Iron-sulfur cluster biosynthesis: characterization of iron nucleation sites for assembly of the [2Fe-2S]2+ cluster core in IscU proteins.
ISU (eukaryotes) and IscU (prokaryotes) are a homologous family of proteins that appear to provide a platform for assembly of [2Fe-2S] centers prior to delivery to a target apoprotein. The intermediate [2Fe-2S] IscU-bound cluster is formed by delivery of iron and sulfur to the apo-IscU, with the latter delivered through an IscS-mediated reaction. The identity of the iron donor is not yet established. In this report we characterize iron-binding sites on IscU that appear to nucleate [2Fe-2S] cluster assembly. This iron-bound form of IscU is shown to be viable for subsequent IscS-mediated assembly of holo-IscU. Following on recent reports, we demonstrate the persulfide form of IscU to be a dead-end complex that is incapable of forming holoprotein after addition of ferrous or ferric ion. The latter observation reflects the low binding affinity of persulfido IscU for iron ion.
Evans Laboratory of Chemistry, The Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
Manunya
M
Nuth
Taejin
T
Yoon
J A
JA
Cowan
D001426:Bacterial Proteins / Q000096:biosynthesis*; D002151:Calorimetry; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins / Q000096:biosynthesis*; D007700:Kinetics; D011485:Protein Binding; D013050:Spectrometry, Fluorescence; D020124:Thermotoga maritima / Q000378:metabolism*
D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D007506:Iron-Sulfur Proteins; C411665:IscU protein, E coli; C080001:nifS protein, Bacteria