title: Crystal structure of the DsbB-DsbA complex reveals a mechanism of disulfide bond generation.
abstract: Oxidation of cysteine pairs to disulfide requires cellular factors present in the bacterial periplasmic space. DsbB is an E. coli membrane protein that oxidizes DsbA, a periplasmic dithiol oxidase. To gain insight into disulfide bond formation, we determined the crystal structure of the DsbB-DsbA complex at 3.7 A resolution. The structure of DsbB revealed four transmembrane helices and one short horizontal helix juxtaposed with Cys130 in the mobile periplasmic loop. Whereas DsbB in the resting state contains a Cys104-Cys130 disulfide, Cys104 in the binary complex is engaged in the intermolecular disulfide bond and captured by the hydrophobic groove of DsbA, resulting in separation from Cys130. This cysteine relocation prevents the backward resolution of the complex and allows Cys130 to approach and activate the disulfide-generating reaction center composed of Cys41, Cys44, Arg48, and ubiquinone. We propose that DsbB is converted by its specific substrate, DsbA, to a superoxidizing enzyme, capable of oxidizing this extremely oxidizing oxidase.
authors.affiliation: Institute for Virus Research, Kyoto University and CREST, Japan Science and Technology Agency, Kyoto 606-8507, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Inaba
authors.forename: Satoshi
authors.initials: S
authors.lastname: Murakami
authors.forename: Mamoru
authors.initials: M
authors.lastname: Suzuki
authors.forename: Atsushi
authors.initials: A
authors.lastname: Nakagawa
authors.forename: Eiki
authors.initials: E
authors.lastname: Yamashita
authors.forename: Kengo
authors.initials: K
authors.lastname: Okada
authors.forename: Koreaki
authors.initials: K
authors.lastname: Ito
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D016227:Benzoquinones / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D003545:Cysteine / Q000378:metabolism; D004220:Disulfides / Q000378:metabolism*; D004583:Electrons; D004926:Escherichia coli / Q000737:chemistry*; D008565:Membrane Proteins / Q000737:chemistry*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019704:Protein Disulfide-Isomerases / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D001426:Bacterial Proteins; D016227:Benzoquinones; D004220:Disulfides; C079503:DsbB protein, Bacteria; D008565:Membrane Proteins; C004532:quinone; D019704:Protein Disulfide-Isomerases; D003545:Cysteine