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Main Title: Light- and temperature-dependent dynamics of chromophore and protein structural changes in bathy phytochrome Agp2
Author(s): Merga, Galaan
Lopez, Maria Fernandez
Fischer, Paul
Piwowarski, Patrick
Nogacz, Żaneta
Kraskov, Anastasia
Buhrke, David
Escobar, Francisco Velazquez
Michael, Norbert
Siebert, Friedrich
Scheerer, Patrick
Bartl, Franz
Hildebrandt, Peter
Type: Article
Abstract: Bacterial phytochromes are sensoric photoreceptors that transform light absorbed by the photosensor core module (PCM) to protein structural changes that eventually lead to the activation of the enzymatic output module. The underlying photoinduced reaction cascade in the PCM starts with the isomerization of the tetrapyrrole chromophore, followed by conformational relaxations, proton transfer steps, and a secondary structure transition of a peptide segment (tongue) that is essential for communicating the signal to the output module. In this work, we employed various static and time-resolved IR and resonance Raman spectroscopic techniques to study the structural and reaction dynamics of the Meta-F intermediate of both the PCM and the full-length (PCM and output module) variant of the bathy phytochrome Agp2 from Agrobacterium fabrum. In both cases, this intermediate represents a branching point of the phototransformation, since it opens an unproductive reaction channel back to the initial state and a productive pathway to the final active state, including the functional protein structural changes. It is shown that the functional quantum yield, i.e. the events of tongue refolding per absorbed photons, is lower by a factor of ca. two than the quantum yield of the primary photochemical process. However, the kinetic data derived from the spectroscopic experiments imply an increased formation of the final active state upon increasing photon flux or elevated temperature under photostationary conditions. Accordingly, the branching mechanism does not only account for the phytochrome's function as a light intensity sensor but may also modulate its temperature sensitivity.
Subject(s): light
Issue Date: 10-Aug-2021
Date Available: 30-Dec-2021
Language Code: en
DDC Class: 540 Chemie und zugeordnete Wissenschaften
Sponsor/Funder: DFG, 221545957, SFB 1078: Protonation Dynamics in Protein Function
TU Berlin, Open-Access-Mittel – 2021
Journal Title: Physical Chemistry Chemical Physics
Publisher: Royal Society of Chemistry (RSC)
Volume: 23
Issue: 33
Publisher DOI: 10.1039/d1cp02494a
Page Start: 18197
Page End: 18205
EISSN: 1463-9084
ISSN: 1463-9076
TU Affiliation(s): Fak. 2 Mathematik und Naturwissenschaften » Inst. Chemie » FG Physikalische Chemie / Biophysikalische Chemie
Appears in Collections:Technische Universität Berlin » Publications

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