ジャーナル: Nature / 年: 2015 タイトル: Structure of the eukaryotic MCM complex at 3.8 Å. 著者: Ningning Li / Yuanliang Zhai / Yixiao Zhang / Wanqiu Li / Maojun Yang / Jianlin Lei / Bik-Kwoon Tye / Ning Gao / 要旨: DNA replication in eukaryotes is strictly regulated by several mechanisms. A central step in this replication is the assembly of the heterohexameric minichromosome maintenance (MCM2-7) helicase ...DNA replication in eukaryotes is strictly regulated by several mechanisms. A central step in this replication is the assembly of the heterohexameric minichromosome maintenance (MCM2-7) helicase complex at replication origins during G1 phase as an inactive double hexamer. Here, using cryo-electron microscopy, we report a near-atomic structure of the MCM2-7 double hexamer purified from yeast G1 chromatin. Our structure shows that two single hexamers, arranged in a tilted and twisted fashion through interdigitated amino-terminal domain interactions, form a kinked central channel. Four constricted rings consisting of conserved interior β-hairpins from the two single hexamers create a narrow passageway that tightly fits duplex DNA. This narrow passageway, reinforced by the offset of the two single hexamers at the double hexamer interface, is flanked by two pairs of gate-forming subunits, MCM2 and MCM5. These unusual features of the twisted and tilted single hexamers suggest a concerted mechanism for the melting of origin DNA that requires structural deformation of the intervening DNA.
凍結剤: ETHANE / チャンバー内湿度: 100 % / 装置: FEI VITROBOT MARK IV
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電子顕微鏡法
顕微鏡
FEI TITAN KRIOS
日付
2015年11月25日
撮影
カテゴリ: CCD / フィルム・検出器のモデル: GATAN K2 (4k x 4k) / デジタル化 - サンプリング間隔: 4 µm / 実像数: 2230 / 平均電子線量: 16 e/Å2 詳細: Every image is the average of 14 frames recorded by the direct electron detector
電子線
加速電圧: 300 kV / 電子線源: FIELD EMISSION GUN
電子光学系
照射モード: FLOOD BEAM / 撮影モード: BRIGHT FIELD / 倍率(公称値): 22500
試料ステージ
試料ホルダーモデル: FEI TITAN KRIOS AUTOGRID HOLDER
実験機器
モデル: Titan Krios / 画像提供: FEI Company
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画像解析
CTF補正
詳細: CTFFIND
最終 再構成
解像度のタイプ: BY AUTHOR / 解像度: 3.8 Å / 解像度の算出法: OTHER / ソフトウェア - 名称: RELION / 使用した粒子像数: 85365