C72S/C353S mutant of Trypanosoma brucei QSOX containing an interdomain disulfide

Experimental Data Snapshot

  • Resolution: 3.30 Å
  • R-Value Free: 0.249 
  • R-Value Work: 0.190 
  • R-Value Observed: 0.196 

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This is version 1.3 of the entry. See complete history


The dynamic disulphide relay of quiescin sulphydryl oxidase.

Alon, A.Grossman, I.Gat, Y.Kodali, V.K.DiMaio, F.Mehlman, T.Haran, G.Baker, D.Thorpe, C.Fass, D.

(2012) Nature 488: 414-418

  • DOI: https://doi.org/10.1038/nature11267
  • Primary Citation of Related Structures:  
    3Q6O, 3QCP, 3QD9, 3T58, 3T59

  • PubMed Abstract: 

    Protein stability, assembly, localization and regulation often depend on the formation of disulphide crosslinks between cysteine side chains. Enzymes known as sulphydryl oxidases catalyse de novo disulphide formation and initiate intra- and intermolecular dithiol/disulphide relays to deliver the disulphides to substrate proteins. Quiescin sulphydryl oxidase (QSOX) is a unique, multi-domain disulphide catalyst that is localized primarily to the Golgi apparatus and secreted fluids and has attracted attention owing to its overproduction in tumours. In addition to its physiological importance, QSOX is a mechanistically intriguing enzyme, encompassing functions typically carried out by a series of proteins in other disulphide-formation pathways. How disulphides are relayed through the multiple redox-active sites of QSOX and whether there is a functional benefit to concatenating these sites on a single polypeptide are open questions. Here we present the first crystal structure of an intact QSOX enzyme, derived from a trypanosome parasite. Notably, sequential sites in the disulphide relay were found more than 40 Å apart in this structure, too far for direct disulphide transfer. To resolve this puzzle, we trapped and crystallized an intermediate in the disulphide hand-off, which showed a 165° domain rotation relative to the original structure, bringing the two active sites within disulphide-bonding distance. The comparable structure of a mammalian QSOX enzyme, also presented here, shows further biochemical features that facilitate disulphide transfer in metazoan orthologues. Finally, we quantified the contribution of concatenation to QSOX activity, providing general lessons for the understanding of multi-domain enzymes and the design of new catalytic relays.

  • Organizational Affiliation

    Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
QSOX from Trypanosoma brucei (TbQSOX)
A, B, C, D
470Trypanosoma bruceiMutation(s): 2 
Gene Names: QSOXTb927.6.1850
Find proteins for Q585M6 (Trypanosoma brucei brucei (strain 927/4 GUTat10.1))
Explore Q585M6 
Go to UniProtKB:  Q585M6
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ585M6
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 3.30 Å
  • R-Value Free: 0.249 
  • R-Value Work: 0.190 
  • R-Value Observed: 0.196 
  • Space Group: P 1 21 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 81.04α = 90
b = 120.31β = 105.44
c = 106.22γ = 90
Software Package:
Software NamePurpose
ADSCdata collection
MOSFLMdata reduction
SCALAdata scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2012-05-30
    Type: Initial release
  • Version 1.1: 2012-08-22
    Changes: Database references
  • Version 1.2: 2012-08-29
    Changes: Database references
  • Version 1.3: 2023-09-13
    Changes: Data collection, Database references, Derived calculations, Refinement description