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首页> 外文期刊>Biochemistry >Differences in the Molecular Structure of β2-Microglobulin between Two Morphologically Different Amyloid Fibrils
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Differences in the Molecular Structure of β2-Microglobulin between Two Morphologically Different Amyloid Fibrils

机译：两种形态不同的淀粉样蛋白原纤维中β2-微球蛋白分子结构的差异

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摘要

Differences in themolecular structures of β2-microglobulin between the twomorphologically differentnamyloid fibrils having a needlelike [long-straight (LS)] and flexible [wormlike (WL)] character were investigatednby infrared, Raman, and vacuum-ultraviolet circular dichroism spectroscopy. It turned out that although thenβ-sheet content was comparable between the two kinds of fibrils (53 ( 6% for the LS fibril andn47 ( 6% for the WL fibril), the protonation states of the carboxyl side chains were distinctly different; thendeprotonated (COO-) and protonated (COOH) forms were dominant in the LS and WL fibrils at pH 2.5,nrespectively,meaning that the pKa is specifically lowered in the LS fibril. Such a difference was not observed for thenfibrils of the core fragments. Since site-specific interactions generally cause variation in the pKa of carboxyl sidenchains in proteins, these results suggest that “hook”-like interactions generated by hydrogen bonding and thenformation of a salt bridge are present in the LS fibril, providing enthalpic stabilization. Presumably, the carboxylngroups fix the spatial arrangement of β-strands and β-sheets, bringing about the needlelike morphology. Thenabsence of this regulationwould result in the flexiblemorphology of theWL fibril, providing entropic stabilization
机译：通过红外，拉曼光谱和真空紫外圆二色谱法研究了两种形态不同的具有针状[长直（LS）]和柔性[蠕虫状（WL）]特征的异淀粉状原纤维之间β2-微球蛋白的分子结构差异。结果表明，尽管那时β-片层含量在两种原纤维之间是可比较的（53（LS原纤维为6％，n47（WL原纤维为6％）），但是羧基侧链的质子化状态却明显不同；然后去质子化（在pH值为2.5的LS和WL原纤维中，COO-和质子化（COOH）形式分别占主导地位，这意味着LS原纤维中的pKa特别降低，核心片段的原纤维中未观察到这种差异。特异性相互作用通常会导致蛋白质中羧基侧链的pKa发生变化，这些结果表明，由氢键结合然后形成盐桥的“钩”样相互作用存在于LS原纤维中，从而提供了焓的稳定作用。固定β链和β折叠的空间排列，形成针状形态，然后缺乏这种调节将导致WL原纤维的柔性形态，从而提供熵稳定

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  • 来源
    《Biochemistry》 |2010年第4期|p.742-751|共10页
  • 作者

    Hirotsugu Hiramatsu Ming Lu Koichi Matsuo Kunihiko Gekko Yuji Goto and Teizo Kitagawa;

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    ‡Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Okazaki 444-8787, Japan,§Graduate School ofScience, Hiroshima University, Higashi-Hiroshima 739-8526, Japan, and ) Institute for Protein Research, Osaka University, 3-2Yamadaoka, Suita, Osaka 565-0871, Japan.^Present address: Graduate School of Pharmaceutical Sciences, Tohoku University,Aobayama, Sendai 980-8578, Japan.@Present address: Key Laboratory for Molecular Enzymology andEngineering, Ministry of Education, Jilin University, Changchun, Jilin 130021, P. R. China.#Present address: Toyota Physical and Chemical Research Institute, Nagakute, Aichi 480-1192, Japan.;

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