Figure 4.

Correlated mutational effects in G-quadruplexes with GTP-binding and peroxidase activity. (A) GTP-binding activity of all possible single mutant variants of the reference construct. (B–D) GTP-binding activity of all possible double, triple, and quadruple mutant variants of the reference construct. (E) Peroxidase activity of all possible single mutant variants of the reference construct. (F–H) Peroxidase activity of all possible double, triple and quadruple mutant variants of the reference construct. In panels (B–D) and (F–H), the solid blue line indicates the expected relationship for independent mutational effects. All experiments in panels (A–D) were performed at 10 μM DNA concentration in a buffer containing 200 mM KCl, 1 mM MgCl₂, 20 mM HEPES pH 7.1, and 10 nM ³²P-γ-GTP. All experiments in panels (E–H) were performed at 10 μM DNA concentration in a buffer containing 200 mM KCl, 1 mM MgCl₂, 20 mM HEPES pH 8, 0.05% Triton X-100, 0.5 μM hemin, 1% DMSO, 5 mM ABTS, and 600 μM H₂O₂. In panels (A) and (E), reported values represent the average of three experiments and error bars indicate one standard deviation. In panels (B–D) and (F-H), reported values represent the GTP-binding or peroxidase activity obtained from a single experiment. In all panels, GTP-binding and peroxidase activity is expressed relative to that of the reference construct.