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Here we show that the yeast mitochondrial chaperone Ssc2p, a homolog of mt-Hsp70, plays a critical role in mitochondrial iron homeostasis. Yeast withssc2-1 mutations were identified by a screen for altered iron-dependent gene regulation and mitochondrial dysfunction. These mutants exhibit increased cellular iron uptake, and the iron accumulates exclusively within mitochondria. Yfh1p is homologous to frataxin, the human protein implicated in the neurodegenerative disease, Friedreich's ataxia. Like mutants ofyfh1, ssc2-1 mutants accumulate vast quantities of iron in mitochondria. Furthermore, using import studies with isolated mitochondria, we demonstrate a specific role for Ssc2p in the maturation of Yfh1p within this organelle. This function for a mitochondrial Hsp70 chaperone is likely to be conserved, implying that a human homolog of Ssc2p may be involved in iron homeostasis and in neurodegenerative …