Structural and funtinal analysis of non-cannonical rhodopsins

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K15728
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 43020:Structural biochemistry-related
• Research Institution: The University of Tokyo
• Principal Investigator: Shihoya Wataru 東京大学, 大学院理学系研究科(理学部), 助教 (30809421)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: ロドプシン / クライオ電子顕微鏡法

Outline of Final Research Achievements

Energy transfer from light-harvesting ketocarotenoids to the light-driven proton pump xanthorhodopsins has been previously demonstrated in two unique cases: an extreme halophilic bacterium1 and a terrestrial cyanobacterium. Attempts to find carotenoids that bind and transfer energy to abundant rhodopsin proton pumps from marine photoheterotrophs have thus far failed. Here we detected light energy transfer from the widespread hydroxylated carotenoids zeaxanthin and lutein to the retinal moiety of xanthorhodopsins and proteorhodopsins using functional metagenomics combined with chromophore extraction from the environment. The light-harvesting carotenoids transfer up to 42% of the harvested energy in the violet- or blue-light range to the green-light absorbing retinal chromophore. Our data suggest that these antennas may have a substantial effect on rhodopsin phototrophy in the world's lakes, seas and oceans. However, the functional implications of our findings are yet to be discovered.

Free Research Field

構造生物学

Academic Significance and Societal Importance of the Research Achievements

これらの色素は受容した光エネルギーをレチナール色素に移動させる集光アンテナとして働くこと、集光アンテナを持つロドプシンが水圏微生物に幅広く分布することを明らかにした。今回の発見により、水圏生態系においてロドプシンは集光アンテナを駆使し、従来の試算を上回る量の光エネルギーを受容することが示唆された。生態系を理解する上で、光エネルギーを受け取る生物の光受容効率を把握し、生態系に流れ込む光エネルギー量を正確に算出することは避けては通れない課題である。本研究の成果は、全球レベルでの水圏生態系の理解の深化につながると期待される。