A Stabilizing α/β-Hydrophobic Core Greatly Contributes to Hyperthermostability of Archaeal [P62A]Ssh10b

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• 作者：Xianyang Fang ; Qiu Cui ; Yufeng Tong ; Yingang Feng ; Lu Shan ; Li Huang ; Jinfeng Wang
• 刊名：Biochemistry
• 出版年：2008
• 出版时间：October 28, 2008
• 年：2008
• 卷：47
• 期：43
• 页码：11212-11221
• 全文大小：283K
• 年卷期：v.47,no.43(October 28, 2008)
• ISSN：1520-4995

文摘

The hyperthermophilic Ssh10b from Sulfolobus shibatae is a member of the Sac10b family, which has been postulated to play a role in chromosomal organization in Archaea. Ssh10b is capable of significantly constraining negative DNA supercoils at elevated temperatures. In this study, the solution structure of the dimeric P62A mutant Ssh10b ([P62A]Ssh10b) was determined by multidimensional NMR spectroscopy. The backbone ¹⁵N dynamics, H/D exchange with and without the denaturant GdmSCN, and chemical and thermal denaturation experiments were performed to investigate the molecular basis of high thermostability of [P62A]Ssh10b. Data analysis has revealed an α/β-hydrophobic core consisting of two α-helices and one β-sheet which are stabilized by cooperative hydrophobic and hydrogen-bonding interactions. This stabilizing α/β-hydrophobic core of [P62A]Ssh10b exhibiting highly restricted internal motions is composed of residues having highly protected amide protons which exchange with solvent mostly by means of a global unfolding process. The K40N mutation greatly destabilizes the mutant [P62A]Ssh10b because this mutation disturbs the packing of α-helix against the β-sheet reducing the stability of the α/β-hydrophobic core in the mutant protein. In comparison with homologous mesophilic and thermophilic proteins, it can be presumed that the stabilizing α/β-hydrophobic core in the [P62A]Ssh10b structure greatly contributes to the high thermostability of the protein.