Structural studies on the disulfide bond isomerisation pathway

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dc.contributor.advisor Metcalf, Peter en Haebel, Peter Wilhelm en 2007-07-07T11:18:46Z en 2007-07-07T11:18:46Z en 2001 en
dc.identifier THESIS 02-084 en
dc.identifier.citation Thesis (PhD--Biological Sciences)--University of Auckland, 2001 en
dc.identifier.uri en
dc.description Full text is available to authenticated members of The University of Auckland only. en
dc.description.abstract Disulfide bonds are important for the structure and function and many proteins, including hormones, receptors, antibodies and bacterial toxins. Two complementary pathways facilitate the formation of correct disulfide bonds during oxidative protein folding in the periplasm of Escherichia coli. New disulfide bonds are non-specifically formed by the disulfide bond formation pathway. The disulfide bond isomerisation pathway, consisting of DsbC and DsbD, rearranges incorrect disulfide bonds that trap proteins in non-functional conformations. The protein disulfide bond isomerase DsbC interacts with these misfolded proteins and facilitates the refolding by isomerising incorrect disulfide bonds. To improve the current understanding of disulfide bond isomerisation the crystal structures of oxidised DsbC and DsbC Cl0lS, a mimic of the active reduced form, have been determined. The 1.9Å structure of DsbC revealed a V-shaped homodimeric molecule with each monomer consisting of two domains connected by a hinged linker helix. The N-terminal domains meet at the base of the V, forming the dimer interface. The catalytic C-terminal domains are located at the outer arms of the V and contain a thioredoxin fold with an active site CGYC motif. A 40 x 4O x 25 Å3 central uncharged cleft between the two active sites is proposed to bind substrate proteins, suggesting a model for DsbC catalysed disulfide bond isomerisation. DsbC is specifically activated by the N-terminal α domain of the transmembrane electron transporter DsbD. An intermediate of the electron transport reaction was trapped, yielding a covalent DsbC-DsbDα complex. The 2.3 Å crystal structure of the complex shows DsbDα binding into the central cleft of the V-shaped DsbC dimer, which assumes a closed conformation on complex formation. DsbDα is a new type of thiol oxidoreductase with an Ig fold. Comparison of the complex with oxidised DsbDα reveals major conformational changes in a cap structure that regulates the accessibility of the DsbDα active site. These results provide a first insight into a novel electron transport chain across the inner membrane and explain how DsbC is selectively activated by DsbD using electrons derived from the cytoplasm. en
dc.language.iso en en
dc.publisher ResearchSpace@Auckland en
dc.relation.ispartof PhD Thesis - University of Auckland en
dc.relation.isreferencedby UoA99101129914002091 en
dc.rights Restricted Item. Available to authenticated members of The University of Auckland. en
dc.rights Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated. en
dc.rights.uri en
dc.title Structural studies on the disulfide bond isomerisation pathway en
dc.type Thesis en Biological Sciences en The University of Auckland en Doctoral en PhD en
dc.rights.holder Copyright: The author en

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