title: The Structure of the Complex between Yeast Frataxin and Ferrochelatase: CHARACTERIZATION AND PRE-STEADY STATE REACTION OF FERROUS IRON DELIVERY AND HEME SYNTHESIS.
abstract: Frataxin is a mitochondrial iron-binding protein involved in iron storage, detoxification, and delivery for iron sulfur-cluster assembly and heme biosynthesis. The ability of frataxin from different organisms to populate multiple oligomeric states in the presence of metal ions, e.g. Fe(2+) and Co(2+), led to the suggestion that different oligomers contribute to the functions of frataxin. Here we report on the complex between yeast frataxin and ferrochelatase, the terminal enzyme of heme biosynthesis. Protein-protein docking and cross-linking in combination with mass spectroscopic analysis and single-particle reconstruction from negatively stained electron microscopic images were used to verify the Yfh1-ferrochelatase interactions. The model of the complex indicates that at the 2:1 Fe(2+)-to-protein ratio, when Yfh1 populates a trimeric state, there are two interaction interfaces between frataxin and the ferrochelatase dimer. Each interaction site involves one ferrochelatase monomer and one frataxin trimer, with conserved polar and charged amino acids of the two proteins positioned at hydrogen-bonding distances from each other. One of the subunits of the Yfh1 trimer interacts extensively with one subunit of the ferrochelatase dimer, contributing to the stability of the complex, whereas another trimer subunit is positioned for Fe(2+) delivery. Single-turnover stopped-flow kinetics experiments demonstrate that increased rates of heme production result from monomers, dimers, and trimers, indicating that these forms are most efficient in delivering Fe(2+) to ferrochelatase and sustaining porphyrin metalation. Furthermore, they support the proposal that frataxin-mediated delivery of this potentially toxic substrate overcomes formation of reactive oxygen species.
authors.affiliation: From the Center for Molecular Protein Science, Department of Chemistry, Lund University, SE-221 00 Lund, Sweden.
authors.forename: Christopher
authors.initials: C
authors.lastname: Söderberg
authors.affiliation: Department of Molecular Medicine, Morsani College of Medicine and.
authors.forename: Mallory E
authors.initials: ME
authors.lastname: Gillam
authors.affiliation: From the Center for Molecular Protein Science, Department of Chemistry, Lund University, SE-221 00 Lund, Sweden.
authors.forename: Eva-Christina
authors.initials: EC
authors.lastname: Ahlgren
authors.affiliation: Department of Molecular Medicine, Morsani College of Medicine and.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Hunter
authors.affiliation: the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905.
authors.forename: Oleksandr
authors.initials: O
authors.lastname: Gakh
authors.affiliation: the Departments of Pediatric and Adolescent Medicine and Biochemistry and Molecular Biology, Mayo Clinic, College of Medicine, Rochester, Minnesota 55905.
authors.forename: Grazia
authors.initials: G
authors.lastname: Isaya
authors.affiliation: Department of Molecular Medicine, Morsani College of Medicine and the Department of Chemistry, University of South Florida, Tampa, Florida 33612, and gferreir@health.usf.edu.
authors.forename: Gloria C
authors.initials: GC
authors.lastname: Ferreira
authors.affiliation: From the Center for Molecular Protein Science, Department of Chemistry, Lund University, SE-221 00 Lund, Sweden, salam.al-karadaghi@biochemistry.lu.se.
authors.forename: Salam
authors.initials: S
authors.lastname: Al-Karadaghi
mesh_terms: D018360:Crystallography, X-Ray; D005294:Ferrochelatase / Q000737:chemistry* / Q000378:metabolism*; D006418:Heme / Q000096:biosynthesis*; D007501:Iron / Q000378:metabolism*; D033862:Iron-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D007700:Kinetics; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation; D012441:Saccharomyces cerevisiae / Q000254:growth & development / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D000096923:Frataxin
chemical_list: D005294:Ferrochelatase; D006418:Heme; D007501:Iron; D033862:Iron-Binding Proteins; D000096923:Frataxin
keywords: Friedreich ataxia; ataxia; ferrochelatase; frataxin; heme; iron chaperone; iron trafficking; iron-sulfur protein; mitochondria; protoporphyrin