Sequence motif-specific assignment of two [2Fe-2S] clusters in rat xanthine oxidoreductase studied by site-directed mutagenesis

J Biochem. 2000 May;127(5):771-8. doi: 10.1093/oxfordjournals.jbchem.a022669.


The sequence motif-specific assignment of the two distinct [2Fe-2S] clusters in rat xanthine oxidoreductase (XOR) was unequivocally established by site-directed mutagenesis of recombinant enzymes expressed in a baculovirus-insect cell system and electron paramagnetic resonance (EPR) spectroscopy. The conserved cysteine residues, including Cys-115, in the unusual C-terminal -Cys-Xaa(2)-Cys-//-Cys-Xaa(1)-Cys- motif serve as ligands to the Fe/S I center, which is probably located in close proximity to the Mo-pterin center. Other conserved cysteine residues, including Cys-43 and Cys-51, in the N-terminal plant ferredoxin-like motif serve as ligands to the Fe/S II center, which is distantly located from the Mo-pterin center. The present sequence motif-specific assignment of the Fe/S I and II centers is discussed in the light of the structural features of XOR.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Conserved Sequence
  • Cysteine
  • Electron Spin Resonance Spectroscopy
  • Iron-Sulfur Proteins / chemistry*
  • Iron-Sulfur Proteins / genetics
  • Mutagenesis, Site-Directed
  • Oxidation-Reduction
  • Rats
  • Recombinant Proteins
  • Xanthine Dehydrogenase / chemistry*
  • Xanthine Dehydrogenase / genetics
  • Xanthine Oxidase / chemistry*
  • Xanthine Oxidase / genetics


  • Iron-Sulfur Proteins
  • Recombinant Proteins
  • Xanthine Dehydrogenase
  • Xanthine Oxidase
  • Cysteine