Six-histidine-tagged PTPs that fail to counter v-Src toxicity also do not express. Proteins from yeast lysates expressing v-Src with PTP1B-His6 (Lane 1), PTPH1-His6 (Lane 2), PTPα-His6 (Lane 3), Lyp-His6 (Lane 4), PEST-His6 (Lane 5), Shp2-His6 (Lane 6), or no PTP (Lane 7) were separated by SDS-PAGE and transferred to nitrocellulose. The resulting membrane was stained with Ponceau S (A), washed, and immunoblotted with an anti-five- histidine antibody (B).