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UBR-box found in UBR family of E3 ubiquitin ligases (UBR1-7) and similar proteins The UBR-box is a 70-residue zinc finger domain present in the UBR family of E3 ubiquitin ligases (UBR1-7, also called N-recognins) that directly binds N-terminal degradation signals (N-degrons) in substrate proteins to facilitate substrate ubiquitination and proteasomal degradation via the ubiquitin-proteasome system (UPS). UBR1 and UBR2 bind all type-1 and type-2 N-degrons. They mediate ubiquitination and proteolysis of short-lived regulators and misfolded proteins. UBR4 binds both type-1 and type-2 N-degrons and is involved in proteome-wide turnover of cell surface proteins. UBR5 preferentially binds type-1 N-degrons and mediates ubiquitination of short-lived proteins. UBR3, UBR6 (also called FBXO11), and UBR7 may not bind efficiently to N-degrons. UBR3 is a RING-type E3 ubiquitin ligase with a function in olfactory and other sensory systems. UBR6 is an E3 ubiquitin ligase and a type II methyltransferase, which functions as a key regulator of tumor initiation and progression. It does not bind N-terminal signals. UBR7 is a RING-type E3 ubiquitin ligase that may play an important role in spermiogenesis and fertilization. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",