Purification and Characterization of Three Distinct Protein Kinases from Marchantia polymorpha

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Three protein kinases (HK-I, HK-II and HK-III) have been partially purified from the 1.0 M KCl extract of Marchantia polymorpha and biochemically characterized. It was found that (i) the molecular weights of HK-I, HK-II and HK-III were approximately 23 kDa, 47 kDa and 28 kDa, respectively; (ii) these three kinases required divalent cations, such as Mn^<2+> and Mg^<2+> , but not Ca^<2+>, for activity; and (iii) histone Hl was an effective phosphate acceptor for both HK-I and HK-II, whereas the other kinase (HK-III) effectively phosphorylated whole histone (Type II-A from calf thymus) rather than histone Hl. Heparin (20μg/ml), an inhibitor of cozen kinase II, significantly stimulated the phosphorylation of cellular polypeptides by HK-II, which was therm sensitive even at 30'C, rather than that by the other kinases (HO-1 and HK-III). Moreover, experiments in vitro and in vivo to determine the native phosphate acceptors for HK-II indicated that a 60-kDa cellular polypeptide may be one of the native phosphate acceptors for the protein kinase. In addition, the similarity in properties of cdc2-kinase, which plays an important role in the cell cycle (in the transition from the G_2 phase to mitosis) of yeast and many eukaryotic cells, to HK-II is discussed.
日本植物生理学会の論文