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Protein disulfide isomerase isomerizes non‐native disulfide bonds in human proinsulin independent of its peptide‐binding activity
Author(s) -
Winter Jeannette,
Gleiter Stefan,
Klappa Peter,
Lilie Hauke
Publication year - 2011
Publication title -
protein science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.353
H-Index - 175
eISSN - 1469-896X
pISSN - 0961-8368
DOI - 10.1002/pro.592
Subject(s) - protein disulfide isomerase , disulfide bond , proinsulin , chemistry , peptide , isomerase , stereochemistry , biochemistry , enzyme , biology , insulin , endocrinology
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.