title: [4Fe-4S]-cluster-depleted Azotobacter vinelandii ferredoxin I: a new 3Fe iron-sulfur protein.
abstract: Fe(CN)6(-3) oxidation of the aerobically isolated 7Fe Azotobacter vinelandii ferredoxin I, (7Fe)FdI, is a degradative reaction. Destruction of the [4Fe-4S] cluster occurs first, followed by destruction of the [3Fe-3S] cluster. At a Fe(CN)6(-3)/(7Fe)FdI concentration ratio of 20, the product is a mixture of apoprotein and protein containing only a [3Fe-3S] cluster, (3Fe)FdI. This protein mixture, after partial purification, has been characterized by absorption, CD, magnetic CD, and EPR and Fe x-ray absorption spectroscopies. EPR and magnetic CD spectra provide strong evidence that the [3Fe-3S] cluster in (3Fe)FdI is essentially identical in structure to that in (7Fe)FdI. Analysis of the extended x-ray absorption fine structure (EXAFS) of (3Fe)FdI finds Fe scattering at an average Fe...Fe distance of approximately equal to 2.7 A. The structure of the oxidized [3Fe-3S] cluster in solutions of oxidized (3Fe)FdI, and, by extension, of oxidized (7Fe)FdI, is thus different from that obtained by x-ray crystallography on oxidized (7Fe)FdI. Possible interpretations of this result are discussed.
authors.forename: P J
authors.initials: PJ
authors.lastname: Stephens
authors.forename: T V
authors.initials: TV
authors.lastname: Morgan
authors.forename: F
authors.initials: F
authors.lastname: Devlin
authors.forename: J E
authors.initials: JE
authors.lastname: Penner-Hahn
authors.forename: K O
authors.initials: KO
authors.lastname: Hodgson
authors.forename: R A
authors.initials: RA
authors.lastname: Scott
authors.forename: C D
authors.initials: CD
authors.lastname: Stout
authors.forename: B K
authors.initials: BK
authors.lastname: Burgess
mesh_terms: D001395:Azotobacter / Q000032:analysis*; D002942:Circular Dichroism; D004578:Electron Spin Resonance Spectroscopy; D005288:Ferredoxins / Q000032:analysis*; D005292:Ferricyanides; D007506:Iron-Sulfur Proteins / Q000032:analysis*; D008667:Metalloproteins / Q000032:analysis*; D010084:Oxidation-Reduction; D013053:Spectrophotometry; D013054:Spectrophotometry, Atomic
chemical_list: D005288:Ferredoxins; D005292:Ferricyanides; D007506:Iron-Sulfur Proteins; D008667:Metalloproteins