E3 ubiquitin-protein ligase which is a component of the N-end rule pathway (PubMed:15548684, PubMed:16311597, PubMed:18162545, PubMed:20835242, PubMed:28392261). Recognizes and binds proteins bearing specific N-terminal residues that are destabilizing according to the N-end rule, leading to their ubiquitination and subsequent degradation (PubMed:18162545, PubMed:20835242, PubMed:28392261). Recognizes both type-1 and type-2 N-degrons, containing positively charged amino acids (Arg, Lys and His) and bulky and hydrophobic amino acids, respectively (PubMed:18162545). Does not ubiquitinate proteins that are acetylated at the N-terminus (PubMed:20835242). In contrast, it strongly binds methylated N-degrons (PubMed:28392261). Binds leucine and is a negative regulator of the leucine-mTOR signaling pathway, thereby controlling cell growth (PubMed:20298436). {ECO:0000269|PubMed:15548684, ECO:0000269|PubMed:16311597, ECO:0000269|PubMed:18162545, ECO:0000269|PubMed:20298436, ECO:0000269|PubMed:20835242, ECO:0000269|PubMed:28392261}. This is the function of Ensembl gene identifier ENSG00000159459 (UBR1, ubiquitin protein ligase E3 component n-recognin 1).