2. (2pts each) Consid er cargo proteins that are destined for secretion to the e

Question

2. (2pts each) Consid er cargo proteins that are destined for secretion to the extracellular space. Please predict where the cargo will end up (ex. in the cytopias, Each organelle, transport vesicles, multiple places, extracellular space) for: () m, a specific individual condition; & (il) The combination of both conditions. A. (0) Normal Sar1 is mutated so it binds tightly to GDP and cannot exchange it (This leads to Sar1'-GDP being the only form of the protein in the cell.) (i) COPII coat proteins are mutated so they bind both to active Sart and active ARF1 (ii) Both B. () A KDEL signal sequence is added to the C-terminus of the cargo protein. (il) The signal recognition particle is mutated so it can't recognize ER signal sequences. (ii) Both C. (i) v-SNAREs on COPII coated vesicles are mutated to be unable to bind t-SNAREs () A transmembrane domain is added to the cargo protein. (ii) Both D. (i) Receptors in the Golgi are mutated so they are unable to bind to cargo proteins. (i) COPI coat proteins are mutated so they are unable to bind to membranes. (ii) Both

Explanation / Answer

A) 1. COP II vesicle remains attatched to the ER exit membrane as GTP exchange is neede to disassembly of newly formed COP II vesicle to the target membrane.

A) 2. Here if COP II protein get bind to vesicle it means the mutation must be missense mutation and it follow the canonical path of traffiking , and vesicles reaces to the extracellular space.

A) 3. Both effects results inability of disassembly of COP II vesicle from ER membrane.

B) 1. KEDAL sequence sort proteins to the peroxisosomes and secreted protein destined to peroxisome organell.

B) 2. SRP mutation made the proteins reside outside in the cytosol and no protein modication or folding or glycosylation takes place.

B) 3. SRP recognition is initial step for cell sorting if this step is hampered then cell sorting with sorting signal will also be hampered and secretory protein remain in cytosol.

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