Resolution and general properties of different types of ribosomal protein kinases in mouse plasmocytoma

Three different types of protein kinases (ATP: protein phosphotransferase, EC 2.7.1.37) were isolated and partially purified from a mouse plasmacytoma microsomal KCl wash fraction, then chromatographed on DEAE cellulose and phosphocellulose. The three protein kinase activities designated by protein kinase I, II and III were characterized with respect to their capacity to utilize [gamma-32P]ATP and [gamma-32P]GTP, to interact with cyclic AMP, stimulation by cyclic AMP, substrate specificity and sedimentation behaviour on glycerol gradient centrifugation. Protein kinase I was found to be cyclic AMP dependent and preferentially phosphorylated histones. Protein kinase II and III were insensitive to cyclic AMP, protein kinase II preferentially phosphorylated histones and the protein(s) of a ribosomal KCl wash fraction eluted from DEAE cellulose between 0.2 and 0.35 M KCl and termed "PPx". Protein kinase III phosphorylated casein and ribosomal proteins to a great extent. Studies with glycerol density gradient centrifugation indicated that protein kinase I sediments as a component of about 4.4 S, protein kinase II of 4.3 S and protein kinase III of 3 S. Chromatography on phosphocellulose of the protein kinases isolated from purified free polysomes showed the same type of protein kinases as those from microsomes. So it appears unlikely that protein kinase I and II were contaminants from the cytosol.