Figure 3.
The translocation of E1 and E1HD on single-stranded DNA. (A) To monitor translocation activity, E1 was injected while HP1kbp was mechanically unzipped. After waiting for E1 to assemble onto single-stranded DNA, we lowered the force below Funzip and recorded traces. When E1 was bound to the DNA past the hairpin loop, a gradual decrease in extension was observed because of rezipping following the TL helicase as in phase (I). To compare gradual rezipping (I) with translocation along ssDNA (II), we periodically unzipped HP for ∼10 s. Displacement in z (Δz) during the unzipping period is an indication of the translocation of E1 along ssDNA. TR rates were calculated either from the downward slopes in phase (I) or from |Δz|/Δt in phase (II). TR rates calculated from phases (I) and (II) were almost identical. Translocation traces of (B) E1 and (C) E1HD. The TR rates of E1 and E1HD calculated from the traces were 4.19 ± 1.88 and 4.47 ± 1.29 bp/s, respectively, which are consistent within the error.