APC10-like DOC1 domains of E3 ubiquitin ligases that mediate substrate ubiquitination.This model represens the APC10-like DOC1 domain of multi-domain proteins present in E3 ubiquitin ligases. E3 ubiquitin ligases mediate substrate ubiquitination (or ubiquitylation), a component of the ubiquitin-26S proteasome pathway for selective proteolytic degradation. APC10/DOC1 domains such as those present in HECT (Homologous to the E6-AP Carboxyl Terminus) and Cullin-RING (Really Interesting New Gene) E3 ubiquitin ligase proteins, HECTD3, and CUL7, respectively, are also included here. CUL7 is a member of the Cullin-RING ligase family and functions as a molecular scaffold assembling a SCF-ROC1-like E3 ubiquitin ligase complex consisting of Skp1, CUL7, Fbx29 F-box protein, and ROC1 (RING-box protein 1) and promotes ubiquitination. CUL7 is a multi-domain protein with a C-terminal cullin domain that binds ROC1 and a centrally positioned APC10/DOC1 domain. HECTD3 contains a C-terminal HECT domain which contains the active site for ubiquitin transfer onto substrates, and an N-terminal APC10/DOC1 domain which is responsible for substrate recognition and binding. An APC10/DOC1 domain homolog is also present in HERC2 (HECT domain and RLD2), a large multi-domain protein with three RCC1-like domains (RLDs), additional internal domains including zinc finger ZZ-type and Cyt-b5 (Cytochrome b5-like Heme/Steroid binding) domains, and a C-terminal HECT domain. Recent studies have shown that the protein complex HERC2-RNF8 coordinates ubiquitin-dependent assembly of DNA repair factors on damaged chromosomes. Also included in this hierarchy is an uncharacterized APC10/DOC1-like domain found in a multi-domain protein, which also contains CUB, zinc finger ZZ-type, and EF-hand domains. The APC10/DOC1 domain forms a beta-sandwich structure that is related in architecture to the galactose-binding domain-like fold; their sequences are quite dissimilar, however, and are not included here.