COPII Vesicle Formation and SNARE Proteins

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Questions and Answers

What initiates the curvature of the ER membrane in COPII-coated vesicle formation?

Binding of Sar1-GTP to cargo receptors
Binding of Sar1-GTP to the ER membrane (correct)
Recruitment of coat proteins to the vesicle
Hydrolysis of GTP by Sar1

Which proteins are responsible for the outer coating of COPII transport vesicles?

SNARE proteins
Sec23 and Sec24
Sar1 and GTP
Sec13 and Sec31 (correct)

What is the role of SNARE proteins in vesicular transport?

They facilitate membrane fusion between vesicles and target membranes (correct)
They recruit cargo for vesicle formation
They initiate vesicle membrane curvature
They hydrolyze GTP to release energy

What happens during the assembly of COPII-coated vesicles?

<p>Sar1-GTP recruits coat proteins and cargo receptors (D)</p> Signup and view all the answers

Which type of SNARE is found on the vesicle membrane?

<p>v-SNARE (C)</p> Signup and view all the answers

Flashcards

COPII Vesicle

A type of transport vesicle involved in moving proteins from the endoplasmic reticulum (ER) to the Golgi apparatus.

Sar1 Protein

A GTPase protein that acts as a molecular switch, initiating the formation of COPII vesicles by binding to the ER membrane and recruiting coat proteins.

Coat Proteins

Proteins that assemble on the ER membrane to shape the vesicle, recruit cargo receptors, and help bud the vesicle off.

SNARE Proteins

Proteins on the vesicle and target membranes that interact to ensure specific cargo delivery.

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v-SNARE and t-SNARE

v-SNAREs are located on the vesicle membrane, while t-SNAREs are on the target membrane. They pair up to facilitate membrane fusion.

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Study Notes

COPII Vesicle Formation

Sar1, a GTPase, is crucial for COPII vesicle formation.
GDP is exchanged for GTP, activating Sar1, which then inserts its hydrophobic tail into the ER membrane.
This membrane insertion initiates membrane curvature.
Activated Sar1-GTP recruits coat proteins, like Sec23 and Sec24.
Coat proteins facilitate vesicle assembly.
Hydrolysis of GTP reverses the process.
Coat proteins recruit cargo receptors.
Sec13/31 are example outer coat proteins.

Budding of COPII Vesicles

COPII vesicles bud from the ER.

SNARE Protein Function

SNARE proteins on vesicle ("v-SNAREs") and target ("t-SNAREs") membranes form complexes.
These interactions ensure correct vesicle fusion with the target membrane.
Different SNARE complexes ensure specific vesicle-target interactions and cargo delivery.
Membrane fusion occurs after SNARE complex formation.

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Description

This quiz delves into the mechanisms of COPII vesicle formation, highlighting the role of Sar1 and various coat proteins. Additionally, it covers the critical function of SNARE proteins in ensuring correct vesicle fusion with target membranes. Test your understanding of these essential cellular processes.