Heterodimer with SLC3A2, that functions as an antiporter which operates as an efflux route by exporting cationic amino acids from inside the cells in exchange with neutral amino acids plus sodium ions and may participate in nitric oxide synthesis via the transport of L-arginine (PubMed:10080182, PubMed:10655553, PubMed:14603368, PubMed:15756301, PubMed:15776427, PubMed:17329401, PubMed:9829974, PubMed:9878049). Also mediates arginine transport in non-polarized cells, such as monocytes, and is essential for the correct function of these cells (PubMed:15280038, PubMed:31705628). The transport mechanism is electroneutral and operates with a stoichiometry of 1:1 (By similarity). In vitro, Na(+) and Li(+), but also H(+), are cotransported with the neutral amino acids (By similarity). {ECO:0000250|UniProtKB:Q9R0S5, ECO:0000269|PubMed:10080182, ECO:0000269|PubMed:10655553, ECO:0000269|PubMed:14603368, ECO:0000269|PubMed:15280038, ECO:0000269|PubMed:15756301, ECO:0000269|PubMed:15776427, ECO:0000269|PubMed:17329401, ECO:0000269|PubMed:31705628, ECO:0000269|PubMed:9829974, ECO:0000269|PubMed:9878049}. This is the function of SLC7A7 (solute carrier family 7 member 7, ENSG00000155465).