Figure 6.

smFRET histograms showing BLM-mediated unfolding for pd-3Ly1Lp12T, three layer one loop GQ construct with 12 nt long 3′ overhang. (A) BLM cannot unfold this GQ at 150 mM K⁺ in either nt-free or 1 mM ATPγS states. These results show that the ability of BLM to unfold intramolecular GQ in the absence of ATP under physiological ionic conditions is substrate specific. (B) Significant GQ unfolding is observed in both nt-free and ATPγS states when ion concentration is reduced to 50 mM K⁺, in which GQ is less stable and BLM binding to the overhang is more efficient.