ubiquitin-like (Ubl) domain found in small ubiquitin-related modifier SUMO-2, SUMO-3, SUMO-4, and similar proteins
SUMO (also known as "Smt3" and "sentrin" in other organisms) resembles ubiquitin (Ub) in structure, ligation to other proteins and the mechanism of ligation. Ubiquitin is a protein modifier in eukaryotes that is involved in various cellular processes including transcriptional regulation, cell cycle control, and DNA repair. Ubiquitination is comprised of a cascade of E1, E2 and E3 enzymes that results in a covalent bond between the C-terminus of Ub and the epsilon-amino group of a substrate lysine. SUMOs, like Ub, are covalently conjugated to lysine residues in a wide variety of target proteins in eukaryotic cells and regulate numerous cellular processes, such as transcription, epigenetic gene control, genomic instability, and protein degradation. The mammalian SUMOs have four paralogs, SUMO1 through SUMO4. SUMO2 and SUMO3 are more closely related to each other than they are to SUMO1. SUMO2/3 are capable of forming chains on substrate proteins through internal lysine residues. The basic biology of SUMO4 remains unclear. A M55V polymorphism in SUMO4 has been associated with susceptibility to type I diabetes in some genetic studies.
Jiyao W et al.(2023). "The conserved domain database in 2023.",