Structural Basis for Near Infrared Absorption and Noncanonical Photoisomerization in Neorhodopsin
- 1Humboldt University of Berlin
Abstract
In retinal proteins, light absorption leads to a double bond isomerization of the chromophore, followed by conformational relaxations that drive functional protein rearrangements. The balance between photoisomerization and radiative or non-radiative decays of the excited state is adjusted to the demands of the respective photoreceptor function. The molecular determinants controlling the excited state processes remain poorly understood and are the focus of this combined crystallographic, spectroscopic, and theoretical work on the recently discovered neorhodopsin (NeoR). NeoR exhibits a highly red-shifted and fluorescent dark state and selectively photoisomerizes from all-trans to 7-cis. We show that the local electrostatic environment reduces the negative charge density near the Schiff base and suppresses torsional motion around the canonical C13=C14 isomerization site of microbial rhodopsins. Instead, the chromophore-binding pocket permits only low-efficiency C7=C8 isomerization, accompanied by polyene inversion, {beta}-ionone ring displacement, and Schiff base deprotonation. Consequently, unlike other retinal photoreceptors, NeoR undergoes structural changes localized near the {beta}-ionone ring.
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BibTeX
@misc{kovalev2026structural,
title = {{Structural Basis for Near Infrared Absorption and Noncanonical Photoisomerization in Neorhodopsin}},
author = {K. Kovalev and B. Boehlke and P. Nag and M. Grosse and A. Kraskov and S. Katz and P. Hildebrandt and F. Bartl and I. Schapiro and P. Hegemann and M. Broser},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.08.757671},
url = {https://www.biorxiv.org/content/10.64898/2026.10.08.757671v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Structural Basis for Near Infrared Absorption and Noncanonical Photoisomerization in Neorhodopsin
AU - K. Kovalev
AU - B. Boehlke
AU - P. Nag
AU - M. Grosse
AU - A. Kraskov
AU - S. Katz
AU - P. Hildebrandt
AU - F. Bartl
AU - I. Schapiro
AU - P. Hegemann
AU - M. Broser
PY - 2026
DA - 2026/10/08
PB - bioRxiv
DO - 10.64898/2026.10.08.757671
UR - https://www.biorxiv.org/content/10.64898/2026.10.08.757671v1
AB - In retinal proteins, light absorption leads to a double bond isomerization of the chromophore, followed by conformational relaxations that drive functional protein rearrangements. The balance between photoisomerization and radiative or non-radiative decays of the excited state is adjusted to the demands of the respective photoreceptor function. The molecular determinants controlling the excited state processes remain poorly understood and are the focus of this combined crystallographic, spectroscopic, and theoretical work on the recently discovered neorhodopsin (NeoR). NeoR exhibits a highly red-shifted and fluorescent dark state and selectively photoisomerizes from all-trans to 7-cis. We show that the local electrostatic environment reduces the negative charge density near the Schiff base and suppresses torsional motion around the canonical C13=C14 isomerization site of microbial rhodopsins. Instead, the chromophore-binding pocket permits only low-efficiency C7=C8 isomerization, accompanied by polyene inversion, {beta}-ionone ring displacement, and Schiff base deprotonation. Consequently, unlike other retinal photoreceptors, NeoR undergoes structural changes localized near the {beta}-ionone ring.
ER -