Fig. 7. (A) Binding of synthetic peptides (see Fig. 6A) to purified GST-fusion proteins of paxillin (expected M_r approx. 95 kDa) and of the N-terminal domain (amino acids 1-407) of human Pyk2 (expected M_r approx. 70 kDa). Bound and unbound proteins were analyzed by immunoblotting with an anti-GST antibody as well as on Coomassie-stained 15% SDS-polyacrylamide gels. Note the depletion of GST-fusion proteins in the supernatants incubated with the ß3-tail peptide. Note also the nearly complete absence of bovine serum albumin in the bound fractions, which was present in a very large excess over GST-fusion proteins in the binding reactions. (Co, control resin consisting of streptavidin agarose without any added peptide; n.d., not done). (B) Comparison of GST, GST-paxillin and GST-Pyk2NT binding to the ß3-tail peptide. Note the depletion in the unbound fractions of GST-Pyk2NT and GST-paxillin after binding. GST proteins were calibrated to give comparable signals in the supernatants by detection with Anti-GST antibody.