title: An iron-containing superoxide dismutase from Anacystis nidulans.
abstract: Superoxide dismutase (SOD) was isolated and purified from Anacystis nidulans to near electrophoretic homogeneity. The enzyme has a molecular weight of 37,500, as determined by gel filtration and SDS-gel electrophoresis. The enzyme molecule consists of two subunits of identical molecular weight. Proton-induced X-ray elemental analysis (PIXE) showed that the SOD of A. nidulans is an iron-containing enzyme; the Fe:enzyme mol ratio was found to be 1. The EPR spectra indicated that the active center contains high-spin ferric ion. Based on quantitative EPR data, we conclude that eseentially all iron ions were detected in the EPR experiments and were present in the Fe3+ active center. Effective g'-values were calculated from computer-simulated spectra and analysis of the g'-value anisotropy of the +/-3/2 Kramers doublet made the calculation of crystal field parameters possible. The symmetry of the Fe3+ ion in the SOD molecule was found to be close to rhombic (E/D=0.240).
mesh_terms: D001665:Binding Sites; D000458:Cyanobacteria / Q000201:enzymology*; D004578:Electron Spin Resonance Spectroscopy; D007501:Iron / Q000032:analysis*; D046911:Macromolecular Substances; D008968:Molecular Conformation; D008970:Molecular Weight; D013482:Superoxide Dismutase / Q000302:isolation & purification
chemical_list: D046911:Macromolecular Substances; D007501:Iron; D013482:Superoxide Dismutase