Transports arginine, lysine, homoarginine, methylarginine and, to a much lesser extent, ornithine and histidine (PubMed:24652292). Can restore ornithine transport in cells lacking the primary mitochondrial ornithine transporter SLC25A15 (PubMed:19287344). Does not transport carnitine nor acylcarnitines (PubMed:24652292). Functions by both counter-exchange and uniport mechanisms (PubMed:24652292). May be produced at very low levels due to a premature stop codon in the mRNA, leading to nonsense-mediated mRNA decay. Belongs to the mitochondrial carrier (TC 2.A.29) family. Extended N-terminus.