The 2.1-A resolution structure of iron superoxide dismutase from Pseudomonas ovalis.
The 2.1-A resolution crystal structure of native uncomplexed iron superoxide dismutase (EC 1.15.1.1) 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.
Stoddard
B L
BL
Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139.
Howell
P L
PL
Ringe
D
D
Petsko
G A
GA
D000595:Amino Acid Sequence; D001665:Binding Sites; D016166:Free Radical Scavengers; D007501:Iron / Q000378:metabolism*; D008024:Ligands; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011549:Pseudomonas / Q000201:enzymology*; D013237:Stereoisomerism; D013379:Substrate Specificity; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism
D016166:Free Radical Scavengers; D008024:Ligands; D007501:Iron; D013482:Superoxide Dismutase