title: Structural and redox properties of the leaderless DsbE (CcmG) protein: both active-site cysteines of the reduced form are involved in its function in the Escherichia coli periplasm.
abstract: The thiol/disulfide oxidoreductases play important roles in ensuring the correct formation of disulfide bonds, of which the DsbE protein, also called CcmG, is the one implicated in electron transfer for cytochrome c maturation in the periplasm of Escherichia coli. The soluble, N-terminally truncated DsbE was overexpressed and purified to homogeneity. Here we report the structural and redox properties of the leaderless form (DsbEL-). During the redox reaction, the protein undergoes a structural transformation resulting in a more stable reduced form, but this form shows very low reactivity in thiol/ disulfide exchange of cysteine residues and low activity in accelerating the reduction of insulin. The standard redox potential (E'0) for the active thiol/ disulfide was determined to be -0.186 V; only one of the two cysteines (Cys80) was suggested to be the active residue in the redox reaction. From the aspect of biochemical properties, DsbE can be regarded as a weak reductant in the Escherichia coli periplasm. This implies that the function of DsbE in cytochrome c maturation can be ascribed to its active-site cysteines and the structure of the reduced form.
authors.affiliation: Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, People's Republic of China.
authors.forename: Q
authors.initials: Q
authors.lastname: Li
authors.forename: H Y
authors.initials: HY
authors.lastname: Hu
authors.forename: W Q
authors.initials: WQ
authors.lastname: Wang
authors.forename: G J
authors.initials: GJ
authors.lastname: Xu
mesh_terms: D001665:Binding Sites; D002942:Circular Dichroism; D003545:Cysteine / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism*; D008970:Molecular Weight; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000378:metabolism*; D019897:Periplasm / Q000378:metabolism; D033903:Periplasmic Proteins; D017510:Protein Folding; D013050:Spectrometry, Fluorescence
chemical_list: D033903:Periplasmic Proteins; D010088:Oxidoreductases; C077913:periplasmic protein disulfide oxidoreductase; D003545:Cysteine