62. The following is correct when a protein breaks down or is damaged inside of a eukaryotic cell: A. Proteins are tagged with a small protein called ubiquitin (via ubiquitinylation). B. Ubiquitinylated proteins are processed in a special structure called proteasome. C. 20S Proteasomes become 26S proteasomes by addition of a 19S regulatory subunit. D. All of the above E. None of the above
Added by Chris A.
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Statement A claims that proteins are tagged with a small protein called ubiquitin via ubiquitinylation. This is correct; ubiquitin is a small protein that is attached to damaged or misfolded proteins to mark them for degradation. Show more…
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9. Which of the following is a FALSE statement about the proteasome? a. It is triggered to act by the addition of a ubiquitin to a protein. b. Since degradation happens within the proteasome, general proteolysis of all cytosolic proteins is avoided. c. Ubiquitin is degraded along with the protein it tags. d. It serves as a mechanism to remove damaged proteins from the cell, or proteins that signaling processes have triggered the cell to remove. e. All of the above (A, B, C, and D) are true, so there is no false answer.
Sri K.
All are correct statements regarding the protein degradation process involving ubiquitin EXCEPT: a. The ubiquitin is covalently attached to a cysteine residue in the protein to be degraded. b. Three additional proteins (E1, E2, and E3) are involved in the ligation of ubiquitin to the protein. c. The ubiquitin binding to the protein to be degraded leads to a novel branched protein. d. The modified protein is degraded by an ATP-dependent protease complex. e. Ubiquitin is a highly conserved protein. 2. Which of the following is a result of the sumoylation of a protein? a. Addition of SUMO targets a protein for destruction by a slightly different pathway than attachment of ubiquitin. b. Addition of SUMO often changes the conformation of a protein so that it interacts with other proteins in a different manner. c. Addition of SUMO targets a protein for transport into the mitochondria. d. The addition of SUMO occurs during the translation process and is meant to stall translation of certain proteins. e. None of the above.
Madhur L.
Considering all the effort it takes to make proteins, what benefit would the 26S proteasome serve in eukaryotic cells? Occasionally it is necessary to rapidly remove proteins such as during the cell cycle when they are no longer needed and could lead to cancer. Since mRNA has a short half-life, it makes sense that proteins degraded even more quickly should be. Proteins should be checked for errors just like DNA and RNA, and the proteasome can degrade improperly made proteins. Proteins made in the cytoplasm need to be turned into the nucleus, so this system allows for their rapid degradation.
Adi S.
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