title: Copper binding in IscA inhibits iron-sulphur cluster assembly in Escherichia coli.
abstract: Among the iron-sulphur cluster assembly proteins encoded by gene cluster iscSUA-hscBA-fdx in Escherichia coli, IscA has a unique and strong iron binding activity and can provide iron for iron-sulphur cluster assembly in proteins in vitro. Deletion of IscA and its paralogue SufA results in an E. coli mutant that fails to assemble [4Fe-4S] clusters in proteins under aerobic conditions, suggesting that IscA has a crucial role for iron-sulphur cluster biogenesis. Here we report that among the iron-sulphur cluster assembly proteins, IscA also has a strong and specific binding activity for Cu(I) in vivo and in vitro. The Cu(I) centre in IscA is stable and resistant to oxidation under aerobic conditions. Mutation of the conserved cysteine residues that are essential for the iron binding in IscA abolishes the copper binding activity, indicating that copper and iron may share the same binding site in the protein. Additional studies reveal that copper can compete with iron for the metal binding site in IscA and effectively inhibits the IscA-mediated [4Fe-4S] cluster assembly in E. coli cells. The results suggest that copper may not only attack the [4Fe-4S] clusters in dehydratases, but also block the [4Fe-4S] cluster assembly in proteins by targeting IscA in cells.
authors.affiliation: Laboratory of Molecular Medicine, School of Laboratory Medicine and Life Science, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China; Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Tan
authors.forename: Zishuo
authors.initials: Z
authors.lastname: Cheng
authors.forename: Yilin
authors.initials: Y
authors.lastname: Pang
authors.forename: Aaron P
authors.initials: AP
authors.lastname: Landry
authors.forename: Jianghui
authors.initials: J
authors.lastname: Li
authors.forename: Jianxin
authors.initials: J
authors.lastname: Lu
authors.forename: Huangen
authors.initials: H
authors.lastname: Ding
mesh_terms: D019943:Amino Acid Substitution; D001665:Binding Sites; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003300:Copper / Q000378:metabolism*; D004252:DNA Mutational Analysis; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D011485:Protein Binding
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; C487901:IscA protein, E coli; D003300:Copper; D007501:Iron