title: Protein disulfide isomerase isomerizes non-native disulfide bonds in human proinsulin independent of its peptide-binding activity.
abstract: Protein disulfide isomerase (PDI) supports proinsulin folding as chaperone and isomerase. Here, we focus on how the two PDI functions influence individual steps in the complex folding process of proinsulin. We generated a PDI mutant (PDI-aba'c) where the b' domain was partially deleted, thus abolishing peptide binding but maintaining a PDI-like redox potential. PDI-aba'c catalyzes the folding of human proinsulin by increasing the rate of formation and the final yield of native proinsulin. Importantly, PDI-aba'c isomerizes non-native disulfide bonds in completely oxidized folding intermediates, thereby accelerating the formation of native disulfide bonds. We conclude that peptide binding to PDI is not essential for disulfide isomerization in fully oxidized proinsulin folding intermediates.
authors.affiliation: Center for Integrated Protein Science Munich at the Department Chemie, Technische Universität München, 85747 Garching, Germany. jeannette.winter@tum.de
authors.forename: Jeannette
authors.initials: J
authors.lastname: Winter
authors.forename: Stefan
authors.initials: S
authors.lastname: Gleiter
authors.forename: Peter
authors.initials: P
authors.lastname: Klappa
authors.forename: Hauke
authors.initials: H
authors.lastname: Lilie
mesh_terms: D004220:Disulfides / Q000737:chemistry*; D006801:Humans; D007536:Isomerism; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D010084:Oxidation-Reduction; D010455:Peptides / Q000378:metabolism*; D011384:Proinsulin / Q000737:chemistry* / Q000378:metabolism; D011489:Protein Denaturation; D019704:Protein Disulfide-Isomerases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017510:Protein Folding
chemical_list: D004220:Disulfides; D018832:Molecular Chaperones; D010455:Peptides; D011384:Proinsulin; D019704:Protein Disulfide-Isomerases