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. 1998 Apr 15;12(8):1134–1144. doi: 10.1101/gad.12.8.1134

Figure 3.

Figure 3

 RecQ helicase dissociates joint molecules. (A) RecQ helicase unwinds joint molecules during the course of the coupled pairing reaction. The addition of fivefold more RecQ protein (500 nm) to the coupled pairing reaction results in transient intermediates and a lower steady-state yield of these species (lanes 2–5). The helicase activity of RecQ helicase is required to observe this phenomenon because addition of ATPγS, a nonhydrolyzable analog of ATP, affords protection from disruption to the pairing intermediates formed in the reaction (lanes 6–9). The time at which 4 mm ATPγS was added (8 min) is indicated by the vertical arrow. (B) RecQ helicase binds to and unwinds joint molecules formed in its absence. (Lane 1) Linear pUC19 dsDNA marker. (Lanes 2–6) RecA and SSB proteins were incubated with labeled linear pUC19 ssDNA, unlabeled linear pUC19 dsDNA, and pUC1950 scDNA to produce homologous pairing intermediates. RecQ helicase added to similar reactions dissociated the joint molecules formed by RecA protein (lanes 7–11). RecQ helicase (500 nm) was added after taking the 10 min time point in lane 9.