EULIR is a major component of the ubiquitin-proteasome system and plays a role in determining the specificity of ubiquitin conjugation. It is responsible for transferring ubiquitin to targeted substrates from an E2 ubiquitin-conjugating enzyme through the intermediate formation of a thiol ester with ubiquitin. Similar to a number of other E3 ubiquitin ligases, EULIR contains an N-terminal ankyrin repeat domain, a mind bomb (mib) domain and a C-terminal HECT (homologous to E6-AP C-terminus) domain. The HECT domain is responsible for the ubiquitin ligase activity, catalyzing polyubiquitination. EULIR is ubiquitously expressed throughout early development and is important for the complete and proper closure of the neural tube. Mutations in the gene encoding EULIR can result in neural tube defects.