G Protein-Coupled Time Travel: Evolutionary Aspects of GPCR Research

Identification of an atropine-agonized mutant M3 muscarinic acetylcholine receptor (M3R). To generate an M₃R that can be activated by atropine, we applied error-prone random mutagenesis and screened approximately 1 x 10⁷ mutant M₃R clones for atropine sensitivity in a yeast expression system. In one clone we identified the mutations R¹⁷⁹K and A⁴⁸⁹P (A) that enable the M₃R to be activated by atropine (B). Both mutated positions are fully conserved within G_q-coupled muscarinic acetylcholine receptors.