Schaffhausen, B., Benjamin, T.L., Pike, L., Casnellie, J. and Krebs, E. (1982) Epidermal Growth Factor Stimulates the Phosphorylation of Synthetic Tyrosine-Containing Peptides by A431 Cell Membranes. J. Biol. Chem. 257: 12467-12470. Middle T antigen of polyoma virus has an associated tyrosine kinase activity which phosphorylates tyrosine residue 315 on middle T in immunoprecipitates. A peptide representing the sequence of middle T from residue 311 to 319 has been synthesized. This peptide acts as a weak inhibitor of the kinase reaction. An antiserum has been raised against this peptide after conjugation to bovine serum albumin. The antibody is middle T-specific. Middle T antigen precipitated by this serum is largely inactive in the kinase reaction. Dissociation of the immune complex with peptide releases middle T in a kinase-active form. |