A synthetic peptide containing the autophosphorylation site of the transforming protein of Harvey sarcoma virus is phosphorylated by the EGF-stimulated tyrosine kinase

Abstract

The transforming proteins (p21) of Harvey and Kirsten sarcoma viruses threonine kinase activity, which phosphorylates threonine 59 of the p21 proteins themselves. A tridecapeptide: Arg—Arg—Leu 56—Asp—Thr—Thr 59—Gly—Gln—Glu—Tyr—Ser—Ala 66 containing residues 56-66 of p21 is phosphorylated solely on tyrosine by the epidermal growth factor (EGF)-stimulated tyrosine kinase of A431 cell membranes. K m-Values of 240 and 80 μM and V max values of 1.7 and 0.1 nmol.min −1.mg −1 were obtained in the presence and absence of EGF, respectively.