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Unformatted text preview: PROTEIN FOLDING AND DENATURATION How are different tertiary structures formed? 1 DENATURATION IS REVERSIBLE Renaturation refolding unfolded proteins illustrated by the unfolding and refolding of ribonuclease experiments that Frst demonstrated that amino acid sequence determines the structure of globular proteins 2 PROTEIN RE NATURATION: THE RIBONUCLEASE EXPERIMENTS 124- amino acid residues 4 disulFde bonds completely unfolds in the presence of urea and a reducing agent 3 PROTEIN RE NATURATION: THE RIBONUCLEASE EXPERIMENTS Theoretically, 105 ways for the cysteines to form 4 cystines Only one combination is active Only one combination is found in nature 4 ¡ folded, native structure ¢ ¢ add urea and β-mercaptoethanol ¢ completely unfolded, inactive state + 5 ¢ remove urea and mercaptoethanol ¢ protein regains native catalytically active structure 6 THE RIBONUCLEASE EXPERIMENTS Naturally occurring RNAse folds on its own Possible “helping” contaminant co-puriFed with it results supportive of hypothesis, but not deFnitive...
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- Fall '11