Crystal structure of T. acidophilum thioredoxin reductase

Experimental Data Snapshot

  • Resolution: 2.35 Å
  • R-Value Free: 0.260 
  • R-Value Work: 0.225 

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Thioredoxin reductase from Thermoplasma acidophilum: a new twist on redox regulation.

Hernandez, H.H.Jaquez, O.A.Hamill, M.J.Elliott, S.J.Drennan, C.L.

(2008) Biochemistry 47: 9728-9737

  • DOI: https://doi.org/10.1021/bi8006753
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Thioredoxin reductases (TrxRs) regulate the intracellular redox environment by using NADPH to provide reducing equivalents for thioredoxins (Trxs). Here we present the cloning and biochemical characterization of a putative TrxR (Ta0984) and a putative Trx (Ta0866) from Thermoplasma acidophilum. Our data identify Ta0866 as a Trx through its capacity to reduce insulin and be reduced by Escherichia coli TrxR in a NADPH-dependent manner. Our data also establish Ta0984 as a TrxR due to its ability to reduce T. acidophilum Trx ( taTrx), although not in a NADPH- or NADH-dependent manner. To explore the apparent inability of taTrxR to use NADPH or NADH as a reductant, we carried out a complete electrochemical characterization, which suggests that redox potential is not the source of this nonreactivity [Hamill et al. (2008) Biochemistry 47, 9738-9746]. Turning to crystallographic analysis, a 2.35 A resolution structure of taTrxR, also presented here, shows that despite the overall structural similarity to the well-characterized TrxR from E. coli (RMSD 1.30 A (2) for chain A), the "NADPH binding pocket" is not conserved. E. coli TrxR residues implicated in NADPH binding, H175, R176, R177, and R181, have been substituted with E185, Y186, M187, and M191 in the ta protein. Thus, we have identified a Trx and TrxR protein system from T. acidophilum for which the TrxR shares overall structural and redox properties with other TrxRs but lacks the appropriate binding motif to use the standard NADPH reductant. Our discovery of a TrxR that does not use NADPH provides a new twist in redox regulation.

  • Organizational Affiliation

    Department of Chemistry, Massachusetts Institute of Technology, 16-573, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA.

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Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Thioredoxin reductase
A, B
319Thermoplasma acidophilumMutation(s): 0 
Gene Names: Ta0984
Find proteins for Q9HJI4 (Thermoplasma acidophilum (strain ATCC 25905 / DSM 1728 / JCM 9062 / NBRC 15155 / AMRC-C165))
Explore Q9HJI4 
Go to UniProtKB:  Q9HJI4
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ9HJI4
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 1 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on FAD

Download Ideal Coordinates CCD File 
C [auth A],
D [auth B]
C27 H33 N9 O15 P2
Experimental Data & Validation

Experimental Data

  • Resolution: 2.35 Å
  • R-Value Free: 0.260 
  • R-Value Work: 0.225 
  • Space Group: I 2 3
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 165.95α = 90
b = 165.95β = 90
c = 165.95γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
PDB_EXTRACTdata extraction
HKL-2000data reduction
HKL-2000data 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: 2009-02-24
    Type: Initial release
  • Version 1.1: 2011-07-13
    Changes: Version format compliance
  • Version 1.2: 2017-10-25
    Changes: Refinement description