DESCRIPTION: (Adapted from applicant's description) The investigator proposes to identify syk tyrosine phosphorylation sites, determine for each site whether it is tyrosine phosphorylated as a result of syk autophosphory-lation and/or src kinase-mediated transphosphorylation, and analyze the role of the phosphorylation in syk enzymatic activation. The results of this project will provide the foundation for future studies aimed at elucidating the functional role of each of these tyrosine phosphorylations in antigen receptor-mediated signal transduction.