ジャーナル: Proc Natl Acad Sci U S A / 年: 2017 タイトル: Structures of Qβ virions, virus-like particles, and the Qβ-MurA complex reveal internal coat proteins and the mechanism of host lysis. 著者: Zhicheng Cui / Karl V Gorzelnik / Jeng-Yih Chang / Carrie Langlais / Joanita Jakana / Ry Young / Junjie Zhang / 要旨: In single-stranded RNA bacteriophages (ssRNA phages) a single copy of the maturation protein binds the genomic RNA (gRNA) and is required for attachment of the phage to the host pilus. For the ...In single-stranded RNA bacteriophages (ssRNA phages) a single copy of the maturation protein binds the genomic RNA (gRNA) and is required for attachment of the phage to the host pilus. For the canonical Qβ the maturation protein, A, has an additional role as the lysis protein, by its ability to bind and inhibit MurA, which is involved in peptidoglycan biosynthesis. Here, we determined structures of Qβ virions, virus-like particles, and the Qβ-MurA complex using single-particle cryoelectron microscopy, at 4.7-Å, 3.3-Å, and 6.1-Å resolutions, respectively. We identified the outer surface of the β-region in A as the MurA-binding interface. Moreover, the pattern of MurA mutations that block Qβ lysis and the conformational changes of MurA that facilitate A binding were found to be due to the intimate fit between A and the region encompassing the closed catalytic cleft of substrate-liganded MurA. Additionally, by comparing the Qβ virion with Qβ virus-like particles that lack a maturation protein, we observed a structural rearrangement in the capsid coat proteins that is required to package the viral gRNA in its dominant conformation. Unexpectedly, we found a coat protein dimer sequestered in the interior of the virion. This coat protein dimer binds to the gRNA and interacts with the buried α-region of A, suggesting that it is sequestered during the early stage of capsid formation to promote the gRNA condensation required for genome packaging. These internalized coat proteins are the most asymmetrically arranged major capsid proteins yet observed in virus structures.
pH: 7.5 / 詳細: 50 mM HEPES, 300 mM NaCl, 1% (v/v)Glycerol
染色
タイプ: NEGATIVE / 材質: Uranyl Formate 詳細: Sample absorbed on carbon surface was stained with 2% (w/v) Uranyl Formate solution, and finally air-dried after blotting off excess stain.
グリッド
モデル: 400 mesh Cu-Rh maxtaform grids (Electron Microscopy Sciences) that were coated with a thin layer of amorphous carbon. 材質: COPPER/RHODIUM / メッシュ: 400 / 支持フィルム - 材質: CARBON / 支持フィルム - トポロジー: CONTINUOUS / 前処理 - タイプ: GLOW DISCHARGE / 前処理 - 雰囲気: AIR / 詳細: 15mA current
詳細
Mono dispersed protein solution
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電子顕微鏡法
顕微鏡
FEI TECNAI 12
温度
最低: 293.0 K / 最高: 295.0 K
撮影
フィルム・検出器のモデル: TVIPS TEMCAM-F416 (4k x 4k) デジタル化 - サイズ - 横: 4096 pixel / デジタル化 - サイズ - 縦: 4096 pixel / デジタル化 - サンプリング間隔: 15.6 µm / 撮影したグリッド数: 2 / 実像数: 980 / 平均露光時間: 0.79 sec. / 平均電子線量: 35.0 e/Å2 詳細: Automated image acquisition software Leginon was used for data collection.
Automated image acquisition software Leginon was used for data collection.
粒子像選択
選択した数: 385141 詳細: Difference of Gaussian (DOG)-based automated particle picker, implemented in Appion processing package was used for particle selection.
CTF補正
ソフトウェア - 名称: CTFFIND4 詳細: Ctffind4 was used for determining the CTF of each micrograph. Phases of each micrographs were flipped before particle extraction.