The alpha and beta2 adaptor subunits can each be divided into a trunk domain and the appendage domain (or ear domain), separated by a linker region. Clathrin polymerisation is promoted by its binding to the beta2 appendage and hinge domains. The alpha appendage domain interacts with a number of accessory proteins, including eps15, epsin, amphiphysin, AP180, auxilin, numb, and Dab2, thereby regulating the translocation of these proteins to the bud site.
This entry represents a subdomain of the appendage (ear) domain of alpha- and beta-adaptin from AP clathrin adaptor complexes, and the appendage domain of the gamma subunit of coatomer complexes. These domains have a three-layer arrangement, alpha-beta-alpha, with a bifurcated antiparallel beta-sheet [10430869, 10944104, . Although the appendage domains from AP adaptins and coatomers share a similar fold, there is little sequence identity between them. However, they also share similar motif-based cargo recognition and accessory factor recruitment mechanisms.
More information about these proteins can be found at Protein of the Month: Clathrin.