Characterization of the Cullin7 E3 ubiquitin ligase - Heterodimerization of cullin substrate receptors as a novel mechanism to regulate cullin E3 ligase activity

► We present a model in which Cul7-Rbx1 can promote ubiquitination of Cul1 substrates by forming high order complexes with Cul1-Rbx1. ► Binding of Cul1-Rbx1 to Cul7-Rbx1 is mediated via heterodimerization of Fbxw8 with other F-box proteins. ► The formation of this high order complex is likely to increase polyubiquitination efficiency. ► Cul7 can be modified by Nedd8 via Nedd8 E2 conjugating enzyme Ubc12 in vitro.