CPA superfamily

The Cation:Proton Antiporter (CPA) Superfamily is a superfamily of transport proteins named after one of its constituent members, the (CPA2; TC# 2.A.37).
 was considered a member of the superfamily until 2010, when it was discovered to in fact be a member of the VIC superfamily. As of April 2016, the CPA superfamily consists of four members:
Structural variation exists between families. For example, members of the CPA2 family are between 300 and 900 amino acyl residues (aas) in length and exhibit 10 to 14 transmembrane segments (TMSs), while members of the MSS family are shorter than 300 aas and exhibit 4 to 7 TMSs.