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| Subject Categories: Proteins | Microbiology & Pathogens |
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| The EMBO Journal
(2002) 21, 2646–2654, doi: 10.1093/emboj/21.11.2646 |
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| Paradoxical redox properties of DsbB and DsbA in the protein disulfide-introducing reaction cascade |
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| Kenji Inaba1, 2 and Koreaki Ito1, 3 |
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1 Institute for Virus Research, Japan Science and Technology Corporation, Kyoto University, Kyoto 606-8507, Japan 2 PRESTO, Japan Science and Technology Corporation, Kyoto University, Kyoto 606-8507, Japan 3 CREST, Japan Science and Technology Corporation, Kyoto University, Kyoto 606-8507, Japan To whom correspondence should be addressed Koreaki Ito, kito@virus.kyoto-u.ac.jp Received 11 March 2002; Revised 15 April 2002; Accepted 15 April 2002. |
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| Abstract |
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| Protein disulfide bond formation in the bacterial periplasm is catalyzed by the Dsb enzymes in conjunction with the respiratory quinone components. Here we characterized redox properties of the redox active sites in DsbB to gain further insights into the catalytic mechanisms of DsbA oxidation. The standard redox potential of DsbB was determined to be -0.21 V for Cys41/Cys44 in the N-terminal periplasmic region (P1) and -0.25 V for Cys104/Cys130 in the C-terminal periplasmic region (P2), while that of Cys30/Cys33 in DsbA was -0.12 V. To our surprise, DsbB, an oxidant for DsbA, is intrinsically more reducing than DsbA. Ubiquinone anomalously affected the apparent redox property of the P1 domain, and mutational alterations of the P1 region significantly lowered the catalytic turnover. It is inferred that ubiquinone, a high redox potential compound, drives the electron flow by interacting with the P1 region with the Cys41/Cys44 active site. Thus, DsbB can mediate electron flow from DsbA to ubiquinone irrespective of the intrinsic redox potential of the Cys residues involved. |
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| Keywords: disulfide bond, DsbB, Escherichia coli, redox potential, ubiquinone |
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