DNA-mediated signaling by the E. coli helicase, DinG

The protein DinG is an ATP-dependent helicase from E. coli that contains a 4Fe-4S cluster. DNA-modified gold electrodes were used to measure the midpoint redox potential of the DNA-bound protein, which was found to be ∼80 mV vs. Using a 20-mer with a 15-mer single-stranded overhang as a helicase substrate on the DNA-modified electrodes, it was shown that enzymic activity via the hydrolysis of ATP increased the intensity of the electrochem. signal intensity. Whether DinG and EndoIII, a base excision repair enzyme also contg. a 4Fe- 4S cluster, use DNA-mediated charge transport (CT) chem. for inter-protein signaling was tested using several techniques. Using a single mol. at. force microscopy assay, it was shown that DinG and EndoIII preferentially redistribute to strands of DNA that contain DNA damage via long-range DNA-mediated CT. To test this signaling within cells, genetics expts. were used that strongly suggest that DinG and EndoIII utilize DNA-mediated signaling to cooperate in redistributing DinG to its target lesion.