Frataxin function in the mitochondria. The schema illustrates the iron-sulphur cluster (ISC) biosynthesis machinery present in the mitochondrial matrix encompassing the ISCU-NFS1 protein complex associating glutaredoxin 5 (GLRX5) with the frataxin protein. It makes use of iron possibly delivered by the mitochondrial ferritin to synthesize ISC also distributed among several of the mitochondrial proteins (including several membrane-bound respiratory chain components, complexes I, II and III and the matrix-soluble aconitase). In addition to its role in the biogenesis of ISC, the frataxin protein might be associated with ISC after their synthesis. The detoxifying role of vitamin E in the mitochondrial inner membrane is also indicated. ISP, ISC-containing protein; mt, mitochondrial.