AP1S2, also known as AP-1 complex subunit sigma-2, serves as the small subunit of AP-1 complex 1 and is a member of the adaptin protein family. Adaptor protein complex 1 is found at the cytoplasmic face of coated vesicles located at the Golgi complex, where it mediates both the recruitment of clathrin to the membrane and the recognition of sorting signals within the cytosolic tails of transmembrane receptors.