This gene encodes a member of the adaptor complexes small subunit family. The encoded protein is a subunit of the coatomer protein complex, a seven-subunit complex that functions in the formation of COPI-type, non-clathrin-coated vesicles. COPI vesicles function in the retrograde Golgi-to-ER transport of dilysine-tagged proteins. [provided by RefSeq, Feb 2014].