The effect of oxidation on DNA binding of Ku mutants. (A) C493A point mutant and wild type Ku was exposed to increasing concentrations of diamide (0-2 mM) and then DNA binding activity assessed. (B) Wild type and Ku70/80ΔC (950 nM) were incubated with 2 mM diamide and DNA binding assessed, For re-reduced conditions, diamide incubation was followed by incubation with 5 mM DTT. DNA binding was then assessed as described in the legend for Figure 2. (C) Quantification of the results in Panel B was performed via PhosphorImager analysis. Results are presented as the average and standard deviation of triplicate determinations.