Figure 4

Radiometric CK2 assay using CK2-presenting E. coli. The amount of transferred ³²P from γ-[³²P]-ATP onto the synthetic substrate peptide RRRDDDSDDD was quantified in counts per minute (cpm). Reactions were catalyzed by surface display of CK2β [E. coli BL21(DE3) pCK2β], CK2α [E. coli BL21(DE3) pCK2α] and both, the α- and β-subunit of CK2 [E. coli BL21(DE3) pCK2α pCK2β]. Samples with the host strain or completely without cells were used as controls, having no CK2 kinase activity. E. coli BL21(DE3) pCK2α pCK2β was treated with the CK2 inhibitor TBB in a concentration of 10 µM prior to reaction start. The histograms display mean values (±standard deviation, n = 3, *p < 0.005).