Fig. 2: Distinct architectures for unneddylated and neddylated CUL9–RBX1 protomers.
a, Domains of CUL9 and RBX1. Domains in gray were not directly assigned in cryo-EM density. b, Cryo-EM map focused on the cullin dimer between CUL9–RBX1 protomers A and B. Individual protomers are color-coded and displayed within the global map over the hexamer. c, Close-up of focused cullin dimer cryo-EM map refined to 3.6 Å (postprocessed with DeepEMhancer). CUL9 protomers, NEDD8 and two RBX1 units colored individually. RBR domain of protomer B is highlighted with an adjacent line. d, Structure of dimeric CUL9–RBX1 assembly, displaying unneddylated (protomer A) and neddylated (protomer B) conformations. The close-up shows NEDD8 linked to CUL9’s WHB domain, and the NEDD8-interacting CUL9 RBR element UBAL domain in cryo-EM density. e, Part of the unneddylated CUL9–RBX1 protomer A. f, Part of CUL7–RBX1 from CRL7FBXW8 (PDB 7Z8B, SKP1-FBXW8 hidden) corresponding to the region of CUL–RBX1 shown in e. CUL9 and CUL7 structures in e and f are aligned on the WHB domain. Trajectory of weak RBR domain density for CUL9–RBX1 protomer A indicated by the circle. g, Structure of neddylated CUL9–RBX1 protomer B with domains colored as in a. h, Structure of neddylated CRL1-ARIH1 E3–E3 super assembly (PDB 7B5L, UBE2L3, ubiquitin, SKP1, SKP2, CKSHS1, p27, cyclin A and CDK2 hidden). CR2 and CR3 domains of CUL1 are aligned on the corresponding domains of CUL9 in g.
