4,5,6,7-Tetrabromobenzimidazole is a selective ATP-competitive inhibitor of protein kinase CK2 from such divergent sources as yeast, rat liver, Neurospora erassa and Candida tropicalis, with Ki values in the range of 0.5-1uM. It is virtually inactive against PKA, PKC, and a very weak inhibitor of protein kinase CK1.
Zien, P., et al.: Biochemical and Biophysical Res. Commun., 306, 129 (2003)