Biosensors characterize the routes taken by receptors to different active states

A panel of fluorescently labelled G-protein-coupled-receptor proteins expressed in living cells has confirmed that, when bound by an activating ligand molecule, these receptors form different complexes with their G proteins. The activation trajectories induced by different ligands explain ligand-specific efficacies of G-protein activation and preferences for G-protein subtypes. A panel of G-protein-coupled-receptor biosensors provides ‘fingerprints’ of the effects of activating ligands.