On the (un)coupling of the chromophore, tongue interactions, and overall conformation in a bacterial phytochrome
| Autor: | Matthijs R. Panman, Stephan Niebling, Heli Lehtivuori, Sebastian Westenhoff, Andreas Menzel, Heikki Takala, Rahul Nanekar, Janne A. Ihalainen, Oskar Berntsson, Léocadie Henry, Ashley J. Hughes |
|---|---|
| Přispěvatelé: | Medicum, University of Helsinki, Department of Anatomy |
| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
0301 basic medicine
Models Molecular Crystallography X-Ray Biochemistry bakteerit Protein structure photoconversion chromophore-binding domain Transferase structural biology CRYSTAL-STRUCTURE Tyrosine DEINOCOCCUS-RADIODURANS biology Phytochrome Chemistry REARRANGEMENTS Protein Structure and Folding Deinococcus mutagenesis Binding domain Signal Transduction MODULE PLANT PHYTOCHROME Phenylalanine fotobiologia 03 medical and health sciences Bacterial Proteins protein conformation cell signaling protein structure BACTERIOPHYTOCHROME Molecular Biology X-ray crystallography soluviestintä phytochrome AGP1 BINDING DOMAIN Binding Sites ta114 030102 biochemistry & molecular biology ta1182 Deinococcus radiodurans Cell Biology Chromophore biology.organism_classification photoreceptor 030104 developmental biology Structural biology FTIR Biophysics proteiinit 3111 Biomedicine röntgenkristallografia |
| Zdroj: | Journal of Biological Chemistry |
| Popis: | Phytochromes are photoreceptors in plants, fungi, and various microorganisms and cycle between metastable red light-absorbing (Pr) and far-red light-absorbing (Pfr) states. Their light responses are thought to follow a conserved structural mechanism that is triggered by isomerization of the chromophore. Downstream structural changes involve refolding of the so-called tongue extension of the phytochrome-specific GAF-related (PHY) domain of the photoreceptor. The tongue is connected to the chromophore by conserved DIP and PRXSF motifs and a conserved tyrosine, but the role of these residues in signal transduction is not clear. Here, we examine the tongue interactions and their interplay with the chromophore by substituting the conserved tyrosine (Tyr(263)) in the phytochrome from the extremophile bacterium Deinococcus radiodurans with phenylalanine. Using optical and FTIR spectroscopy, X-ray solution scattering, and crystallography of chromophore-binding domain (CBD) and CBD-PHY fragments, we show that the absence of the Tyr(263) hydroxyl destabilizes the -sheet conformation of the tongue. This allowed the phytochrome to adopt an -helical tongue conformation regardless of the chromophore state, hence distorting the activity state of the protein. Our crystal structures further revealed that water interactions are missing in the Y263F mutant, correlating with a decrease of the photoconversion yield and underpinning the functional role of Tyr(263) in phytochrome conformational changes. We propose a model in which isomerization of the chromophore, refolding of the tongue, and globular conformational changes are represented as weakly coupled equilibria. The results also suggest that the phytochromes have several redundant signaling routes. |
| Databáze: | OpenAIRE |
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