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  • Picosecond quantum-classical dynamics reveals that the coexistence of light-induced microbial and animal chromophore rotary motion modulates the isomerization quantum yield of heliorhodopsin
Title: Picosecond quantum-classical dynamics reveals that the coexistence of light-induced microbial and animal chromophore rotary motion modulates the isomerization quantum yield of heliorhodopsin
Rhodopsins are light-responsive proteins forming two vast and evolutionary distinct superfamilies whose functions are invariably triggered by the photoisomerization of a single retinal chromophore. In 2018 a third widespread superfamily of rhodopsins called heliorhodopsins was discovered using functional metagenomics. Heliorhodopsins, with their markedly different structural features with respect to the animal and microbial superfamilies, offer an opportunity to study how evolution has manipulated the chromophore photoisomerization to achieve adaptation. One question is related to the mechanism of such a reaction and how it differs from that of animal and microbial rhodopsins. To address this question, we use hundreds of quantum-classical trajectories to simulate the spectroscopically documented picosecond light-induced dynamics of a heliorhodopsin from the archaea thermoplasmatales archaeon (TaHeR). We show that, consistently with the observations, the trajectories reveal two excited state decay channels. However, inconsistently with previous hypotheses, only one channel is associated with the –C13QC14– rotation of microbial rhodopsins while the second channel is characterized by the –C11QC12– rotation typical of animal rhodopsins. The fact that such –C11QC12– rotation is aborted upon decay and ground state relaxation, explains why illumination of TaHeR only produces the 13-cis isomer with a low quantum efficiency. We argue that the documented lack of regioselectivity in double-bond excited state twisting motion is the result of an ‘‘adaptation’’ that could be completely lost via specific residue substitutions modulating the steric hindrance experienced along the isomerization motion.  more » « less
Award ID(s):
2102619
PAR ID:
10555129
Author(s) / Creator(s):
; ; ; ;
Publisher / Repository:
The Royal Society of Chemistry
Date Published:
Journal Name:
Physical Chemistry Chemical Physics
Volume:
26
Issue:
13
ISSN:
1463-9076
Page Range / eLocation ID:
10343 to 10356
Subject(s) / Keyword(s):
Excited-state electronic structure rhodopsins complex solvent environment photoisomerization
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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