ANALYSIS OF THE SITES IN P56LCK WHOSE PHOSPHORYLATION IS INDUCED BY TETRADECANOYL PHORBOL ACETATE

Abstract

P56lck is a member of the src family of tyrosine kinases that is expressed almost exclusively in lymphocytes. Previous studies have shown that treatment of T cells with activators of protein kinase C induces serine phosphorylation of p56lck. We show here that treatment of Jurkat cells with 12-O-tetradecanoyl phorbol-13-acetate also induces threonine phosphorylation of p56lck. Chymotryptic mapping shows that at least three sites in p56lck. Chymotryptic mapping shows that at least three sites in p56lck undergo phosphorylation in TPA-treated Jurkat cells. Cyanogen bromide cleavage analysis demonstrates that these new phosphorylation sites are located in an amino-terminal 32 kDa fragment containing amino acid residues 14-261.