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. Author manuscript; available in PMC: 2006 Sep 5.
Published in final edited form as: Nature. 2006 Jan 5;439(7072):105–108. doi: 10.1038/nature04331

Figure 4. Effect of force on the behaviour of NS3, and proposed model of action.

Figure 4

a, Fraction of duplex RNA of different lengths that are unwound processively at different forces. The mean processivity of NS3 is 18, 20, 33, 46, 48 and 53 bp at 5, 9, 11, 13, 15 and 17 pN (21, 69, 64, 62, 69 and 67 traces, respectively; 1-bp bins). b, Stepping velocities (red squares; means ± s.d.) and pause duration (blue circles; means and 95% fit confidence intervals) in 5 nM NS3 at 9, 11, 13, 15 and 17 pN (18, 35, 19, 53 and 39 traces, respectively). Pause durations plotted here were determined from a single-exponential fit of the pause duration histograms (Supplementary Fig. 4). c, Proposed model of NS3 translocation and unwinding. The helix opener site (red ellipse) unwinds the substrate in substeps of 2–5 bp (x and y designate substep sizes) triggered by ATP (V max, K m). The translocator (blue circle) contacts dsRNA every 11 bp, and possibly elsewhere during the cycle as well, which requires ATP binding (k b) and an [ATP]-independent kinetic step (k o).