Component 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. AP47 is a subunit of the plasma membrane adapter. Adaptor protein complex 1 (AP-1) is a heterotetramer composed of two large adaptins (gamma- and beta'-type subunits), a medium adaptin (mu-type subunit AP47) and a small adaptin (sigma-type subunit AP19). Component of the coat surrounding the cytoplasmic face of coated vesicles located at the Golgi complex. Regulated by phosphorylation. Belongs to the adaptor complexes medium subunit family.