As examples, membrane proteins can have direct interactions, while proteins that are soluble in the lumen of the donor organelle bind indirectly to AP complexes by binding to membrane proteins that traverse the membrane and bind at their lumenal end to the desired cargo molecule.
Membrane proteins can interact directly, while soluble proteins within the lumen of the donor organelle bind indirectly to AP complexes by binding to membrane proteins that traverse the membrane and then bind at their lumenal end to the desired cargo molecule.