Final answer:
Adaptins are responsible for selecting the correct molecules to be packaged into vesicles for transport, aiding clathrin in vesicle formation during receptor-mediated endocytosis.
Step-by-step explanation:
Molecules to be packaged into vesicles for transport are selected by adaptins. Adaptins help in the formation of vesicles by aiding the clathrin protein to shape the vesicle and capture the right molecules for transport. This detailed process occurs during the receptor-mediated endocytosis, where cargo molecules bound with their receptors are encapsulated into vesicles. Although clathrin and dynamin are involved in the vesicle formation and pinching off respectively, and SNAREs are involved in the fusion of vesicles with the target membranes, it is adaptins that are responsible for selecting the correct cargo molecules for packaging into the vesicles.