This family consists of the N terminal region of various alpha, beta and gamma subunits of the AP-1, AP-2 and AP-3 adaptor protein complexes. The adaptor protein (AP) complexes are involved in the formation of clathrin-coated pits and vesicles [1]. The N-terminal region of the various adaptor proteins (APs) is constant by comparison to the C-terminal which is variable within members of the AP-2 family[2]; and it has been proposed that this constant region interacts with another uniform component of the coated vesicles [2].

1: Linking cargo to vesicle formation: receptor tail interactions with coat proteins. Kirchhausen T, Bonifacino JS, Riezman H; Curr Opin Cell Biol 1997;9:488-495. PMID:9261055

2: Structural and functional division into two domains of the large (100- to 115-kDa)chains of the clathrin-associated protein complex AP-2. RAKirchhausen T, Nathanson KL, Matsui W, Vaisberg A, Chow EP, Burne C, Keen JH, Davis AE; Proc Natl Acad Sci U S A 1989;86:2612-2616. PMID:2495531