Tyrosine phosphorylation of pp125^FAKfollowing cell adhesion to immobilized Fg. Adherent CHO cells bound to Fg-coated wells or nonadherent cells on BSA-coated wells were lysed in RIPA buffer and immunoprecipitated using an anti-FAK antibody (FAK) or normal rabbit IgG (NR). Immunoprecipitates were separated on SDS-PAGE, transferred to a PVDF membrane, and probed with HRP-conjugated PY20 to assess the tyrosine phosphorylation state of FAK. Note that adhesion of Pen^a and Pen^b transfectants to immobilized Fg induces similar levels of tyrosine phosphorylation of FAK. The gel is representative of 3 experiments.