Part of the AP-3 complex, an adapter-related complex which is not clathrin-associated. The complex is associated with the Golgi region as well as more peripheral structures. It facilitates the budding of vesicles from the Golgi membrane (By similarity). Involved in vacuolar trafficking and contributes to hyphal growth and pathogenesis. Adaptor protein complex 3 (AP-3) is a heterotetramer composed of 2 large adaptins, a medium adaptin and a small adaptin. Component of the coat surrounding the cytoplasmic face of coated vesicles located at the Golgi complex. Belongs to the adaptor complexes small subunit family.