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. Modulates the RNA-binding activity of ACO1 (By similarity). 4 Fe(2+) + 4 H(+) + O2 = 4 Fe(3+) + 2 H2O Monomer (probable predominant form). Oligomer (PubMed:11823441). Interacts with LYRM4 and HSPA9. Interacts with ACO1. Interacts with ISCU. Interacts with FECH; one iron-bound FXN monomer seems to interact with a FECH homodimer. Interacts with SDHA and SDHB. Interacts with ACO2; the interaction is dependent on citrate (By similarity). PubMed:17597094 describes localization exclusively in mitochondria. Heart, liver, skeletal muscle, kidney, spleen and thymus. Weakly expressed in the brain and lung. Expression in the ventricular zone which corresponds to dividing neuronal precursors begins at day 12.5, increases during embryonic development and persists at postnatal day 7 (P7) in the ependymal layer, which is the remnant of the ventricular zone. Weak expression seen in the spinal cord and medulla oblongata, starting at 14.5 dpc and expression also observed in dorsal root ganglia, starting at 14.5 dpc. At P14, expression in the dorsal root ganglia is restricted to the cortical region where the sensory neuron cell bodies are located. In non-neural tissues strong expression seen in the developing liver from 10.5 dpc. Expression detected in the heart and in the cortex of the developing kidney at 12.5 dpc and later. Very high expression observed in the brown adipose tissue. Expression seen in small islands around the neck and back at 14.5 dpc, then in large masses at 16.5 dpc and 18.5 dpc and at P14 is absent in brown adipose tissue. Expression also seen in the thymus and developing gut at 14.5 dpc and until postnatal life. At P14, expression in thymus is restricted to the proliferating cells in the cortical zone and is also prominent in the spleen. Found in the lung at 14.5 dpc. 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 (By similarity). Loss of cell division and lethal in fibroblasts. Belongs to the frataxin family.