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The article offers information on a study regarding the crystallization of Arrestin proteins during the regulation of cellular signaling cascades which are activated by ubiquitous G-protein-coupled receptors (GPCRs). It reports that the formation of crystal structures of arrestin proteins unveils that they have undergone similar structural changes on their activation.

The complex pharmacology of G-protein-coupled receptors (GPCRs) is defined by their multi-state conformational dynamics. Single-molecule Förster Resonance Energy Transfer (smFRET) is well suited to quantify dynamics for individual protein molecules; however, its application to GPCRs is challenging. Therefore, smFRET has been limited to studies of inter-receptor interactions in cellular membranes and receptors in detergent environments. Here, we performed smFRET experiments on functionally active human A2A adenosine receptor (A2AAR) molecules embedded in freely diffusing lipid nanodiscs to study their intramolecular conformational dynamics. We propose a dynamic model of A2AAR activation that involves a slow (>2 ms) exchange between the active-like and inactive-like conformations in both apo and antagonist-bound A2AAR, explaining the receptor's constitutive activity. For the agonist-bound A2AAR, we detected faster (390 ± 80 µs) ligand efficacy-dependent dynamics. Our work establishes a general smFRET platform for GPCR investigations that can potentially be used for drug screening and/or mechanism-of-action studies. Single-molecule FRET experiments with human A2A adenosine receptor in its apo and agonist-bound states in lipid nanodiscs provide insights into its conformational dynamics and activation. [ABSTRACT FROM AUTHOR]