Crystal structures of human CK2α2 in new crystal forms arising from a subtle difference in salt concentration

The catalytic subunits of protein kinase CK2 are classified into two subtypes: CK2α1 and CK2α2. CK2α1 is an attractive drug‐discovery target for various diseases such as cancers and nephritis. CK2α2 is defined as an off‐target of CK2α1 and is a potential target in the development of male contraceptive drugs. High‐resolution crystal structures of both isozymes are likely to provide crucial clues for the design of selective inhibitors of CK2α1 and/or CK2α2. To date, several crystal structures of CK2α1 have been solved at high resolutions of beyond 1.5 Å. However, crystal structures of CK2α2 have barely achieved a low resolution of around 3 Å because of the formation of needle‐shaped crystals. In this study, new crystal forms were exploited and one provided a crystal structure of CK2α2 at 1.89 Å resolution. This result, together with the structure of CK2α1, will assist in the development of highly selective inhibitors for both isozymes. New crystal forms of human CK2α2 were discovered and one showed improved crystallographic resolution to a maximum of 1.89 Å.