2025-09-05 東京大学,理化学研究所,海洋研究開発機構,東北大学,海洋研究開発機構 変動海洋エコシステム高等研究所
図1:ロドプシン-集光アンテナ複合体の立体構造
左からXR-サリニキサンチン複合体(好塩細菌由来)、Kin4B8-ゼアキサンチン複合体(淡水性細菌由来)、NM-R1-ゼアキサンチン複合体、NM-R1-ミクソール複合体、NM-R3-ミクソール複合体を示す。それぞれのカロテノイド分子を赤色または橙色で示している。NM-R1、NM-R3の立体構造はクライオ電子顕微鏡を用いた単粒子構造解析(注4)により決定した。
<関連情報>
- https://www.aori.u-tokyo.ac.jp/research/news/2025/20250904.html
- https://www.nature.com/articles/s41564-025-02109-1
カロテノイドはロドプシンに結合し、海洋バクテロイダータ門における光周期促進色素として機能する Carotenoids bind rhodopsins and act as photocycle-accelerating pigments in marine Bacteroidota
Takayoshi Fujiwara,Toshiaki Hosaka,Masumi Hasegawa-Takano,Yosuke Nishimura,Kento Tominaga,Kaho Mori,Satoshi Nishino,Yuno Takahashi,Tomomi Uchikubo-Kamo,Kazuharu Hanada,Takashi Maoka,Shinichi Takaichi,Keiichi Inoue,Mikako Shirouzu & Susumu Yoshizawa
Nature Microbiology Published:04 September 2025
DOI:https://doi.org/10.1038/s41564-025-02109-1
Abstract
Microbial rhodopsins are photoreceptor proteins widely distributed in marine microorganisms that harness light energy and support marine ecosystems. While retinal is typically the sole chromophore in microbial rhodopsins, some proteorhodopsins, which are proton-pumping rhodopsins abundant in the ocean, use carotenoid antennae to transfer light energy to retinal. However, the mechanism by which carotenoids enhance rhodopsin functions remains unclear. Here, using the marine Bacteroidota isolate Nonlabens marinus S1-08T, we reconstituted complexes of rhodopsins with the carotenoid myxol and detected energy transfer to retinal in both proteorhodopsin and chloride ion-pumping rhodopsin. Carotenoid binding facilitated light harvesting and accelerated the photocycle, thereby improving the light utilization efficiency of proteorhodopsin. Cryogenic electron microscopy structural analysis further revealed the molecular architecture of the carotenoid–rhodopsin complexes. The ability to bind carotenoids is conserved in rhodopsins of the marine-dominant phylum Bacteroidota, which are widely transcribed in the photic zone. These findings reveal how carotenoids enhance rhodopsin functions in marine Bacteroidota.
