The 2.1-A resolution structure of iron superoxide dismutase from Pseudomonas ovalis.
|Title||The 2.1-A resolution structure of iron superoxide dismutase from Pseudomonas ovalis.|
|Publication Type||Journal Article|
|Year of Publication||1990|
|Authors||Stoddard BL, Howell PL, Ringe D, Petsko GA|
|Date Published||1990 Sep 25|
|Keywords||Amino Acid Sequence, Binding Sites, Free Radical Scavengers, Iron, Ligands, Molecular Sequence Data, Protein Conformation, Pseudomonas, Stereoisomerism, Substrate Specificity, Superoxide Dismutase|
The 2.1-A resolution crystal structure of native uncomplexed iron superoxide dismutase (EC 18.104.22.168) 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.