Multiple Turnover Transfer of [2Fe2S] Clusters by the Iron-Sulfur Cluster Assembly Scaffold Proteins IscU and IscA
| Autor: | Francesco Bonomi, Larry E. Vickery, Stefania Iametti, Dennis T. Ta |
|---|---|
| Rok vydání: | 2005 |
| Předmět: |
Iron-Sulfur Proteins
Scaffold protein Iron-sulfur cluster assembly Circular dichroism biology Chemistry Circular Dichroism Escherichia coli Proteins Cell Biology medicine.disease_cause Biochemistry Acceptor Catalysis Biophysics Cluster (physics) biology.protein medicine Ferredoxins ISCU Carrier Proteins Molecular Biology Escherichia coli Biogenesis |
| Zdroj: | Journal of Biological Chemistry. 280:29513-29518 |
| ISSN: | 0021-9258 |
| DOI: | 10.1074/jbc.m504344200 |
| Popis: | IscU/Isu and IscA/Isa (and related NifU and SufA proteins) have been proposed to serve as molecular scaffolds for preassembly of [FeS] clusters to be used in the biogenesis of iron-sulfur proteins. In vitro studies demonstrating transfer of preformed scaffold-[FeS] complexes to apoprotein acceptors have provided experimental support for this hypothesis, but investigations to date have yielded only single-cluster transfer events. We describe an in vitro assay system that allows for real-time monitoring of [FeS] cluster formation using circular dichroism spectroscopy and use this to investigate de novo [FeS] cluster formation and transfer from Escherichia coli IscU and IscA to apo-ferredoxin. Both IscU and IscA were found to be capable of multiple cycles of [2Fe2S] cluster formation and transfer suggesting that these scaffold proteins are capable of acting "catalytically." Kinetic studies further showed that cluster transfer exhibits Michaelis-Menten behavior indicative of complex formation of holo-IscU and holo-IscA with apoferredoxin and consistent with a direct [FeS] cluster transfer mechanism. Analysis of the dependence of the rate of cluster transfer, however, revealed enhanced efficiency at low ratios of scaffold to acceptor protein suggesting participation of a transient, labile scaffold-[FeS] species in the transfer process. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|