The methods outlined in this article describe experiments that can probe the first steps in receptor:G protein interaction using defined, recombinant receptors and G proteins. The protocols have the advantages that the receptors are inserted properly in a cell membrane and that the investigator has complete control of the proteins reconstituted with the receptor. Specific mutations in the receptors or G proteins are studied easily and the protocols allow precise examination of the stoichiometry of the receptor:alpha:beta gamma interaction.