Effect of Mutation of Proline 93 on Redox Unfolding/Folding of Bovine Pancreatic Ribonuclease A

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• 作者：Aoneng Cao ; Ervin Welker ; and Harold A. Scheraga
• 刊名：Biochemistry
• 出版年：2001
• 出版时间：July 24, 2001
• 年：2001
• 卷：40
• 期：29
• 页码：8536 - 8541
• 全文大小：58K
• 年卷期：v.40,no.29(July 24, 2001)
• ISSN：1520-4995

文摘

Both the reductive unfolding and oxidative regeneration of a P93A mutant and wild-type RNaseA have been studied at 15 C and pH 8.0. The rate of reduction of the 40-95 disulfide bond is acceleratedabout 120-fold by the P93A mutation, while the reduction of the 65-72 disulfide bond is not acceleratedby this mutation (within the experimental error). Moreover, the reduction of native P93A to des[40-95]is about 10 times faster than the further reduction of the same des[40-95] species. These results demonstratethat the reduction of the mutant proceeds through a local unfolding event and provides strong support forour model in which the reduction of wild-type RNase A to the des species proceeds through two independentlocal conformational unfolding events. The oxidative regeneration rate of the P93A mutant is comparableto that of wild-type RNase A, suggesting that a cis 92-93 peptide group that is present in native wild-type RNase A and in native des[40-95], is not obligatory for the formation of the third (final) nativedisulfide bond of des[40-95] by reshuffling from an unstructured 3S precursor. Thus, the trans to cisisomerization of the Tyr92-Pro93 peptide group during the regeneration of wild-type RNase A may occurafter the formation of the third native disulfide bond.