title: IscA/SufA paralogues are required for the [4Fe-4S] cluster assembly in enzymes of multiple physiological pathways in Escherichia coli under aerobic growth conditions.
abstract: IscA/SufA paralogues are the members of the iron-sulfur cluster assembly machinery in Escherichia coli. Whereas deletion of either IscA or SufA has only a mild effect on cell growth, deletion of both IscA and SufA results in a null-growth phenotype in minimal medium under aerobic growth conditions. Here we report that cell growth of the iscA/sufA double mutant (E. coli strain in which both iscA and sufA had been in-frame-deleted) can be partially restored by supplementing with BCAAs (branched-chain amino acids) and thiamin. We further demonstrate that deletion of IscA/SufA paralogues blocks the [4Fe-4S] cluster assembly in IlvD (dihydroxyacid dehydratase) of the BCAA biosynthetic pathway in E. coli cells under aerobic conditions and that addition of the iron-bound IscA/SufA efficiently promotes the [4Fe-4S] cluster assembly in IlvD and restores the enzyme activity in vitro, suggesting that IscA/SufA may act as an iron donor for the [4Fe-4S] cluster assembly under aerobic conditions. Additional studies reveal that IscA/SufA are also required for the [4Fe-4S] cluster assembly in enzyme ThiC of the thiamin-biosynthetic pathway, aconitase B of the citrate acid cycle and endonuclease III of the DNA-base-excision-repair pathway in E. coli under aerobic conditions. Nevertheless, deletion of IscA/SufA does not significantly affect the [2Fe-2S] cluster assembly in the redox transcription factor SoxR, ferredoxin and the siderophore-iron reductase FhuF. The results suggest that the biogenesis of the [4Fe-4S] clusters and the [2Fe-2S] clusters may have distinct pathways and that IscA/SufA paralogues are essential for the [4Fe-4S] cluster assembly, but are dispensable for the [2Fe-2S] cluster assembly in E. coli under aerobic conditions.
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, U.S.A.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Tan
authors.forename: Jianxin
authors.initials: J
authors.lastname: Lu
authors.forename: Jacob P
authors.initials: JP
authors.lastname: Bitoun
authors.forename: Hao
authors.initials: H
authors.lastname: Huang
authors.forename: Huangen
authors.initials: H
authors.lastname: Ding
mesh_terms: D000332:Aerobiosis; D000597:Amino Acids, Branched-Chain / Q000096:biosynthesis / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D006836:Hydro-Lyases / Q000235:genetics / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D013831:Thiamine / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D000597:Amino Acids, Branched-Chain; D001426:Bacterial Proteins; D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; C487901:IscA protein, E coli; C499169:SufA protein, E coli; D014157:Transcription Factors; C070724:SoxR protein, Bacteria; D007501:Iron; D006836:Hydro-Lyases; C020052:dihydroxyacid dehydratase; D013831:Thiamine