Promotes the biosynthesis of heme and assembly and repair of iron-sulfur clusters by delivering Fe(2+) to proteins involved in these pathways. May play a role in the protection against iron-catalyzed oxidative stress through its ability to catalyze the oxidation of Fe(2+) to Fe(3+); the oligomeric form but not the monomeric form has in vitro ferroxidase activity. May be able to store large amounts of iron in the form of a ferrihydrite mineral by oligomerization; however, the physiological relevance is unsure as reports are conflicting and the function has only been shown using heterologous overexpression systems. Modulates the RNA-binding activity of ACO1. 4 Fe(2+) + 4 H(+) + O2 = 4 Fe(3+) + 2 H2O Monomer (probable predominant form). Oligomer. Monomers and polymeric aggregates of >1 MDa have been isolated from mitochondria. A small fraction of heterologous overexpressed recombinant frataxin forms high-molecular weight aggregates that incorporate iron (PubMed:11823441, PubMed:12755598, PubMed:15641778, PubMed:15581888). Interacts with LYRM4 (PubMed:17331979). Interacts with ACO1 (PubMed:20053667). Interacts with ISCU isoform 1 and isoform 2 (PubMed:12785837, PubMed:16091420). Interacts with FECH; one iron-bound FXN monomer seems to interact with a FECH homodimer (PubMed:15123683). Interacts with SDHA and SDHB (PubMed:15961414). Interacts with ACO2; the interaction is dependent on citrate (By similarity). Interacts with HSPA9 (PubMed:17331979, PubMed:26702583). PubMed:18725397 reports localization exclusively in mitochondria. Expressed in the heart, peripheral blood lymphocytes and dermal fibroblasts. Processed in two steps by mitochondrial processing peptidase (MPP). MPP first cleaves the precursor to intermediate form and subsequently converts the intermediate to yield frataxin mature form (frataxin(81-210)) which is the predominant form. The additional forms, frataxin(56-210) and frataxin(78-210), seem to be produced when the normal maturation process is impaired; their physiological relevance is unsure. The disease is caused by variants affecting the gene represented in this entry. The unusual migration profile of mature frataxin on SDS-PAGE due to its acidic N-terminus most likely contributed to conflicting reports for the N-terminus of the mature protein. Unlike prokaryotic and yeast frataxin homologs, which self-assemble at high iron concentrations, oligomerization of human frataxin is not induced by iron. The existence of a specialized mitochondrial ferritin in mammalia (FTMT) is suggesting that iron storage would be redundant function, at least in mammalian mitochondria. Not highly expressed and may be artifactual. Belongs to the frataxin family.