Respiratory chain strongly oxidizes the CXXC motif of DsbB in the Escherichia coli disulfide bond formation pathway

摘要: Escherichia coli DsbB has four essential cysteine residues, among which Cys41 and Cys44 form a CXXC redox active site motif the Cys104-Cys130 disulfide bond oxidizes cysteines of DsbA, formation factor in periplasm. Functional respiratory chain is required for cell to keep DsbA oxidized. In this study, we characterized roles coupling with chain. Cys104 was found inactive complex under respiration-defective conditions. While DsbB, normal aerobic conditions, oxidized state, having two intramolecular bonds, oxidation Cys130 requires presence Cys41-Cys44. Remarkably, Cys41-Cys44 refractory reduction by high concentration dithiothreitol, unless membrane solubilized detergent. This reductant resistance both function oxygen, since became sensitive reducing agent when prepared from quinone- or heme-depleted cells sample deaerated. Thus, Cys41-Val-Leu-Cys44 kept strongly oxidizing integrated into set components.