Extended Data Figure 5. The position of Apc11^RING in the APC/C is more similar to Rbx1^RING of activated cullin-Rbx1 structures.

(a) Identification of Apc11 in apo APC/C. Left panel: EM density map for apo APC/C with the coordinates of Apc2^CTD-Apc11 fitted (from APC/C^Cdh1.Emi1 structure). Right panel. EM density for APC/C^Apc11-ΔRING. The difference density corresponds to Apc11^RING. EM density maps from ⁴. (b) Superimposed Apc2^CTD onto Cul1^CTD (PDB: 1LDK) ⁶¹. (c) Superimposed Apc2^CTD onto Cul5^CTD (PDB: 3DQV) ²⁷. In the inactive conformation of Cul1-Rbx1, Rbx1^RING packs against WHB. In APC/C^Cdh1.Emi1 the location of Apc11^RING remains in contact with Apc2^CTD but has rotated ~180° relative to inactive CRL structures being similar to the swung out conformation of Rbx1^RING of neddylated and activated Cul5-Rbx1 ²⁷. (d and e) The relative orientation of Apc2^NTD and Apc2^CTD is also dramatically different from Cul1 (Ref. ⁶¹). This is due to a 70° rotation within cullin repeat 3 (between helices A-B and C-D-E), and a ~20° rotation around the 4HB - cullin repeat 3 interface. Similar less pronounced structural variations are observed within the CRL family. (d) Apc2-Apc11 (this study). (e) Cul1-Rbx1 (PDB: 1LDK) ⁶¹. (f) The position of the Apc2^CTD-Apc11 module differs slightly about the Apc2^NTD-Apc2^CTD interface between APC/C^Cdh1.Emi1 and APC/C^{Cdh1.Hsl1.UbcH10-Ub}.