G-protein-coupled receptor kinase specificity for arrestin recruitment to the adrenergic receptor revealed by

  fluorescence resonance energy transfer

The G-protein-coupled receptor kinases function to regulate cell signaling by phosphorylating hepta-helical receptors, thereby promoting receptor interaction with beta-arrestins. This switches a receptor from G-protein activation to G-protein desensitization, receptor internalization, and beta-arrestin-dependent signal activation that can be seen through fluorescence resonance energy transfer .