Answer: Clathrin cages assemble, vesicles form but cannot be pinched of but no disassembly occurs so the vesicles remain coated in clathrin.
Explanation:
Endocytosis is a cellular mechanism that allows the introduction of extracellular material into the cell. Clathrin-coated vesicles act to incorporate different molecules that are recognized by specific proteins located in the clathrin-coated pits. Upon invagination of a portion of the plasma membrane, the material is transported to its final intracellular destination.
<u>Clathrin is a protein that forms the lining of cell membrane microcavities where various receptors are located. Once a particle is recognized by the receptors, invagination of the plasma membrane occurs, which then fuses to form an endocellular vesicle.</u> When vesicle budding occurs, the vesicle is detached from its attachment to the membrane with the help of a GTPase protein called dynamin. Then, the vesicle is freed from clathrin by the action of a type of ATP-ase called Hsp70-ATP and docks to late endosomes that are immediate precursors of lysosomes, fusing the membranes of both. The fission of the clathrin-coated vesicle is controlled by the GTPase dynamin and it has been proposed that dynamin acts by generating the necessary force to strangle the "neck" and cleave the vesicles from the membrane. So they are mainly involved in the cleavage of newly formed vesicles from the membrane of one cell compartment, their orientation, and their fusion with another compartment. Also, without the dynamin, vesicles are not freed from clathrin.
<u>In the absence of dynamin, vesicles are formed but the membrane fusion or pinching off will not occur. Then, invaginated coated pits will be found.</u>
