Kinetic analysis and reversibility assay of CK2 inhibition by coumestrol. A. Lineweaver-Burk plots of inhibition of CK2 by coumestrol: ● 0 μM, ■ 0.1 μM, ▲ 0.5 uM. Substrate concentration was fixed at 200 μM. The plots illustrate that coumestrol is an ATP competitive CK2 inhibitor. The data represents means of duplicate experiments. B. Reversibility study of coumestrol. Coumestrol was pre-incubated with 100 ug/ml of CK2 for 1 hour and then a kinase assay was performed at a final concentration of coumestrol at 100 uM as described in Methods. CK2 kinase activity is represented as relative CK2 activity to control. Data points represent the average of triplicate experiments and bars indicate standard deviation.