Mediates the uptake of the cationic amino acids arginine, lysine and ornithine in a sodium-independent manner. Highly expressed in thymus, uterus and testis. Detected at lower levels in brain, mammary gland, prostate, salivary gland and fetal spleen. In brain, highest expression in thalamus, hippocampus and amygdala. N-glycosylated. Belongs to the amino acid-polyamine-organocation (APC) superfamily. Cationic amino acid transporter (CAT) (TC 2.A.3.3) family.