Figure 1

The family of HECT E3s. All members of the HECT E3 family are characterized by the C-terminal HECT domain, which consists of approximately 350 amino acid residues and represents the catalytic domain. The HERC family comprises six members, which are characterized by the presence of one or several RLD domains (as representative, the structure of HERC5 is schematically shown). The Nedd4/Nedd4-like family has nine members that are characterized by an N-terminal C2 domain and the presence of several WW domains (as representative, the schematic structure of Smurf2 is shown). The schematic structure of E6-AP, the founding member of the HECT E3 family, is shown as representative of the third subfamily (“E6” denotes the binding site of E6-AP for the HPV E6 oncoprotein). Members of this subfamily (SI-HECT E3s) are characterized by the notion that they contain neither RLDs nor WW domains.