2VOC

THIOREDOXIN A ACTIVE SITE MUTANTS FORM MIXED DISULFIDE DIMERS THAT RESEMBLE ENZYME-SUBSTRATE REACTION INTERMEDIATE


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.50 Å
  • R-Value Free: 0.237 
  • R-Value Work: 0.185 
  • R-Value Observed: 0.188 

Starting Model: experimental
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This is version 2.1 of the entry. See complete history


Literature

Thioredoxin A active-site mutants form mixed disulfide dimers that resemble enzyme-substrate reaction intermediates.

Kouwen, T.R.Andrell, J.Schrijver, R.Dubois, J.Y.Maher, M.J.Iwata, S.Carpenter, E.P.van Dijl, J.M.

(2008) J Mol Biol 379: 520-534

  • DOI: https://doi.org/10.1016/j.jmb.2008.03.077
  • Primary Citation of Related Structures:  
    2VOC

  • PubMed Abstract: 

    Thioredoxin functions in nearly all organisms as the major thiol-disulfide oxidoreductase within the cytosol. Its prime purpose is to maintain cysteine-containing proteins in the reduced state by converting intramolecular disulfide bonds into dithiols in a disulfide exchange reaction. Thioredoxin has been reported to contribute to a wide variety of physiological functions by interacting with specific sets of substrates in different cell types. To investigate the function of the essential thioredoxin A (TrxA) in the low-GC Gram-positive bacterium Bacillus subtilis, we purified wild-type TrxA and three mutant TrxA proteins that lack either one or both of the two cysteine residues in the CxxC active site. The pure proteins were used for substrate-binding studies known as "mixed disulfide fishing" in which covalent disulfide-bonded reaction intermediates can be visualized. An unprecedented finding is that both active-site cysteine residues can form mixed disulfides with substrate proteins when the other active-site cysteine is absent, but only the N-terminal active-site cysteine forms stable interactions. A second novelty is that both single-cysteine mutant TrxA proteins form stable homodimers due to thiol oxidation of the remaining active-site cysteine residue. To investigate whether these dimers resemble mixed enzyme-substrate disulfides, the structure of the most abundant dimer, C32S, was characterized by X-ray crystallography. This yielded a high-resolution (1.5A) X-ray crystallographic structure of a thioredoxin homodimer from a low-GC Gram-positive bacterium. The C32S TrxA dimer can be regarded as a mixed disulfide reaction intermediate of thioredoxin, which reveals the diversity of thioredoxin/substrate-binding modes.


  • Organizational Affiliation

    Department of Medical Microbiology, University Medical Center Groningen and University of Groningen, Hanzeplein 1, PO Box 30001, 9700 RB Groningen, The Netherlands.


Macromolecules
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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
THIOREDOXIN
A, B
112Bacillus subtilis subsp. subtilis str. 168Mutation(s): 1 
UniProt
Find proteins for P14949 (Bacillus subtilis (strain 168))
Explore P14949 
Go to UniProtKB:  P14949
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP14949
Sequence Annotations
Expand
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
PEG
Query on PEG

Download Ideal Coordinates CCD File 
C [auth A]DI(HYDROXYETHYL)ETHER
C4 H10 O3
MTHSVFCYNBDYFN-UHFFFAOYSA-N
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.50 Å
  • R-Value Free: 0.237 
  • R-Value Work: 0.185 
  • R-Value Observed: 0.188 
  • Space Group: P 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 36.765α = 83.33
b = 38.395β = 66.62
c = 41.878γ = 78.08
Software Package:
Software NamePurpose
REFMACrefinement
DENZOdata reduction
SCALEPACKdata scaling
PHASERphasing

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2009-03-10
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Advisory, Version format compliance
  • Version 2.0: 2018-02-28
    Changes: Atomic model, Database references, Source and taxonomy
  • Version 2.1: 2023-12-13
    Changes: Data collection, Database references, Derived calculations, Other, Refinement description