title: Formation of a stable cyano-bridged dinuclear iron cluster following oxidation of the superoxide reductases from Treponema pallidum and Desulfovibrio vulgaris with K(3)Fe(CN)(6).
abstract: Superoxide reductases catalyze the monovalent reduction of superoxide anion to hydrogen peroxide. Spectroscopic evidence for the formation of a dinuclear cyano-bridged adduct after K(3)Fe(CN)(6) oxidation of the superoxide reductases neelaredoxin from Treponema pallidum and desulfoferrodoxin from Desulfovibrio vulgaris was reported. Oxidation with K(3)Fe(CN)(6) reveals a band in the near-IR with lambda(max) at 1020 nm, coupled with an increase of the iron content by almost 2-fold. Fourier transform infrared spectroscopy provided additional evidence with CN-stretching vibrations at 2095, 2025-2030, and 2047 cm(-)(1), assigned to a ferrocyanide adduct of the enzyme. Interestingly, the low-temperature electronic paramagnetic resonance (EPR) spectra of oxidized TpNlr reveal at least three different species indicating structural heterogeneity in the coordination environment of the active site Fe ion. Given the likely 6-coordinate geometry of the active site Fe(3+) ion in the ferrocyanide adduct, we propose that the rhombic EPR species can serve as a model of a hexacoordinate form of the active site.
authors.affiliation: Section of Hematology Research, Department of Biochemistry, Biomedical Mass Spectrometry Facility, Mayo Clinic, Rochester, Minnesota 55905, USA.
authors.forename: Françoise
authors.initials: F
authors.lastname: Auchère
authors.forename: Patrícia
authors.initials: P
authors.lastname: Raleiras
authors.forename: Linda
authors.initials: L
authors.lastname: Benson
authors.forename: Sergei Yu
authors.initials: SY
authors.lastname: Venyaminov
authors.forename: Pedro
authors.initials: P
authors.lastname: Tavares
authors.forename: José J G
authors.initials: JJ
authors.lastname: Moura
authors.forename: Isabel
authors.initials: I
authors.lastname: Moura
authors.forename: Frank
authors.initials: F
authors.lastname: Rusnak
mesh_terms: D001426:Bacterial Proteins; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D002384:Catalysis; D016969:Desulfovibrio vulgaris / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D005292:Ferricyanides / Q000378:metabolism*; D007501:Iron / Q000737:chemistry* / Q000378:metabolism*; D033862:Iron-Binding Proteins; D008958:Models, Molecular; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000737:chemistry* / Q000378:metabolism*; D013482:Superoxide Dismutase; D014210:Treponema pallidum / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D002352:Carrier Proteins; D005292:Ferricyanides; D033862:Iron-Binding Proteins; D007501:Iron; D010088:Oxidoreductases; C121849:superoxide reductase; D013482:Superoxide Dismutase; C414179:nlr protein, Desulfovibrio gigas; C028033:potassium ferricyanide