Sodium-dependent, high-affinity amino acid transporter that mediates the uptake of L-glutamate and also L-aspartate and D-aspartate (PubMed:9379843). Functions as a symporter that transports one amino acid molecule together with two or three Na(+) ions and one proton, in parallel with the counter-transport of one K(+) ion. Mediates Cl(-) flux that is not coupled to amino acid transport; this avoids the accumulation of negative charges due to aspartate and Na(+) symport (By similarity). Plays a redundant role in the rapid removal of released glutamate from the synaptic cleft, which is essential for terminating the postsynaptic action of glutamate (Probable). H(+)(out) + K(+)(in) + L-glutamate(out) + 3 Na(+)(out) = H(+)(in) + K(+)(out) + L-glutamate(in) + 3 Na(+)(in) H(+)(out) + K(+)(in) + L-aspartate(out) + 3 Na(+)(out) = H(+)(in) + K(+)(out) + L-aspartate(in) + 3 Na(+)(in) D-aspartate(out) + H(+)(out) + K(+)(in) + 3 Na(+)(out) = D-aspartate(in) + H(+)(in) + K(+)(out) + 3 Na(+)(in) Homotrimer. Brain specific. Contains eight transmembrane regions plus two helical hairpins that dip into the membrane. These helical hairpin structures play an important role in the transport process. The first enters the membrane from the cytoplasmic side, the second one from the extracellular side. During the transport cycle, the regions involved in amino acid transport, and especially the helical hairpins, move vertically by about 15-18 Angstroms, alternating between exposure to the aqueous phase and reinsertion in the lipid bilayer. In contrast, the regions involved in trimerization do not move. Belongs to the dicarboxylate/amino acid:cation symporter (DAACS) (TC 2.A.23) family. SLC1A6 subfamily.