Figure 4. Leading-strand synthesis by Pol III holoenzyme with DnaB.
Leading-strand synthesis by Pol III holoenzyme coupled with DnaB helicase. (a) Duplex λ DNA with a premade replication fork is stretched under laminar flow, and Pol III holoenzyme, DnaB and DnaC are introduced into the chamber. Synthesis is observed as a shortening of the tethered DNA. (b) Examples of leading-strand synthesis traces, in the absence (left) and presence (right) of DnaG. (c) Distribution of leading-strand synthesis processivities, fit with a single-exponential decay. Leading-strand synthesis was observed as single shortening events with an average processivity of 10.5 kb. (d) Distribution of synthesis rates, fit with a Gaussian distribution.