Mechanism of Vesicle Docking

Overview of Vesicle Docking Mechanism

• Definition: Vesicle docking is the process by which vesicles attach to their target membranes to deliver biological cargo.

Key Proteins Involved in Vesicle Docking

• SNARE Proteins:

  • Definition: SNARE proteins facilitate the docking and fusion of vesicles at target membranes.
  • Types:
  • t-SNARE: Present on the target membrane, facilitates interaction with vesicle components.
  • v-SNARE: Present on the vesicle, interacts with t-SNARE for complex formation.
  • Components:
  • SNAP (Soluble NSF Attachment Protein): Interacts with another protein, forming part of the SNARE complex.
  • NSF (N-Ethylmaleimide Sensitive Fusion Protein): An ATPase protein that helps in dissociating SNARE complexes after fusion.

• RAB GTPase:

  • Function: Acts as a recognition molecule that helps guide vesicle docking by interacting with target membranes.
  • Role: Ensures vesicles attach to the correct membrane.

• RAB Effector Proteins:

  • Purpose: Assist in tethering the vesicle to the target membrane, a critical step for docking.

Mechanism of Vesicle Docking

• Step 1: Tethering

  • The RAB GTPase on the vesicle interacts with the RAB effector on the target membrane which facilitates the initial tethering of the vesicle to the membrane.

• Step 2: SNARE Complex Formation

  • As the vesicle moves closer to the target membrane, the v-SNARE and t-SNARE proteins on their respective surfaces come into proximity, leading to the formation of a trans-SNARE complex.

• Step 3: GTP Hydrolysis

  • The bound GTP on the RAB protein is hydrolyzed to GDP, which stabilizes the vesicle's attachment to the target membrane and completes the fusion process.

• Step 4: Dissociation of SNARE Proteins

  • After the vesicle has fused, the SNARE complex must dissociate to allow for the reuse of the proteins in future docking.
  • The NSF protein hydrolyzes ATP to facilitate the separation of SNARE proteins into their respective t-SNARE and v-SNARE components.

Conclusion

• Through the actions of SNARE proteins, RAB GTPase, and RAB effector proteins, vesicles dock and fuse to their target membranes, a crucial process for cellular transport and communication.