title: The metal site of stellacyanin: EXAFS studies of the Cu(II), Cu(I), Ni(II) and Co(II) derivatives.
abstract: Extended X-ray absorption fine structure (EXAFS) studies of Cu(II) (oxidized), Cu(I) (reduced), Ni(II) and Co(II) stellacyanin from Rhus vernicifera are reported. For Cu(II) stellacyanin, the coordination by three close ligands, viz. 2 N and 1 S, with the presence of smaller shells pointing to imidazole coordination, indicates similarities with the coordination in other so-called type 1 or 'blue'-copper proteins. Upon reduction, slightly longer ligand distances and an additional sulphur ligand are found. Ni(II) and Co(II) stellacyanin resemble Cu(I) and Cu(II) stellacyanin, respectively, in ligand distances, but have a tendency for three rather than two N (or O) ligands in the first shell. The results are compared with the three-dimensional model derived from 1H-NMR relaxation measurements for Co(II) stellacyanin, and are consistent with the proposal that apart from the three close ligands found in all blue-copper proteins, a sulphur from a disulphide bridge and the amide oxygen from an asparagine residue come to within coordinating distance of the metal in stellacyanin.
authors.affiliation: Department of Chemistry, University of Manchester, Warrington, U.K.
authors.forename: M C
authors.initials: MC
authors.lastname: Feiters
authors.forename: S
authors.initials: S
authors.lastname: Dahlin
authors.forename: B
authors.initials: B
authors.lastname: Reinhammar
mesh_terms: D001665:Binding Sites; D003035:Cobalt; D003300:Copper; D004577:Electron Probe Microanalysis; D004578:Electron Spin Resonance Spectroscopy; D008667:Metalloproteins; D009532:Nickel; D010940:Plant Proteins
chemical_list: D008667:Metalloproteins; D010940:Plant Proteins; C003343:stellacyanin protein, plant; D003035:Cobalt; D003300:Copper; D009532:Nickel