CYSTEINE(3) OF SRC FAMILY PROTEIN-TYROSINE KINASES DETERMINES PALMITOYLATION AND LOCALIZATION IN CAVEOLAE

Recent work has demonstrated that p56(lck), a member of the Src family of protein tyrosine kinases (PTKs), is modified by palmitoylation of a cysteine residue(s) within the first 10 amino acids of the protein ( in addition to amino-terminal myristoylation that is a common modifica tion of the Src family of PTKs). This is now extended to three other m embers of this family by showing incorporation of [H-3]palmitate into p59(fyn), p55(fgr), and p56(hck), but not into p60(src). The [H-3]palm itate was released by treatment with neutral hydroxylamine, indicating a thioester linkage to the protein. Individual replacement of the two cysteine residues within the first 10 amino acids of p59(fyn) and p56 (lck) with serine indicated that Cys(3) was the major determinant of p almitoylation, as well as association of the PTK with glycosyl-phospha tidylinositol-anchored proteins. Introduction of Cys(3) into p60(src) led to its palmitoylation. p59(fyn) but not p60(src) partitioned into Triton-insoluble complexes that contain caveolae, microinvaginations o f the plasma membrane. Mapping of the requirement for partitioning int o caveolae demonstrated that the amino-terminal sequence Met-Gly-Cys i s both necessary and sufficient within the context of a Src family PTK to confer localization into caveolae. Palmitoylation of this motif in p59(fyn) also modestly increased its overall avidity for membranes. T hese results highlight the role of the amino-terminal motif Met-Gly-Cy s in determining the structure and properties of members of the Src fa mily of PTKs.