β-COP, a 110 kd protein associated with non-clathrin-coated vesicles and the golgi complex, shows homology to β-adaptin

We have cloned and sequenced β-COP, a peripheral 110 kd Golgi membrane protein. β-COP shows significant homology to β-adaptin. It is present in a membrane-bound form and in a cytosolic complex of 13-14S, with a Stokes radius of ∼10 nm and an estimated M_r of ∼550,000. By immunofluorescence labeling, β-COP is associated with the structures of the Golgi complex. Immunoelectron microscopy has localized β-COP to non-clathrin-coated vesicles and cisternae of the Golgi complex. These coated vesicles accumulate in rat liver Golgi fractions treated with GTPγS and strongly label for-COP Our data suggest that β-COP is a component of a coat associated with vesicles and cisternae of the Golgi complex.