ACTIVATION OF ADP-RIBOSYLATION FACTOR-1 GTPASE-ACTIVATING PROTEIN BY PHOSPHATIDYLCHOLINE-DERIVED DIACYLGLYCEROLS

Disassembly of the coatomer from Golgi vesicles requires that the smal l GTP-binding protein ADP-ribosylation factor 1 (ARF1) hydrolyzes its bound GTP by the action of a GTPase-activating protein. In vitro, the binding of the ARF1 GTPase-activating protein to lipid vesicles and it s activity on membrane-bound ARF1(GTP) are increased by diacylglycerol s with monounsaturated acyl chains, such as those arising in vivo as s econdary products from the hydrolysis of phosphatidylcholine by ARF-ac tivated phospholipase D. Thus, the phospholipase D pathway may provide a feedback mechanism that promotes GTP hydrolysis on ARF1 and the con sequent uncoating of vesicles.