Epidermal growth factor stimulates tyrosine phosphorylation of pig epidermal fibrous keratin

Epidermal growth factor (EGF) stimulated phosphorylation of pig epidermal proteins, one of which was pig epidermal keratin. In order to further characterize phosphorylated proteins and specify the EGF-dependent protein phosphorylation, we attempted to identify phosphorylated keratin proteins and to analyze phosphorylated phosphoamino acids of keratin proteins stimulated by EGF. Four major polypeptide bands of pig epidermal keratin were immunoprecipitated by antihuman callus keratin antibody which reacted with fine networks of fibrous keratin of pig epidermal cells grown in vitro. Four major polypeptide bands were greatly phosphorylated by EGF in a dose-dependent manner. The analysis of phosphorylated phosphoamino acids revealed that EGF stimulated tyrosine phosphorylation of pig epidermal fibrous keratin.