Figure 1.

Schematic illustration of the split luciferase β-arrestin2 recruitment assay. Complementary fragments of the Emerald luciferase were fused to β-arrestin2 and the D₁R, the D_2longR, the D₃R or the D_4.4R. Upon agonist stimulation of the receptor, β-arrestin2 is recruited and the luciferase fragments come into close proximity to form a functional enzyme, which catalyzes the oxidation of D-luciferin to oxyluciferin, accompanied by the emission of light (λ_max = 535 nm).