title: Human Mitochondrial Ferredoxin 1 (FDX1) and Ferredoxin 2 (FDX2) Both Bind Cysteine Desulfurase and Donate Electrons for Iron-Sulfur Cluster Biosynthesis.
abstract: Ferredoxins play an important role as an electron donor in iron-sulfur (Fe-S) cluster biosynthesis. Two ferredoxins, human mitochondrial ferredoxin 1 (FDX1) and human mitochondrial ferredoxin 2 (FDX2), are present in the matrix of human mitochondria. Conflicting results have been reported regarding their respective function in mitochondrial iron-sulfur cluster biogenesis. We report here biophysical studies of the interaction of these two ferredoxins with other proteins involved in mitochondrial iron-sulfur cluster assembly. Results from nuclear magnetic resonance spectroscopy show that both FDX1 and FDX2 (in both their reduced and oxidized states) interact with the protein complex responsible for cluster assembly, which contains cysteine desulfurase (NFS1), ISD11 (also known as LYRM4), and acyl carrier protein (Acp). In all cases, ferredoxin residues close to the Fe-S cluster are involved in the interaction with this complex. Isothermal titration calorimetry results showed that FDX2 binds more tightly to the cysteine desulfurase complex than FDX1 does. The reduced form of each ferredoxin became oxidized in the presence of the cysteine desulfurase complex when l-cysteine was added, leading to its conversion to l-alanine and the generation of sulfide. In an in vitro reaction, the reduced form of each ferredoxin was found to support Fe-S cluster assembly on ISCU; the rate of cluster assembly was faster with FDX2 than with FDX1. Taken together, these results show that both FDX1 and FDX2 can function in Fe-S cluster assembly in vitro.
authors.affiliation: Mitochondrial Protein Partnership, Center for Eukaryotic Structural Genomics, and ‡National Magnetic Resonance Facility at Madison, Biochemistry Department, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Kai
authors.initials: K
authors.lastname: Cai
authors.affiliation: Mitochondrial Protein Partnership, Center for Eukaryotic Structural Genomics, and ‡National Magnetic Resonance Facility at Madison, Biochemistry Department, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Marco
authors.initials: M
authors.lastname: Tonelli
authors.affiliation: Mitochondrial Protein Partnership, Center for Eukaryotic Structural Genomics, and ‡National Magnetic Resonance Facility at Madison, Biochemistry Department, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Ronnie O
authors.initials: RO
authors.lastname: Frederick
authors.affiliation: Mitochondrial Protein Partnership, Center for Eukaryotic Structural Genomics, and ‡National Magnetic Resonance Facility at Madison, Biochemistry Department, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: John L
authors.identifier: 0000-0003-1799-6134
authors.initials: JL
authors.lastname: Markley
mesh_terms: D000213:Acyl Carrier Protein / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D013437:Carbon-Sulfur Lyases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D003545:Cysteine; D004583:Electrons; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005288:Ferredoxins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D007501:Iron / Q000737:chemistry* / Q000378:metabolism; D033862:Iron-Binding Proteins / Q000235:genetics / Q000378:metabolism; D035925:Iron-Regulatory Proteins / Q000235:genetics / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D010084:Oxidation-Reduction; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013455:Sulfur / Q000737:chemistry* / Q000378:metabolism; D000096923:Frataxin
chemical_list: D000213:Acyl Carrier Protein; D013437:Carbon-Sulfur Lyases; D003545:Cysteine; D005288:Ferredoxins; D007501:Iron; D033862:Iron-Binding Proteins; D035925:Iron-Regulatory Proteins; D007506:Iron-Sulfur Proteins; D011994:Recombinant Proteins; D013455:Sulfur; D000096923:Frataxin; C506160:ISCU protein, human; C544445:LYRM4 protein, human; C513492:NFS1 protein, human