Journal Article

A non-essential function for yeast frataxin in iron–sulfur cluster assembly

Geoffrey Duby, Françoise Foury, Anna Ramazzotti, Johannes Herrmann and Thomas Lutz

in Human Molecular Genetics

Volume 11, issue 21, pages 2635-2643
Published in print October 2002 | ISSN: 0964-6906
Published online October 2002 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/11.21.2635
A non-essential function for yeast frataxin in iron–sulfur cluster assembly

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Friedreich's ataxia is caused by a deficit in frataxin, a small mitochondrial protein of unknown function that has been conserved during evolution. Previous studies have pointed out a role for frataxin in mitochondrial iron–sulfur (Fe–S) metabolism. Here, we have analyzed the incorporation of Fe–S clusters into yeast ferredoxin imported into isolated energized mitochondria from cells grown in the presence of glycerol, an obligatory respiratory carbon source. Similar amounts of apo-ferredoxin precursor were imported into mitochondria and processed in wild-type and yfh1-deleted (ΔYF111) strains. However, the incorporation of Fe–S clusters into apo-ferredoxin was significantly reduced in ΔYFH1 mitochondria. The newly assembled ferredoxin was stable, excluding the possibility that the decreased incorporation was a result of increased oxidative damage. When ΔYFH1 cells were grown in raffinose medium, the formation of holo-ferredoxin was low, as a consequence of the decrease in ferredoxin precursor import into mitochondria. However, the decrease in the conversion rate of apo- into holo-ferredoxin was in the same range as for glycerol-grown cells, indicating that the extent of the defect in Fe–S protein assembly is similar under different physiological conditions. These data show that frataxin is not essential for Fe–S protein assembly, but improves the efficiency of the process. The large variations observed in the activity of Fe–S cluster proteins under different physiological conditions result from secondary defects in the physiology of ΔYFH1 cells.

Journal Article.  5009 words.  Illustrated.

Subjects: Genetics and Genomics

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