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Structural elements regulating the photochromicity in a cyanobacteriochrome

The three-dimensional (3D) crystal structures of the GAF3 domain of cyanobacteriochrome Slr1393 (Synechocystis PCC6803) carrying a phycocyanobilin chromophore could be solved in both 15-Z dark-adapted state, Pr, λ(max) = 649 nm, and 15-E photoproduct, Pg, λ(max) = 536 nm (resolution, 1.6 and 1.86 Å,...

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Autores principales: Xu, Xiuling, Höppner, Astrid, Wiebeler, Christian, Zhao, Kai-Hong, Schapiro, Igor, Gärtner, Wolfgang
Formato: Online Artículo Texto
Lenguaje:English
Publicado: National Academy of Sciences 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7007540/
https://www.ncbi.nlm.nih.gov/pubmed/31964827
http://dx.doi.org/10.1073/pnas.1910208117
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author Xu, Xiuling
Höppner, Astrid
Wiebeler, Christian
Zhao, Kai-Hong
Schapiro, Igor
Gärtner, Wolfgang
author_facet Xu, Xiuling
Höppner, Astrid
Wiebeler, Christian
Zhao, Kai-Hong
Schapiro, Igor
Gärtner, Wolfgang
author_sort Xu, Xiuling
collection PubMed
description The three-dimensional (3D) crystal structures of the GAF3 domain of cyanobacteriochrome Slr1393 (Synechocystis PCC6803) carrying a phycocyanobilin chromophore could be solved in both 15-Z dark-adapted state, Pr, λ(max) = 649 nm, and 15-E photoproduct, Pg, λ(max) = 536 nm (resolution, 1.6 and 1.86 Å, respectively). The structural data allowed identifying the large spectral shift of the Pr-to-Pg conversion as resulting from an out-of-plane rotation of the chromophore’s peripheral rings and an outward movement of a short helix formed from a formerly unstructured loop. In addition, a third structure (2.1-Å resolution) starting from the photoproduct crystals allowed identification of elements that regulate the absorption maxima. In this peculiar form, generated during X-ray exposition, protein and chromophore conformation still resemble the photoproduct state, except for the D-ring already in 15-Z configuration and tilted out of plane akin the dark state. Due to its formation from the photoproduct, it might be considered an early conformational change initiating the parental state-recovering photocycle. The high quality and the distinct features of the three forms allowed for applying quantum-chemical calculations in the framework of multiscale modeling to rationalize the absorption maxima changes. A systematic analysis of the PCB chromophore in the presence and absence of the protein environment showed that the direct electrostatic effect is negligible on the spectral tuning. However, the protein forces the outer pyrrole rings of the chromophore to deviate from coplanarity, which is identified as the dominating factor for the color regulation.
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spelling pubmed-70075402020-02-18 Structural elements regulating the photochromicity in a cyanobacteriochrome Xu, Xiuling Höppner, Astrid Wiebeler, Christian Zhao, Kai-Hong Schapiro, Igor Gärtner, Wolfgang Proc Natl Acad Sci U S A PNAS Plus The three-dimensional (3D) crystal structures of the GAF3 domain of cyanobacteriochrome Slr1393 (Synechocystis PCC6803) carrying a phycocyanobilin chromophore could be solved in both 15-Z dark-adapted state, Pr, λ(max) = 649 nm, and 15-E photoproduct, Pg, λ(max) = 536 nm (resolution, 1.6 and 1.86 Å, respectively). The structural data allowed identifying the large spectral shift of the Pr-to-Pg conversion as resulting from an out-of-plane rotation of the chromophore’s peripheral rings and an outward movement of a short helix formed from a formerly unstructured loop. In addition, a third structure (2.1-Å resolution) starting from the photoproduct crystals allowed identification of elements that regulate the absorption maxima. In this peculiar form, generated during X-ray exposition, protein and chromophore conformation still resemble the photoproduct state, except for the D-ring already in 15-Z configuration and tilted out of plane akin the dark state. Due to its formation from the photoproduct, it might be considered an early conformational change initiating the parental state-recovering photocycle. The high quality and the distinct features of the three forms allowed for applying quantum-chemical calculations in the framework of multiscale modeling to rationalize the absorption maxima changes. A systematic analysis of the PCB chromophore in the presence and absence of the protein environment showed that the direct electrostatic effect is negligible on the spectral tuning. However, the protein forces the outer pyrrole rings of the chromophore to deviate from coplanarity, which is identified as the dominating factor for the color regulation. National Academy of Sciences 2020-02-04 2020-01-21 /pmc/articles/PMC7007540/ /pubmed/31964827 http://dx.doi.org/10.1073/pnas.1910208117 Text en Copyright © 2020 the Author(s). Published by PNAS. https://creativecommons.org/licenses/by-nc-nd/4.0/ https://creativecommons.org/licenses/by-nc-nd/4.0/This open access article is distributed under Creative Commons Attribution-NonCommercial-NoDerivatives License 4.0 (CC BY-NC-ND) (https://creativecommons.org/licenses/by-nc-nd/4.0/) .
spellingShingle PNAS Plus
Xu, Xiuling
Höppner, Astrid
Wiebeler, Christian
Zhao, Kai-Hong
Schapiro, Igor
Gärtner, Wolfgang
Structural elements regulating the photochromicity in a cyanobacteriochrome
title Structural elements regulating the photochromicity in a cyanobacteriochrome
title_full Structural elements regulating the photochromicity in a cyanobacteriochrome
title_fullStr Structural elements regulating the photochromicity in a cyanobacteriochrome
title_full_unstemmed Structural elements regulating the photochromicity in a cyanobacteriochrome
title_short Structural elements regulating the photochromicity in a cyanobacteriochrome
title_sort structural elements regulating the photochromicity in a cyanobacteriochrome
topic PNAS Plus
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7007540/
https://www.ncbi.nlm.nih.gov/pubmed/31964827
http://dx.doi.org/10.1073/pnas.1910208117
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