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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Hydrogen-bonding networks and RNA bases revealed by cryo electron microscopy suggest a triggering mechanism for calcium switches
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Hydrogen-bonding networks and RNA bases revealed by cryo electron microscopy suggest a triggering mechanism for calcium switches

机译：低温电子显微镜揭示的氢键网络和RNA碱基表明钙转换的触发机制

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摘要

Helical assemblies such as filamentous viruses, flagella, and F-actin represent an important category of structures in biology. As the first discovered virus, tobacco mosaic virus (TMV) was at the center of virus research. Previously, the structure of TMV was solved at atomic detail by X-ray fiber diffraction but only for its dormant or high-calcium-concentration state, not its low-calcium-concentration state, which is relevant to viral assembly and disassembly inside host cells. Here we report a helical reconstruction of TMV in its calcium-free, metastable assembling state at 3.3 A resolution by cryo electron microscopy, revealing both protein side chains and RNA bases. An atomic model was built de novo showing marked differences from the high-calcium, dormant-state structure. Although it could be argued that there might be inaccuracies in the latter structure derived from X-ray fiber diffraction, these differences can be interpreted as conformational changes effected by calcium-driven switches, a common regulatory mechanism in plant viruses. Our comparisons of the structures of the low- and high-calcium states indicate that hydrogen bonds formed by Asp116 and Arg92 in the place of the calcium ion of the dormant (high-calcium) state might trigger allosteric changes in the RNA base-binding pockets of the coat protein. In turn, the coat protein-RNA interactions in our structure favor an adenine-X-guanine (A*G) motif over the G*A motif of the dormant state, thus offering an explanation underlying viral assembly initiation by an AAG motif.
机译：螺旋状装配体，例如丝状病毒，鞭毛和F-肌动蛋白，代表了生物学中重要的结构类别。作为最早发现的病毒，烟草花叶病毒（TMV）是病毒研究的中心。以前，TMV的结构是通过X射线纤维衍射在原子细节上求解的，但仅针对其休眠或高钙浓度状态，而不是其低钙浓度状态，这与宿主细胞内的病毒装配和拆卸有关。在这里，我们通过冷冻电子显微镜报道了在3.3 A分辨率下无钙，亚稳态组装状态的TMV的螺旋形重建，揭示了蛋白质侧链和RNA碱基。从头开始建立了一个原子模型，该模型显示出与高钙，休眠状态结构的明显差异。尽管可以争论的是，后者的结构可能是由X射线纤维衍射得出的，但这些差异可以解释为由钙驱动的开关（植物病毒的一种常见调节机制）所影响的构象变化。我们对低钙态和高钙态的结构的比较表明，由Asp116和Arg92形成的氢键代替处于休眠（高钙）态的钙离子可能会触发RNA碱基结合口袋的变构变化。外壳蛋白的含量。反过来，在我们的结构中，外壳蛋白-RNA相互作用倾向于在休眠状态的G * A基序上形成腺嘌呤-X-鸟嘌呤（A * G）基序，从而提供了通过AAG基序启动病毒装配的解释。

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    Peng Ge; Z. Hong Zhou;

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    Department of Microbiology, Immunology, and Molecular Genetics and the University of California, Los Angeles, CA 90095-7364,California NanoSystems Institute, University of California, Los Angeles, CA 90095-7364,Structural Computational Biology and Molecular Biophysics Program, Baylor College of Medicine, Houston, TX 77030;

    Department of Microbiology, Immunology, and Molecular Genetics and the University of California, Los Angeles, CA 90095-7364,California NanoSystems Institute, University of California, Los Angeles, CA 90095-7364,Structural Computational Biology and Molecular Biophysics Program, Baylor College of Medicine, Houston, TX 77030;

  • 收录信息 美国《科学引文索引》(SCI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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