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Solution structure of the bb′ domains of human protein disulfide isomerase
Author(s) -
Denisov Alexey Y.,
Määttänen Pekka,
Dabrowski Christian,
Kozlov Guennadi,
Thomas David Y.,
Gehring Kalle
Publication year - 2009
Publication title -
the febs journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 204
eISSN - 1742-4658
pISSN - 1742-464X
DOI - 10.1111/j.1742-4658.2009.06884.x
Subject(s) - protein disulfide isomerase , chemistry , isomerase , ribonuclease , biochemistry , peptide , foldase , protein folding , endoplasmic reticulum , stereochemistry , enzyme , groel , rna , escherichia coli , gene
Protein disulfide isomerase is the most abundant and best studied of the disulfide isomerases that catalyze disulfide bond formation in the endoplasmic reticulum, yet the specifics of how it binds substrate have been elusive. Protein disulfide isomerase is composed of four thioredoxin‐like domains ( abb′a′ ). Cross‐linking studies with radiolabeled peptides and unfolded proteins have shown that it binds incompletely folded proteins primarily via its third domain, b′ . Here, we determined the solution structure of the second and third domains of human protein disulfide isomerase ( b and b′ , respectively) by triple‐resonance NMR spectroscopy and molecular modeling. NMR titrations identified a large hydrophobic surface within the b′ domain that binds unfolded ribonuclease A and the peptides mastoparan and somatostatin. Protein disulfide isomerase‐catalyzed refolding of reduced ribonuclease A in vitro was inhibited by these peptides at concentrations equal to their affinity to the bb′ fragment. Our findings provide a structural basis for previous kinetic and cross‐linking studies which have shown that protein disulfide isomerase exhibits a saturable, substrate‐binding site.