Mitochondrial arginine transporter that catalyzes the counter-exchange of arginine with lysine, ornithine, arginine, histidine and citrulline. Substrate preference in reconstituted proteoliposomes is arginine > homoarginine > citrulline > histidine > lysine > ornithine. May be involved in the delivery of arginine, released from seed reserves, to mitochondrial arginase and the export of ornithine. May contribute to proline accumulation in response to hyperosmotic stress. Inhibited by mercuric chloride. Optimum pH is 8.0. High expression in flowers, stamens, petals and pollen. Expressed in roots, leaves and stems. By hyperosmotic stress and dark-induced senescence. No visible phenotype under normal growth conditions. Belongs to the mitochondrial carrier (TC 2.A.29) family.