Structual study of photo-activated meta state of squid rhodopsin

2019 Fiscal Year Final Research Report

• Project/Area Number: 16K07317
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Research Field: Biophysics
• Research Institution: Nagoya University
• Principal Investigator: Murakami Midori 名古屋大学, 理学研究科, 講師 (20324387)
• Project Period (FY): 2016-04-01 – 2020-03-31
• Keywords: 光生物 / ロドプシン / X線結晶構造解析

Outline of Final Research Achievements

The helix architecture of squid photo-activated metarhodopsin(Meta) is similar to that of the dark adapted form. The retinal chromophore is in an all-trans configuration with nearly same axial length to that of bovine Meta. The beta-ionone ring rotates ~ 60 degree to direct nearly parallel to the polyene chain plane. This rotation pushes surrounding aromatic rings of nearby residues to enlarge the binding pocket. These structural changes within the active site weaken the interhelical interactions at the cytoplasmic side. The salt bridge of the DRY motif between helices 3 and 6 is unlocked, resulting in being in partially open form in squid Meta.
The protonated Schiff base of retinal hydrogen bonds to the OH group of Tyr111 in helix 3, and Asn87 and Asn185 are located within 4A from the Schiff base. The counterion Glu180 is kept ~5A from the Schiff base by hydrogen bonds with Ser187, Tyr190, Tyr277 and Asn185. These residues form a hydrogen bonding network within the active site.

Free Research Field

光生物

Academic Significance and Societal Importance of the Research Achievements

光活性型が閉じたヘリックス構造をもつことが明らかとなり、βイオノン環の動きを制御することが循環型の光活性化に必要であることが示唆された。近年発展している光遺伝学のツールとしては、循環型の光活性をもつ微生物型のロドプシンが利用されているが、この結果を生かしてヒトなど高等動物に適したツールとして高等生物のロドプシンを適用することが可能となると考えられる。