P62dok (downstream of tyrosine kinases) was identified as a target of protein tyrosine kinases. Following phosphorylation, p62[dok] binds to Ras GTPase activatin protein (RasGap), indicating a role for p62[dok] in intracellular signaling pathways. p62[dok] contains several motifs that signify its important interactions with signaling proteins. These domains include the pleckstrin homology (PH) domain in the amino terminus, numerous tyrosines in the C-terminus, and ten PXXP motifs. p56[dok2] (Dok-R, FRIP) is 35% identical to p62[dok], and contains a PH domain, a central Dok homology motif (DKH), multiple tyrosine phosphorylation sites, and six PXXP motifs. Similar to p62[dok], p56[dok2] binds p120 RasGap, and may act as an adaptor molecule between RasGap and receptor complexes. p56[dok2] is expressed in tissues of hematopoietic origin, and is phosphorylated by the cytokines, IL-2, IL-3, and IL-4. In addition, p56[dok2] may act as an adaptor signaling molecule for the endothelial-specific receptor tyrosine kinase (RTK), Tek/Tie2. Thus, p56[dok2] is a second member of the Dok RasGap-binding family of proteins, which act as adaptor molecules in RTK signaling.