PDBsum entry 3f8r

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Oxidoreductase PDB id
Protein chains
308 a.a. *
NAP ×8
Waters ×360
* Residue conservation analysis
PDB id:
Name: Oxidoreductase
Title: Crystal structure of sulfolobus solfataricus thioredoxin reductase b3 in complex with two NADP molecules
Structure: Thioredoxin reductase (trxb-3). Chain: a, b, c, d. Engineered: yes
Source: Sulfolobus solfataricus. Organism_taxid: 2287. Expressed in: escherichia coli. Expression_system_taxid: 562.
1.95Å     R-factor:   0.208     R-free:   0.257
Authors: A.Ruggiero,M.Masullo,M.R.Ruocco,P.Arcari,A.Zagari, L.Vitagliano
Key ref: A.Ruggiero et al. (2009). Structure and stability of a thioredoxin reductase from Sulfolobus solfataricus: a thermostable protein with two functions. Biochim Biophys Acta, 1794, 554-562. PubMed id: 19110078 DOI: 10.1016/j.bbapap.2008.11.011
13-Nov-08     Release date:   13-Jan-09    
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Protein chains
Pfam   ArchSchema ?
Q8X236  (Q8X236_SULSF) -  NADH oxidase/thioredoxin reductase
324 a.a.
308 a.a.*
Key:    PfamA domain  Secondary structure  CATH domain
* PDB and UniProt seqs differ at 1 residue position (black cross)

 Enzyme reactions 
   Enzyme class: E.C.  - Nadh dehydrogenase.
[IntEnz]   [ExPASy]   [KEGG]   [BRENDA]
      Reaction: NADH + acceptor = NAD+ + reduced acceptor
Bound ligand (Het Group name = NAP)
matches with 91.00% similarity
+ acceptor
= NAD(+)
+ reduced acceptor
      Cofactor: Flavoprotein; Iron-sulfur
Molecule diagrams generated from .mol files obtained from the KEGG ftp site
 Gene Ontology (GO) functional annotation 
  GO annot!
  Cellular component     cytoplasm   1 term 
  Biological process     oxidation-reduction process   2 terms 
  Biochemical function     nucleotide binding     5 terms  


DOI no: 10.1016/j.bbapap.2008.11.011 Biochim Biophys Acta 1794:554-562 (2009)
PubMed id: 19110078  
Structure and stability of a thioredoxin reductase from Sulfolobus solfataricus: a thermostable protein with two functions.
A.Ruggiero, M.Masullo, M.R.Ruocco, P.Grimaldi, M.A.Lanzotti, P.Arcari, A.Zagari, L.Vitagliano.
Recent investigations have demonstrated that disulfide bridges may play a crucial role in the stabilization of proteins in hyperthermophilic organisms. A major role in the process of disulfide formation is played by ubiquitous proteins belonging to the thioredoxin superfamily, which includes thioredoxins (Trx), thioredoxin reductases (TrxR), and disulfide oxidases/isomerases (PDO/PDI). Here we report a characterization of the structure and stability of the TrxR (SsTrxRB3) isolated from the archaeon Sulfolobus solfataricus. This protein is particularly interesting since it is able to process different substrates (Trxs and PDO) and it is endowed with an additional NADH oxidase activity. The crystal structure of the wild-type enzyme, of its complex with NADP and of the C147A mutant provides interesting clues on the enzyme function. In contrast to what is observed for class II TrxRs, in the structure of the oxidized enzyme, the FAD binding site is occupied by a partially disordered NAD molecule. In the active site of the C147A mutant, which exhibits a marginal NADH oxidase activity, the FAD is canonically bound to the enzyme. Molecular modeling indicates that a FAD molecule can be accommodated in the site of the reduced SsTrxRB3. Depending on the oxidation state, SsTrxRB3 can bind a different cofactor in its active site. This peculiar feature has been related to its dual activity. Denaturation experiments followed by circular dichroism indicate that electrostatic interactions play an important role in the stabilization of this thermostable protein. The analysis of the enzyme 3D-structure has also provided insights into the bases of SsTrxRB3 stability.

Literature references that cite this PDB file's key reference

  PubMed id Reference
19768676 A.Ruggiero, M.Masullo, D.Marasco, M.R.Ruocco, P.Grimaldi, P.Arcari, A.Zagari, and L.Vitagliano (2009).
The dimeric structure of Sulfolobus solfataricus thioredoxin A2 and the basis of its thermostability.
  Proteins, 77, 1004-1008.
PDB code: 3hhv
19690371 K.G.Kirkensgaard, P.Hägglund, C.Finnie, B.Svensson, and A.Henriksen (2009).
Structure of Hordeum vulgare NADPH-dependent thioredoxin reductase 2. Unwinding the reaction mechanism.
  Acta Crystallogr D Biol Crystallogr, 65, 932-941.
PDB code: 2whd
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