A ubiquitin ligase complex consisting of UBR1 and RAD6 components. It polyubiquitinates proteins containing non-acetylated N-terminal residues causing their subsequent degradation by the proteasome as part of the Ac/N-End Rule pathway. It recognizes non-acetylated N-terminal methionine if it is followed by a hydrophobic residue. Additionally, it acts in an N-end rule independent manner as a component of a novel quality control pathway for proteins synthesized on cytosolic ribosomes. [ http://www.ncbi.nlm.nih.gov/pubmed/19531475 ]