Figure 3.

DnaB unwinding and translocation rates and fits to active/passive theory. (A) Hairpin unwinding and rezipping rates (mean ± SE) measured at various forces (± SD). The mean rezipping rate, which is equivalent to the translocation rate of DnaB on ssDNA, is force-independent, with mean r = 390 ± 15 nt/s. The unwinding data are well fit by a weakly active model with a step size n = 1 bp and a destabilization energy U = 0.5 k_BT (Fig. S5 and Table S3). (B) Unwinding rate as measured in the fork assays (mean ± SE) at various forces (± SD). The occluded-strand data are well fit by a moderately active model with a step size n = 1 bp and a destabilization energy U = 1.6 k_BT (Fig. S5 and Table S3). Analysis of the unwinding rates from the encircled-strand assay requires further consideration (see text and Fig. 5).