1.A.6 (ENaC) and 1.A.7 (P2X receptor) have similar 3-d structures and are likely to be homologous (Kawate et al, 2009; Gonzales et al, 2009)
1.A.6 - The Epithelial Na+ Channel (ENaC) Family
Le, T. and M.H. Saier, Jr. (1997). Phylogenetic characterization of the epithelial Na+ channel (ENaC) family. Mol. Membr. Biol. 13: 149-157.
Gonzales, E.B., T. Kawate, and E. Gouaux. (2009). Pore architecture and ion sites in acid-sensing ion channels and P2X receptors. Nature 460: 599-604.
Kawate, T., J.C. Michel, W.T. Birdsong, and E. Gouaux. (2009). Crystal structure of the ATP-gated P2X(4) ion channel in the closed state. Nature 460: 592-598.
1.A.7 - The ATP-gated P2X Receptor Cation Channel (P2X Receptor) Family