title: Deletion of the Proposed Iron Chaperones IscA/SufA Results in Accumulation of a Red Intermediate Cysteine Desulfurase IscS in Escherichia coli.
abstract: In Escherichia coli, sulfur in iron-sulfur clusters is primarily derived from L-cysteine via the cysteine desulfurase IscS. However, the iron donor for iron-sulfur cluster assembly remains elusive. Previous studies have shown that, among the iron-sulfur cluster assembly proteins in E. coli, IscA has a unique and strong iron-binding activity and that the iron-bound IscA can efficiently provide iron for iron-sulfur cluster assembly in proteins in vitro, indicating that IscA may act as an iron chaperone for iron-sulfur cluster biogenesis. Here we report that deletion of IscA and its paralog SufA in E. coli cells results in the accumulation of a red-colored cysteine desulfurase IscS under aerobic growth conditions. Depletion of intracellular iron using a membrane-permeable iron chelator, 2,2'-dipyridyl, also leads to the accumulation of red IscS in wild-type E. coli cells, suggesting that the deletion of IscA/SufA may be emulated by depletion of intracellular iron. Purified red IscS has an absorption peak at 528 nm in addition to the peak at 395 nm of pyridoxal 5'-phosphate. When red IscS is oxidized by hydrogen peroxide, the peak at 528 nm is shifted to 510 nm, which is similar to that of alanine-quinonoid intermediate in cysteine desulfurases. Indeed, red IscS can also be produced in vitro by incubating wild-type IscS with excess L-alanine and sulfide. The results led us to propose that deletion of IscA/SufA may disrupt the iron delivery for iron-sulfur cluster biogenesis, therefore impeding sulfur delivery by IscS, and result in the accumulation of red IscS in E. coli cells.
authors.affiliation: From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803.
authors.forename: Jing
authors.initials: J
authors.lastname: Yang
authors.affiliation: From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, the Laboratory of Molecular Medicine, Wenzhou Medical University, Wenzhou, Zhejiang 325035, China.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Tan
authors.affiliation: the Laboratory of Molecular Medicine, Wenzhou Medical University, Wenzhou, Zhejiang 325035, China.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhang
authors.affiliation: the Department of Biochemistry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, and.
authors.forename: Robert H
authors.initials: RH
authors.lastname: White
authors.affiliation: the Laboratory of Molecular Medicine, Wenzhou Medical University, Wenzhou, Zhejiang 325035, China jxlu313@163.com.
authors.forename: Jianxin
authors.initials: J
authors.lastname: Lu
authors.affiliation: From the Department of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, hding@lsu.edu.
authors.forename: Huangen
authors.initials: H
authors.lastname: Ding
mesh_terms: D000409:Alanine / Q000737:chemistry; D013437:Carbon-Sulfur Lyases / Q000235:genetics* / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D017353:Gene Deletion; D007501:Iron / Q000737:chemistry; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D011732:Pyridoxal Phosphate / Q000737:chemistry; D011994:Recombinant Proteins / Q000378:metabolism; D013440:Sulfides / Q000737:chemistry
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; C487901:IscA protein, E coli; D018832:Molecular Chaperones; D011994:Recombinant Proteins; C499169:SufA protein, E coli; D013440:Sulfides; D011732:Pyridoxal Phosphate; D007501:Iron; D013437:Carbon-Sulfur Lyases; C080546:cysteine desulfurase; D003545:Cysteine; D000409:Alanine
keywords: enzyme mechanism; iron metabolism; iron-sulfur protein; metalloenzyme; pyridoxal phosphate; sulfur