Figure 1.
Determination of the pharmacological profile of MT1/MT2 heterodimers by BRET (bioluminescence resonance energy transfer). Co-expression of MT1-Rluc (Renilla luciferase) and MT2-YFP (yellow variant of the green fluorescence protein) fusion proteins results in the formation of at least three different oligomeric receptor species, MT1-Rluc homodimers, MT2-YFP homodimers and MT1-Rluc/MT2-YFP heterodimers. Whereas all three species are detected in classical 125I-MLT-binding assays, BRET occurs only between MT1-Rluc and MT2-YFP. The observed ligand-promoted BRET change of melatonin receptor ligands is therefore exclusively generated by the MT1/MT2 heterodimer and not ‘contaminated' by the other dimeric receptor species.