Direct binding of C-terminal region of p130(Cas) to SH2 and SH3 domains of Src kinase

p130(Cas) is a major tyrosine-phosphorylated protein that tightly binds v-Crk in v-crk-transformed cells and v-Src in v-src-transformed cells. The ''substrate domain'' of p130(Cas) contains 15 possible Src homology (SH) a-binding motifs, most of which conform to the binding motif for the Crk SH2 domain. Another region near its C terminus contains possible binding motifs for the Src SH2 domain and proline-rich sequences that are candidates for SH3-binding sites. Using GST fusion proteins, we revealed that both SH2 and SH3 domains of Src bind p130(Cas), whereas v-Crk binds p130(Cas) through its SH2 domain. We located the binding site of p130(Cas) for the Src SH3 domain at the sequence RPLPSPP in the region near its C terminus. Mutations within this sequence or at Tyr(762) Of p130(Cas) caused a significant reduction in the association of p130(Cas) with Src, and no association was detected when both of them were deleted. The kinase activity in v-Crk-transformed cells was also associated with p130(Cas) through this region. On the other hand, the deletion of the substrate domain abolished the binding with v-Crk, The association through the C-terminal region of p130(Cas) with Src kinase may facilitate effective hyperphosphorylation of tyrosine residues in the substrate domain of p130(Cas), resulting in the binding of SH2-containing molecules to p130(Cas).