Quantitative analysis of the Ptyr 155-kD protein in anti-SHC immunoprecipitates from K562 lysates. K562 cells either untreated (lane A) or treated overnight with the tyrosine kinase inhibitor, CGP57148 (lane B), were lysed. NP-40 lysates (200 × 10⁶ cell equivalents) were immunoprecipitated with an anti-SHC polyclonal antibody and the resulting precipitates were separated in a 6% SDS-PAGE gel. The resolved proteins were then detected by silver staining. Standard molecular weight marker proteins (50 ng/protein) were run simultaneously (M).