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Study questions for lecture 10

Study questions for lecture 10 - resident in the cytosol...

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1 . Where are proteins synthesized? On ribosome which are located in the cytosol 2. What is the fate of a protein with no sorting signal? Remain as permanent residents in the cytosol 3. How would you determine a signal sequence and prove that it functions like one? Design an experiment to test whether the first 20 aminoacids of your protein of interest are necessary and/or sufficient to act as a signal sequence that directs import into the ER. Experiment 1: One way to show that a signal sequence is required and sufficient to target a protein to specific intracellular compartment is to create a fusion protein in which the signal sequence is attached by genetic engineering techniques to a protein that is normally
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Unformatted text preview: resident in the cytosol. After the cDNA encoding this protein is transfected into cells, the location of the fusion protein is determined by immunostaining or by cell fractionation. Experiment 2: Proteins going to the ER have an N-terminal signal sequence that directs them to that organelle, whereas those destined to remain in the cytosol lack the sequence. Recombinant DNA techniques can be used to change the location of the two proteins: for example removing signal sequence from ER protein and attach it to a cytosolic protein, the proteins would end up in wrong location in the cell. This proves that ER signal sequence is both necessary and sufficient to direct a protein to the ER....
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