TPCN1 is a widely expressed, 816 amino acid voltage-gated cation channel protein with predominant expression in lung, liver, heart and kidney. In the kidney, TPCN1 localizes to the inner medullary collecting ducts. In contrast with the distantly related four-domain voltage-gated calcium and sodium channels and the more closely related four-domain ion transport protein located on the surface of sperm cells (CatSper), TPCN1 is a two-domain channel. Similar to the four-domain channel structure, each of the two homologous domains that comprise TPCN1 contains six transmembrane segments (S1-S6) with a pore loop between S5 and S6 and a voltage sensor segment that is positively charged. TPCN1 has hydrophilic N- and C-termini that localize to the cytoplasm.