Expression, purification, and crystallization of human CK2α in complex with the natural flavonoid quercetin

Over 300 polypeptide substrates can undergo catalysis by the constitutively active Ser/Thr kinase, human casein kinase 2 alpha (hCK2α).Quercetin, a naturally occurring polyphenolic compound, is well-known for inhibiting hCK2α, thereby regulating cellular signaling pathways.In this study, we crystallized the hCK2α-quercetin complex to elucidate the inhibitory mechanism of quercetin on hCK2α through the complex structure.The hanging drop vapor diffusion method was employed for crystallizing the hCK2α-quercetin complex, and the resulting crystal diffracted to a resolution of 2.11 Å. X-ray diffraction data analysis revealed that the crystal of the hCK2α-quercetin complex belonged to the P4 3 2 1 2 space group, with unit cell dimensions of a = b = 127.604Å, c = 124.314Å, and α = β = γ = 90.00°.In an initial density map, quercetin was bound well into hCK2α.