E3 ubiquitin-protein ligase which is a component of the N-end rule pathway (By similarity). 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 (By similarity). In complex with ced-3, required for the ced-3-mediated cleavage and subsequent degradation of the heterochronic protein lin-28 to regulate seam cell fate patterning during larval development (PubMed:28602583). Negatively regulates glutamate metabolism through the aspartate aminotransferase got-1.2 (PubMed:29649217). Modulation of glutamate levels most likely controls locomotory behavior, in particular backwards locomotion or 'reversals' (PubMed:29649217). 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 ubc-1 (Probable). Component of a complex containing at least ced-3, ubr-1 and possibly ate-1 (PubMed:28602583). Within complex interacts with ced-3 (via the p17 subunit); this interaction is required for the ced-3-mediated cleavage and subsequent degradation of the heterochronic protein lin-28 (PubMed:28602583). Expressed in pharyngeal muscles, body wall muscles and a subset of neurons throughout postembryonic development (PubMed:29649217). Prominently expressed in premotor interneurons, but not expressed in ventral cord motor neurons (PubMed:29649217). Weakly expressed in hypodermal seam cells (PubMed:29649217). The RING-H2 zinc finger is an atypical RING finger with a His ligand in place of the fourth Cys of the classical motif. RNAi-mediated knockdown enhances the excessive seam cell proliferation phenotype of the ain-1 ku322 mutant. Belongs to the UBR1 family.