1t6q
Nickel Superoxide Dismutase (NiSOD) CN-treated Apo Structure
OverviewOverview
The 1.30 A resolution crystal structure of nickel superoxide dismutase (NiSOD) identifies a novel SOD fold, assembly, and Ni active site. NiSOD is a hexameric assembly of right-handed 4-helix bundles of up-down-up-down topology with N-terminal hooks chelating the active site Ni ions. This newly identified nine-residue Ni-hook structural motif (His-Cys-X-X-Pro-Cys-Gly-X-Tyr) provides almost all interactions critical for metal binding and catalysis, and thus will likely be diagnostic of NiSODs. Conserved lysine residues are positioned for electrostatic guidance of the superoxide anion to the narrow active site channel. Apo structures show that the Ni-hook motif is unfolded prior to metal binding. The active site Ni geometry cycles from square planar Ni(II), with thiolate (Cys2 and Cys6) and backbone nitrogen (His1 and Cys2) ligands, to square pyramidal Ni(III) with an added axial His1 side chain ligand, consistent with electron paramagentic resonance spectroscopy. Analyses of the three NiSOD structures and comparisons to the Cu,Zn and Mn/Fe SODs support specific molecular mechanisms for NiSOD maturation and catalysis, and identify important structure-function relationships conserved among SODs.
About this StructureAbout this Structure
1T6Q is a Single protein structure of sequence from Streptomyces coelicolor. Full crystallographic information is available from OCA.
ReferenceReference
Nickel superoxide dismutase structure and mechanism., Barondeau DP, Kassmann CJ, Bruns CK, Tainer JA, Getzoff ED, Biochemistry. 2004 Jun 29;43(25):8038-47. PMID:15209499 Page seeded by OCA on Sat May 3 09:36:03 2008