Small GTPases of the Rho family, Rho, Rac, and Cdc42, are critical regulators of the actin cytoskeleton and many other cellular processes. Rho GTPases are activated by Dbl-homology (DH)-domain-containing guanine nucleotide exchange factors (GEFs). DOCK 11 (dedicator of cytokinesis 11), also known as ACG or ZIZ2 (zizimin2), is a 2073 amino acid protein belonging to the DOCK family of cytokinesis-regulating proteins that is mainly expressed in peripheral blood leukocytes. DOCK 11 functions as a GEF that binds and activates Cdc42 by exchanging bound GDP for free GTP. Cdc42 mediates cell polarity, gene expression, cell cycle progression and cell–cell contacts. Similar to other DOCK family members, DOCK 11 contains a PH domain and two internal DOCK homology regions designated DHR1 and DHR2.