title: Reaction of cyanide with cytochrome ba3 from Thermus thermophilus: spectroscopic characterization of the Fe(II)a3-CN.Cu(II)B-CN complex suggests four 14N atoms are coordinated to CuB.
abstract: Cytochrome ba3 from Thermus thermophilus reacts slowly with excess HCN at pH 7.4 to create a form of the enzyme in which CuA, cytochrome b, and CuB remain oxidized, while cytochrome a3 is reduced by one electron, presumably with the formation of cyanogen. We have examined this form of the enzyme by UV-visible, resonance Raman, EPR, and electron nuclear double resonance spectroscopies in conjunction with permutations of 13C- and 15N-labeled cyanide. The results support a model in which one CN- binds through the carbon atom to ferrous a3, supporting a low-spin (S = 0) configuration on the Fe; bridging by this cyanide to the CuB is weak or absent. Four 14N atoms, presumably donated by histidine residues of the protein, provide a strong equatorial ligand field about CuB; a second CN- is coordinated through the carbon atom to CuB in an axial position.
authors.affiliation: Isotope and Structural Chemistry Group, University of California.
authors.forename: K K
authors.initials: KK
authors.lastname: Surerus
authors.forename: W A
authors.initials: WA
authors.lastname: Oertling
authors.forename: C
authors.initials: C
authors.lastname: Fan
authors.forename: R J
authors.initials: RJ
authors.lastname: Gurbiel
authors.forename: O
authors.initials: O
authors.lastname: Einarsdóttir
authors.forename: W E
authors.initials: WE
authors.lastname: Antholine
authors.forename: R B
authors.initials: RB
authors.lastname: Dyer
authors.forename: B M
authors.initials: BM
authors.lastname: Hoffman
authors.forename: W H
authors.initials: WH
authors.lastname: Woodruff
authors.forename: J A
authors.initials: JA
authors.lastname: Fee
mesh_terms: D001665:Binding Sites; D003300:Copper / Q000378:metabolism*; D003486:Cyanides / Q000378:metabolism*; D003573:Cytochrome b Group / Q000302:isolation & purification / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV / Q000302:isolation & purification / Q000378:metabolism*; D006418:Heme / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D009584:Nitrogen; D011487:Protein Conformation; D013053:Spectrophotometry; D013059:Spectrum Analysis, Raman; D016963:Thermus thermophilus / Q000378:metabolism*
chemical_list: D003486:Cyanides; D003573:Cytochrome b Group; D006418:Heme; D003300:Copper; D007501:Iron; C058557:cytochrome ba3; D003576:Electron Transport Complex IV; D009584:Nitrogen