Figure 4.

Three ways of examining seven transmembrane domain (7TM) receptor oligomers by bimolecular fluorescence complementation (BiFC). Multicolour BiFC allows competitive formation of alternative 7TM receptor dimers to be assessed by the development of cyan fluorescent protein (CFP) or yellow fluorescent protein (YFP)-like BiFC fluorescence (A). Alternatively, BiFC YFP formed by a 7TM receptor dimer can act as an energy transfer acceptor. Typically, Renilla luciferase (LUC) provides the donor for bioluminescence resonance energy transfer (BRET), carried as a full-length protein by a third 7TM receptor monomer (B) or reconstituted by complementation in a second 7TM receptor dimer (tetrameric interaction, C).