SLC7A7, also called y+L-type amino acid transporter 1 (y+LAT1), forms a heterodimeric complex with the heavy chain of the cell surface antigen 4F2 (4F2hc/CD98hc/SLC3A2). SLC7A7 is mainly expressed at the basolateral membrane of epithelial cells in the renal tubules and small intestine, and transports cationic amino acids such as lysine, arginine, and ornithine. Functionally deficient variants of the SLC7A7 gene have been observed in patients with lysinuric protein intolerance, which is characterized by increased urinary excretion of cationic amino acids and reduced absorption from intestine, incidentally causing metabolic derangement after protein-rich meals.