5: Basic mechanisms of the vesicular transport

Question 1

Major steps of vesicle formation (budding)

Answer 1

1. concentration of cargo including SNAREs via interaction with receptors
2. change in lipid composition (?)
3. assembling of the coat
4. shaping of the vesicle (depicted state)
5. pinching off from the donor membrane

Question 2

Major steps of vesicle fusion

Answer 2

1. tethering of vesicles (Rab controlled)
2. uncoating
3. pairing of SNAREs (docking) and assembling of the SNARE complexes (depicted-state)
4. fusion of the lipid bilayers

Question 3

Types of activation of coat assembling

Answer 3

1. small GTPases
2. Phosphoinositols - a second layer for activation
3. membrane fusions senso stricto

Question 4

Specificity during vesicular transport

Answer 4

1. at every donor compartment a special type of coat is formed
2. every coat binds a specific set of cargos including only specific vSNAREs
3. interaction of the coat with a particular motor determines the main transport direction
4. interaction of the coat with tethering molecules link specific types of vesicles with the correct target membranes
5. necessity of a correct combination of a vSNARE with SM-proteins and tSNAREs controls that a vesicle docks the correct membrane
6. each step regulated by specific small GTPase