Extracellular intersubunit interfaces. (A) Partial sequence alignments of the extracellular domains of human α-, β-, and γENaC and chicken ASIC1a. Putative interfacing residues are indicated by gold boxes. (B) ENaC structural models: areas of interest in αENaC are shown in red, βENaC in blue, and γENaC in green. The structure on the left side shows membrane-spanning and extracellular domains. The right structures show close-up views (corresponding to the boxed portion of the left structure) from the side (top structure) and rotated 90° to view channel from the top (bottom structure). Side chains of putative interfacing residues are shown in orange. Some regions of the bottom structure are hidden for clarity.