E3 ubiquitin-protein ligase which is a component of the N-end rule pathway (PubMed:17462990). Does not bind to proteins bearing specific N-terminal residues that are destabilizing according to the N-end rule, leading to their ubiquitination and subsequent degradation (PubMed:17462990). May play a role in Shh signaling by mediating the ubiquitination of Kif7 (PubMed:27195754). May be important for MYH9 function in certain tissues, possibly by regulating the ubiquitination of MYH9 and consequently affecting its interaction with MYO7A (PubMed:27331610). S-ubiquitinyl-[E2 ubiquitin-conjugating enzyme]-L-cysteine + [acceptor protein]-L-lysine = [E2 ubiquitin-conjugating enzyme]-L-cysteine + N(6)-ubiquitinyl-[acceptor protein]-L-lysine. Protein modification; protein ubiquitination. Interacts with UBE2A and UBE2B. Expressed in numerous cells of the smell, touch, vision, hearing and taste senses. Expressed in cells of the olfactory pathway, including the olfactory cell layer of the main olfactory epithelium (MOE), a mitral neuron cell layer of the olfactory bulb (OB), and a pyramidal cell layer of the piriform cortex of the olfactory cortex (OC). Expressed in the vomeronasal sensory epithelium of the vomeronasal organ (VNO) and the mitral cells of the accessory olfactory bulb. Expressed in tactile tissues, including the dorsal root ganglion, trigeminal ganglion and follicle-sinus complexes. Expressed in cells between hair follicle and sinus and also in the region of the rete ridge collar. Expressed in taste buds of the fungiform, circumvallate, and foliate papillae. Expressed in the spiral ganglion, the organ of Corti of the cochlea in the inner ear, in the sensory epithelium of macula and vestibular ganglion of the balancing system (at protein level). Expressed in the liver and skeletal muscle. Knockout mice for Ubr3 in a B6-enriched background exhibited neonatal lethality associated with suckling impairment, but can be partially rescued if the litter size is reduced. Survived adult knockout mice for Ubr3 had female-specific behavioral anosmia (decreased sense of smell). Belongs to the UBR1 family.