A complementary DNA encoding an amiloride-sensitive Na+ channel has been cloned and characterized from rat colon. The protein encoded by the cDNA has a sequence of 699 amino acids (79 kDa) containing several putative membrane spanning domains and potential phosphorylation sites. It forms a channel that has the electrophysiological and pharmacological properties characteristic of the epithelial Na+ channel. Homologies (including in transmembrane domains) have been found between a part of the channel sequence and the Mec4 gene product of Caenorhabditis elegans, a protein associated with mutation-induced neuronal degeneration.
