BCR, also named as BCR1 and D22S11, is a GTPase-activating protein for RAC1 and CDC42. BCR promotes the exchange of RAC or CDC42-bound GDP by GTP, thereby activating them. BCR displays serine/threonine kinase activity. BCR catalyzes the reaction: ATP + a protein = ADP + a phosphoprotein. A chromosomal aberration involving BCR is a cause of chronic myeloid leukemia (CML). The antibody is specific to BCR.