title: Iron-sulfur interconversions in the anaerobic ribonucleotide reductase from Escherichia coli.
abstract: The anaerobic ribonucleotide reductase from Escherichia coli contains an iron-sulfur cluster which, in the reduced [4Fe-4S](+) form, serves to reduce S-adenosylmethionine and to generate a catalytically essential glycyl radical. The reaction of the reduced cluster with oxygen was studied by UV-visible, EPR, NMR, and Mössbauer spectroscopies. The [4Fe-4S](+) form is shown to be extremely sensitive to oxygen and converted to [4Fe-4S](2+), [3Fe-4S](+/0), and to the stable [2Fe-2S](2+) form. It is remarkable that the oxidized protein retains full activity. This is probably due to the fact that during reduction, required for activity, the iron atoms, from 2Fe and 3Fe clusters, readily reassemble to generate an active [4Fe-4S] center. This property is discussed as a possible protective mechanism of the enzyme during transient exposure to air. Furthermore, the [2Fe-2S] form of the protein can be converted into a [3Fe-4S] form during chromatography on dATP-Sepharose, explaining why previous preparations of the enzyme were shown to contain large amounts of such a 3Fe cluster. This is the first report of a 2Fe to 3Fe cluster conversion.
authors.affiliation: Laboratoire de Chimie et Biochimie des Centres Rédox Biologiques, DBMS-CB, CEA/CNRS/Université Joseph Fourier 17 Avenue des Martyrs, F-38054 Grenoble Cedex 09, France. mulliez@cbcrb.ceng.cea.fr
authors.forename: E
authors.initials: E
authors.lastname: Mulliez
authors.forename: S
authors.initials: S
authors.lastname: Ollagnier-de Choudens
authors.forename: C
authors.initials: C
authors.lastname: Meier
authors.forename: M
authors.initials: M
authors.lastname: Cremonini
authors.forename: C
authors.initials: C
authors.lastname: Luchinat
authors.forename: A X
authors.initials: AX
authors.lastname: Trautwein
authors.forename: M
authors.initials: M
authors.lastname: Fontecave
mesh_terms: D000693:Anaerobiosis; D004578:Electron Spin Resonance Spectroscopy; D004926:Escherichia coli / Q000201:enzymology*; D007501:Iron / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D010084:Oxidation-Reduction; D012264:Ribonucleotide Reductases / Q000737:chemistry / Q000378:metabolism*; D015204:Spectroscopy, Mossbauer; D013455:Sulfur / Q000378:metabolism*
chemical_list: D013455:Sulfur; D007501:Iron; D012264:Ribonucleotide Reductases