title: DsbB elicits a red-shift of bound ubiquinone during the catalysis of DsbA oxidation.
abstract: DsbB is an Escherichia coli plasma membrane protein that reoxidizes the Cys30-Pro-His-Cys33 active site of DsbA, the primary dithiol oxidant in the periplasm. Here we describe a novel activity of DsbB to induce an electronic transition of the bound ubiquinone molecule. This transition was characterized by a striking emergence of an absorbance peak at 500 nm giving rise to a visible pink color. The ubiquinone red-shift was observed stably for the DsbA(C33S)-DsbB complex as well as transiently by stopped flow rapid scanning spectroscopy during the reaction between wild-type DsbA and DsbB. Mutation and reconstitution experiments established that the unpaired Cys at position 44 of DsbB is primarily responsible for the chromogenic transition of ubiquinone, and this property correlates with the functional arrangement of amino acid residues in the neighborhood of Cys44. We propose that the Cys44-induced anomaly in ubiquinone represents its activated state, which drives the DsbB-mediated electron transfer.
authors.affiliation: Institute for Virus Research, Kyoto University, Kyoto 606-8507, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Inaba
authors.forename: Yoh-hei
authors.initials: YH
authors.lastname: Takahashi
authors.forename: Nobutaka
authors.initials: N
authors.lastname: Fujieda
authors.forename: Kenji
authors.initials: K
authors.lastname: Kano
authors.forename: Hideto
authors.initials: H
authors.lastname: Miyoshi
authors.forename: Koreaki
authors.initials: K
authors.lastname: Ito
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D001665:Binding Sites; D002462:Cell Membrane / Q000378:metabolism; D003545:Cysteine / Q000737:chemistry; D004220:Disulfides; D004579:Electron Transport; D004926:Escherichia coli / Q000378:metabolism; D006639:Histidine / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism / Q000502:physiology*; D008954:Models, Biological; D008956:Models, Chemical; D009154:Mutation; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011392:Proline / Q000737:chemistry; D019704:Protein Disulfide-Isomerases / Q000378:metabolism / Q000502:physiology*; D013053:Spectrophotometry; D013104:Spheroplasts / Q000378:metabolism; D013997:Time Factors; D014451:Ubiquinone / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins; D004220:Disulfides; C079503:DsbB protein, Bacteria; D008565:Membrane Proteins; D016877:Oxidants; D014451:Ubiquinone; D006639:Histidine; D011392:Proline; D019704:Protein Disulfide-Isomerases; D003545:Cysteine; D010100:Oxygen