Mitochondrial transporter that specifically mediates the mitochondrial uptake of dimethylarginine and trimethyllysine amino acids, and which is required for carnitine biosynthesis (PubMed:41075780, PubMed:41075794). Involved in carnitine biosynthesis by mediating the mitochondrial import of trimethyllysine, a precursor for carnitine biosynthesis (PubMed:41075780, PubMed:41075794). Transports both symmetric and asymmetric dimethylarginine (PubMed:41075794). Does not transport unmethylated arginine and lysine (PubMed:41075794). {ECO:0000269|PubMed:41075780, ECO:0000269|PubMed:41075794}. This is the function of SLC25A45 (solute carrier family 25 member 45, ENSG00000162241).