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リボソームの延長因子SelBのGTPase活性化への経路
Niels Fischer1, Piotr Neumann2, Lars V Bock3
1Department of Structural Dynamics, Max Planck Institute for Biophysical Chemistry, Am Fassberg 11, 37077 Göttingen, Germany.
Nature
|November 15, 2016
まとめ
セレノシステイン (Sec) の組み込みは,細菌の特定のtRNAとSelB因子に依存しています. Cryo-EM構造は,Sec-tRNASecによるUGAコドンの再コーディングが,翻訳中にSelB GTPaseの活性化を誘発する方法を示しています.
科学分野:
- 分子生物学
- 構造生物学
- 生物化学
背景:
- セレノシステイン (Sec) は,バクテリアの特化したtRNA (tRNASec) と翻訳因子 (SelB) を介して組み込まれた21番目のアミノ酸です.
- Sec-tRNASecは,mRNAの幹ループ構造に隣接すると,典型的には翻訳を終了するUGAストップコドンを再コードする.
研究 の 目的:
- エシェリキア・コロイにおけるSec-tRNASecによるUGAコドンの再コーディングの基礎となる構造的メカニズムを解明する.
- SelBがSec挿入をどのように促進し,そのGTPaseの活性が翻訳中にどのように調節されるかを理解する.
主な方法:
- 単粒子の冷凍電子顕微鏡 (cryo-EM) を用いて,6つの主要な中間物質の構造を決定した.
- リボソーム結合のSec-tRNASecとSelB複合体は,UGA再コーディング過程で分析された.
主要な成果:
- 構造は,SelBによるSec-tRNASecの特定の結合と,tRNAの大きな構成変化を明らかにする.
- リボソームは,サルシン-リシンループ (SRL) に関する30Sサブユニットの開閉とSec-tRNASecの移動を含む重要な再編成を経験する.
- コドン認識はSELBをSRLにドッキングし,GTPaseの活性化につながります.
結論:
- この研究では,Sec-tRNASec結合とUGAコドンの認識が特定のリボソーム構造変化を誘発するダイナミックなメカニズムが明らかになりました.
- これらの構造的再編成は,SELBをSRLに誘導し,GTPase機能を活性化させ,効率的なセレノシステイン吸収を保証するために不可欠です.
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