Amino acid transporter that plays an important role in the absorption of amino acids in the intestinal tract. Mediates the uptake of a broad range of neutral and cationic amino acids (with the exception of proline) in a Na(+)/Cl(-)-dependent manner . Transports non-alpha-amino acids such as beta-alanine with low affinity, and has a higher affinity for dipolar and cationic amino acids such as leucine and lysine . Can also transport carnitine, butirylcarnitine and propionylcarnitine coupled to the transmembrane gradients of Na(+) and Cl(-) .
Subcellular locations: Membrane, Apical cell membrane
Levels are highest in adult and fetal lung, in trachea and salivary gland. Lower levels detected in mammary gland, stomach and pituitary gland, and very low levels in colon, uterus, prostate and testis.