FGD5 is a 1,462 amino acid cytosolic protein that contains a DH domain, a FYVE-type zinc finger and two PH domains. FGD family members encode guanine nucleotide exchange factors that specifically activate the Rho GTPase Cdc42. All FGD proteins contain equivalent signaling domains and a conserved structural organization, which strongly suggests that these signaling domains form a canonical core structure for members of the FGD family of RhoGEF proteins. These proteins also control essential signals required during embryonic development.