Lecture 10 - SNAREs I

Question 1

What is synaptic vesicle fusion and where does it occur?

Answer 1

Synaptic vesicle fusion is the process by which neurotransmitters stored in synaptic vesicles are released into the synapse, allowing communication between neurons and muscles. It occurs at the presynaptic terminal of neurons.

Question 2

What are the key features of a SNARE molecule?

Answer 2

SNARE molecules are proteins that play a crucial role in vesicle fusion and neurotransmitter release in cells. The key features of a SNARE molecule include a coiled-coil domain, a transmembrane domain, and a highly conserved SNARE motif.

Question 3

What is the coiled-coil domain in a SNARE molecule?

Answer 3

The coiled-coil domain in a SNARE molecule is a stretch of amino acids that form a stable, rod-like structure. It consists of two to three alpha-helices that wind around each other, creating a stable protein structure.

Question 4

What is the transmembrane domain in a SNARE molecule?

Answer 4

The transmembrane domain in a SNARE molecule is a region of the protein that spans the membrane of a vesicle or a target membrane. It anchors the SNARE protein to the membrane and allows it to participate in vesicle fusion.

Question 5

What is the SNARE motif in a SNARE molecule?

Answer 5

The SNARE motif in a SNARE molecule is a highly conserved sequence of amino acids that is involved in the formation of a SNARE complex between vesicles and target membranes. It consists of four alpha-helices, one from the vesicle and three from the target membrane, that form a four-helix bundle.

Question 6

Why are SNARE molecules required to drive membrane fusion?

Answer 6

SNARE molecules are required to drive membrane fusion because they form a complex that brings the two opposing membranes into close proximity and catalyzes the fusion reaction. This complex is essential for the fusion of vesicles with their target membranes in many cellular processes, including neurotransmitter release, hormone secretion, and membrane trafficking. Without SNAREs, these processes cannot occur efficiently or at all.

Question 7

What is the experimental evidence for the role of SNAREs in membrane fusion?

Answer 7

1. In vitro reconstitution: In vitro experiments using purified SNARE proteins have shown that they are sufficient to drive membrane fusion.
2. Antibody inhibition: Antibodies that bind to SNARE proteins can prevent membrane fusion from occurring, providing evidence that SNAREs are necessary for the process.
3. Gene knockouts: Studies in which SNARE genes have been knocked out or disrupted have demonstrated impaired membrane fusion in vivo.
4. Fluorescence microscopy: Fluorescently labelled SNARE proteins have been observed to accumulate at sites of membrane fusion, providing direct visual evidence of their involvement in the process.
5. Electron microscopy: Electron microscopy studies have shown that SNARE complexes form tight, stable bundles that bring the membranes into close proximity, facilitating the fusion process.