title: Mössbauer studies of Escherichia coli biotin synthase: evidence for reversible interconversion between [2Fe-2S](2+) and [4Fe-4S](2+) clusters.
abstract: The nature and properties of the iron-sulphur (Fe-S) cluster in as-prepared and reduced biotin synthase of Escherichia coli have been investigated by Mössbauer spectroscopy. Our data clearly demonstrate that in the as-prepared sample, the cluster is present as [2Fe-2S](2+) with isomer shift, delta = 0.29 mm/s and quadrupole splitting, DeltaE(Q) = 0.53 mm/s, indicating incomplete cysteinyl-S coordination. Anaerobic reduction by dithionite in the presence of 55% (v/v) glycerol converts this form to [4Fe-4S](2+) (delta = 0.45 mm/s and DeltaE(Q) = 1.11 mm/s) and is accompanied by some destruction to Fe(2+). This cluster conversion is reversible and when exposed to air, the [4Fe-4S](2+) cluster is quantitatively reconverted to the [2Fe-2S](2+) cluster without any further cluster degradation.
authors.affiliation: Laboratoire de Chimie Organique et Biologique, Université Paris VI - CNRS UMR 7613, 4 place Jussieu, 75252, Paris, France.
authors.forename: B
authors.initials: B
authors.lastname: Tse Sum Bui
authors.forename: D
authors.initials: D
authors.lastname: Florentin
authors.forename: A
authors.initials: A
authors.lastname: Marquet
authors.forename: R
authors.initials: R
authors.lastname: Benda
authors.forename: A X
authors.initials: AX
authors.lastname: Trautwein
mesh_terms: D000388:Air; D004926:Escherichia coli / Q000201:enzymology*; D007501:Iron / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000378:metabolism; D015204:Spectroscopy, Mossbauer; D013466:Sulfurtransferases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007506:Iron-Sulfur Proteins; D007501:Iron; D013466:Sulfurtransferases; C057985:biotin synthetase