Yeast cells were transformed with a plasmid containing complementary DNA encoding the alpha subunit of the Torpedo californica acetylcholine receptor. These cells synthesized a protein that had the expected molecular weight, antigenic specificity, and ligand-binding properties of the alpha subunit. The subunit was inserted into the yeast plasma membrane, demonstrating that yeast has the apparatus to express a membrane-bound receptor protein and to insert such a foreign protein into its plasma membrane. The alpha subunit constituted approximately 1 percent of the total yeast membrane. The alpha subunit constituted approximately 1 percent of the total yeast membrane proteins, and its density was about the same in the plasma membrane of yeast and in the receptor-rich electric organ of Electrophorus electricus. In view of the available technology for obtaining large quantities of yeast proteins, it may now be possible to obtain amplified amounts of interesting membrane-bound proteins for physical and biochemical studies.