Correct option is D
The correct answer is (d) Dynamin. Dynamin is a GTPase enzyme that plays a critical role in the scission of the neck of the invaginating coated pit to form a free endocytic vesicle during clathrin-mediated endocytosis. At the pre-synaptic terminal, this process ensures the recycling of synaptic vesicles, which is crucial for neurotransmission. Dynamin wraps around the neck of the coated pit and, through GTP hydrolysis, provides the mechanical force required to sever the membrane, allowing vesicle formation.
Information Booster:
- Dynamin is a GTPase that catalyzes the final step in vesicle scission.
- Clathrin forms a coat around vesicles but does not participate in membrane scission.
- AP2 is an adaptor protein complex that helps in cargo selection and clathrin recruitment.
- Synaptojanin regulates vesicle uncoating by dephosphorylating phosphoinositides, aiding in vesicle recycling.
- Dynamin dysfunction is linked to neurodegenerative diseases due to impaired synaptic vesicle recycling.
Additional Knowledge:
(a) Synaptojanin:
This is incorrect. Synaptojanin is a phosphoinositide phosphatase involved in uncoating clathrin-coated vesicles during vesicle recycling. It facilitates the dissociation of clathrin and other associated proteins after vesicle scission but does not directly mediate the pinching-off process.
(b) AP2:
This is incorrect. The adaptor protein complex AP2 is involved in cargo selection and recruitment of clathrin to the plasma membrane, enabling vesicle formation. It is essential for the initial stages of endocytosis but does not participate in the membrane scission.
(c) Clathrin:
This is incorrect. Clathrin forms a lattice-like coat around the invaginating pit, providing structural support. However, it does not mediate the actual pinching-off of the vesicle.
(d) Dynamin:
This is the correct answer. Dynamin assembles at the neck of the budding vesicle and, through GTP hydrolysis, drives the scission of the membrane to release the vesicle into the cytoplasm.
