定およびBL中間体の赤外分光差スペクトル測定の成功は、吸収される青色光情報がどのようにしてシグナル伝達されるのか、青視物質における光情報伝達機構を理解するための構造情報を与えた。