Schematic illustration of a generalized overview of mitochondrial Fe metabolism. Iron is supplied to the mitochondrion from the cytosolic labile Fe pool by an unknown mechanism. It is transported by as yet unidentified transporter(s) into the matrix where it can be directed to a number of different pathways, including storage in mitochondrial ferritin, [Fe-S] synthesis, heme metabolism, or other as yet unknown pathways (see “The mitochondrion is a major site of [Fe-S] synthesis” for further details). ALA indicates δ-aminolevulinic acid; ALAS, δ-aminolevulinic acid synthase; CoPIII, coproporphyrinogen III; Fch, ferrochelatase; [Fe-S], iron sulphur cluster; Fxn, frataxin; IRP1, iron-regulatory protein 1; m-Ferr, mitochondrial ferritin; and PIX, protoporphyrin IX.