Development of a rapid approach to identification of tyrosine phosphorylation sites: application to PKC delta phosphorylated upon activation of the high affinity receptor for IgE in rat basophilic leukemia cells.

In rat basophilic leukemia cells (RBL-2H3) activation of the high affinity receptor for IgE induces tyrosine phosphorylation of PKC delta. We carried out solid phase synthesis of 15 amino acid long oligopeptides corresponding to the sequences around each of the 19 tyrosine residues in PKC delta. Only three oligopeptides, corresponding to tyrosine 52, 155, and 565, were phosphorylated when exposed to lyn kinase. Single mutants in each of these three tyrosine residues of PKC delta were prepared. Upon expression in the RBL-2H3 cells, only the mutant in tryosine 52 showed abolition of the IgE-antigen induced tyrosine phosphorylation.