Figure 6.

A model of the ENaC pore showing the outer channel vestibule, the selectivity filter, and the inner pore. The cross-section shows the preM2 segments and the second putative transmembrane α-helices (M2) of two α subunits (black, on each side) and a β subunit (gray, in the back). The γ subunit located on the side of the viewer (4) is not shown. The outer vestibule is lined by the preM2 segment where amiloride binds to αS583 and the corresponding Gly residues in β and γ subunits (7). The vestibule narrows down to the selectivity filter formed by a ring of Ser residues (αS589 and analogs) responsible for molecular sieving.