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Biocatalysis and Bioprocess Engineering | Bioprocess Engineering and Supporting Technologies
Omega Rhodopsins: A Versatile Class of Microbial Rhodopsins
1Division of Life Science, Gyeongsang National University, 501 Jinju-daero, Jinju, Gyeongsangnam-do 52828, Republic of Korea
2Electron Microscopy Research Center, Republic of Korea
3Department of Systems Biology, Division of Life Sciences, and Institute for Life Science and Biotechnology, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea
Received: December 5, 2019; Accepted: March 27, 2020
J. Microbiol. Biotechnol. 2020; 30(5): 633-641
Published May 28, 2020 https://doi.org/10.4014/jmb.1912.12010
Copyright © The Korean Society for Microbiology and Biotechnology.
Abstract
Microbial rhodopsins are a superfamily of photoactive membrane proteins with the covalently bound retinal cofactor. Isomerization of the retinal chromophore upon absorption of a photon triggers conformational changes of the protein to function as ion pumps or sensors. After the discovery of proteorhodopsin in an uncultivated γ-proteobacterium, light-activated proton pumps have been widely detected among marine bacteria and, together with chlorophyll-based photosynthesis, are considered as an important axis responsible for primary production in the biosphere. Rhodopsins and related proteins show a high level of phylogenetic diversity; we focus on a specific class of bacterial rhodopsins containing the ‘3 omega motif.’ This motif forms a stack of three non-consecutive aromatic amino acids that correlates with the B–C loop orientation and is shared among the phylogenetically close ion pumps such as the NDQ motif-containing sodiumpumping rhodopsin, the NTQ motif-containing chloride-pumping rhodopsin, and some protonpumping rhodopsins including xanthorhodopsin. Here, we reviewed the recent research progress on these ‘omega rhodopsins,’ and speculated on their evolutionary origin of functional diversity.
Keywords
3 omega motif, actinorhodopsin (ActR), chloride pump rhodopsin (ClR), microbial rhodopsin, sodium pump rhodopsin (NaR), xanthorhodopsin (XR)
Graphical Abstract

References
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