Figure 6.

APC/C ubiquitination reaction. (a) Apo APC/C. In the absence of coactivator the catalytic module adopts a ‘down’ inactive conformation. UbcH10 binding to Apc11^RING is blocked by Apc5, and Apc5 prevents the correct location of Apc2^WHB required to engage UbcH10. EM density for Apc11^RING is weak indicating RING domain flexibility. PDB 5G05 from Zhang et al. [60]. (b) Complex of APC/C^{Cdh1.substrate} with a UbcH10 ∼ ubiquitin conjugate. Apc2^WHB becomes ordered and engages UbcH10. dUb: modelled donor ubiquitin conjugated to UbcH10. The C-terminus of dUb is indicated with a red sphere. PDB 5A31, from Chang et al. [80]. PDB for Apc2^WHB 4YII Chang et al. [111]. (c) APC/C^{Cdh1.substrate}-Ube2S∼Ub complex. Ube2S is partially built. aUb: acceptor ubiquitin bound to the Apc11^RING exosite. PDB 5L9T, from Brown et al. [112]. The figure is based on previous work [60,80,111,112].