The largest class of RhoGEFs is composed of proteins containing the "Dbl-homology" (DH) domain, which almost always is found together with a pleckstrin-homology (PH) domain to form a combined DH/PH domain structure.[2][3]
A distinct class of RhoGEFs is those proteins containing the DOCK/CZH/DHR-2 domain. This structure has no sequence similarity with DBL-homology domains.[4]