Structural insights into the mechanism and dynamics of proteorhodopsin biogenesis and retinal scavenging.

Autor: Hirschi S; Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland. stephan.hirschi@bioch.ox.ac.uk.; Department of Biochemistry, University of Oxford, OX1 3QU, Oxford, UK. stephan.hirschi@bioch.ox.ac.uk., Lemmin T; Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland. thomas.lemmin@unibe.ch., Ayoub N; Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland., Kalbermatter D; Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland., Pellegata D; Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland., Ucurum Z; Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland., Gertsch J; Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland., Fotiadis D; Institute of Biochemistry and Molecular Medicine, University of Bern, 3012, Bern, Switzerland. dimitrios.fotiadis@unibe.ch.
Jazyk: angličtina
Zdroj: Nature communications [Nat Commun] 2024 Aug 13; Vol. 15 (1), pp. 6950. Date of Electronic Publication: 2024 Aug 13.
DOI: 10.1038/s41467-024-50960-3
Abstrakt: Microbial ion-pumping rhodopsins (MRs) are extensively studied retinal-binding membrane proteins. However, their biogenesis, including oligomerisation and retinal incorporation, remains poorly understood. The bacterial green-light absorbing proton pump proteorhodopsin (GPR) has emerged as a model protein for MRs and is used here to address these open questions using cryo-electron microscopy (cryo-EM) and molecular dynamics (MD) simulations. Specifically, conflicting studies regarding GPR stoichiometry reported pentamer and hexamer mixtures without providing possible assembly mechanisms. We report the pentameric and hexameric cryo-EM structures of a GPR mutant, uncovering the role of the unprocessed N-terminal signal peptide in the assembly of hexameric GPR. Furthermore, certain proteorhodopsin-expressing bacteria lack retinal biosynthesis pathways, suggesting that they scavenge the cofactor from their environment. We shed light on this hypothesis by solving the cryo-EM structure of retinal-free proteoopsin, which together with mass spectrometry and MD simulations suggests that decanoate serves as a temporary placeholder for retinal in the chromophore binding pocket. Further MD simulations elucidate possible pathways for the exchange of decanoate and retinal, offering a mechanism for retinal scavenging. Collectively, our findings provide insights into the biogenesis of MRs, including their oligomeric assembly, variations in protomer stoichiometry and retinal incorporation through a potential cofactor scavenging mechanism.
(© 2024. The Author(s).)
Databáze: MEDLINE
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