title: Components involved in assembly and dislocation of iron-sulfur clusters on the scaffold protein Isu1p.
abstract: 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.
authors.affiliation: Institut für Zytobiologie und Zytopathologie, Philipps-Universität Marburg, Robert-Koch Strasse 6, D-35033 Marburg, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Mühlenhoff
authors.forename: Jana
authors.initials: J
authors.lastname: Gerber
authors.forename: Nadine
authors.initials: N
authors.lastname: Richhardt
authors.forename: Roland
authors.initials: R
authors.lastname: Lill
mesh_terms: D000325:Adrenodoxin / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D033862:Iron-Binding Proteins / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins; D008954:Models, Biological; D018832:Molecular Chaperones / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D000096923:Frataxin
chemical_list: D000325:Adrenodoxin; D033862:Iron-Binding Proteins; D007506:Iron-Sulfur Proteins; D024101:Mitochondrial Proteins; D018832:Molecular Chaperones; D029701:Saccharomyces cerevisiae Proteins; D000096923:Frataxin; C121520:ISU1 protein, S cerevisiae; C120375:YAH1 protein, S cerevisiae