Phytochrome proteins control the growth, reproduction, and photosynthesis of plants, fungi, and bacteria. Light is detected by a bilin cofactor, but it remains elusive how this leads to activation of the protein through structural changes. We present serial femtosecond X-ray crystallographic data of the chromophore-binding domains of a bacterial phytochrome at delay times of 1 ps and 10 ps after photoexcitation. The data reveal a twist of the D-ring, which leads to partial detachment of the chromophore from the protein. Unexpectedly, the conserved so-called pyrrole water is photodissociated from the chromophore, concomitant with movement of the A-ring and a key signalling aspartate. The changes are wired together by ultrafast backbone and water movements around the chromophore, channeling them into signal transduction towards the output domains. We suggest that the observed collective changes are important for the phytochrome photoresponse, explaining the earliest steps of how plants, fungi and bacteria sense red light.
Crystallography data have been submitted to protein data bank (PDB)dark:ID: D_1292104678 and PDB ID: 6T3L1ps:ID: D_1292104679 and PDB ID: 6T3URaw diffraction images are in the process of being uploaded to CXIDB
PAS-GAF fragment from Deinococcus radiodurans phytochrome in dark stateProtein Data Bank, 6T3L.
PAS-GAF fragment from Deinococcus radiodurans phytochrome 1ps after photoexcitationProtein Data Bank, 6T3U.
- Sebastian Westenhoff
- Sebastian Westenhoff
- Sebastian Westenhoff
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
- Werner Kühlbrandt, Max Planck Institute of Biophysics, Germany
© 2020, Claesson et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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