Differential phosphorylation of the progesterone receptor by insulin, epidermal growth factor, and platelet-derived growth factor receptor tyrosine protein kinases.

摘要: Abstract Purified preparations of insulin, epidermal growth factor (EGF), and platelet-derived (PDGF) receptors were compared for their abilities to phosphorylate purified hen oviduct progesterone receptors. The specific activities all three peptide hormone-induced receptor kinases first defined using a synthetic tridecapeptide tyrosine protein kinase substrate. Next, equivalent ligand-activated the tested receptor. Both insulin EGF phosphorylated at high affinity, exclusively residues with maximal stoichiometries that near unity. In contrast, PDGF did not recognize as Insulin decreased Km subunits substrates, but had no significant effect on Vmax values. On other hand, increased substrates. Phosphorylation by differed in two additional ways. 1) EGF-activated 80- 105-kDa an equal extent, whereas insulin-activated preferentially 80-kDa subunit. 2) Phosphopeptide fingerprinting analyses revealed while one identical major site both subunits, they specificities sites.