Figure 5.

ssDNA compaction during DnaB translocation. (A) The ratio u_enc/u_occ versus force, calculated using the measured values of u_enc in Fig. 3 B and the interpolation from the measurements of u_occ in Fig. 3B. The line indicates a bootstrap estimate of the best fit of Eq. 4 to the ratio u_enc/u_occ. (B) Compaction-inchworm model of helicase translocation: in one enzymatic cycle, the helicase modulates the tether extension by releasing 1 nt from the rear and binding 1 nt at the front. Under applied tension (as in the encircled-strand assay, but not the occluded-strand assay), these extension changes involve mechanical work that alter the helicase translocation rate (Eq. 4).