CrkL is associated with kinase active syk.

(A) Platelets were treated with collagen or buffer for 5 minutes. CrkL was purified from the soluble extracts by immunoprecipitation as described above. Immune complexes were incubated in kinase buffer with or without 1 mM ATP for 30 minutes. Tyrosine phosphorylation was then examined by immunoblotting with 4G10. (B) Both SH2 and amino terminal SH3 domains of CrkL are involved in the association of CrkL with syk in vitro. The procedures are the same as in Figure 2A, except that anti-syk monoclonal antibody is used to detect syk in the precipitates.