Expression of cDNAs for acetylcholine receptor subunits in the yeast cell plasma membrane

Yeast cells transformed with a plasmid containing cDNA encoding the alpha or delta subunit of the Torpedo californica acetylcholine receptor synthesize a protein. The expected molecular mass, antigenic specificity, and ligand-binding properties (in the case of the alpha subunit) of the subunits in yeast are similar to those of the subunits in T. californica membranes. The subunits are inserted into the yeast plasma membrane, demonstrating for the first time that yeast has the apparatus to express and insert foreign proteins into its plasma membrane. The alpha subunit constitutes approximately 1% of the yeast membrane proteins, and its density is about the same in the plasma membrane of yeast as in the receptor-rich electric organ of Electrophorus electricus. In view of the widely available technology for obtaining large quantities of yeast proteins, yeast cells may prove ideal for amplifying the amounts of interesting membrane-bound proteins available so that physical and biochemical studies can be made easily.