Identification of enzymatically active Ca2+/calmodulin-dependent protein kinase in centrosomes of hemopoietic cells

In this study, we report the identification of enzymatically active, multifunctional calcium/calmodulin-dependent protein kinase in centrosomes of FDCP1 cells using subcellular fractionation and immunofluorescence techniques. Centrosomes were isolated from detergent lysates of FDCP cells by sucrose density gradient centrifugation and contain tubulin (M(r) = 58 kDa) and centrin (M(r) = 20 kDa) by immunoblotting. Analysis of these fractions with anti-calcium/calmodulin kinase II antibody revealed the presence of the 52 kDa and 56 kDa doublet corresponding to the alpha and the beta/beta' subunits of the enzyme complex. In vitro kinase reactions with isolated centrosomes and in the presence of calcium and calmodulin results in the phosphorylation of several centrosomal proteins.