title: Characterisation of the PQQ cofactor radical in quinoprotein ethanol dehydrogenase of Pseudomonas aeruginosa by electron paramagnetic resonance spectroscopy.
abstract: The binding pocket of the pyrroloquinoline quinone (PQQ) cofactor in quinoprotein alcohol dehydrogenases contains a characteristic disulphide ring formed by two adjacent cysteine residues. To analyse the function of this unusual structural motif we have investigated the wild-type and a double cysteine:alanine mutant of the quinoprotein ethanol dehydrogenase from Pseudomonas aeruginosa by electron paramagnetic resonance (EPR) spectroscopy. Thus, we have obtained the principal values for the full rhombic g-tensor of the PQQ semiquinone radical by high-field (94 GHz) EPR necessary for a discrimination of radical species in dehydrogenases containing PQQ together with other redox-active cofactors. Our results show that the characteristic disulphide ring is no prerequisite for the formation of the functionally important semiquinone form of PQQ.
authors.affiliation: Institut für Experimentalphysik, Fachbereich Physik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany.
authors.forename: Christopher W M
authors.initials: CW
authors.lastname: Kay
authors.forename: Bina
authors.initials: B
authors.lastname: Mennenga
authors.forename: Helmut
authors.initials: H
authors.lastname: Görisch
authors.forename: Robert
authors.initials: R
authors.lastname: Bittl
mesh_terms: D000429:Alcohol Oxidoreductases / Q000737:chemistry* / Q000235:genetics; D001426:Bacterial Proteins / Q000737:chemistry; D001665:Binding Sites; D003545:Cysteine; D004220:Disulfides; D004578:Electron Spin Resonance Spectroscopy; D016297:Mutagenesis, Site-Directed; D010084:Oxidation-Reduction; D045542:PQQ Cofactor / Q000737:chemistry*; D011550:Pseudomonas aeruginosa / Q000201:enzymology*
chemical_list: D001426:Bacterial Proteins; D004220:Disulfides; D045542:PQQ Cofactor; D000429:Alcohol Oxidoreductases; C019641:alcohol dehydrogenase (acceptor); D003545:Cysteine