UBR-box found in RING-type E3 ubiquitin-protein ligase UBR4 and similar proteins
UBR4 (EC 2.3.2.27; also called 600 kDa retinoblastoma protein-associated factor, N-recognin-4, retinoblastoma-associated factor of 600 kDa, RBAF600, p600, or zinc finger UBR1-type protein 1) is a RING-type E3 ubiquitin ligase of the Arg/N-end rule degradation pathway. It recognizes and binds to proteins bearing specific N-terminal residues that are destabilizing according to the N-end rule, leading to their ubiquitination and subsequent degradation. UBR4 acts as a multifunctional protein with roles in anoikis, viral transformation, and protein degradation, as well as in neurogenesis, neuronal migration, neuronal signaling, and survival. The family also includes Arabidopsis thaliana auxin transport protein BIG (also called protein attenuated shade avoidance 1, protein corymbosa1, protein dark over-expression of cab 1, protein low phosphate-resistant root 1, protein transport inhibitor response 3, or protein umbrella 1). It is a calossin-like protein required for auxin efflux and polar auxin transport (PAT) influencing auxin-mediated developmental responses in Arabidopsis.
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