title: Multi-frequency EPR evidence for a binuclear CuA center in cytochrome c oxidase: studies with a 63Cu- and 65Cu-enriched, soluble domain of the cytochrome ba3 subunit II from Thermus thermophilus.
abstract: We have recorded multi-frequency EPR spectra of 63Cu- and 65Cu-labeled, water-soluble CuA-protein from the cytochrome ba3 of T. thermophilus. The spectrum taken at the highest frequency (34.03 GHz) shows no hyperfine structure and is nominally axial with apparent gz approximately 2.18 and gxy approximately 2.00. The spectrum taken at the lowest frequency (3.93 GHz) shows a rich hyperfine structure. Analyses of the spectra show that the observed splitting arises from an interaction of the unpaired electron with two Cu nuclei and support the notion that CuA is a mixed-valent [Cu(II)/Cu(I)] complex in which the unpaired electronic spin is distributed evenly over the two Cu ions.
authors.affiliation: Department of Biology, University of California at San Diego, La Jolla 92093, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Fee
authors.forename: D
authors.initials: D
authors.lastname: Sanders
authors.forename: C E
authors.initials: CE
authors.lastname: Slutter
authors.forename: P E
authors.initials: PE
authors.lastname: Doan
authors.forename: R
authors.initials: R
authors.lastname: Aasa
authors.forename: M
authors.initials: M
authors.lastname: Karpefors
authors.forename: T
authors.initials: T
authors.lastname: Vänngård
mesh_terms: D001665:Binding Sites; D003300:Copper / Q000032:analysis* / Q000378:metabolism; D003573:Cytochrome b Group / Q000737:chemistry* / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D003576:Electron Transport Complex IV / Q000737:chemistry* / Q000378:metabolism*; D007554:Isotopes; D046911:Macromolecular Substances; D011487:Protein Conformation; D016963:Thermus thermophilus / Q000201:enzymology*
chemical_list: D003573:Cytochrome b Group; D007554:Isotopes; D046911:Macromolecular Substances; D003300:Copper; C058557:cytochrome ba3; D003576:Electron Transport Complex IV