Figure 2.

Unwinding of G4 DNA by E.coli RecQ DNA helicase. (A) ³²P-labeled G4 DNA (50 nM) formed from TP oligonucleotide was incubated with RecQ (50 nM) in the presence or absence of 2 mM ATP, 2 mM ATPγS and 2 mM Mg²⁺, as indicated. (B) ³²P-labeled G4 DNA or G2′ DNA (5 nM) formed from (T₄G₄)₂, which carries two iterations of the Oxytricha telomeric repeat, was incubated with RecQ (50 nM) in the presence or absence of 2 mM ATP, 2 mM ATPγS and 2 mM Mg²⁺, as indicated. (C) ³²P-labeled G4 DNA (50 nM) formed from the TP oligonucleotide was incubated with RecQ (50 nM) in the presence of 2 mM Mn²⁺, Ca²⁺, Cu²⁺ or Zn²⁺, to replace Mg²⁺ in the reaction.