Control of Yeast Mating Signal Transduction by a Mammalian β 2 -adrenergic Receptor and G s α Subunit

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Abstract
To facilitate functional and mechanistic studies of receptor—G protein interactions, the human β 2 -adrenergic receptor (hβ-AR) has been expressed in Saccharomyces cerevisiae . This was achieved by placing a modified hβ-AR gene under control of the galactose-inducible GAL1 promoter. After induction by galactose, functional hβ-AR was expressed at a concentration several hundred times as great as that found in any human tissue. As determined from competitive ligand binding experiments, hβ-AR expressed in yeast displayed characteristic affinities, specificity, and stereoselectivity. Partial activation of the yeast pheromone response pathway by β-adrenergic receptor agonists was achieved in cells coexpressing hβ-AR and a mammalian G protein (G s ) α subunit-demonstrating that these components can couple to each other and to downstream effectors when expressed in yeast. This in vivo reconstitution system provides a new approach for examining ligand binding and G protein coupling to cell surface receptors.