Paradoxical redox properties of DsbB and DsbA in the protein disulfide-introducing reaction cascade

AUTOR(ES)

Inaba, Kenji

FONTE

Oxford University Press

RESUMO

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.

Documentos Relacionados

• Mutational Analysis of the Disulfide Catalysts DsbA and DsbB
• Four cysteines of the membrane protein DsbB act in concert to oxidize its substrate DsbA
• Evidence that the pathway of disulfide bond formation in Escherichia coli involves interactions between the cysteines of DsbB and DsbA.
• The Dithiol:Disulfide Oxidoreductases DsbA and DsbB of Rhodobacter capsulatus Are Not Directly Involved in Cytochrome c Biogenesis, but Their Inactivation Restores the Cytochrome c Biogenesis Defect of CcdA-Null Mutants
• Two cysteines in each periplasmic domain of the membrane protein DsbB are required for its function in protein disulfide bond formation.