Regulation of vesicular transport by GTP-binding proteins.

Intracellular protein trafficking occurs in a series of transport vesicles. Vesicle trafficking is regulated both by heterotrimeric and monomeric GTP-binding proteins (G proteins). Recent studies have explored effector systems used by heterotrimeric G proteins and by monomeric ADP-ribosylation factor G proteins for regulation of vesicle budding. New members of the Rab monomeric G protein family have been identified in polarized cells and new evidence confirms the function of Rab proteins in vesicle targeting. From these data we can begin to reconstruct the signal transduction pathways that regulate intracellular transport.