Figure 4

DNA phosphorothioation protects TDH enzyme and scavenge H₂O₂, hydroxyl radicals in vivo. (A) To assess the damage to TDH, the cells were treated for 20 minutes and total protein was extracted; TDH activity was then anaerobically assayed. The data shown represent the results of three independent experiments, and the error bars indicate the standard deviations. The data were analyzed by Student’s t test. **P < 0.01; ns, not significantly different. (B) MG1655 and Hpx⁻/Dnd whole cells were incubated with 1 mM H₂O₂, and the disappearance of H₂O₂ was monitored. The data shown represent the results of three independent experiments, and the error bars indicate the standard deviations. (C) Hydroxyl radicals in MG1655 and Hpx⁻/Dnd cells were induced by adding 50 or 75 μM exogenous H₂O₂. The signals were detected using POBN-ethanol spin trapping. The cell densities were equivalent in all samples. The data are representative of three independent experiments. The six peaks represent the hydroxyl radical signals.