DIRECT AND GTP-DEPENDENT INTERACTION OF ADP-RIBOSYLATION FACTOR-1 WITH COATOMER SUBUNIT-BETA

A site-directed photocrosslink approach was used to elucidate componen ts that interact directly with ADP-ribosylation factor (ARF)-GTP durin g coat assembly, Two ARF mutants were generated that contain a photola bile amino acid at positions distant to each other within the ARF mole cule. Here we show that one of the tma positions specifically interact s with coatomer subunit beta both on Golgi membranes and in isolated c oat protein complex type I (COPI)-coated vesicles. Thus, a direct and GTP-dependent interaction of coatomer via beta-coat protein complex (C OP) with ARP is involved in the coating of COPI-coated vesicles. These data implicate a bivalent interaction of the complex with the donor m embrane during vesicle formation.