Figure 3: Regulation of BLM unwinding activity by G4 folding.
From: Mechanistic insight into the interaction of BLM helicase with intra-strand G-quadruplex structures
(a,b) Left—cartoon of the substrates used. Right—images of individual DNA substrate molecules before and after the unwinding reaction, where donor molecules are shown at the left and corresponding acceptor molecules are at the right. Unwinding was not seen for the G4 substrate (a), whereas complete unwinding was seen for the regular tailed duplex substrate (b). (c) Quantification of BLM unwinding efficiency at 50 nM BLM and 2 mM ATP for the G4 substrate at various buffer conditions. (i) Regular tailed duplex (b) in the presence of 50 mM KCl. (ii) hairpin substrate (Supplementary Fig. 1A) in the presence of 50 mM KCl. (iii–v) G4 substrate in the presence of: (iii) 2 mM KCl; (iv) 50 mM LiCl and (v) 50 mM KCl. (Error bar=s.e.m.; n=4). (d) BLM unwinding activity of the G4 substrate as a function of KCl concentration (Error bar=s.e.m.; n=5).
