CPA1 was considered a member of the superfamily until 2010, when it was discovered to in fact be a member of the
VIC superfamily.[2][3][4] 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.
Chang, Abraham B.; Lin, Ron; Keith Studley, W.; Tran, Can V.; Saier, Milton H. (2004). "Phylogeny as a guide to structure and function of membrane transport proteins". Molecular Membrane Biology. 21 (3): 171–181.
doi:
10.1080/09687680410001720830.
PMID15204625.