title: A primary role for disulfide formation in the productive folding of prokaryotic Cu,Zn-superoxide dismutase.
abstract: Enzymatic activation of Cu,Zn-superoxide dismutase (SOD1) requires not only binding of a catalytic copper ion but also formation of an intramolecular disulfide bond. Indeed, the disulfide bond is completely conserved among all species possessing SOD1; however, it remains obscure how disulfide formation controls the enzymatic activity of SOD1. Here, we show that disulfide formation is a primary event in the folding process of prokaryotic SOD1 (SodC) localized to the periplasmic space. Escherichia coli SodC was found to attain β-sheet structure upon formation of the disulfide bond, whereas disulfide-reduced SodC assumed little secondary structure even in the presence of copper and zinc ions. Moreover, reduction of the disulfide bond made SodC highly susceptible to proteolytic degradation. We thus propose that the thiol-disulfide status in SodC controls the intracellular stability of this antioxidant enzyme and that the oxidizing environment of the periplasm is required for the enzymatic activation of SodC.
authors.affiliation: From the Laboratory for Mechanistic Chemistry of Biomolecules, Department of Chemistry, Keio University, Yokohama, Kanagawa 223-8522 Japan.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Sakurai
authors.affiliation: From the Laboratory for Mechanistic Chemistry of Biomolecules, Department of Chemistry, Keio University, Yokohama, Kanagawa 223-8522 Japan.
authors.forename: Itsuki
authors.initials: I
authors.lastname: Anzai
authors.affiliation: From the Laboratory for Mechanistic Chemistry of Biomolecules, Department of Chemistry, Keio University, Yokohama, Kanagawa 223-8522 Japan furukawa@chem.keio.ac.jp.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Furukawa
mesh_terms: D001665:Binding Sites; D003300:Copper / Q000378:metabolism; D004220:Disulfides / Q000737:chemistry; D004789:Enzyme Activation; D004795:Enzyme Stability; D004926:Escherichia coli / Q000201:enzymology; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D011487:Protein Conformation; D017510:Protein Folding; D017433:Protein Structure, Secondary; D059748:Proteolysis; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015032:Zinc / Q000378:metabolism
chemical_list: D004220:Disulfides; D029968:Escherichia coli Proteins; D003300:Copper; D013482:Superoxide Dismutase; C116114:sodC protein, E coli; D015032:Zinc
keywords: Copper; Disulfide; Protein Folding; Superoxide Dismutase (SOD); Zinc