title: Redox-dependent domain rearrangement of protein disulfide isomerase coupled with exposure of its substrate-binding hydrophobic surface.
abstract: Protein disulfide isomerase (PDI) is a major protein in the endoplasmic reticulum, operating as an essential folding catalyst and molecular chaperone for disulfide-containing proteins by catalyzing the formation, rearrangement, and breakage of their disulfide bridges. This enzyme has a modular structure with four thioredoxin-like domains, a, b, b', and a', along with a C-terminal extension. The homologous a and a' domains contain one cysteine pair in their active site directly involved in thiol-disulfide exchange reactions, while the b' domain putatively provides a primary binding site for unstructured regions of the substrate polypeptides. Here, we report a redox-dependent intramolecular rearrangement of the b' and a' domains of PDI from Humicola insolens, a thermophilic fungus, elucidated by combined use of nuclear magnetic resonance (NMR) and small-angle X-ray scattering (SAXS) methods. Our NMR data showed that the substrates bound to a hydrophobic surface spanning these two domains, which became more exposed to the solvent upon oxidation of the active site of the a' domain. The hydrogen-deuterium exchange and relaxation data indicated that the redox state of the a' domain influences the dynamic properties of the b' domain. Moreover, the SAXS profiles revealed that oxidation of the a' active site causes segregation of the two domains. On the basis of these data, we propose a mechanistic model of PDI action; the a' domain transfers its own disulfide bond into the unfolded protein accommodated on the hydrophobic surface of the substrate-binding region, which consequently changes into a "closed" form releasing the oxidized substrate.
authors: Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki, Aichi, Japan.
authors: Olivier
authors: O
authors: Serve
authors: Yukiko
authors: Y
authors: Kamiya
authors: Aya
authors: A
authors: Maeno
authors: Michiko
authors: M
authors: Nakano
authors: Chiho
authors: C
authors: Murakami
authors: Hiroaki
authors: H
authors: Sasakawa
authors: Yoshiki
authors: Y
authors: Yamaguchi
authors: Takushi
authors: T
authors: Harada
authors: Eiji
authors: E
authors: Kurimoto
authors: Maho
authors: M
authors: Yagi-Utsumi
authors: Takeshi
authors: T
authors: Iguchi
authors: Kenji
authors: K
authors: Inaba
authors: Jun
authors: J
authors: Kikuchi
authors: Osamu
authors: O
authors: Asami
authors: Tsutomu
authors: T
authors: Kajino
authors: Toshihiko
authors: T
authors: Oka
authors: Masayoshi
authors: M
authors: Nakasako
authors: Koichi
authors: K
authors: Kato
mesh_terms: D001203:Ascomycota / Q000201:enzymology / Q000378:metabolism; D001665:Binding Sites; D018360:Crystallography, X-Ray; D057927:Hydrophobic and Hydrophilic Interactions; D008954:Models, Biological; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction; D019704:Protein Disulfide-Isomerases / Q000737:chemistry* / Q000378:metabolism*; D017510:Protein Folding; D017434:Protein Structure, Tertiary / Q000502:physiology; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction
chemical_list: D019704:Protein Disulfide-Isomerases