Docking protein 1 is constitutively tyrosine phosphorylated in hematopoietic progenitors isolated from chronic myelogenous leukemia (CML) patients in the chronic phase. It may be a critical substrate for p210(bcr/abl), a chimeric protein whose presence is associated with CML. Docking protein 1 contains a putative pleckstrin homology domain at the amino terminus and ten PXXP SH3 recognition motifs. Docking protein 2 binds p120 (RasGAP) from CML cells. It has been postulated to play a role in mitogenic signaling.