Structure and function of myotonin protein kinase causing myotonic dystrophy and analysis of its pathological aspects

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1. An Hl histone kinase has been partially purified from rabbit skeletal muscle through sequential column chromatographies on DEAE-Sephacel, Hl histone-Sepharose and hydroxylapatite.2. The molecular mass of the Hl histone kinase was estimated to be approximately 45-50 kDa by the gel filtration and in-gel assay methods.3. The Hl histone kinase activity was not seriously influenced by the addition of cAMP,Ca^<2+> and phospholipid or calmodulin which were known as activators of several second messenger-dependent protein kinases, or by the addition of protein kinase A inhibitor peptide and heparin known as the inhibitor of casein kinase II.But, the activity was moderately inhibited by protein kinase C inhibitor peptide.4. Substrate specificity of the Hl histone kinase was similar to that of protein kinase C,however different from those of protein kinase A,cdc2 kinase and casein kinases.5. The Hl histone kinase phosphorylated serine residue (s) at the carboxyl-terminal portion of this histone obtained by bisecting it with N-bromosuccinimide as well as protein kinase C.6. The properties of this Hl histone kinase were similar with, but not exactly same as those of the catalytic fragment of protein kinase C.The relation between the Hl histone kinase obtained in this study and the protein serine/threonine kinase, which might be involved in causing myotonic dystrophy, or protein kinase C has been remained to be studied.