ジャーナル: Cell / 年: 2008 タイトル: The structure of the phage T4 DNA packaging motor suggests a mechanism dependent on electrostatic forces. 著者: Siyang Sun / Kiran Kondabagil / Bonnie Draper / Tanfis I Alam / Valorie D Bowman / Zhihong Zhang / Shylaja Hegde / Andrei Fokine / Michael G Rossmann / Venigalla B Rao / 要旨: Viral genomes are packaged into "procapsids" by powerful molecular motors. We report the crystal structure of the DNA packaging motor protein, gene product 17 (gp17), in bacteriophage T4. The ...Viral genomes are packaged into "procapsids" by powerful molecular motors. We report the crystal structure of the DNA packaging motor protein, gene product 17 (gp17), in bacteriophage T4. The structure consists of an N-terminal ATPase domain, which provides energy for compacting DNA, and a C-terminal nuclease domain, which terminates packaging. We show that another function of the C-terminal domain is to translocate the genome into the procapsid. The two domains are in close contact in the crystal structure, representing a "tensed state." A cryo-electron microscopy reconstruction of the T4 procapsid complexed with gp17 shows that the packaging motor is a pentamer and that the domains within each monomer are spatially separated, representing a "relaxed state." These structures suggest a mechanism, supported by mutational and other data, in which electrostatic forces drive the DNA packaging by alternating between tensed and relaxed states. Similar mechanisms may occur in other molecular motors.
モード: BRIGHT FIELD / 倍率(公称値): 38000 X / 最大 デフォーカス(公称値): 3500 nm / 最小 デフォーカス(公称値): 2000 nm
撮影
電子線照射量: 20 e/Å2 / フィルム・検出器のモデル: KODAK SO-163 FILM
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解析
EMソフトウェア
ID
名称
カテゴリ
1
EMfit
モデルフィッティング
2
SPIDER
3次元再構成
CTF補正
詳細: phase flipping of each micrograph
対称性
点対称性: C5 (5回回転対称)
3次元再構成
手法: Spider / 解像度: 34 Å / 粒子像の数: 1716 / ピクセルサイズ(公称値): 6.48 Å / ピクセルサイズ(実測値): 6.48 Å / 対称性のタイプ: POINT
原子モデル構築
プロトコル: RIGID BODY FIT / 空間: REAL / Target criteria: Sumf 詳細: METHOD--N- and C-terminal domains were separately fitted into their corresponding cryoEM densities REFINEMENT PROTOCOL--Rigid body