Protein with a unique structure having two opposing regulatory activities toward small GTP-binding proteins. The C-terminus is a GTPase-activating protein (GAP) domain which stimulates GTP hydrolysis by RAC1, RAC2 and CDC42. Accelerates the intrinsic rate of GTP hydrolysis of RAC1 or CDC42, leading to down-regulation of the active GTP-bound form (PubMed:7479768, PubMed:1903516, PubMed:17116687). The central Dbl homology (DH) domain functions as guanine nucleotide exchange factor (GEF) that modulates the GTPases CDC42, RHOA and RAC1. Promotes the conversion of CDC42, RHOA and RAC1 from the GDP-bound to the GTP-bound form (PubMed:7479768, PubMed:23940119). The amino terminus contains an intrinsic kinase activity (PubMed:1657398). Functions as an important negative regulator of neuronal RAC1 activity (By similarity). Regulates macrophage functions such as CSF1-directed motility and phagocytosis through the modulation of RAC1 activity (PubMed:17116687). Plays a major role as a RHOA GEF in keratinocytes being involved in focal adhesion formation and keratinocyte differentiation (PubMed:23940119). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Homotetramer. Interacts with PDZK1 (PubMed:15494376). May interact with CCPG1 (By similarity). Interacts with FES/FPS, ABL1, PIK3R1 and GRB2 (PubMed:15302586, PubMed:1712671, PubMed:9407116). Interacts with HCK (PubMed:9407116). Interacts with SH2D5 (PubMed:25331951). Interacts with DLG4 (PubMed:20962234). The region involved in binding to ABL1 SH2-domain is rich in serine residues and needs to be Ser/Thr phosphorylated prior to SH2 binding. This region is essential for the activation of the ABL1 tyrosine kinase and transforming potential of the chimeric BCR-ABL oncogene. The DH domain is involved in interaction with CCPG1. The amino terminus contains an intrinsic kinase activity. The central Dbl homology (DH) domain functions as guanine nucleotide exchange factor (GEF) that modulates the GTPases CDC42, RHOA and RAC1. Promotes the conversion of CDC42, RHOA and RAC1 from the GDP-bound to the GTP-bound form. The C-terminus is a Rho-GAP domain which stimulates GTP hydrolysis by RAC1, RAC2 and CDC42. The protein has a unique structure having two opposing regulatory activities toward small GTP-binding proteins. Autophosphorylated. Phosphorylated by FES/FPS on tyrosine residues, leading to down-regulation of the BCR kinase activity. Phosphorylation at Tyr-177 by HCK is important for interaction with GRB2. The gene represented in this entry is involved in disease pathogenesis. A chromosomal aberration involving BCR has been found in patients with chronic myeloid leukemia. Translocation t(9;22)(q34;q11) with ABL1. The translocation produces a BCR-ABL found also in acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). Extended N-terminus.