Accepts ubiquitin from the E1 complex and catalyzes its covalent attachment to other proteins . In vitro catalyzes 'Lys-48'-linked polyubiquitination . Involved in endoplasmic reticulum-associated degradation (ERAD) . Required for sterol-induced ubiquitination of 3-hydroxy-3-methylglutaryl coenzyme A reductase and its subsequent proteasomal degradation .
Subcellular locations: Endoplasmic reticulum, Lipid droplet