Involved in the high-affinity, sodium-independent transport of cystine and neutral and dibasic amino acids (system B(0,+)-like activity). Thought to be responsible for the high-affinity reabsorption of cystine in the kidney proximal tubule. Disulfide-linked heterodimer with the amino acid transport protein SLC3A1. Interacts with CAV1. Expressed in the brush border membrane in the kidney (at protein level). Belongs to the amino acid-polyamine-organocation (APC) superfamily.