Fig. 7: Mechanism of G4 unfolding by ScPif1.
From: Eukaryotic Pif1 helicase unwinds G-quadruplex and dsDNA using a conserved wedge
a The DNA sequence of T7-AT11. b AT11 is a four-layer G4 comprising of two parallel-stranded subunits connected by a central linker. One ScPif1 molecule binds to the T7-AT11 substrate DNA with the wedge contacting the ssDNA/G4 junction. c The interaction of the wedge with the first G-tetrad would deliver the first guanine nucleotide G9 into the ssDNA binding channel coupled with ATP hydrolysis-mediated translocation. d Further translocation of ScPif1 along ssDNA would move G10 to occupy the G9 position such that the G9-G10 column in the first and second G-tetrads would be stripped first to form the G3-triplex intermediate. e The remaining G-columns could be stripped one by one to complete the whole unfolding process.
