SLC36A4 belongs to the SLC36 family of amino acid transporters based on sequence similarity with other family members (e.g., SLC36A1; MIM 606561). SLC36 proteins contain about 500 amino acids and have 9 to 11 transmembrane domains. Unlike other SLC36 family members, which are proton-coupled amino acid transporters, SLC36A4 is a high-affinity/low-capacity non-proton-coupled amino acid transporter (Pillai and Meredith, 2011 [PubMed 21097500]).[supplied by OMIM, Feb 2011].