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| Subject Categories: Cellular Metabolism |
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| The EMBO Journal
(2003) 22, 4815–4825, doi:10.1093/emboj/cdg446 |
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| Components involved in assembly and dislocation of iron–sulfur clusters on the scaffold protein Isu1p |
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| Ulrich Mühlenhoff, Jana Gerber, Nadine Richhardt and Roland Lill |
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Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Robert-Koch Stra e 6, D-35033 Marburg, GermanyTo whom correspondence should be addressed Roland Lill, Lill@mailer.uni-marburg.de Received 31 March 2003; Revised 30 June 2003; Accepted 22 July 2003. |
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| Abstract |
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| The mitochondrial proteins Isu1p and Isu2p play an essential role in the maturation of cellular iron–sulfur (Fe/S) proteins in eukaryotes. By radiolabelling of yeast cells with 55Fe we demonstrate that Isu1p binds an oxygen-resistant non-chelatable Fe/S cluster providing in vivo evidence for a scaffolding function of Isu1p during Fe/S cluster assembly. Depletion of the cysteine desulfurase Nfs1p, the ferredoxin Yah1p or the yeast frataxin homologue Yfh1p by regulated gene expression causes a strong decrease in the de novo synthesis of Fe/S clusters on Isu1p. In contrast, depletion of the Hsp70 chaperone Ssq1p, its co-chaperone Jac1p or the glutaredoxin Grx5p markedly increased the amount of Fe/S clusters bound to Isu1p, even though these mitochondrial proteins are crucial for maturation of Fe/S proteins. Hence Ssq1p/Jac1p and Grx5p are required in a step after Fe/S cluster synthesis on Isu1p, for instance in dissociation of preassembled Fe/S clusters from Isu1p and/or their insertion into apoproteins. We propose a model that dissects Fe/S cluster biogenesis into two major steps and assigns its central components to one of these two steps. |
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| Keywords: chaperones, ferredoxin, glutaredoxin, iron–sulfur proteins, mitochondria |
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