Unique structural features of the monomeric Cu,Zn superoxide dismutase from Escherichia coli, revealed by X-ray crystallography

• DOI: 10.1006/jmbi.1997.1400
• Publication Date: 2002-10-07T11:22:43Z
• Authors: Alessandra Pesce; Clemente Capasso; Andrea Battistoni; Silvia Folcarelli; Giuseppe Rotilio; Alessandro Desideri; Martino Bolognesi
• Keywords: Models, Molecular; 0301 basic medicine; Binding Sites; enzyme evolution; Sequence Homology, Amino Acid; Protein Conformation; Superoxide Dismutase; Molecular Sequence Data; X-ray crystal structure; Crystallography, X-Ray; 3. Good health; copper enzyme; 03 medical and health sciences; monomeric superoxide dismutase; Escherichia coli; Cu,Zn superoxide dismutase; monomeric superoxide dismutase; copper enzymes; enzyme evolution; X-ray crystal structure; Amino Acid Sequence; Cu,Zn superoxide dismutase; Settore BIO/10 - BIOCHIMICA

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.