Cullins are an evolutionarily conserved, structurally-related gene family, with an N-terminal bearing cullin repeats followed by a cullin homology domain and a neddylation site. Cullins act as scaffolds to assemble multi-subunit Cullin-RING E3 ubiquitin ligase (CRL) complexes. A CRL complex is characterised by a cullin-RING-type E3 ubiquitin ligase interaction, which acts as the catalytic core and recruits the E2 ubiquitin-conjugating enzyme, and a cullin-adaptor protein-substrate recognition protein interaction which links the E3 ligase to its target for ubiquitination. (Adapted from FBrf0224296).