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Issue 17, 2020
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Transient IR spectroscopy identifies key interactions and unravels new intermediates in the photocycle of a bacterial phytochrome

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Abstract

Phytochromes are photosensory proteins in plants, fungi, and bacteria, which detect red- and far-red light. They undergo a transition between the resting (Pr) and photoactivated (Pfr) states. In bacterial phytochromes, the Pr-to-Pfr transition is facilitated by two intermediate states, called Lumi-R and Meta-R. The molecular structures of the protein in these states are not known and the molecular mechanism of photoconversion is not understood. Here, we apply transient infrared absorption spectroscopy to study the photocycle of the wild-type and Y263F mutant of the phytochrome from Deinococcus radiodurans (DrBphP) from nano- to milliseconds. We identify two sequentially forming Lumi-R states which differ in the local structure surrounding the carbonyl group of the biliverdin D-ring. We also find that the tyrosine at position 263 alters local structure and dynamics around the D-ring and causes an increased rate of Pfr formation. The results shed new light on the mechanism of light-signalling in phytochrome proteins.

Graphical abstract: Transient IR spectroscopy identifies key interactions and unravels new intermediates in the photocycle of a bacterial phytochrome

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Article information


Submitted
27 Dec 2019
Accepted
03 Mar 2020
First published
03 Mar 2020

This article is Open Access

Phys. Chem. Chem. Phys., 2020,22, 9195-9203
Article type
Paper

Transient IR spectroscopy identifies key interactions and unravels new intermediates in the photocycle of a bacterial phytochrome

J. Kübel, M. Chenchiliyan, S. A. Ooi, E. Gustavsson, L. Isaksson, V. Kuznetsova, J. A. Ihalainen, S. Westenhoff and M. Maj, Phys. Chem. Chem. Phys., 2020, 22, 9195
DOI: 10.1039/C9CP06995J

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