Mitochondrial iron transporter that mediates iron uptake. Probably required for heme synthesis of hemoproteins and Fe-S cluster assembly in non-erythroid cells. The iron delivered into the mitochondria, presumably as Fe(2+), is then probably delivered to ferrochelatase to catalyze Fe(2+) incorporation into protoprophyrin IX to make heme (By similarity). Isoform 1 and isoform 2 are both localized in the mitochondrion. Ubiquitous. Expressed in placenta, lung, kidney, pancreas, liver, brain, skeletal muscle and heart. Belongs to the mitochondrial carrier (TC 2.A.29) family.