... aprotinin, leupeptin and pepstatin, twice in kinasebuffer, and used for in vitro kinase assays. In vitro kinase assaysRecombinant human protein kinase CK2 holoenzyme(0.5 U, corresponding to ... N-Terminal domain; B, Rio1family-specific domain (R-domain); CK, serine-rich acidic domain (pos. 402–435, CK2 domain); and K, lysine-rich C-terminal domain (K domain,pos. 436–484). (B) N- and ... progression through the G1 phase [11].Keywordsatypical protein kinase; casein kinase 2substrate; cell-cycle phase- dependentdegradation; protein–protein interactions;Rio1 protein kinase21CorrespondenceM....