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ID: 99899 • Letter: H
Question
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Please I need help to undersand this
Background: In the discussion section of “Compartmental Specificity of Cellular Membrane Fusion Encoded in SNARE Proteins,” the authors wrote: “It is likely that the specificity of membrane flow--although already greatly restricted by the level of specificity inherent in their SNARE proteins (Fig. 4)--is nonetheless buttressed by patterns of localization and activation of the SNAREs by regulatory proteins, including tethering and Rab GTPase proteins.”
Furthermore, one limitation of the research presented in “Compartmental Specificity of Cellular Membrane Fusion Encoded in SNARE Proteins” is that the fusion reactions in the experiments were relatively inefficient and required relatively high concentrations of SNARE proteins, when compared with fusion reactions in cells.
Question: Are SNARE proteins, Rab proteins, or both sufficient, at physiological levels, for compartmental specificity of membrane fusion.
Methods: The researchers reconstituted different combinations of SNARE proteins, SNARE accessory factors (i.e., NSF, -SNAP), Rab proteins (i.e., Rab5), and Rab effectors (i.e., the other components) into liposomes at physiological concentrations. They then measured fusion of acceptor and donor proteoliposomes (with cognate t-SNARES and v-SNAREs).
Summarize the observations. For full credit, be sure to identify control(s).
What conclusion(s) do the observations support?
Reflect: How, if at all, do your in-class and take-home answers differ?
Donor: proteoliposome (STX13/NTI1A/STX6 PRA1) 60 50 Acceptor: proteoliposome (VAMP4 + PRA1) 47.6 ± 5.2 33.4 ± 1.6 30 20 LL 10 15.9 ± 3.6 12.6 8.0± 1.2 1.4 ± 1.9 7.5 ± 2.8 2.4 ± 5.9 1.0 2.5 3.0 ± 1.5 -0.2 ± 1.6 1 23 4 5 6 7 8 9 10 11 12 1 osol NSF SNAP Rab5-GDI Rabaptin-5-rabex-5 hVPS34-PIK3R4 EEA1 Rabenosyn-5-hVPS45+++ Donor: proteoliposome (STX13/VTI1A/STX6+ PRA1) Acceptor: proteoliposome (VAMP4+ PRA1) 30 20Explanation / Answer
Ans.) SNARE proteins belong to a large protein superfamily consisting of around 60 members in mammalian cells. SNAREs are one of the most essential components of the fusion phenomena and could also activate separately many additional cytosolic accessory proteins. Intracellular membrane fusion is intervened by the development of a four-helix package contained SNARE proteins. Each cell communicates countless proteins that are confined to specific layer compartments, proposing that the constancy of vesicle trafficking may to some degree be dictated by particular SNARE matching. In any case, the wantonness of SNARE blending in vitro recommends that the data for membrane compartment association is not encoded in the natural capacity of SNAREs to frame edifices. In general, pairing of SNARE protein underlies vesicle trafficking attachment and that particular SNARE cooperations with different proteins may encourage the right matching.
The Rab protein are also belongs to family protein superfamily i.e. the Ras superfamily of monomeric G proteins and around 70 different types of Rabs protein have been detected in humans. The GTPase activity of Rab protein controls the vesicle fusion.As it is evident SNARE proteins are responsible for membrane fusion while Rab proteins involved in vesicle fusion. Hence SNARE proteins are more effective for compartmental specificity of membrane fusion