ケトステロイドイソメラーゼにおける陽子転移反応に対する突然変異の影響:分子動力学シミュレーションからの洞察
Dhruva K Chakravorty1, Sharon Hammes-Schiffer
1Department of Chemistry, 104 Chemistry Building, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
Journal of the American Chemical Society
|May 11, 2010
まとめ
ケトステロイドイソメラーゼ (KSI) アクティブサイト残基Tyr14とAsp99の変異は,ディエノラート中間体を不安定化することによって,触媒速度を低下させます. シミュレーションにより,変異体における水素結合と静電相互作用が変化し,陽子伝送効率に影響を及ぼしていることが明らかになった.
科学分野:
- バイオケミストリー バイオケミストリー
- 酵素学 酵素学とは
- コンピューティング・ケミストリー
背景:
- ケトステロイドイソメラーゼ (KSI) は,必須の陽子伝達反応を触媒化する.
- Tyr14とAsp99からの水素結合は,ワイルドタイプ (WT) KSIにおけるディエノラート中間物質を安定させる.
- 活性部位の残留物の役割を理解することは,酵素機構の解明に極めて重要です.
研究 の 目的:
- KSIの触媒メカニズムにTyr14およびAsp99変異の影響を調査する.
- 陽子移動中の水素結合,形状,相互作用の変化を分析する.
- シミュレーション結果を実験的運動データと相関させるため.
主な方法:
- 経験的なバレンスの結合 (EVB) モデルを用いた分子動力学 (MD) シミュレーション.
- 水素結合パターン,構造動力学,相互作用エネルギーの分析.
- 陽子伝送段階における自由エネルギープロファイルと速度定数の計算.
主要な成果:
- Y14FとD99Lの変異により,ダイノラート中間体の自由エネルギーが大幅に増加し,最初の陽子転送速度が低下しました.
- WT KSIは2つの活性サイト水素結合を維持し,突然変異者は通常1つしか持たないので,中間安定化に影響を与えました.
- 中間物質の静電安定化は,WT KSIと比較して,変異体において減少した.
結論:
- 変異により,KSIの事前組織された活性部位構造が変化し,触媒効率が低下する.
- ミュータントにおける変化した水素結合と静電相互作用は,ディエノラート中間物質を不安定化する.
- 酵素活性部位は,事前組織化されている場合でも,効率的な触媒化のために特定の構成動態を必要とします.
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