Purification and some properties of superoxide dismutase from Deinococcus radiophilus, the UV-resistant bacterium.
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.
Yun
Young Sun
YS
Division of Life Sciences and Research Institute for Biotechnology, Chungbuk National University, Cheongju, Chungbuk, 361-763, Korea.
Lee
Young Nam
YN
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
D013482:Superoxide Dismutase