Vesicular Transport

ENDOCYTOSIS AND EXOCYTOSIS
Membrane-bound vesicles transport….
- Cargo in their lumen and membranes from the donor compartment to the
recipient compartment
- Vesicles bud from specialised coated regions of the donor compartment

3 membrane coat proteins:

COP II – coats vesicles which transport proteins from ER to the Golgi

COP I – coats vesicles transport proteins from the Golgi back to the ER

Clathrin – coats vesicles transport proteins between the Golgi, lysosomes and plasma
membrane

2 Functions of coat proteins:
- Target transport from the donor to the recipient compartments
- Trigger budding of the vesicle from the donor membrane




Structure of clathrin
- Made up of 3 large and 3 small polypeptide chains: form a 3-legged triskelion
- 3-legged triskelion forms a basket-like convex framework of pentagons and
hexagons on the cytoplasmic side of the membrane
Clathrin attach to the cytosolic side of the membrane by:
1. Adaptin binds to the transmembrane receptors that bind
to soluble cargo for transport.
2. Clathrin attaches to the adaptin to form a coat on the vesicle.