Functional and molecular characterization of the frataxin homolog from Arabidopsis thaliana.

Frataxin is a highly conserved protein from bacteria to mammals that has been proposed to participate in iron-sulfur cluster assembly and mitochondrial iron homeostasis. In higher organisms, the frataxin gene is nuclear-encoded and the protein is required for maintenance of normal mitochondrial iron levels and respiration. We describe here AtFH, a plant gene with significant homology to other members of the frataxin family. Plant frataxin has five segments of beta regions and two alpha helices, which are characteristics of human frataxin, as well as a potential N-terminal targeting peptide for the mitochondrial localization. Transcription analysis showed that AtFH is ubiquitously expressed with high levels in flowers. Complementation of a Saccharomyces cerevisiae mutant (Deltayfh) lacking the frataxin gene proved that AtFH is a functional protein, because it restored normal rates of respiration, growth and sensitivity to H2O2 of the null mutant. Our results support the involvement of AtFH in mitochondrial respiration and survival during oxidative stress in plants. This is the first report of a functional frataxin gene in plants.