Protein construct: Wild-type E. coli DNA gyrase, the (gyrA)2(gyrB)2 complex, composed of the gyrA subunit (MW 97 kDa) and gyrB subunit (90 kDa) purified from a bacterial expression system.
MW: 374 kDa
Enzyme concentration: 2 µM
Enzyme activity assay: The DNA gyrase DNA supercoiling activity is measured by using the DNA Topoisomerase II (Gyrase) Assay Kit (Catalog No. DSA020K)
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 E. coli DNA Topoisomerase II (Gyrase) – for 100 assays (Catalog No. TOP2-100EC) 50 µl 100 x E.coli gyrase (2 µM). It is for 100 assays.
Reference
1. Asha M.K. et al, In vitro anti-Helicobacter pylori activity of a flavonoid rich extract of Glycyrrhiza glabra and its probable mechanisms of action, Joual of Ethnopharmacology, Vol.145(2), pp.581- 586 (2013).
2. Mora-Pale M et al, Antimicrobial mechanism of resveratrol-trans-dihydrodimer produced from peroxidase-catalyzed oxidation of resveratrol. Biotechnol Bioeng.Vol 112, pp2417–2428 (2015).
Assay Protocol using DNA Topoisomerase II (Gyrase) Assay Kit
The following assay protocol is based on a 96-well assay plate format using a standard black 96-well plate (Greiner 655076). For 384-well plate assays using a standard black 384-well plate (Matrix 4318), please reduce the reagent volumes proportionally.
1. Reaction:
The total volume of each reaction mixture is 40µl including: 24µl of H2O, 4µl of 10 x buffer, 4µl of 10 x relaxed DNA (250µg/ml relaxed plasmid DNA), 4µl of 10 x enzyme, 4µl of 10 mM ATP. Incubate the reaction mixture at 37°C for 60 min.
Note: The final concentrations are 20 mM Tris-HCl, pH 8, 35 mM NH4OAc, 4.6 % glycerol, 1 mM DTT, 0.005% Brij35, 8 mM MgCl2, 25µg/ml relaxed plasmid DNA, 1 mM ATP and 20 nM topoisomerase II. The 10 x enzyme is prepared by dilution of the 100x enzyme in 1x assay buffer. A negative control reaction can be the reaction mixture without addition of ATP. Magnesium is essential for the reaction and assay. EDTA should be avoided.
2. Assay
(1) Make 1 x H19 Dilution Buffer by dilution of the 10 x H19 Dilution Buffer 10-fold with water. Freshly prepare the H19 dye by dilution of 1µl the 1500 x H19 dye stock solution with 1.5 ml of 1 x H19 Dilution Buffer (1500 x dilution). Mix the solution evenly by inverting the tube a few times.
(2) Mix 250µl of the freshly prepared H19 dye with each reaction solution (40µl). Incubate the mixture at room temperature for 5 min.
(3) Measure the fluorescence intensity at 535 nm using the excitation wavelength at 485 nm.