Abstract
Aquatic bacterial rhodopsin proton pumps have been recently reported to utilize hydroxylated carotenoids1,2. Here, by combining a marine chromophore extract with purified archaeal rhodopsins identified in marine metagenomes, we report on light energy transfer from diverse hydroxylated carotenoids (lutein, diatoxanthin, and fucoxanthin) to heimdallarchaeial rhodopsins (HeimdallRs)3,4 from uncultured marine planktonic members of the “Ca. Kariarchaeaceae” (“Ca. Asgardarchaeota”)5. These light-harvesting antennas absorb in the blue-light range and transfer energy to the green-light absorbing retinal chromophore within HeimdallRs. Furthermore, antenna enhancement of proton pumping by HeimdallRs is also observed under white-light illumination along with a carotenoid-binding–induced structural change in the protein. Our results indicate that the use of light-harvesting antennas in microbial rhodopsins is observed not only in bacteria but also in marine archaea.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
↵* e-mail: wtrshh9{at}gmail.com; nureki{at}bs.s.u-tokyo.ac.jp; inoue{at}issp.u-tokyo.ac.jp; alephreish{at}gmail.com; arielitoc1{at}gmail.com; beja{at}technion.ac.il
Data availability
All data are available in the main text or the Supplementary Information. Results of the bioinformatic analyses are deposited in the Figshare repository https://doi.org/10.6084/m9.figshare.26906593. Atomic coordinates of the crystal structure of HeimdallR1 have been deposited in the Protein Data Bank under XXX.
