Protein structural dynamics in native environments tracked by in cell time-resolved X-ray solution scattering

The cell interior is a complex environment characterised by molecular crowding and spatial confinement that affect chemical/thermodynamic equilibria. Our hypothesis is that cell conditions can also affect out-of-equilibrium structural dynamics. Phytochromes are photoreceptors regulating signalling responses in plants and microorganisms, initiated by photoconversion of red light-absorbing (Pr) state to an active far-red light-absorbing (Pfr) state. We have demonstrated that time-resolved X-ray scattering can be successfully applied to monitor hemoglobin dynamics within intact erythrocytes. The main objective of this proposal is to apply the in-cell TR-XSS approach to unravel how cell conditions affect the kinetics and dynamics of functionally relevant structural changes triggered by light in phytochromes. The proposed experiments will deliver the first in-cell description of the photoconversion pathway accompanying the signalling mechanism of phytochromes.