Figure 12.

APC/C^MCC adopts open and closed states that allows for reciprocal control by the MCC. (a) In APC/C^MCC-closed, the MCC inhibits both substrate (for example, securin and cyclin B) and UbcH10 recognition. Upper panel: overall APC/C^MCC structure. Lower panel: shows how binding of the MCC in APC/C^MCC-closed causes an upward movement of Apc5^NTD and Apc4^HBD (compare with b) and concomitant disordering of the N-terminal helix of Apc15 (Apc15^NTH). (b) In APC/C^MCC-open, the catalytic module is exposed, Apc5^NTD rotates, Apc4^HBD translates down by 10 Å, and Apc15^NTH is ordered. Movements of Apc4^HBD, Apc5^NTD and Apc11^RING domain are indicated with arrows. (c) In the APC/C^MCC-UbcH10 complex, APC/C^MCC adopts the open conformation with Apc15^NTH ordered and UbcH10 docking to its canonical position on Apc11^RING and Apc2^WHB. The C-terminal tail of Cdc20^MCC engages the catalytic site of UbcH10 for auto-ubiquitination of Lys485 and Lys490. In APC/C^MCC-closed, the C-terminal IR tail of Cdc20^MCC engages the C-box binding site of Apc8A. From Alfieri et al. [92].