The Branched Chain Amino Acid:Cation Symporter (LIVCS) Family (TC 2.A.26) Characterized members of this family transport all three of the branched chain aliphatic amino acids (leucine (L), isoleucine (I) and valine (V)). They function by a Na+ or H+ symport mechanism and display 12 putative transmembrane helical spanners. [Transport and binding proteins, Amino acids, peptides and amines]