The protein encoded by this gene is part of the clathrin coat assembly complex which links clathrin to receptors in coated vesicles. These vesicles are involved in endocytosis and Golgi processing. This protein, as well as beta-prime-adaptin, gamma-adaptin, and the medium (mu) chain AP47, form the AP-1 assembly protein complex located at the Golgi vesicle. [provided by RefSeq, Jul 2008].