1 Whenever vesicles fuse with target membranes their v-SNAREs are transferred to
ID: 81580 • Letter: 1
Question
1 Whenever vesicles fuse with target membranes their v-SNAREs are transferred to the target membrane tSNAREs.
For an actively secreting cell this could eventually lead to an accumulation of v-SNAREs in the
plasma membrane. How might the cell avoid this accumulation?
2 Soluble proteins that need to reside in the ER have a retrieval signal, the amino acids KDEL. This signal is detected by a KDEL-receptor protein, which is a membrane protein that binds the KDEL signal on proteins that have escaped to the Golgi. The receptor packages the proteins into vesicles for transport back to the ER.
A. What would be the fate of an ER resident protein that had its KDEL signal removed?
B. Do you think the KDEL-receptor is more concentrated in the ER or the Golgi? Explain
C. What coat protein will be on the vesicles for return to the ER?
D. Does the KDEL-receptor itself need an ER retrieval signal? Explain briefly.
Explanation / Answer
The vesicular Snare or v snare are proteins that are located on the vesicle. Both the v snare and t snare are having supercoiled structure. They form complex with the the t snare of the target membrane by inter twining with one another This complex helps in docking the vesicle to the target membrane of the axon terminal. After the vesicle has fused with the target membrane, it releases it contents into the synaptic cleft ( space between terminal neuron and the dendrite of the other neuron). After the vesicles us become completely fused with the membrane ATP hydrolysis by NSF causes the breakdown of the v SNARE t SNARE complex. Complex can be disassembled by the ATPase N-ethylmaleimide-sensitive factor (NSF) in the presence of soluble cofactors (SNAP proteins). These steps are thought to represent molecular events involved in docking and subsequent exocytosis of synaptic vesicles.The freed v snare then returns back to the cytoplasm to hire new vesicle into the target membrane
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