Adaptins are components of the adapter complexes which link clathrin to receptors in coated vesicles. Clathrin-associated protein complexes are believed to interact with the cytoplasmic tails of membrane proteins, leading to their selection and concentration. AP-2alpha is a subunit of the plasma membrane adapter. Adaptor protein complex 2 (AP-2) is a heterotetramer composed of two large adaptins (alpha-type and beta-type subunits), a medium adaptin (mu-type subunit AP50) and a small adaptin (sigma-type subunit AP17). Component of the coat surrounding the cytoplasmic face of coated vesicles in the plasma membrane. Expressed in the Garland cells, imaginal disks, adult midgut precursors, the antenno-maxillary complex, the endoderm, the fat bodies, and the visceral mesoderm and cells of the CNS and PNS including neuroblasts, the presumptive stomatogastric nervous system, and the lateral chordotonal sense organs. Partially edited. Target of Adar. Belongs to the adaptor complexes large subunit family. Truncated N-terminus.