Epidermal growth factor stimulates phosphorylation of pig epidermal keratin protein

Endogenous protein phosphorylation of pig epidermis by epidermal growth factor (EGF) was studied to elucidate biologic roles of EGF on epidermal cells. EGF stimulated phosphorylation of keratin proteins (Mr: 65,000, 60,000, 56,000, and 51,000) identified by the Ouchterlony immunodiffusion analysis, a low Mr protein (16,000 dalton) of the urea-SDS-mercaptoethanol soluble fraction, and a 30,000 dalton Tris-HCl soluble protein. The phosphorylated epidermal proteins such as keratin proteins and a 30,000 dalton protein of the Tris-HCl soluble fraction were slightly dephosphorylated following the addition of unlabeled phosphate. Anti-EGF serum eliminated the EGF-stimulated phosphorylation of keratin proteins, a low Mr protein, and a 30,000 dalton Tris-HCl soluble protein. The overall results indicate that EGF specifically stimulated phosphorylation of several epidermal proteins, one of which was keratin protein.