Cell Breakdown and Cell Turnover Flashcards
How does a cell identify a protein that needs to be degraded due to damage?
The protein would have been tagged with ubiquitin.
What three enzymes form the ubiquitin-conjugating system, which functions to attach ubiquitin to a protein?
Ubiquitin-activating enzyme (E1), Ubiquitin-conjugating enzyme (E2) and Ubiquitin-protein ligase (E3).
What protein digests the proteins marked with ubiquitin for destruction?
The proteasome protein.
What does the proteasome protein consist of?
Two 19S regulatory subunits bind to a 20S core to form the complete 26S proteasome.
What are the three functions of the 19S regulatory subunit of the proteasome enzyme?
1) It binds specifically to ubiquitin chains.
2) It cleaves off the ubiquitin molecules from the protein to be degraded allowing it to be reused.
3) It unfolds the protein to be destroyed and directs it to the 20S catalytic core.
What is the difference between necrotic and apoptotic cells?
Necrotic cells are cells that have undergone an ‘accidental’ form of cell death, whilst apoptotic cells are cells that have undergone a form of “programmed cell death”.
Explain what happens during the extrinsic pathway of apoptosis.
1) A Fas ligand binds to a Fas death receptor on the target cell which will lead to the formation of a ‘Disc’ (Death-inducing signalling complex).
2) This will then lead to the activation and cleavage of procaspase -8, -10 or both.
How can the intrinsic pathway of apoptosis be triggered?
It is triggered by the release of cytochrome c from mitochondria.
What are Prion diseases?
Prion diseases are diseases that are caused by improperly folded proteins.
What are Infectious Prions?
Infectious prions are aggregated forms of PrP, which arose due to aggregation of abnormal PrP that contain β-strands instead of of α-helices.
(PrP is normally present in the brain).
What is a suitable therapy for multiple myeloma?
Treatment using Bortezomib (Velcade), which acts as an inhibitor of the (eukaryotic) proteasome protein.
What is the protein degradation system in bacteria?
ThiS.
How can HT1171 can be used to treat Tuberculosis.
It will act as an inhibitor of the M. tuberculosis proteasome without having an affect on the human proteasome despite having similarities in their structures.
