PALMITYLATION OF SRC FAMILY TYROSINE KINASES REGULATES FUNCTIONAL INTERACTION WITH A B-CELL SUBSTRATE

Palmitylation of Src family tyrosine kinases has been shown to play a role in directing their membrane localization. Here we demonstrate tha t palmitylation can also regulate recognition and tyrosine phosphoryla tion of the B cell Src kinase substrate Ig alpha. Blk and Src, which a re not palmitylated, phosphorylate co-expressed Ig alpha in Cos cells, whereas palmitylated Src kinases do not. Addition of a palmitylation site to Blk abrogates its phosphorylation of the substrate, while muta tion of Fyn's palmitylation sites results in recognition and phosphory lation of Ig alpha. These results indicate that palmitylation, a rever sible protein modification, aids in regulating recognition of physiolo gic substrates by Src family tyrosine kinases. (C) 1997 Academic Press .