the in vitro phosphorylation of the rat histone with a cyclic amp-dependent protein kinase isolated from rat pancreas led to the identification of four sites of phosphorylation : two major ones , at serine residues 32 and 36 , and two minor ones , specific of the rat protein kinase , at serine residues 87 and 91 .
C0031715
phosphorylation
C0031727
kinase