The Sensitive Balance between the Fully Folded and Locally Unfolded Conformations of a Model Peroxiredoxin
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- 作者：Arden Perkins ; Kimberly J. Nelson ; Jared R. Williams ; Derek Parsonage ; Leslie B. Poole ; P. Andrew Karplus
- 刊名：Biochemistry
- 出版年：2013
- 出版时间：December 3, 2013
- 年：2013
- 卷：52
- 期：48
- 页码：8708-8721
- 全文大小：722K
- 年卷期：v.52,no.48(December 3, 2013)
- ISSN：1520-4995
文摘
To reduce peroxides, peroxiredoxins (Prxs) require a key 鈥減eroxidatic鈥?Cys that, in a substrate-ready fully folded (FF) conformation, is oxidized to sulfenic acid and then, after a local unfolding (LU) of the active site, forms a disulfide bond with a second 鈥渞esolving鈥?Cys. For Salmonella typhimurium alkyl hydroperoxide reductase C (StAhpC) and some other Prxs, the FF structure is only known for a peroxidatic Cys鈫扴er variant, which may not accurately represent the wild-type enzyme. Here, we obtain the structure of authentic reduced wild-type StAhpC by dithiothreitol treatment of disulfide form crystals that fortuitously accommodate both the LU and FF conformations. The unique environment of one molecule in the crystal reveals a thermodynamic linkage between the folding of the active site loop and C-terminal regions, and comparisons with the Ser variant show structural and mobility differences from which we infer that the Cys鈫扴er mutation stabilizes the FF active site. A structure for the C165A variant (a resolving Cys to Ala mutant) in the same crystal form reveals that this mutation destabilizes the folding of the C-terminal region. These structures prove that subtle modifications to Prx structures can substantially influence enzymatic properties. We also present a simple thermodynamic framework for understanding the various mixtures of FF and LU conformations seen in these structures. On the basis of this framework, we rationalize how physiologically relevant regulatory post-translational modifications may modulate activity, and we propose a nonconventional strategy for designing selective Prx inhibitors.