Vesicular Budding and 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 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

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