Notes on Protein Transport Mechanisms

Gated Transport

• Definition: Movement of molecules between the cytosol and the nucleus.
• Mechanism:
  • Utilizes nuclear pores, which are large protein complexes that span the nuclear envelope.
  • Allows selective permeability, permitting the passage of molecules based on size and signaling sequences.

Transmembrane Transport

• Definition: Transport of proteins between the cytosol and the endoplasmic reticulum (ER).
• Mechanism:
  • Involves the insertion of proteins into the membrane or lumen during translation by ribosomes.
  • Utilizes translocator proteins that facilitate this process.
  • Key feature: It can occur co-translationally or post-translationally.

Vesicular Transport

• Definition: Movement of cargo between organelles using membrane-enclosed vesicles.
• Organelles involved:
  • Endoplasmic reticulum (ER)
  • Golgi apparatus
  • Plasma membrane (PM)
  • Endosomes
  • Lysosomes
• Mechanism:
  • Involves the budding of vesicles from a donor organelle and fusion with a target compartment.
  • Can transport a variety of cargo including proteins, lipids, and other molecules.