Protein construct: Wild-type P. aeruginosa DNA helicase purified from a bacterial expression system.
MW: 52 kDa
Enzyme concentration: 20 µM
Enzyme activity assay: The ATPase activity of DNA helicase is measured by using the DNA Helicase ATPase assay Kit (Catalog No. DNAB100K).
Storage temperature: -20 or -80°C. Do not freeze-and-thaw repeatedly.
Enzyme dilution: Use the 1 x assay to dilute the enzyme just before the assay. Do not store diluted enzyme solution
The P. aeruginosa DNA Helicase – for 100 assays (Catalog No. DNAB-100PA) includes 33 µl of 100 x P. aeruginosa DNA helicase (20 µM). It is for 100 assays.
Enzymes and Substrates
Bacterial enzymes
Reference
Nakano T., et al, Translocation and Stability of Replicative DNA Helicases upon Encountering DNA-Protein Cross-links, J. Biol. Chem. 288: 4649-4658 (2013).
Assay Protocol using the DNA Helicase ATPase assay Kit
1. Reagent preparation:
For each 10 assay reactions,
(1) Prepare 297 µl of premix composed of 261 µl of H2O, 33 µl of 10 x Buffer and 3.3 µl of 100 x P. aeruginosa DNA helicase.
(2) Prepare 33 µl of 10 x Enzyme substrate by mixing 3.3 µl of 100 x ATP and 3.3 µl of 100 x DNA and 26.4 µl of water.
2. Reaction:
Mix 27 µl of the premix with 3 µl of the 10 x Enzyme substrate in each well. Incubate the reaction mixture at 37°C for 60 min.
3. Detection:
Add 45 µl of the Dye MPA3000 into the 30 µl of the reaction mixture. Incubate for 5 min. Measure the light absorbance at 650 nm.
Note: The final concentrations for the ATPase assays of the helicases are 20 mM HEPES, pH 7.5, 20 mM potassium glutamate, 1 mM DTT, 0.005% Triton X-100, 10 mM MgCl2, 20 µg /ml DNA, 0.25 mM ATP and 200 nM DNA helicase. A negative control reaction can be the reaction mixture without addition of ATP or enzyme.
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