Sodium-dependent amino acid transporter. Mediates electrogenic symport of neutral amino acids and sodium ions. Has a broad specificity, with a preference for Ala, followed by His, Cys, Asn, Ser, Gly, Val, Thr, Gln and Met. May mediate sodium-independent transport of cationic amino acids, such as Arg and Lys. Amino acid uptake is pH-dependent, with low transport activities at pH 6.5, intermediate at pH 7.0 and highest between pH 7.5 and 8.5. Optimum pH is 7.5-8.5. Detected in embryonic and adult liver, and at lower levels in adult muscle, kidney and pancreas. Detected in placenta syncytiotrophoblasts throughout gestation. Detected in fetal blood vessels. The disulfide bond plays an important role in substrate transport, but has no effect on trafficking to the cell surface. Belongs to the amino acid/polyamine transporter 2 family.