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Unformatted text preview: All lectures are being podcast and available at https://media4.ucsc.edu/webcast/ Exam: Tuesday October 20th: coming up. You will need to bring a Parscore pink, whole page scantron sheet to exams. These are available at the bookstore. You will need to bring a #2 pencil. You need to bring a calculator. The problem sets are your study guide. The old exam shows you what kind of problems there will be. Chapter 13: use the lecture as guide; I have skipped a few sections What I dont talk about, you are not responsible for. Review section by TA Friday 10/16: social sciences 110 at 5-7. Hsp70 chaperone proteins use the energy from ATP hydrolysis to direct protein folding Hsp70 proteins recognize a small stretch of hydrophobic amino acids and bind to target protein, hydrolyzing ATP to ADP, undergoing a conformational change that tightens binding between the proteins. ATP binds again and hsp70 dissociates. Repeated cycles of Hsp binding and unbinding are required to fold a protein. Hsp60 chaperone proteins use the energy from ATP hydrolysis to direct protein folding hsp60 forms a barrel which becomes an "isolation chamber" to refold misfolded proteins, again using ATP energy (2 ATPs). Incorrectly folded proteins enter the isolation chamber through hydrophobic protein binding sites at the mouth. A cap protein binds to isolate the protein in the chamber. Protein stays in chamber for 15 seconds and is ejected upon ATP hydrolysis. 4) If the protein isnt functional due to improper folding then unfolded proteins are transported out of the ER (dislocated) and degraded by the proteasome Proteins with degradation signals are tagged with ubiquitin by an elaborate ubiquitin conjugating system Ubiquitinating enzyme consists of three subunits: E1 covalently binds to ubiquitin and then transfers it to E2. This reaction requires ATP. E1 is called the ubiquitin activating enzyme. E2 and E3 provide the target specificity and transfer ubiquitin to lysine on target protein. E2 is called the ubiquitin conjugating enzyme. E3 is called the ubiquitin ligase (even though ligating the ubiquitin actually requires both E2 and E3) Human cell has roughly 300 different E2-E3 combinations, and thus has a wide range of targets for ubiquitin tagging. 5) Feed back mechanisms exist to help the cell deal with unfolded proteins. Accumulation of unfolded proteins cause the which induces expression of chaperone genes. Lipids are made in the ER Figure 10-11 Molecular Biology of the Cell ( Garland Science 2008) The next issue is where so proteins go from there: the Golgi apparatus (and back) and beyond There are three kinds of vesicles, each of which has a different protein coat 2 main functions of coats: 1) concentrates membrane proteins i.e. the ones to be transported 2) curved lattice deforms the membrane, creating a vesicle that can pinch off Vesicles that leave the ER undergo homotypic fusion to create a vesicular tubular cluster The Sar1 GTPase controls assembly of coat proteins (COPII) and vesicle formation...
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