BIO1140 Study Group #9 Answer Key

BIO1140 Study Group #9 Answer Key - ʼ s with an...

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BIO1140 Study Group #9 Answer Key 1. Using the accompanying diagram, describe the four steps involved with protein targetting. 1. Translation 2. Interaction with receptor & unfolding -signals on protein (a “signal peptide”) -proteins aid unfolding (chaperones) 3. Translocation 4. Refolding/processing -proteases may remove signals -proteins aid unfolding (chaperones) 2. Describe how proteins are transported across the ER. What is the nature of the signal peptide? What is the fate of the signal peptide? Transport across the membrane into the ER (the lumen) is the Frst step for targeting to many locations-ER, Golgi, several vesicles and outside of the cell. A signal peptide is required, as is a receptor. In the absence of further information the protein is exported. This is referred to as the “default pathway”. What is the nature of the signal peptide? What is the fate of the signal peptide? The signal peptide for ER transport is an length of 20-50 aa
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Unformatted text preview: ʼ s with an hydrophobic core. These are recognized by the signal recognition particle and the complex binds to the SRP receptor. When translation resumes the signal peptide is cleaved by the signal peptidase. We refer to the original protein as the preprotein. An example: prelysozyme becomes lysozyme when the SP is removed. 3. Describe the journey of a protein, starting from the inside of the nucleus, and ending outside the cell. Step 1 Step 2 Step 3 Step 4 4. In what kinds of systems are there multiple signals? Also, give an example and describe one. System: Multiple membrane system. Example: Mitochondrion enter matrix (M) via receptor and remove targeting signal with signal peptidase. e.g. DHFR enter inter membrane space (IMS) via receptor and remove spacer sequence. e.g.cytochrome Example 2 : Chloroplast IMS M...
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This note was uploaded on 03/30/2012 for the course SCIENCE BIO1140 taught by Professor Fenwick during the Spring '09 term at University of Ottawa.

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BIO1140 Study Group #9 Answer Key - ʼ s with an...

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