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9 Cards in this Set
- Front
- Back
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1. What is important to protein targeting to direct a protein to a specific location?
What is this? |
Signal sequence
Short AA sequences at the amino terminus of newly synthesized polypeptides **it is removed while protein is being transported or after it has reached destination |
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2. How does protein targeting work for proteins to be secreted?
Four steps.... |
1. Secreted proteins marked by series of AA on amino terminal
2. Signal recognition particle (SRP) attaches to signal sequence 3. Dragged to docking protein (or SRP receptor) at pores of rough ER 4. Synthesized polypeptide passes through RER membrane (use energy from ATP to deliver peptide into lumen) |
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3. What happens once polypeptide passes through RER membrane and is in lumen?
Five steps... |
1. Signal peptidase cleaves signal peptide
2. Ribosome dissociates from ER once peptide is complete 3. Folding and modification 4. Transport vesicles move protein from ER to golgi (further modification) 5. Proteins are sorted into secretory or transport vesicles which bud off from trans side of golgi |
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4. What are proteases?
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Enzymes that cleave proteins into smaller segments, sometimes completely degrading them
**have constant breaking down process that is recycled |
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5. Why would proteases by used?
Three reasons... |
1. Some proteins are in inactive form until they have segments cut off
2. Signal sequences must be cleaved to have functional protein 3. Mistakes with defective proteins so much be destroyed |
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6. How does the half life of proteins vary?
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1. Regulatory proteins have short life span (targeted for early destruction)
2. Damaged proteins or proteins that were improperly manufactured have short half life |
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7. By what 2 principles does protein degradation take place?
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1. Vesicles containing proteins marked for degradation can fuse with lysozomes
2. Protein can be marked with small peptide (ubiquitin) and then degraded by proteases in proteasomes |
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8. What is required to attach ubiquitin to protein marked for degradation?
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Three enzymes
1. Ubiquitin activating enzyme (E1) 2. Ubiquitin conjugating enzyme (E2) 3. Ubiquitin protein ligase (E3) |
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9. What happens during "polyubiquitination"?
What do proteasomes destroy? How is a proteasome structured? |
Multiple copies of ubiquitin are added to the ubiquitin already attached to ill-fated protein
Only polyubiquinated proteins Cyclinder or a barrel like structure that is hallow with additional protein components added to ends |
