title: Mobilization of the iron centre in IscA for the iron-sulphur cluster assembly in IscU.
abstract: The biogenesis of iron-sulphur clusters requires the co-ordinated delivery of both iron and sulphur. It is now clear that sulphur in iron-sulphur clusters is derived from L-cysteine by cysteine desulphurases. However, the iron donor for the iron-sulphur cluster assembly still remains elusive. Our previous studies indicated that Escherichia coli IscA, a member of the iron-sulphur cluster assembly machinery, is an iron-binding protein that can provide iron for the iron-sulphur cluster assembly in a proposed scaffold IscU. To determine how the iron centre in IscA is transferred for the iron-sulphur cluster assembly in IscU, we explore the mobility of the iron centre in IscA. The UV-visible and EPR measurements show that L-cysteine, but not IscU, is able to mobilize the iron centre in IscA and make the iron available for the iron-sulphur cluster assembly in IscU. Other related biological thiols such as N-acetyl-L-cysteine or reduced glutathione have no effect on the iron centre of IscA, suggesting that L-cysteine is unique in mobilizing the iron centre of IscA. Nevertheless, L-cysteine alone is not sufficient to transfer the iron from IscA to IscU. Both L-cysteine and cysteine desulphurase (IscS) are required for the IscA-mediated assembly of iron-sulphur clusters in IscU. The results suggest that L-cysteine may have two distinct functions in the biogenesis of iron-sulphur clusters: to mobilize the iron centre in IscA and to provide sulphur via cysteine desulphurase (IscS) for the iron-sulphur cluster assembly in IscU.
authors.affiliation: Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
authors.forename: Baojin
authors.initials: B
authors.lastname: Ding
authors.forename: Edward S
authors.initials: ES
authors.lastname: Smith
authors.forename: Huangen
authors.initials: H
authors.lastname: Ding
mesh_terms: D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry / Q000502:physiology*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis* / Q000737:chemistry
chemical_list: D002352:Carrier Proteins; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; C487901:IscA protein, E coli; C411665:IscU protein, E coli; D007501:Iron; D003545:Cysteine