Adaptor proteins select cargo proteins that will be incorporated into clathrin-coated vesicles. An adaptor protein such as AP2 …

A) can induce membrane curvature even before clathrin molecules bind.
B) acts as a coincidence detector, assembling only when a number of requirements are met.
C) binds to phosphoinositides in the cytosolic leaflet of the membrane.
D) alternates between a locked cytosolic form and an unlocked membrane-bound form.
E) All of the above.