The 2.1-A resolution structure of iron superoxide dismutase from Pseudomonas ovalis

Biochemistry. 1990 Sep 25;29(38):8885-93. doi: 10.1021/bi00490a002.


The 2.1-A resolution crystal structure of native uncomplexed iron superoxide dismutase (EC from Pseudomonas ovalis was solved and refined to a final R factor of 24%. The dimeric structure contains one catalytic iron center per monomer with an asymmetric trigonal-bipyramidal coordination of protein ligands to the metal. Each monomer contains two domains, with the trigonal ligands (histidines 74 and 160; aspartate 156) contributed by the large domain and stabilized by an extended hydrogen-bonded network, including residues from opposing monomers. The axial ligand (histidine 26) is found on the small domain and does not participate extensively in the stabilizing H-bond network. The open axial coordination position of the iron is devoid of bound water molecules or anions. The metal is located 0.5 A out of the plane of the trigonal ligands toward histidine 26, providing a slightly skewed coordination away from the iron binding site. The molecule contains a glutamine residue in the active site which is conserved between all iron enzymes sequenced to data but which is conserved among all manganese SODs at a separate position in the sequence. This residue shows the same structural interactions in both cases, implying that iron and manganese SODs are second-site revertants of one another.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Binding Sites
  • Free Radical Scavengers
  • Iron / metabolism*
  • Ligands
  • Molecular Sequence Data
  • Protein Conformation
  • Pseudomonas / enzymology*
  • Stereoisomerism
  • Substrate Specificity
  • Superoxide Dismutase / chemistry*
  • Superoxide Dismutase / metabolism


  • Free Radical Scavengers
  • Ligands
  • Iron
  • Superoxide Dismutase