[Phosphorylation of lysine-rich histones by swine brain histokinase]

The phosphorylation of lysine-rich histones F1, F2a2 and F2b of calf thymus has been investigated using homogeneous histone kinase from pig brain. 32P-labelled phosphopeptides from tryptic digests of corresponding histones were obtained. According to N-terminal analysis and the quantitative determination of amino acid composition of the obtained radioactive peptides the sites of phosphorylation were identified in the primary structure of lysine-rich histones, namely, Ser-38 for the polypeptide chain of histone F1, Ser-19 or 18 for histone F2a2 and Ser-14 and 36 for histone F2b. Thus, the high specificity of brain histone kinase in vitro was demonstrated.