title: Unique structural features of the monomeric Cu,Zn superoxide dismutase from Escherichia coli, revealed by X-ray crystallography.
abstract: 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.
authors.affiliation: Dipartimento di Fisica and INFM, Universita' di Genova, Largo Rosanna Benzi, 10, 16132 Genova, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Pesce
authors.forename: C
authors.initials: C
authors.lastname: Capasso
authors.forename: A
authors.initials: A
authors.lastname: Battistoni
authors.forename: S
authors.initials: S
authors.lastname: Folcarelli
authors.forename: G
authors.initials: G
authors.lastname: Rotilio
authors.forename: A
authors.initials: A
authors.lastname: Desideri
authors.forename: M
authors.initials: M
authors.lastname: Bolognesi
mesh_terms: 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
chemical_list: D013482:Superoxide Dismutase