Unique structural features of the monomeric Cu,Zn superoxide dismutase from Escherichia coli, revealed by X-ray crystallography.
The first three-dimensional structure of a functional monomeric Cu, Zn superoxide dismutase (from Escherichia coli, E_SOD) is reported at 2.0 A resolution (R-factor=16.8%). Compared to the homologous eukaryotic enzymes, E_SOD displays a perturbed antiparallel beta-barrel structure. The most striking structural features observed include extended amino acid insertions in the surface 1, 2-loop and S-S subloop, modification of the disulfide bridge connection, and loss of functional electrostatic residues, suggesting a modified control of substrate steering toward the catalytic center. The active site Cu2+ displays a distorted coordination sphere due to an unusually long bond to the metal-bridging residue His61. Inspection of the crystal packing does not show regions of extended contact indicative of a dimeric assembly. The molecular surface region involved in subunit dimerization in eukaryotic superoxide dismutases is structurally altered in E_SOD and displays a net polar nature.
Pesce
A
A
Dipartimento di Fisica and INFM, Universita' di Genova, Largo Rosanna Benzi, 10, 16132 Genova, Italy.
Capasso
C
C
Battistoni
A
A
Folcarelli
S
S
Rotilio
G
G
Desideri
A
A
Bolognesi
M
M
D000595:Amino Acid Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004926:Escherichia coli / Q000201:enzymology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017386:Sequence Homology, Amino Acid; D013482:Superoxide Dismutase / Q000737:chemistry* / Q000378:metabolism
D013482:Superoxide Dismutase