WB (peptide competition) analysis of COS cells overexpressing human wild-type PAG3 alone (Lane 1) co-transfected with human wild-type PAG3 and mouse Pyk2 (Lane 2-5), or mutant (Y724F/Y763F) PAG3 and mouse Pyk2 (Lane 6) using GTX18031 PAG3 (phospho Tyr724) antibody prior incubated with the non-phosphopeptide corresponding to the immunogen (Lane 3), a generic phosphotyrosine-containing peptide (Lane 4), or, the phosphopeptide immunogen (Lane 5) control. The data show that only the immunogen phosphopeptide blocks the signal, demonstrating the specificity of the antibody.