FIG. 7.

DBP unwinds the 36:51-mer and 51:64-mer partial duplexes. (A and B) Dose dependence of the unwinding reaction. Reaction mixtures (10 μl) containing 0.005 pmol of ³²P-labeled *36:51-mer (A) or *51:64-mer (B) and other components of the unwinding assay (see Materials and Methods) were incubated with DBP for 30 min at 23°C. No protein was added to the reactions shown in lanes 1. Other reaction mixtures contained the following amounts of DBP collected after chromatography on DEAE-Toyopearl: lanes 2, 2.9 ng, lanes 3, 7.6 ng, and lanes 4, 19 ng. After treatment with 1% SDS and 0.5 mg of proteinase K per ml for 20 min at 23°C, 5-μl portions of reaction mixtures were analyzed by electrophoresis in a 6% polyacrylamide gel. (C) Time course of unwinding of the 51:64-mer partial duplex. A 49-μl reaction mixture containing 0.035 pmol of ³²P-labeled *51:64-mer and other components of the unwinding assay was assembled. A 7-μl portion was removed to serve as a starting point (lane 1), and then 18 μl of DBP (114 ng) collected after chromatography on DEAE-Toyopearl was added and the reaction mixture was incubated at 23°C. At the indicated times, 10-μl portions from the reaction mixture were removed and treated with 1% SDS and 0.5 mg of proteinase K per ml for 20 min at 23°C. Portions (5 μl) from the samples were analyzed by electrophoresis in a 6% polyacrylamide gel. The sequences of the *36:51-mer and *51:64-mer are shown at the bottom. The asterisk indicated the radioactive label.