Figure 6.

CBF-A mutant T267K fails to unwind G′2 3′-tail d(CGG)₇. Wild-type or T267K variant CBF-A protein mutated in the ATP/GTP-binding motif at 48 pmol each, were incubated at 37°C for 15 min with 0.17 pmol of 5′-³²P G′2 3′-tail d(CGG)₇ under standard tetraplex DNA destabilization assay conditions. Incubation of control samples with no added protein, termination of the destabilization reaction and electrophoretic resolution of intact and destabilized G′2 3′-tail d(CGG)₇ were conducted as detailed in the legend to Figure 4. Quantification of phosphorimages of four independent determinations reveal that wild-type and T267K CBF-A proteins destabilized 53 ± 3 and 4 ± 3%, respectively, of the tetraplex substrate.