Figure 3. Statistics of UvrD translocation.

(a) Distribution of UvrD translocation speed fit to a Gaussian (black curve). The mean and s.d. of the distribution are 193 nt s⁻¹ and 22 nt s⁻¹, respectively. (b) The number of molecules still remaining on DNA after translocating a given distance. The black curve is the fit to an exponential decay with a translocation processivity (the inverse of decay constant) of 1,260±60 nt. (c) The translocation speed was measured as a function of applied tension to DNA at a constant ATP concentration of 1 mM. The error bars correspond to s.d. The extension of one nucleotide under the applied tension was estimated using the extensible freely jointed chain model, and this length was used to convert the speed to nt s⁻¹ and distance to nt for a–c.