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 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). Kidney, small intestine, liver and placenta. The disease is caused by variants affecting the gene represented in this entry. Belongs to the amino acid-polyamine-organocation (APC) superfamily.