Purification and Characterization of Three Distinct Protein Kinases from Marchantia polymorpha

Three protein kinases (HK-I, HK-II and HK-III) have been partiallypurified from the 1.0 M KC1 extract of Marchantia polymorphaand biochemically characterized. It was found that (i) the molecularweights of HK-I, HK-II and HK-III were approximately 23 kDa,47 kDa and 28 kDa, respectively; (ii) these three kinases requireddivalent cations, such as Mn²⁺ and Mg²⁺, but not Ca²⁺, for activity;and (iii) histone H1 was an effective phosphate acceptor forboth HK-I and HK-II, whereas the other kinase (HK-III) effectivelyphosphorylated whole histone (Type II-A from calf thymus) ratherthan histone H1. Heparin (20µg/ml), an inhibitor of caseinkinase II, significantly stimulated the phosphorylation of cellularpolypeptides by HK-II, which was thermo sensitive even at 30?C,rather than that by the other kinases (HK-I and HK-III). Moreover,experiments in vitro and in vivo to determine the native phosphateacceptors for HK-II indicated that a 60-kDa cellular polypeptidemay be one of the native phosphate acceptors for the proteinkinase. In addition, the similarity in properties of cdc2-kinase,which plays an important role in the cell cycle (in the transitionfrom the G₂ phase to mitosis) of yeast and many eukaryotic cells,to HK-II is discussed. (Received May 2, 1990; Accepted December 6, 1990)