title: Purification and some properties of superoxide dismutase from Deinococcus radiophilus, the UV-resistant bacterium.
abstract: The superoxide dismutase (SOD, EC 1.15.1.1) of Deinococcus radiophilus, a bacterium extraordinarily resistant to UV, ionizing radiations, and oxidative stress, was purified 1,920-fold with a 58% recovery yield from the cell-free extract of stationary cells by steps of ammonium sulfate fractionation and Superdex G-75 gel-filtration chromatography. A specific activity of the purified enzyme preparation was ca. 31,300 U mg(-1) protein. D. radiophilus SOD is Mn/FeSOD, judging by metal analysis and its insensitivity to cyanide and a partial sensitivity to H2O2. The molecular weights of the purified enzyme estimated by gel chromatography and polyacrylamide gel electrophoresis are 51.5+/-1 and 47.1+/-5 kDa, respectively. The SOD seems to be a homodimeric protein with a molecular mass of 26 +/- 0.5 kDa per monomer. The purified native SOD showed very acidic pI of ca. 3.8. The enzyme was stable at pH 5.0-11.0, but quite unstable below pH 5.0. SOD was thermostable up to 40 degrees C, but a linear reduction in activity above 50 degrees C. Inhibition of the purified SOD activity by beta-naphthoquinone-4-sulfonic acid, rho-diazobenzene sulfonic acid, and iodine suggests that lysine, histidine, and tyrosine residues are important for the enzyme activity. The N-terminal peptide sequence of D. radiophilus Mn/FeSOD (MAFELPQLPYAYDALEPHIDA(> D) is strikingly similar to those of D. radiodurans MnSOD and Aerobacter aerogenes FeSOD.
authors.affiliation: Division of Life Sciences and Research Institute for Biotechnology, Chungbuk National University, Cheongju, Chungbuk, 361-763, Korea.
authors.forename: Young Sun
authors.initials: YS
authors.lastname: Yun
authors.forename: Young Nam
authors.initials: YN
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D034301:Deinococcus / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects; D004795:Enzyme Stability; D007526:Isoelectric Point; D008969:Molecular Sequence Data; D008970:Molecular Weight; D018384:Oxidative Stress; D011836:Radiation Tolerance; D017386:Sequence Homology, Amino Acid; D013482:Superoxide Dismutase / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D013482:Superoxide Dismutase