title: Architecture of the Yeast Mitochondrial Iron-Sulfur Cluster Assembly Machinery: THE SUB-COMPLEX FORMED BY THE IRON DONOR, Yfh1 PROTEIN, AND THE SCAFFOLD, Isu1 PROTEIN.
abstract: The biosynthesis of Fe-S clusters is a vital process involving the delivery of elemental iron and sulfur to scaffold proteins via molecular interactions that are still poorly defined. We reconstituted a stable, functional complex consisting of the iron donor, Yfh1 (yeast frataxin homologue 1), and the Fe-S cluster scaffold, Isu1, with 1:1 stoichiometry, [Yfh1]24·[Isu1]24 Using negative staining transmission EM and single particle analysis, we obtained a three-dimensional reconstruction of this complex at a resolution of ∼17 Å. In addition, via chemical cross-linking, limited proteolysis, and mass spectrometry, we identified protein-protein interaction surfaces within the complex. The data together reveal that [Yfh1]24·[Isu1]24 is a roughly cubic macromolecule consisting of one symmetric Isu1 trimer binding on top of one symmetric Yfh1 trimer at each of its eight vertices. Furthermore, molecular modeling suggests that two subunits of the cysteine desulfurase, Nfs1, may bind symmetrically on top of two adjacent Isu1 trimers in a manner that creates two putative [2Fe-2S] cluster assembly centers. In each center, conserved amino acids known to be involved in sulfur and iron donation by Nfs1 and Yfh1, respectively, are in close proximity to the Fe-S cluster-coordinating residues of Isu1. We suggest that this architecture is suitable to ensure concerted and protected transfer of potentially toxic iron and sulfur atoms to Isu1 during Fe-S cluster assembly.
authors.affiliation: From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and.
authors.forename: Wasantha
authors.initials: W
authors.lastname: Ranatunga
authors.affiliation: From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and.
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Gakh
authors.affiliation: From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and.
authors.forename: Belinda K
authors.initials: BK
authors.lastname: Galeano
authors.affiliation: From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and.
authors.forename: Douglas Y
authors.initials: DY
authors.lastname: Smith
authors.affiliation: the Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, SE-221 00 Lund, Sweden.
authors.forename: Christopher A G
authors.initials: CA
authors.lastname: Söderberg
authors.affiliation: the Center for Molecular Protein Science, Institute for Chemistry and Chemical Engineering, Lund University, P. O. Box 124, SE-221 00 Lund, Sweden.
authors.forename: Salam
authors.initials: S
authors.lastname: Al-Karadaghi
authors.affiliation: Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota 55905 and.
authors.forename: James R
authors.initials: JR
authors.lastname: Thompson
authors.affiliation: From the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, and the Mayo Clinic Children's Research Center, and isaya@mayo.edu.
authors.forename: Grazia
authors.initials: G
authors.lastname: Isaya
mesh_terms: D018360:Crystallography, X-Ray; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*; D013455:Sulfur / Q000378:metabolism*; D000096923:Frataxin
chemical_list: D007501:Iron; D033862:Iron-Binding Proteins; D007506:Iron-Sulfur Proteins; D024101:Mitochondrial Proteins; D029701:Saccharomyces cerevisiae Proteins; D013455:Sulfur; D000096923:Frataxin; C121520:ISU1 protein, S cerevisiae
keywords: Friedreich ataxia; frataxin; iron-sulfur protein; mitochondria; protein complex