The function of UBE2R2 (ubiquitin conjugating enzyme E2 R2, Ensembl gene identifier ENSG00000107341) is as follows. E2 ubiquitin-conjugating enzyme that accepts ubiquitin from an E1 ubiquitin-activating protein, and catalyzes its covalent attachment to other proteins by an E3 ubiquitin-protein ligase complex (PubMed:12037680, PubMed:20061386, PubMed:38326650). In vitro catalyzes monoubiquitination and 'Lys-48'-linked polyubiquitination (PubMed:12037680, PubMed:20061386, PubMed:38326650). Works in collaboration with various Cul1-RING and Cul2-RING E3 ligase complexes (PubMed:38326650). May be involved in degradation of katenin (PubMed:12037680). {ECO:0000269|PubMed:12037680, ECO:0000269|PubMed:20061386, ECO:0000269|PubMed:38326650}.