Institute of Molecular Biology and Biophysics, ETH Zurich, Schafmattstrasse 20, CH-8093 Zurich, Switzerland.
J Mol Biol. 2012 Nov 2;423(4):496-502. doi: 10.1016/j.jmb.2012.08.011. Epub 2012 Aug 24.
The three-dimensional structures of prion proteins (PrPs) in the cellular form (PrP(C)) include a stacking interaction between the aromatic rings of the residues Y169 and F175, where F175 is conserved in all but two so far analyzed mammalian PrP sequences and where Y169 is strictly conserved. To investigate the structural role of F175, we characterized the variant mouse prion protein mPrPF175A. The NMR solution structure represents a typical PrP(C)-fold, and it contains a 3(10)-helical β2-α2 loop conformation, which is well defined because all amide group signals in this loop are observed at 20°C. With this "rigid-loop PrP(C)" behavior, mPrPF175A differs from the previously studied mPrPY169A, which contains a type I β-turn β2-α2 loop structure. When compared to other rigid-loop variants of mPrP(121-231), mPrPF175A is unique in that the thermal unfolding temperature is lowered by 8°C. These observations enable further refined dissection of the effects of different single-residue exchanges on the PrP(C) conformation and their implications for the PrP(C) physiological function.
朊病毒蛋白（PrP）的三维结构在细胞形式（PrP(C))中包括残基 Y169 和 F175 的芳环之间的堆积相互作用，其中 F175 在迄今为止分析的所有哺乳动物 PrP 序列中都保守，而 Y169 则严格保守。为了研究 F175 的结构作用，我们对变异小鼠朊病毒蛋白 mPrPF175A进行了表征。NMR 溶液结构代表了典型的 PrP(C)-折叠结构，并且包含一个 3(10)-螺旋 β2-α2 环构象，由于该环中的所有酰胺基团信号在 20°C 下都被观察到，因此该构象定义明确。由于具有这种“刚性环 PrP(C)”行为，mPrPF175A与先前研究的 mPrPY169A不同，后者包含 I 型 β-转角 β2-α2 环结构。与 mPrP(121-231)的其他刚性环变体相比，mPrPF175A的独特之处在于其热解折叠温度降低了 8°C。这些观察结果使我们能够进一步精细地剖析不同单一位点交换对 PrP(C)构象的影响及其对 PrP(C)生理功能的影响。
