Docking protein 1 is a protein that in humans is encoded by the DOK1 gene. The protein encoded by this gene is part of a signal transduction pathway downstream of receptor tyrosine kinases. The encoded protein is a scaffold protein that helps form a platform for the assembly of multiprotein signaling complexes. Several transcript variants encoding different isoforms have been found for this gene. 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.