The APC superfamily consists of numerous families of porters that transport amino acids and their dereivatives. See: Chang A.B., Lin R., Studley W.K., Tran C.V., Saier M.H. Jr. 2004. Phylogeny as a Guide to Structure and Function of Membrane Transport Proteins. Mol Membr Biol. 21(3):171-81.
2.A.3 - The Amino Acid-Polyamine-Organocation (APC) Family
Wong, F.H., J.S. Chen, V. Reddy, J.L. Day, M.A. Shlykov, S.T. Wakabayashi, and M.H. Saier, Jr. (2012). The amino acid-polyamine-organocation superfamily. J. Mol. Microbiol. Biotechnol. 22: 105-113. These porters have the LeuT fold (Ferrada E and Superti-Furga G, 2022 [PMID 36164651]).
These proteins have two 5 TMS repeats except for NCS2, AE and SulP which have two 7 TMS repeats.
See: Vastermark A, Wollwage S, Houle ME, Rio R and Saier MH Jr. (2014). Expansion of the APC superfamily of secondary carriers, Proteins. 82:2797-2811. PMID: 25043943. and
Västermark Å and Saier MH Jr. (2014) Evolutionary relationship between 5+5 and 7+7 inverted repeat folds within the amino acid-polyamine-organocation superfamily. Proteins. 82:336-46. PMID: 24038584.
2.A.15 - The Betaine/Carnitine/Choline Transporter (BCCT) Family
2.A.18 - The Amino Acid/Auxin Permease (AAAP) Family
2.A.21 - The Solute:Sodium Symporter (SSS) Family
2.A.22 - The Neurotransmitter:Sodium Symporter (NSS) Family
2.A.25 - The Alanine or Glycine:Cation Symporter (AGCS) Family
2.A.26 - The Branched Chain Amino Acid:Cation Symporter (LIVCS) Family
2.A.30 - The Cation-Chloride Cotransporter (CCC) Family
2.A.31 - The Anion Exchanger (AE) Family
2.A.39 - The Nucleobase:Cation Symporter-1 (NCS1) Family
2.A.40 - The Nucleobase/Ascorbate Transporter (NAT) or Nucleobase:Cation Symporter-2 (NCS2) Family
2.A.42 - The Hydroxy/Aromatic Amino Acid Permease (HAAAP) Family
2.A.46 - The Benzoate:H+ Symporter (BenE) Family
2.A.53 - The Sulfate Permease (SulP) Family
2.A.55 - The Metal Ion (Mn2+-iron) Transporter (Nramp) Family
2.A.72 - The K+ Uptake Permease (KUP) Family
2.A.114 - The Putative Peptide Transporter Carbon Starvation CstA (CstA) Family
2.A.120 - The Proline/Amino Acid Permease (PAAP) Family