A synthetic peptide derived from the site I
sequence of FAK specifically interacts with the SH3 domain of Cas. GST
alone (lanes 1 and 2) or fused to the SH3 domain of Cas (lanes 3-8),
cortactin (lanes 9 and 10), or Src (lanes 11 and 12), or the N terminus
of paxillin (lanes 13 and 14) was preincubated with increasing amounts
of wild-type peptide (EAPPKPSRPGYPSPRSS, 0 to 100 μM), followed by
incubation with 500 μg of CE cell lysate. Protein complexes were
captured, resolved by SDS-PAGE, and blotted for the presence of FAK
(top) and FRNK (bottom) with the polyclonal antiserum BC3.