Patent ID: 8647887

Claim:
A method of detecting a compound, the method comprising, i) contacting a sample with a cell-free composition comprising at least one G protein coupled receptor embedded in a lipid bilayer, and which is capable of binding the compound, wherein the G protein coupled receptor comprises one or more subunits that are the same or different, and wherein at least one of the subunits of the G protein coupled receptor comprises a bioluminescent protein and an acceptor molecule, ii) simultaneously or sequentially with step i) providing a substrate of the bioluminescent protein, and allowing the bioluminescent protein to modify the substrate, iii) determining if step ii) modulates bioluminescent resonance energy transfer (BRET) between the bioluminescent protein and the acceptor molecule, wherein the spatial location and/or dipole orientation of the bioluminescent protein relative to the acceptor molecule is altered when the compound binds the G protein coupled receptor, and wherein when expressed in a cell the N-terminus of the G protein coupled receptor, or subunits thereof, is outside the cell and the C-terminus inside the cell, and wherein the amplitude of the change in the BRET ratio is indicative of the relative amount of the compound in the sample, wherein a) the bioluminescent protein forms part of the fifth non-transmembrane loop of the subunit, and the acceptor molecule forms part of the C-terminus, or b) the acceptor molecule forms part of the fifth non-transmembrane loop of the subunit, and the bioluminescent protein forms part of the C-terminus, and wherein the method is at least 2 fold more sensitive than if a non-bioluminescent protein is used as a donor molecule and a modulation of fluorescence resonance energy transfer (FRET) is determined.