title: Reduction of protein disulfide bonds in an oxidizing environment. The disulfide bridge of cholera toxin A-subunit is reduced in the endoplasmic reticulum.
abstract: Following retrograde transport to the endoplasmic reticulum (ER) the A-subunit of cholera toxin (CTX-A) is partially cleaved into CTX-A1 and CTX-A2 by reduction of a disulfide bridge [Majoul et al. (1996) J. Cell Biol. 133, 777-789], although the redox state in the ER favors disulfide formation. We show here that the disulfide bridge of CTX-A is cleaved in vitro already at GSH/GSSG ratios between 1 and 3. Protein disulfide isomerase (PDI) exerts only a minor accelerating effect. Various mixed disulfide intermediates (CTX-A1-S-S-CTX-A1; PDI-S-S-A2; PDI-S-S-A1) appear during CTX-A reduction. These results indicate that in the ER protein disulfide formation and protein disulfide reduction can take place simultaneously.
authors.affiliation: Abteilung Klinische Biochemie, Universität Göttingen, Germany.
authors.forename: I
authors.initials: I
authors.lastname: Majoul
authors.forename: D
authors.initials: D
authors.lastname: Ferrari
authors.forename: H D
authors.initials: HD
authors.lastname: Söling
mesh_terms: D000818:Animals; D001665:Binding Sites; D002522:Chlorocebus aethiops; D002772:Cholera Toxin / Q000737:chemistry / Q000378:metabolism*; D004220:Disulfides / Q000737:chemistry / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D010084:Oxidation-Reduction; D014709:Vero Cells
chemical_list: D004220:Disulfides; D002772:Cholera Toxin