title: Reduction of CuA induces a conformational change in cytochrome c oxidase from Paracoccus denitrificans.
abstract: Cytochrome c oxidase (cytochrome aa3) from Paracoccus denitrificans contains a tightly bound manganese(II) ion, which responds to reduction of the enzyme by a change in its EPR signal (Seelig et al. (1981) Biochim. Biophys. Acta 636, 162-167). In this paper, the nature of this phenomenon is studied and the bound manganese is used as a reporter group to monitor a redox-linked conformational change in the protein. A reductive titration of the cyanide-inhibited enzyme shows that the change in the manganese EPR signal is associated with reduction of CuA. The change appears to reflect a rearrangement in the rhombic octahedral coordination environment of the central Mn2+ atom and is indicative of a redox-linked conformational transition in the enzyme. The manganese is likely to reside at the interface of subunits I and II, near the periplasmic side of the membrane. One of its ligands may be provided by the transmembrane segment X of subunit I, which has been suggested to contribute ligands to cytochrome a and CuB as well. Another manganese ligand is a water oxygen, as indicated by broadening of the manganese EPR signal in the presence of H2(17)O.
authors.affiliation: Department of Medical Chemistry, University of Helsinki, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Haltia
mesh_terms: D003300:Copper / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D003576:Electron Transport Complex IV / Q000032:analysis / Q000737:chemistry*; D008345:Manganese / Q000032:analysis; D010084:Oxidation-Reduction; D010231:Paracoccus denitrificans / Q000201:enzymology*; D011487:Protein Conformation
chemical_list: D008345:Manganese; D003300:Copper; D003576:Electron Transport Complex IV