 Crystal structure of ASIC1 and site-directed mutagenesis studies suggest that ENaC has a central ion channel located along the central symmetry axis in between the three subunits.In terms of structure, the proteins that belong to this family consist of about 510 to 920 amino acid residues.They are made of an intracellular N-terminus region followed by a transmembrane domain, a large extracellular loop, a second transmembrane segment, and a C-terminal intracellular tail.