Photoactivatable Rac1: a photosensor tilt by time-resolved crystallography and a partially open switch I when GDP-bound
- 1Dioscuri Centre for Structural Dynamics of Receptors, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University
Abstract
The LOV2 domain of Avena sativa phototropin 1 is widely used to control proteins with light, but how its signal reaches a fused effector has not been visualized. We followed photoactivatable Rac1 by time-resolved serial crystallography at room temperature. Within 350 {micro}s, a fifth of the photosensors form the flavin-cysteine adduct and tilt as a rigid body on Rac1 about an axis through the domain interface, while the J helix stays docked and Rac1 keeps GTP and dark-state switches up to 1.85 ms. Dark crystals contain a variable GDP-bound sub-population, so light data must be referenced to interleaved dark frames. In this sub-population, switch I is only partially open, held at a Ca2+ ion that bridges LOV2 and Rac1, a conformation that can persist in simulations without the lattice. The photosensor thus first acts on Rac1 at the interface that also holds switch I in the GDP-bound state.
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BibTeX
@misc{pachota2026photoactivatable,
title = {{Photoactivatable Rac1: a photosensor tilt by time-resolved crystallography and a partially open switch I when GDP-bound}},
author = {M. Pachota and M. K. Shankar and M. Wisniewska and A. Koczurowska and C. M. Casadei and A. Solecka and S. M. Kapetanaki and B. Olasz and L. Lopes Cavalcante and R. Ke and D. Lang and M. Bjelcic and A. Asghar and M. Milas and T. Ursby and M. Chenchiliyan and J. Nan and E. Rosta and P. Nogly},
howpublished = {bioRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.27.762334},
url = {https://www.biorxiv.org/content/10.64898/2026.10.27.762334v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Photoactivatable Rac1: a photosensor tilt by time-resolved crystallography and a partially open switch I when GDP-bound
AU - M. Pachota
AU - M. K. Shankar
AU - M. Wisniewska
AU - A. Koczurowska
AU - C. M. Casadei
AU - A. Solecka
AU - S. M. Kapetanaki
AU - B. Olasz
AU - L. Lopes Cavalcante
AU - R. Ke
AU - D. Lang
AU - M. Bjelcic
AU - A. Asghar
AU - M. Milas
AU - T. Ursby
AU - M. Chenchiliyan
AU - J. Nan
AU - E. Rosta
AU - P. Nogly
PY - 2026
DA - 2026/10/27
PB - bioRxiv
DO - 10.64898/2026.10.27.762334
UR - https://www.biorxiv.org/content/10.64898/2026.10.27.762334v1
AB - The LOV2 domain of Avena sativa phototropin 1 is widely used to control proteins with light, but how its signal reaches a fused effector has not been visualized. We followed photoactivatable Rac1 by time-resolved serial crystallography at room temperature. Within 350 {micro}s, a fifth of the photosensors form the flavin-cysteine adduct and tilt as a rigid body on Rac1 about an axis through the domain interface, while the J helix stays docked and Rac1 keeps GTP and dark-state switches up to 1.85 ms. Dark crystals contain a variable GDP-bound sub-population, so light data must be referenced to interleaved dark frames. In this sub-population, switch I is only partially open, held at a Ca2+ ion that bridges LOV2 and Rac1, a conformation that can persist in simulations without the lattice. The photosensor thus first acts on Rac1 at the interface that also holds switch I in the GDP-bound state.
ER -