A CONFORMATION-SPECIFIC ANTIPEPTIDE ANTIBODY TO THE BETA-TYPE PLATELET-DERIVED GROWTH-FACTOR RECEPTOR ALSO RECOGNIZES THE ACTIVATED EPIDERMAL GROWTH-FACTOR RECEPTOR

Earlier we reported the generation of a conformation-specific antibody (Ab P2) to the beta-type platelet-derived growth factor receptor (Bishayee, S., Majumdar, S., Scher, C.D., and Khan, S. (1988) Mol. Cell. Biol. 8, 3696-3702). Ab P2 is directed to a 16-amino acid peptide (Glu-Gly-Tyr-Lys-Lys-Lys-Tyr-Gln-Gln-Val-Asp-Glu-Glu-Phe-Leu-Arg) of the cytoplasmic domain of the receptor, and it recognized the phosphorylated platelet-derived growth factor receptor but not the unphosphorylated receptor. We now report that Ab P2 also interacts with the epidermal growth factor receptor and that the recognition is specific for a conformation induced by phosphorylation of the receptor; however, Ab P2 is not directed to phosphotyrosine. Studies conducted with P2-derived peptides suggest that the conformation-specific antibody is directed to an acidic tripeptide, Asp-Glu-Glu, and this sequence is also present in the cytoplasmic domain of the epidermal growth factor receptor. With respect to the C terminus amino acid or ATP-binding site, Asp-Glu-Glu is located in different regions in these receptors; nevertheless, this tripeptide along with the surrounding amino acids is cryptic in the unphosphorylated receptor, and tyrosine phosphorylation uncovers this site. This suggests that the Asp-Glu-Glu sequence may be important in receptor functions.