チャペロニンの過剰発現は遺伝的多様性と酵素の進化を促進します
Nobuhiko Tokuriki1, Dan S Tawfik
1Department of Biological Chemistry, Weizmann Institute of Science, Rehovot 76100, Israel.
Nature
|June 5, 2009
まとめ
E. coli のようなチャペロニンは,GroEL/GroES のバッファー変異を起こし,進化のスピードを早める. これらの熱ショックタンパク質の過剰発現は,不安定なタンパク質の変種の折り畳みを助けることによって,酵素適応を加速します.
科学分野:
- 分子生物学は分子生物学である.
- 進化生物学の進化生物学について
- バイオケミストリー バイオケミストリー
背景:
- タンパク質の変異はしばしば安定性を低下させ,有害である.
- チャペロン (熱ショックタンパク質) は,突然変異を緩衝し,適応を促進する可能性があります.
- 不安定化および適応性突然変異のバッファリングにおけるチャペロニンの役割については,さらなる調査が必要である.
研究 の 目的:
- Escherichia coliのGroEL/GroESチャペロニンが,不安定化および適応変異をバッファリングする能力を調査する.
- チャペロニンの過剰発現がタンパク質の進化と適応の速度に影響するかどうかを判断する.
主な方法:
- 4つの異なる酵素を用いた in vitro 変異漂移実験が行われました.
- GroEL/GroESチャペロニンは,突然変異の蓄積とタンパク質の折りたたみに対する影響を評価するために過剰表現されました.
- タンパク質核の突然変異や重大な不安定化効果を有する酵素変異種を分析した.
主要な成果:
- GroEL/GroESの過剰発現は,累積変異の数を2倍にしました.
- チャペロニンは,不安定化変異を持つ酵素変異の折り畳みを促進しました (平均>3.5 kcal mol ((-1) vs. ~1 kcal mol ((-1) チャペロニンなし).
- 酵素特異性の差異は,GroEL/GroES過剰発現下で著しく速く発生し,より多くの適応変種が改善された活性 (>10倍) を示した.
結論:
- タンパク質の安定性は,タンパク質の進化における重要な制約である.
- チャペロニンは重要なバッファリングメカニズムとして機能し,安定性の制約を緩和し,適応的進化を加速します.
- シェーパロン機能を理解することは,進化過程とタンパク質工学を理解するために不可欠です.
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