A 2A adenosine receptor functional states characterized by 19 F-NMR

Significance G protein-coupled receptor (GPCR) signaling from the extracellular orthosteric drug binding site across the cell membrane to the intracellular contact sites with G proteins and arrestins is enabled by inherent structural plasticity, which can be observed by NMR spectroscopy. Here, we use 19 F-NMR to characterize ensembles of different, simultaneously populated conformations of the human A 2A adenosine receptor in function-related equilibria. The NMR data support an activation model involving both induced fit and reequilibration of conformational ensembles, and experiments with a constitutively active mutant of A 2A adenosine receptor (A 2A AR) established correlations between NMR parameters and GPCR basal activity. The present quantitative measurements with observation of judiciously engineered 19 F-NMR probes complement a previous qualitative overall view of A 2A AR dynamics from high-resolution NMR.