Identification of myosin II kinase from sea urchin eggs as protein kinase CK2

Here we purified and identified a myosin II kinase from sea urchin eggs. Th e activity of this myosin II kinase in the egg extract was not significantl y affected by Ca2+/calmodulin (CaM). Using sequential column chromatographi es, we purified the myosin II kinase from the egg extract as a complex comp osed of 36- (p36) and 28-kDa (p28) proteins. Partial amino acid sequences o f these two components were highly coincident with those of the alpha and b eta subunits of protein kinase CK2 (formerly casein kinase II) in sea urchi n eggs, respectively. To confirm that the purified myosin II kinase was CK2 , we obtained a cDNA which encodes p36 from a cDNA library of sea urchin eg gs. The amino acid sequence derived from the obtained cDNA showed over 70% homology to CK2 from various eukaryotes. Furthermore, recombinant p36, as w ell as the purified myosin II kinase, phosphorylated MRLC. One dimensional phosphopeptide mapping revealed that the phosphorylation site(s) of MRLC by both recombinant p36 and the purified myosin II kinase was identical. Thes e clearly showed that the Ca2+/CaM-independent myosin II kinase activity in sea urchin eggs was identical to CK2. (C) 2001 Elsevier Science B.V. All r ights reserved.