Inhibition of DNA helicase II unwinding and ATPase activities by DNA-interacting ligands. Kinetics and specificity.

摘要: Although DNA helicases play important roles in the processing of DNA, little is known about effects DNA-interacting ligands on these helicases. Therefore, a wide variety DNA-binding unwinding and ATPase reactions catalyzed by Escherichia coli helicase II were examined. minor groove binders simple intercalators did not inhibit II. However, intercalators, such as mitoxantrone nogalamycin, which position functionalities major upon binding duplex potent inhibitors To determine mechanism inhibited II, DNA-dependent activities measured using spectrum double- single-stranded substrates. Using either 71-base pair (bp) M13mp7 partially duplexed substrate or 245-bp bluntended, fully substrate, apparent Ki value for inhibition both was approximately 1 microM substrates, suggesting that same substrates requires presence double-stranded structure. strengthen this conclusion, ability to activity determined two poly(dT) after heat denaturation. far less effectively. Thus, results indicate intercalation into with accompanying placement groove, generates complex impedes resulting ATP hydrolysis activity. Furthermore, we report here I IV Rep protein from E. coli, demonstrating observed unique enzyme.