Volume 25, Issue 6, Pages 933-938.e3 (June 2017) Time-Resolved X-Ray Solution Scattering Reveals the Structural Photoactivation of a Light-Oxygen-Voltage Photoreceptor  Oskar Berntsson, Ralph P. Diensthuber, Matthijs R. Panman, Alexander Björling, Ashley J. Hughes, Léocadie Henry, Stephan Niebling, Gemma Newby, Marianne Liebi, Andreas Menzel, Robert Henning, Irina Kosheleva, Andreas Möglich, Sebastian Westenhoff  Structure  Volume 25, Issue 6, Pages 933-938.e3 (June 2017) DOI: 10.1016/j.str.2017.04.006 Copyright © 2017 Elsevier Ltd Terms and Conditions

Structure 2017 25, 933-938.e3DOI: (10.1016/j.str.2017.04.006) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 1 LOV Photochemistry and Photosensor Domain Topology (A) Canonical photocycle for a flavin chromophore within a LOV domain. (B–E) Topology of the photosensory domain of AsLOV (B, PDB: 2V0U), NcVVD (C, PDB: 2PD7), aureochrome 1a (D, PDB: 5DKK), and BsYtvA (E, as seen in the YF1 crystal structure, PDB: 4GCZ) showing the positioning of A′α helix (yellow), LOV domain (blue), Jα linker (green), and effector domain. A second monomer of BsYtvA is shown in gray. Corresponding domains are colored the same. The FMN chromophores are shown as orange sticks. Structure 2017 25, 933-938.e3DOI: (10.1016/j.str.2017.04.006) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 2 X-Ray Solution Scattering Data (A) Experimental and reconstructed data computed from the kinetic model are shown for selected time points. The data were recorded at BioCARS (Advanced Photon Source). (Bottom panel) The light-adapted state as extracted from the kinetic model is also shown together with an average for delay times >100 ms of a dataset recorded at cSAXS (Swiss Light Source). The modulus of the scattering vector is defined as q = 4πsin(θ)/λ, with 2θ as the scattering angle and λ as the X-ray wavelength. (B) Kinetic decomposition of X-ray scattering shows the rise of the steady-state spectrum. The black dashed line shows the decay of the triplet state as measured by absorption spectroscopy at a wavelength of 650 nm (Losi et al., 2002). (C) Change in pair distance distribution function corresponding to the >100-ms steady-state difference scattering. Structure 2017 25, 933-938.e3DOI: (10.1016/j.str.2017.04.006) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 3 Structural Analysis of BsYtvA-LOV (A) Theoretical difference scattering of the best-fitting pairs and experimental difference scattering of BsYtvA-LOV. (B) The pair with the lowest R is plotted. The dark-adapted and light-adapted structures are shown in blue and yellow, respectively, and the chromophores are shown as sticks. The structures are aligned on the left monomer. The distance represented by the dashed red line increases by 3 Å upon illumination. (C) Definition of the angles θ and φ. (D) Histogram of the distribution of the changes in the angles θ and φ. (E) The accepted dark-light pairs, all aligned on the left monomer, reveal a concerted separation of the two monomers. Structure 2017 25, 933-938.e3DOI: (10.1016/j.str.2017.04.006) Copyright © 2017 Elsevier Ltd Terms and Conditions

Figure 4 Cα Distance Difference Matrix (A) Light-minus-dark Cα distance changes averaged over the 431 accepted pairs. (B) Corresponding Cα distance changes for the BsYtvA-LOV dark-adapted and light-adapted crystal structures (PDB: 2PR5 and 2PR6, respectively). Structure 2017 25, 933-938.e3DOI: (10.1016/j.str.2017.04.006) Copyright © 2017 Elsevier Ltd Terms and Conditions