Phosphorylation of hen progesterone receptor by cAMP dependent protein kinase

Progesterone receptor A and B subunits from laying hen oviducts were highly purified and their phosphorylation by cAMP-dependent protein kinase from bovine heart was studied. Both proteins are phosphorylated by the kinase using physiological or subphysiological concentrations of the enzyme. This result indicates that the receptors are good substrates. The reaction is dependent upon exogenous enzyme; no phosphorylation is seen in the absence of protein kinase.