The manganese superoxide dismutase of Escherichia coli K-12 associates with DNA.

摘要: Abstract Superoxide dismutases (SODs) are vital components in the resistance of aerobic organisms to toxicity oxygen. Escherichia coli contains two highly homologous cytoplasmic SODs, a manganese- and an iron-containing enzyme (MnSOD, FeSOD). We previously demonstrated that MnSOD FeSOD have different physiological functions is more effective preventing oxidative damage DNA. In this report, purified E. was shown bind nonspecifically DNA by electrophoretic mobility shift assay nitrocellulose-filter binding methodologies. From assay, equilibrium dissociation constants for interaction with variety double-stranded single-stranded oligonucleotides ranged from 1.5 +/- 0.2 8.4 1.3 microM at 20 degrees C. This range concentrations corresponds aerobically grown coli. vivo supported colocalization nucleoid immunoelectron microscopy. Both were inhomogeneously distributed cytosol, concentration each being higher center cell relatively low near inner membrane. contrast, there no evidence physiologically relevant Binding vitro weak, Kd > 40-220 microM, 7-40 times than found vivo. addition, distribution did not correlate membrane lower cytosol. These results demonstrate associates Combined prior data demonstrating preferentially protects while equal enzymatic activity does (Hopkin, K. A., Papazian, M. Steinman, H. (1992) J. Biol. Chem. 267, 24253-24258), our suggest acts as "tethered antioxidant"; association localizes dismutase target stress increases protection damage. model has implications therapeutic use SODs antioxidants.