Purification and characterization of a protein kinase in Tetrahymena cilia

Abstract

A protein kinase was detected in Tetrahymena cilia and partially purified by hydroxyapatite column chromatography and Sephadex G-200 gel filtration. This enzyme preferred casein to histone and protamine as substrate protein. The apparent K m for casein was about 0.6 mg/ml and that for ATP was about 25 μM when casein was used as substrate protein. The pH optimum for casein phosphorylation was about 8.5. 10 mM Mg 2+ was required for its maximal activity. In the absence of Mg 2+, other divalent cations such as Mn 2+ and Co 2+ could partially substitute for Mg 2+. The molecular weight of the enzyme was estimated to be about 53 000. The ciliary protein kinase was found to catalyzed the phosphorylation of tubulin prepared from ciliary axonemes. Furthermore, adenosine 3′,5′-monophosphate showed little effect on the phosphorylation of casein, histone, protamine and tubulin.