PURIFICATION AND CHARACTERIZATION OF 3 DISTINCT PROTEIN-KINASES FROM MARCHANTIA-POLYMORPHA

Three protein kinases (HK-I, HK-II and HK-III) have been partially purified from the 1.0 M KCI 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 Mn2+ and Mg2+, but not Ca2+, for activity; and (iii) histone H1 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 H1. Heparin (20-mu-g/ml), an inhibitor of casein kinase II, significantly stimulated the phosphorylation of cellular polypeptides by HK-II, which was thermo sensitive even at 30-degrees-C, rather than that by the other kinases (HK-I 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 G2 phase to mitosis) of yeast and many eukaryotic cells, to HK-II is discussed.