Anoctamin and transmembrane channel-like proteins are evolutionarily related

Abstract

The anoctamin (ANO) family of proteins, consisting of 10 members in mammals, are transmembrane proteins that have Ca(2+)-activated Cl(-) channel activity. The transmembrane channel-like (TMC) family of proteins, consisting of 8 members in mammals, are also transmembrane proteins of which mutations are implicated in various human conditions, such as hearing loss and epidermodysplasia verruciformis. Here we show that ANO and TMC proteins share high sequence similarity and probably the same membrane topology, indicating that these proteins are evolutionarily related. We found many conserved amino acid residues between the two families of proteins, especially in regions spanning the transmembrane domains TM1, TM4-TM5, and TM6-TM7. These findings imply that these proteins form one large family, which we term ANO/TMC superfamily and that TMC proteins also function as channels for Cl- or other ions. The ANO/TMC superfamily proteins are present in almost all diverse groups of eukaryotic organisms, suggesting that the proteins function in important biological processes, such as ion homeostasis, in eukaryotic cells.