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首页> 外文期刊>Journal of Molecular Biology >CONFORMATIONAL TRANSITIONS IN PEPTIDES CONTAINING TWO PUTATIVE ALPHA-HELICES OF THE PRION PROTEIN
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CONFORMATIONAL TRANSITIONS IN PEPTIDES CONTAINING TWO PUTATIVE ALPHA-HELICES OF THE PRION PROTEIN

机译：包含两个蛋白质蛋白的α甲油基的肽中的构象转变

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Prions are composed largely, if not entirely, of the scrapie isoform of the prion protein (PrP5c). Conversion of the cellular isoform (PrPC) to PrPSc is accompanied by a diminution in the alpha-helical content and an increase in the beta-sheet structure. To investigate the structural basis of this transition, peptide fragments corresponding to Syrian hamster PrP residues 90 to 145 and 109 to 141, which contain the most conserved residues of the prion protein and the first two putative alpha-helical regions in a PrPC model, were studied using infrared spectroscopy and circular dichroism. The peptides could be induced to form alpha-helical structures in aqueous solutions in the presence of organic solvents, such as trifluoroethanol and hexafluoroisopropanol, or detergents, such as sodium dodecyl sulfate and dodecyl phosphocholine. NaCl at physiological concentration or acetonitrile induced the peptides to acquire substantial beta-sheet. The intermolecular nature of the beta-sheet was evident in the formation of rod-shaped polymers as detected by electron microscopy. Resistance to hydrolysis by proteinase K and epitope mapping argue that the beta-sheet structures were formed by the interaction of residues lying between 109 and 141. A similar range of residues was shown by nuclear magnetic resonance spectroscopy to be capable of forming alpha-helices. The alpha-helical structures seem to require a hydrophobic support from either intermolecular interactions or the hydrophobic environment provided by micelles, in agreement with the predicted hydrophobic nature of the packing surface among the four putative helices of PrPC and the outer surfaces of the first two helices. Our results suggest that perturbation of the packing environment of the highly conserved residues is a possible mechanism for triggering the conversion of PrPC to PrPSc where alpha-helices appear to be converted into beta-sheets. [References: 42]
机译：ions病毒主要（即使不是全部）由pr病毒蛋白（PrP5c）的瘙痒病亚型组成。细胞同工型（PrPC）向PrPSc的转化伴随着α-螺旋含量的减少和β-折叠结构的增加。为了研究这种过渡的结构基础，分别对应于叙利亚仓鼠PrP残基90至145和109至141的肽片段，它们在PrPC模型中包含most蛋白的最保守残基和前两个推定的α螺旋区。使用红外光谱和圆二色性进行了研究。在有机溶剂（例如三氟乙醇和六氟异丙醇）或去污剂（例如十二烷基硫酸钠和十二烷基磷酸胆碱）存在下，可以诱导肽在水溶液中形成α-螺旋结构。生理浓度的NaCl或乙腈诱导该肽获得大量的β-折叠。通过电子显微镜检测，β-片层的分子间性质在棒状聚合物的形成中是明显的。对蛋白酶K水解的抗性和表位作图表明，β-折叠结构是由位于109和141之间的残基相互作用形成的。核磁共振波谱表明，类似范围的残基能够形成α螺旋。 α-螺旋结构似乎需要分子间相互作用或胶束提供的疏水环境的疏水性支持，这与PrPC的四个推定螺旋和前两个螺旋的外表面中填料表面的预测疏水性一致。我们的结果表明，高度保守的残基的堆积环境的扰动是触发PrPC转化为PrPSc的可能机制，其中α螺旋似乎转化为β-折叠。 [参考：42]

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