一般的なRNAキャピングリボ酵素は,キャップ交換中にステレオ化学を保持します
1Department of Molecular Biology and Biochemistry, Simon Fraser University, 8888 University Drive, BC, Canada.
Journal of the American Chemical Society
|October 19, 2006
まとめ
この研究は,RNA-キャピングリボ酵素が,他のリボ酵素とは異なり,反応中にステレオ化学を保持することを示しています. これは,化学的必要性によるRNAとタンパク質のキャピング触媒の共通の進化の経路を示唆しています.
科学分野:
- バイオケミストリー バイオケミストリー
- 分子生物学は分子生物学である.
- RNAのカタリシス
背景:
- リボ酵素は,触媒的活性を持つRNA分子である.
- 多くの既知のリボ酵素は,反応中にリン中心でステレオ化学を逆転させます.
- RNAキャピングはmRNAの安定性と翻訳に不可欠です.
研究 の 目的:
- RNAを遮断するリボ酵素反応のステレオ化学的結果を調査する.
- このリボエンザイムによるRNAキャピングの運動メカニズムを解明する.
- 触媒機構を,既知のタンパク質ベースのキャピング酵素と比較するために.
主な方法:
- ステレオケミカルに定義されたRNAキャップ (RpとSpイソマー) の合成.
- リボジームを改変した核酸基板と放射性マーケルのATPでインキュベーションする.
- カッピング,ピロホスファート放出,水解の運動分析.
- 反応産物の立体化学分析.
主要な成果:
- RNA-キャピングリボ酵素は,逆転リボ酵素とは異なり,センターでステレオ化学を保持しています.
- Rpで覆われた基板は反応したが,Spで覆われた基板は反応しなかった.
- カッピング運動はミカエリス-メンテン行動に従っており,ピロホスファートの放出は基質濃度から独立している.
- 制限速度と水解速度の合計は,ピロホスファートの放出速度に等しく,早期の速度制限ステップを示しています.
結論:
- RNA-キャピングリボ酵素のメカニズムは,2つの反転ステップを伴うが,それらはコヴァレンスの中間体によって分離されている.
- このメカニズムは,タンパク質キャピング酵素に類似しており,化学的制約によって誘発される収束進化を示唆しています.
- 立体化学的保持は,このリボ酵素のキャピングメカニズムを区別する重要な特徴です.
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