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Publication Abstract from PubMed

Heliorhodopsins (HeRs) represent a distinct class of microbial rhodopsins (MRs) with an inverted membrane topology compared to other MRs. Previous structural studies have shown that HeRs lack a proton acceptor residue, and protons are never released from the protein. In this study, we present the cryo-electron microscopy (cryo-EM) structure of HeR bound to a nanobody. The structure reveals an acetate-like molecule in the Schiff base cavity (SBC) on the intracellular side of HeR under neutral condition. Structural comparisons and analyses suggest that the acetate molecule may function as a proton acceptor for the protonated retinal Schiff base (RSB) and act as a mediator for the intramolecular signaling transduction in HeR during light stimulation. These structural insights shed new light on the mechanism and function of HeR.

Cryo-EM structure of a nanobody-bound heliorhodopsin.,Xia R, Sun M, Lu Y, Wang N, Zhang A, Guo C, Xu Z, Cai X, He Y Biochem Biophys Res Commun. 2025 Mar 1;750:151398. doi: , 10.1016/j.bbrc.2025.151398. Epub 2025 Jan 25. PMID:39889627^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.