EDD, the ER ubiquitin ligase from the HECT ligases, contains an N-terminal ubiquitin-associated domain which binds ubiquitin. Ubiquitin is recognised by helices alpha-1 and -3 in in the UBA domain. EDD is involved in DNA damage repair pathways and binds to mono-ubiquitinated proteins [1].

1: Structural basis of ubiquitin recognition by the ubiquitin-associated (UBA) domain of the ubiquitin ligase EDD. Kozlov G, Nguyen L, Lin T, De Crescenzo G, Park M, Gehring K; J Biol Chem. 2007;282:35787-35795. PMID:17897937