Final answer:
Clathrin has a triskelion shape that allows it to form spherical lattices and facilitate receptor-mediated endocytosis. Dynamin wraps around the vesicle neck and upon GTP hydrolysis, constricts and aids in the vesicle's pinch-off from the plasma membrane.
Step-by-step explanation:
The shape of clathrin is crucial for its function. Clathrin molecules are composed of three heavy chains and three light chains that come together to form a three-legged structure known as a triskelion. When many clathrin molecules assemble, they can create a spherical lattice on the plasma membrane that forms a coated pit, which is essential for the process of receptor-mediated endocytosis. The clathrin-coated pits help in selectively concentrating specific proteins, like cargo receptors, which are crucial for the internalization of molecules into the cell.
Dynamin is another protein that plays a significant role in receptor-mediated endocytosis. It acts by wrapping around the neck of the budding vesicle and, when it hydrolyzes GTP, it provides the energy that is necessary for it to constrict. This constriction leads to the pinch-off of the clathrin-coated vesicle, separating it from the plasma membrane so that it can be transported into the cell.
In summary, the triskelion shape of clathrin facilitates the formation of vesicular structures essential for cellular transport processes, while dynamin provides the necessary energy for detachment and release of these vesicles into the cytosol.