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Vesicular Budding & Fusion
Steps of vesicular budding and fusion (+ proteins involved)
- Cargo selection (cargo receptor, adaptor protein)
- Vesicular budding (adaptor proteins, coat proteins)
- Fission from donor membrane (dynamin)
- Vesicular coat dissociates
- Vesicular targeting and transport (Rab-GTPase, tethering protein)
- Fusion with target membrane (V-snare and T-snare)
Proteins of vesicular budding and fusion
- Cargo receptors – select and concentrate molecules to be transported in vesicle
- Adaptor proteins - bind cargo receptor and coat proteins
- Coat proteins - form protein scaffold around vesicle that facilitate vesicular budding
- Dynamin – GTPase involved in vesicular fission
- RabGTPase - associates with vesicle after coat has dissociated. Facilitates transport of vesicle to appropriate target membrane. Locks vesicle to target membrane by attaching tethering proteins
- Tethering proteins – anchored in target membrane, attach rabGTPase. Move vesicle close to target membrane for vesicular fusion.
- V-snares(vesicular) and T-snares(target membrane) - Play role in vesicular fusion
Coat proteins direct vesicle transport
- Clathrin +adaptin 1: Golgi -> Lysosome
- Clathrin + adaptin 2: Plasma membrane -> Endosomes (endocytosis)
- COP 1: Cis golgi -> ER AND Later cisternae -> Earlier ones (retrograde transport)
- COP II: ER -> Cis golgi