| In combination with Ubc 4 or UbcH 10 , a heterodimeric complex of APC 2 and APC 11 is sufficient to catalyze the ubiquitination of human securin and cyclin B 1 . ^^^ Both APC 11 and UbcH 10 bind to the C terminal cullin homology domain of APC 2 , whereas Ubc 4 interacts with APC 11 directly . ^^^ |