ジャーナル: Nucleic Acids Res / 年: 2018 タイトル: Structure of a human cap-dependent 48S translation pre-initiation complex. 著者: Boris Eliseev / Lahari Yeramala / Alexander Leitner / Manikandan Karuppasamy / Etienne Raimondeau / Karine Huard / Elena Alkalaeva / Ruedi Aebersold / Christiane Schaffitzel / 要旨: Eukaryotic translation initiation is tightly regulated, requiring a set of conserved initiation factors (eIFs). Translation of a capped mRNA depends on the trimeric eIF4F complex and eIF4B to load ...Eukaryotic translation initiation is tightly regulated, requiring a set of conserved initiation factors (eIFs). Translation of a capped mRNA depends on the trimeric eIF4F complex and eIF4B to load the mRNA onto the 43S pre-initiation complex comprising 40S and initiation factors 1, 1A, 2, 3 and 5 as well as initiator-tRNA. Binding of the mRNA is followed by mRNA scanning in the 48S pre-initiation complex, until a start codon is recognised. Here, we use a reconstituted system to prepare human 48S complexes assembled on capped mRNA in the presence of eIF4B and eIF4F. The highly purified h-48S complexes are used for cross-linking/mass spectrometry, revealing the protein interaction network in this complex. We report the electron cryo-microscopy structure of the h-48S complex at 6.3 Å resolution. While the majority of eIF4B and eIF4F appear to be flexible with respect to the ribosome, additional density is detected at the entrance of the 40S mRNA channel which we attribute to the RNA-recognition motif of eIF4B. The eight core subunits of eIF3 are bound at the 40S solvent-exposed side, as well as the subunits eIF3d, eIF3b and eIF3i. elF2 and initiator-tRNA bound to the start codon are present at the 40S intersubunit side. This cryo-EM structure represents a molecular snap-shot revealing the h-48S complex following start codon recognition.
全体 : human cap-dependent 48S translation pre-initiation complex
全体
名称: human cap-dependent 48S translation pre-initiation complex
要素
複合体: human cap-dependent 48S translation pre-initiation complex
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超分子 #1: human cap-dependent 48S translation pre-initiation complex
超分子
名称: human cap-dependent 48S translation pre-initiation complex タイプ: complex / ID: 1 / 親要素: 0 / 含まれる分子: #1-#50 詳細: This map comprises human 40S, mRNA, initiator tRNA, eIF2 and eIF4B RRM obtained from multiple sources as described in the publication.
由来(天然)
生物種: Homo sapiens (ヒト)
分子量
理論値: 2.0 MDa
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実験情報
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構造解析
手法
クライオ電子顕微鏡法
解析
単粒子再構成法
試料の集合状態
particle
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試料調製
緩衝液
pH: 7.5 詳細: 20 mM Tris HCl, 50 mM KOAc, 2.5 mM MgCl2, 2 mM DTT, 0.25 mM spermidine 0.25 mM GMPPNP
グリッド
モデル: Quantifoil R2/2
凍結
凍結剤: ETHANE / チャンバー内湿度: 100 % / チャンバー内温度: 277 K / 装置: FEI VITROBOT MARK IV
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電子顕微鏡法
顕微鏡
FEI TITAN KRIOS
撮影
フィルム・検出器のモデル: FEI FALCON II (4k x 4k) 検出モード: INTEGRATING / 平均電子線量: 30.0 e/Å2