Final answer:
When Rabs have bound to GTP, they play a crucial role in intracellular vesicle trafficking by regulating the movement and fusion of vesicles within cells.
Step-by-step explanation:
When Rabs are bound to GTP, they play a crucial role in intracellular vesicle trafficking. Rabs are a type of small GTPase protein that is involved in regulating the movement and fusion of vesicles within cells. When Rabs are in the GTP-bound state, they undergo conformational changes that allow them to interact with other proteins and control various steps in the vesicle trafficking process.