title: X-ray crystallographic characterisation of type-2-depleted ascorbate oxidase from zucchini.
abstract: The type-2 depleted form of ascorbate oxidase from zucchini has been prepared in crystals and characterised by X-ray crystallography and EPR spectroscopy. The X-ray structure analysis by difference-Fourier techniques and refinement shows that, on average, about 1.3 Cu atoms/ascorbate oxidase monomer are removed. The copper is lost from the trinuclear site whereby the EPR-active type-2 copper is depleted most; type-1 copper is not affected. This observation indicates preferential formation of a 1 Cu-depleted form with the hole equally distributed over all three copper sites. Each of these 1 Cu-depleted species may represent an anti-ferromagnetically coupled copper pair which is EPR-silent and could explain the disappearance of the type-2 EPR signal.
authors.affiliation: Max-Planck-Institut für Biochemie, Martinsried, Federal Republic of Germany.
authors.forename: A
authors.initials: A
authors.lastname: Messerschmidt
authors.forename: W
authors.initials: W
authors.lastname: Steigemann
authors.forename: R
authors.initials: R
authors.lastname: Huber
authors.forename: G
authors.initials: G
authors.lastname: Lang
authors.forename: P M
authors.initials: PM
authors.lastname: Kroneck
mesh_terms: D001204:Ascorbate Oxidase / Q000737:chemistry*; D001665:Binding Sites; D003300:Copper / Q000032:analysis*; D004578:Electron Spin Resonance Spectroscopy; D005583:Fourier Analysis; D007527:Isoenzymes / Q000737:chemistry*; D008958:Models, Molecular; D010944:Plants / Q000201:enzymology*; D011487:Protein Conformation; D014961:X-Ray Diffraction
chemical_list: D007527:Isoenzymes; D003300:Copper; D001204:Ascorbate Oxidase