Direct and GTP-dependent interaction of ADP ribosylation factor 1 with coatomer subunit β

A site-directed photocrosslink approach was used to elucidate components that interact directly with ADP- ribosylation factor (ARF)-GTP during coat assembly. Two ARF mutants were generated that contain a photolabile amino acid at positions distant to each other within the ARF molecule. Here we show that one of the two positions specifically interacts with coatomer subunit β both on Golgi membranes and in isolated coat protein complex type I (COPI)-coated vesicles. Thus, a direct and GTP-dependent interaction of coatomer via β-coat protein complex (COP) with ARF is involved in the coating of COPI-coated vesicles. These data implicate a bivalent interaction of the complex with the donor membrane during vesicle formation.