Fe-S cluster biogenesis in isolated mammalian mitochondria: coordinated use of persulfide sulfur and iron, and requirements for GTP, NADH, and ATP [Cell Biology]

November 14th, 2014 by Pandey, A., Pain, J., Ghosh, A. K., Dancis, A., Pain, D.

Iron-sulfur (Fe-S) clusters are essential cofactors, and mitochondria contain several Fe-S proteins including the [4Fe-4S] protein aconitase and the [2Fe-2S] protein ferredoxin. Fe-S cluster assembly of these proteins occurs within mitochondria. Although considerable data exist for yeast mitochondria, this biosynthetic process has never been directly demonstrated in mammalian mitochondria. Using [35S]cysteine as the source of sulfur, here we show that mitochondria isolated from CAD cells, a murine neuronal cell line, can synthesize and insert new Fe-35S clusters into aconitase and ferredoxins. The process requires GTP, NADH, ATP and iron, and hydrolysis of both GTP and ATP is necessary. Importantly, we have identified the [35S]-labeled persulfide on the NFS1 cysteine desulfurase as a genuine intermediate en route to Fe-S cluster synthesis. In physiological settings, the persulfide sulfur is released from NFS1 and transferred to a scaffold protein, where it combines with iron to form an Fe-S cluster intermediate. We find that the release of persulfide sulfur from NFS1 requires iron, showing that the use of iron and sulfur for the synthesis of Fe-S cluster intermediates is a highly coordinated process. The release of persulfide sulfur also requires GTP and NADH, probably mediated by a GTPase and a reductase, respectively. ATP, a cofactor for a multifunctional Hsp70 chaperone, is not required at this step. The experimental system as described here may help to define the biochemical basis of diseases that are associated with impaired Fe-S cluster biogenesis in mitochondria such as Friedreich's ataxia.
  • Posted in Journal of Biological Chemistry, Publications
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