Mitochondrial transporter of arginine, lysine, homoarginine, methylarginine and, to a much lesser extent, ornithine and histidine (PubMed:19287344, PubMed:24652292). Does not transport carnitine nor acylcarnitines (PubMed:24652292). Functions by both counter-exchange and uniport mechanisms (PubMed:24652292). Plays a physiological role in the import of basic amino acids into mitochondria for mitochondrial protein synthesis and amino acid degradation (PubMed:19287344, PubMed:24652292).