Phosphorylation of calf thymus H1 histone by calcium-activated,phospholipid-dependent protein kinase

Ca²⁺-activated, phospholipid-dependent protein kinase recently found in mammalian tissues (Takai, Y., Kishimoto, A., Iwasa, Y., Kawahara, Y., Mori, T., and Nishizuka, Y. (1979) $\text{J.}$$\text{Biol.}$$\text{Chem.}$$\text{254}$, 3692–3695) is able to phosphorylate five fractions of calf thymus histone. H1 histone serves as a preferential substrate, and approximately two moles of phosphate are incorporated into every mole of this histone. Analysis on the N-bromosuccinimide-bisected fragments of this radioactive histone has revealed that the enzyme phosphorylates preferentially seryl and threonyl residues located in the carboxyl-terminal half of this histone molecule.