UBR-box found in ubiquitin-protein ligase E3-alpha-1 (UBR1), E3-alpha-2 (UBR2), E3-alpha-3 (UBR3) and similar proteins
This family includes UBR1, UBR2, and UBR3 (all belonging to EC 2.3.2.27). Both UBR1 (also called E3alpha-I or N-recognin-1) and UBR2 (also called E3-alpha-II or N-recognin-2), are RING-type E3 ubiquitin ligases of the Arg/N-end rule degradation pathway. They recognize and bind to proteins bearing specific N-terminal residues that are destabilizing according to the N-end rule, leading to their ubiquitination and subsequent degradation. Deficiency of UBR1 causes Johanson-Blizzard syndrome. UBR2 is associated with chromatin and controls chromatin dynamics and gene expression in both germ cells and somatic cells. It plays an important role in spermatogenesis. UBR3, also called ubiquitin-protein ligase E3-alpha-III (E3alpha-III), or N-recognin-3, or zinc finger protein 650, is a RING-type E3 ubiquitin ligase with a function in olfactory and other sensory systems. It negatively regulates the mono-ubiquitination of non-muscle Myosin II, a protein associated with hearing loss in humans. It acts as a positive regulator of Hedgehog (Hh) signaling in Drosophila and vertebrates. It also plays an important role for genome stability by controlling cellular levels of the essential DNA repair protein APE1.
Jiyao W et al.(2023). "The conserved domain database in 2023.",