Disclosed herein are constitutively activated, non-endogenous versions of endogenous human G protein-coupled receptors comprising (a) the following amino acid sequence region (C-terminus to N-terminus orientation) and/or (b) the following nucleic acid sequence region (3' to 5' orientation) transversing the transmembrane-6 (TM6) and intracellular loop-3 (IC3) regions of the GPCR: (a) P<SUP>1 </SUP>AA<SUB>15</SUB>X and/or (b) p<SUP>codon </SUP>(AA-codon)<SUB>15 </SUB>X<SUB>codon</SUB>, respectively. In a most preferred embodiment, P<SUP>1 </SUP>and P<SUP>codon </SUP>are endogenous proline and an endogenous nucleic acid encoding region encoding proline, respectively, located within TM6 of the non-endogenous GPCR; AA<SUB>15 </SUB>and (AA-codon)<SUB>15 </SUB>are 15 endogenous amino acid residues and 15 codons encoding endogenous amino acid residues, respectively; and X and X<SUB>codon </SUB>are non-endogenous lysine and a non-endogenous nucleic acid encoding region encoding lysine, respectively, located within IC3 of the non-endogenous GPCR. Because it is most preferred that the non-endogenous human GPCRs which incorporate these mutations are incorporated into mammalian cells and utilized for the screening of candidate compounds, the non-endogenous human GPCR incorporating the mutation need not be purified and isolated per se (i.e., these are incorporated within the cellular membrane of a mammalian cell), although such purified and isolated non-endogenous human GPCRs are well within the purview of this disclosure.
Non-endogenous, constitutively activated human G protein-coupled receptors