Fig. 6.

(A) Monitoring the rate of DNA unwinding by AddAB helicase-nuclease using SSBG23CC51V-FDA5M. AddAB-DNA complexes were rapidly mixed with or without ATP in the presence of the SSB probe. In the presence of ATP, the DNA is rapidly unwound at a maximum rate of 262 nM of nucleotides per second per molecule of AddAB. (B) A schematic illustration showing the basis of the SSB biosensor (F-SSB) assay in a helicase reaction. As the helicase translocates forward unwinding the dsDNA, F-SSB binds to the unwound single strands and its fluorescence increases by 9-fold.