English: MAD1 homodimer in unattached kinetochores is bound to two c-MAD2 and forms a catalytic receptor for cytozolic o-MAD2. Complex MAD1-cMAD2-oMAD2 catalyzes conformational change of inactive oMAD2 to the active c-MAD2 form. C-MAD2 then binds to Cdc20 and mediates APC/C inhibition and mitotic arrest.
{{Information |Description={{en|1=MAD1 homodimer in unattached kinetochores is bound to two c-MAD2 and forms a catalytic receptor for cytozolic o-MAD2. Complex MAD1-cMAD2-oMAD2 catalyzes conformational change of inactive oMAD2 to the active c-MAD2 form. C