Rhodoposin is the primary dim-light receptor in the mammalian visual system and a prototype for understanding the structure and dynamics of G protein-coupled receptors. Here, we explore the picosecond-scale response of the protein using a combination of X-ray scattering experiments using an X-ray free electron laser and molecular dynamics simulations. The results indicate that, despite the structural diversity of the inactive dark state, photon-induced ligand isomerization causes a pressure wave to radiate through the protein. Although the individual activation events show significant variation, the ensemble as a whole show some specific characteristics, where the individual helices respond in a specific order. The results indicate that caution must be used when interpreting such experiments, because simple rigid-body displacements do not adequately model the underlying diversity of the protein's motions.

Exploring the ultra-fast response of rhodosin activation using time-resolved X-ray scattering and molecular dynamics simulations

ACS Fall 2021

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