ELECTROPHYSIOLOGICAL AND BIOCHEMICAL-EVIDENCE THAT DEG ENAC CATION CHANNELS ARE COMPOSED OF 9 SUBUNITS/

Members of the DEG/ENaC protein family form ion channels with diverse functions, DEG/ENaC subunits associate as hetero-and homomultimers to generate channels; however the stoichiometry of these complexes is unk nown, To determine the subunit stoichiometry of the human epithelial N a+ channel (hENaC), we expressed the three wild-type hENaC subunits (a lpha, beta, and gamma) with subunits containing mutations that alter c hannel inhibition by methanethiosulfonates. The data indicate that hEN aC contains three alpha, three beta, and three gamma subunits, Sucrose gradient sedimentation of alpha hENaC translated in vitro, as well as alpha-, beta-, and gamma hENaC coexpressed in cells, was consistent w ith complexes containing nine subunits. FaNaCh and BNC1, two related D EG/ENaC channels, produced complexes of similar mass. Our results sugg est a novel nine-subunit stoichiometry for the DEG/ENaC family of ion channels.