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quiz2_solutions - mutant protein is just as active as the...

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Name: _________________________________________________ MCB100A/CHEM130A In-Section Quiz #2 (Aathavan K, 7 th Oct 2005) (Open Book, 15 minutes) 1. A. Rank the following in the order of increasing tolerance to mutations in a protein: hydrophobic core, hydrophilic surface, catalytic site. Explain your ordering briefly (atmost 2-3 sentences) (3) Catalytic site (functionally important residues – often very very specific) Hydrophobic core (tolerates most hydrobic residues, and polar uncharged residues) Hydrophilic Surface (tolerates almost all sorts of residues) B Define Convergent Evolution (1) When similar traits develop independently in two different species whose different ancestors didn’t have that trait.
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2. Consider Ribonuclease-A from Anfinsen’s original experiment. You have mutated one of the cysteines into a serine (there are now only 7 cysteines), but the
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Unformatted text preview: mutant protein is just as active as the wild-type. You now repeat the Anfinsen experiment on this mutant protein: i.e, unfolded the protein with urea, reduced all the disulfide bonds, put the protein in oxidizing environment to reform disulfide bonds, and then allowed to refold by removing the Urea). What percent of the original activity would you expect to recover. (6). Note: Consider in this experiment, like in the original one, only intra-molecular disulfide bonds are formed but not inter-molecular bonds. Clearly show the logic of your calculation. You can form only 3 disulfide bonds. And the number of ways of doing this is = 105 3! 2 3 So activity recovered = 100/105 = 0.95% which is the same as the case with 8 cystines...
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