Figure 10

Stimulation of double strand DNA exonuclease activities of SXT-Exo and lambda-Exo by SSAP and Ssb proteins. Panel A. SXT-Exo (2 pmol of trimers), PstI-linearized pUC18 (5 ng, 0.003 pmol) and 2 pmol of the protein indicated in the text (BSA, lambda-Bet, SXT-Bet or SXT-Ssb) in Tris-HCl (25 mM, pH7.4), 50 mM NaCl, 0.5 mM MnCl₂; were incubated at 25°C for 30 mins before EDTA quenching. dsDNA levels were immediately quantified using PicoGreen reagent. The level of DNA digestion by SXT-Exo in the absence of added protein (-) was normalized to a value of 100%. Panel B. In analogous sets of experiments, lambda-Exo (2 pmol of trimers), PstI-linearized pUC18 (5 ng, 0.003 pmol) and 2 pmol of BSA, lambda-Bet, SXT-Bet or SXT-Ssb; in Tris-HCl (25 mM, pH7.4), 50 mM NaCl, 5 mM MgCl₂; were incubated at 25°C for 10 mins. Digestion levels were normalized to those of lambda-Exo in the absence of added protein (-). See methods section for detailed experimental procedure. Six independent replicates were performed for each experiment, and error bars indicate standard deviation from the mean values. Analysis using ANOVA indicated all results were statistically significant (P < 0.05) when compared to the no-protein control (-), with respective P values indicated above each bar.