This invention provides isolated nucleic acids encoding chimeric G proteins, vectors comprising nucleic acids encoding chimeric G proteins, cells comprising such vectors, processes of determining agonists and antagonists of mammalian G protein-coupled receptors utilizing chimeric G proteins, processes of determining compounds which bind to mammalian G protein-coupled receptors utilizing chimeric G proteins, processes for making a composition of matter which specifically binds to a mammalian G protein-coupled receptor utilizing chimeric G proteins, processes for preparing a composition which comprises admixing a carrier and a pharmaceutically effective amount of a chemical compound identified by a process of the invention utilizing chimeric G proteins, processes of identifying a ligand for a mammalian G protein-coupled receptor utilizing chimeric G proteins, and processes of screening a plurality of independent clones to identify and isolate a clone encoding a mammalian G protein-coupled receptor utilizing chimeric G proteins.