This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
[{'content': 'Ubiquitin is involved in \nSelect and explain. \nA. Protein folding, B. Protein degradation, C. Synthesis of nucleic acid, D. Glycosylation of proteins', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In animals, many proteins are degraded by the ubiquitin- protease pathway. This pathway was discovered by Aaron Ciechanover, A Hershko and Irwin Roose who got Nobel Prize. Proteosome 26s Protein * Comprises more than 30 polypeptide subunits, which are arranged in the form of a hollow cylinder. * Active sites of its proteolytic subunits face the interior of the cylinder, thus preventing the indiscriminate degradation of cellular proteins. * Proteins requiring degradation are targeted to the proteasome by "Ubiquitination"--the process in which there is covalent attachment of one or more ubiquitin molecules. Ubiquitin: It is a small, approximately 7s residue protein that is highly conserved among eukaryotes. Ubiquitination: It is catalyzed by a large family of enzymes called "E3 Ligases", which attach ubiquitin to the side chain amino group of lysyl residues.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 131', 'role': 'assistant'}]