Drosophila melanogaster RECQ5/QE DNA helicase: stimulation by GTP binding

The Drosophila melanogaster RECQ5/QE gene encodes a member of the DNA helicase family comprising the Escherichia coli RecQ protein and products of the human Bloom’s, Werner’s, and Rothmund-Thomson syndrome genes. The full-length product of RECQ5/QE was expressed in the baculovirus system and was purified. Gel filtration experiments indicated that RECQ5/QE was present in an oligomeric state. The RECQ5/QE protein hydrolyzed ATP and even more actively GTP in the presence of single-stranded DNA. ATP drove the DNA helicase activity of RECQ5/QE, whereas GTP had little effect. GTP exhibited a stimulatory effect on DNA unwinding when it was used together with ATP. This effect was more apparent with non-hydrolyzable GTP analogs, such as GTPγS and GMPPNP. These results indicate that GTP binding to RECQ5/QE triggers its DNA helicase activity. GTP binding increased the rate of strand separation without affecting the S_0.5 (K_m) values for the substrates during the DNA helicase reaction. The data collectively suggest that the RECQ5/QE protein is activated upon GTP binding through the ATP-binding site.