ジャーナル: Proc Natl Acad Sci U S A / 年: 2011 タイトル: Hydrogen-bonding networks and RNA bases revealed by cryo electron microscopy suggest a triggering mechanism for calcium switches. 著者: Peng Ge / Z Hong Zhou / 要旨: 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 ...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 Å 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.
凍結剤: ETHANE / チャンバー内湿度: 100 % / チャンバー内温度: 93 K / 装置: FEI VITROBOT MARK IV 詳細: Vitrification instrument: FEI Vitrobot Mark IV. 2 uL sample 手法: 10 second wait time, 1-2 second blot time, 1-2 second drain time, blot force 1
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電子顕微鏡法
顕微鏡
FEI TITAN KRIOS
温度
平均: 90 K
アライメント法
Legacy - 非点収差: objective lens astigmatism was corrected at 250,000 times magnification Legacy - Electron beam tilt params: 0
日付
2009年6月15日
撮影
カテゴリ: FILM / フィルム・検出器のモデル: KODAK SO-163 FILM デジタル化 - スキャナー: NIKON SUPER COOLSCAN 9000 デジタル化 - サンプリング間隔: 0.869 µm / 実像数: 386 / 平均電子線量: 25 e/Å2 / ビット/ピクセル: 16