Studies on a Ca2+- and Cyclic Nucleotide-Independent H1 Histone Kinase Purified from Rabbit Skeletal Muscle

In an attempt to elucidate the regulatory mechanism of microsomal function by protein phosphorylation, one of the major protein kinases obtained during the preparation of the microsomal fraction of rabbit skeletal muscle was partially purified and characterized. This enzyme was a protein serine/threonine kinase and showed similar, but not completely same properties as those of Ca 2+-phospholipid-dependent protein kinase (protein kinase C), judging from its elution profile from an anion-exchange column, molecular mass, responses to protein kinase activators or inhibitors and the substrate specificity. These results suggest a possible implication of this Ca 2+- and cyclic nucleotide-independent H1 histone kinase in protein phosphorylation of microsomal protein(s), although the exact role and the mechanism of regulation of this enzyme are not clear at this time.