How thioredoxin can reduce a buried disulphide bond

Joris Messens, Inge Van Molle, P. Vanhaesebrouck, Maya Limbourg, Freddy JACOBS, Khadija WAHNI, José C. Martins, Remy Loris, Lode Wyns

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

We present a study of the interaction between thioredoxin and the model enzyme pI258 arsenate reductase (ArsC) from Staphylococcus aureus. ArsC catalyses the reduction of arsenate to arsenite. Three redox active cysteine residues (Cys10, Cys82 and Cys89) are involved. After a single catalytic arsenate reduction event, oxidized ArsC exposes a disulphide bridge between Cys82 and Cys89 on a looped-out redox helix. Thioredoxin converts oxidized ArsC back towards its initial reduced state. In the absence of a reducing environment, the active-site P-loop of ArsC is blocked by the formation of a second disulphide bridge (Cys10-Cys15). While fully reduced ArsC can be recovered by exposing this double oxidized ArsC to thioredoxin, the P-loop disulphide bridge is itself inaccessible to thioredoxin. To reduce this buried Cys10-Cys15 disulphide-bridge in double oxidized ArsC, an intra-molecular Cys10-Cys82 disulphide switch connects the thioredoxin mediated inter-protein thiol-disulphide transfer to the buried disulphide. In the initial step of the reduction mechanism, thioredoxin appears to be selective for oxidized ArsC that requires the redox helix to be looped out for its interaction. The formation of a buried disulphide bridge in the active-site might function as protection against irreversible oxidation of the nucleophilic cysteine, a characteristic that has also been observed in the structurally similar low molecular weight tyrosine phosphatase. (C) 2004 Elsevier Ltd. All rights reserved.
Original languageEnglish
Pages (from-to)527-537
Number of pages11
JournalJournal of Molecular Biology
Volume339
Issue number3
Publication statusPublished - 4 Jun 2004

Bibliographical note

J. Mol. Biol. 339, 527-537

Keywords

  • disulfide bond formation
  • ArsC
  • redox potential
  • kinetics
  • NMR

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