This domain is found in eukaryotic aspartyl protease DDI1 (DNA Damage Inducible protein 1; MEROPS identifier A28.001). The remarkable structural similarity between this central domain of DDI1 and the retroviral proteases suggests that DDI1 functions proteolytically during regulated protein turnover [, ]. DDI1 has been shown to activate an endoplasmic-reticulum isoform of the transcription factor SKN-1 in Caenorhabditis elegans when the proteasome is dysfunctional []. DDI1 also has an amino-terminal ubiquitin-like domain and/or a UBA (ubiquitin-associated) domain [].
DDI1 (DNA damage inducible protein 1) has an amino-terminal ubiquitin-like domain, an retroviral protease-like (RVP-like) domain, and a UBA (ubiquitin-associated) domain. This entry represents the amino-terminal ubiquitin-like domain of DDI1 [, , ].Ubiquitin is a globular protein, the last four C-terminal residues (Leu-Arg-Gly-Gly) extending from the compact structure to form a 'tail', important for its function. The latter is mediatedby the covalent conjugation of ubiquitin to target proteins, by an isopeptide linkage between the C-terminal glycine and the epsilon amino group of lysine residues in the target proteins.
