Intrinsic gating mechanisms of epithelial sodium channels.

The hypothesis that there is a highly conserved, positively charged region distal to the second transmembrane domain in alpha-ENaC (epithelial sodium channel) that acts as a putative receptor site for the negatively charged COOH-terminal beta- and gamma-ENaC tails was tested in mutagenesis experiments. After expression in Xenopus oocytes, alpha-ENaC constructs in which positively charged arginine residues were converted into negatively charged glutamic acids could not be inhibited by blocking peptides. These observations provide insight into the gating machinery of ENaC.