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 Ser, Gly, Cys, Asn, Thr, Pro and Met. May mediate sodium-independent transport of cationic amino acids, such as Arg and Lys. Amino acid uptake is pH-dependent, with highest transport activity between pH 7.5 and 8.5 (By similarity). 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.