title: Novel features of the ISC machinery revealed by characterization of Escherichia coli mutants that survive without iron-sulfur clusters.
abstract: Biological assembly of iron-sulfur (Fe-S) clusters is mediated by complex systems consisting of multiple proteins. Escherichia coli possesses two distinct systems called the ISC and SUF machineries encoded by iscSUA-hscBA-fdx-iscX and sufABCDSE respectively. Deletion of both pathways results in absence of the biosynthetic apparatus for Fe-S clusters, and consequent lethality, which has hampered detailed genetic studies. Here we report that modification of the isoprenoid biosynthetic pathway can offset the indispensability of the Fe-S cluster biosynthetic systems and show that the resulting Δisc Δsuf double mutants can grow without detectable Fe-S cluster-containing proteins. We also constructed a series of mutants in which each isc gene was disrupted in the deletion background of sufABCDSE. Phenotypic analysis of the mutants revealed that Fdx, an essential electron-transfer Fe-S protein in the ISC machinery, is dispensable under anaerobic conditions, which is similar to the situation with IscA. Furthermore, we found that several suppressor mutations in IscU, an Fe-S scaffold protein responsible for the de novo Fe-S cluster assembly, could bypass the essential role of the chaperone system HscA and HscB. These findings pave the way toward a detailed molecular analysis to understand the mechanisms involved in Fe-S cluster biosynthesis.
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Naoyuki
authors.initials: N
authors.lastname: Tanaka
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Miaki
authors.initials: M
authors.lastname: Kanazawa
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tonosaki
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Nao
authors.initials: N
authors.lastname: Yokoyama
authors.affiliation: Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Kuzuyama
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama, 338-8570, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Takahashi
mesh_terms: D053898:Biosynthetic Pathways; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000378:metabolism; D056726:Genetic Association Studies; D007501:Iron / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000235:genetics* / Q000378:metabolism*; D005810:Multigene Family; D009154:Mutation; D013455:Sulfur / Q000378:metabolism; D013729:Terpenes / Q000378:metabolism
chemical_list: D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; D013729:Terpenes; D013455:Sulfur; D007501:Iron