Figure 4. G-quadruplex (G4) formation by the vlsE 17 bp direct repeat.

A) DNA sequences of the oligonucleotides used to assay for intermolecular G-quadruplex formation. The shortened oligos are all deleted forms of the full length 17-mer direct repeat. B. Electrophoretic mobility shift assay for G-quadruplex formation using 5′ ³²P-labeled oligonucleotides from Panel A. The 5′ end-labeled oligos were annealed by heating at 95°C for 5 minutes followed by slow cooling for 15 hours to room temperature in presence of 200 mM LiCl or KCl. The products of the annealing reaction were run at 40 volts on a 10 cm, 20% native polyacrylamide gel in TBE buffer containing 25 mM K₂B₄O₇ run at 4°C. Separated products were detected on a Perkin-Elmer Cyclone phosphorimager. SS represents single stranded oligonucleotide and G4 indicates the position of intermolecular G-quadruplex DNA.