Analysis of Ptyr proteins constitutively present in p210^bcr/abl-expressing cells. NP-40 lysates (50 μg), obtained from p210^bcr/abl-negative (HL60, TF-1, and M07) and p210^bcr/abl-positive (R10−, R10⁺, K562, and RWLeu4) cell lines as well as CP CML progenitor cells (CP CML), were separated by SDS-PAGE and transferred to Immobilon. The membrane was probed with anti-Ptyr MoAb, 4G10, and developed with the ECL detection system. Molecular weight markers are indicated on the left side of the panel and are in kilodaltons. The asterisk on the right side of panel indicates a Ptyr protein in primary CP CML cells that reacts with an antibody raised against p62^dok. This suggests it may be a degradation product or isoform of p62^dok.