Fig. 2.

Cbl family E3 ligases and UBE3A E3 ligase are single proteins that associate with an E2 Ubc and the target substrate. The SCF and APC/C E3 ubiquitin ligases are multimeric complexes. The APC/C has only two known adapter subunits, Cdc20 and Cdh1 (not to be confused with E-cadherin, which is sometimes also referred to as Cdh1). The SCF can associate with several different substrate adapter proteins known as F-box proteins