1秒間の球状アミノ酸の置換が,いかにして,数百ミリボルトの減量中点の潜在変化を引き起こすのか
Emine Yikilmaz1, Jason Porta, Laurie E Grove
1Department of Chemistry, University of Kentucky, Lexington, KY 40506-0055, USA.
Journal of the American Chemical Society
|July 14, 2007
まとめ
スーパーオキシドディスミュータゼ (SOD) 酵素の活性度は,メタルイオンによって調整されます.
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
- プロテイン工学は,タンパク質の
背景:
- スーパーオキシードディスミュータゼ (SOD) 酵素は,スーパーオキシードラジカルの不均衡を触媒化する.
- 活性サイトメタルイオンの還元中位ポテンシャル (Em) は,SODの触媒活性において極めて重要です.
- Fe含有SOD (FeSOD) は,Fe3+/Fe2+リドックスカップルを利用し,プロトネーションイベントの影響を受けます.
研究 の 目的:
- E. coliのFeSOD変異体におけるEm値上昇の構造的および電子的根拠を調査する.
- 保存されたGln残基の変異がFeSODの酸化還元特性にどのように影響するかを理解するためです.
- 酵素活性調節における酸化還元結合型陽子伝達の役割を明らかにする.
主な方法:
- サイト・ダイレクト・ミュータゲネシス (Gln to His,Gln to Glu).
- スペクトロスコーピテクニック: EPR,MCD,NMR.
- X線結晶学 (1.1 Å 解像度).
- 密度関数理論 (DFT) による計算.
主要な成果:
- Q69HとQ69Eの変異により,FeSODのEmが著しく上昇した.
- 顕微鏡検査データは,両方の変異体において,WTのような活性部位電子構造を示した.
- Q69E-FeSODは,減少した状態で変異した陽子伝送ダイナミクスと水素結合を示した.
- Q69E-Fe2+SODの結晶構造は,Glu69.9による強いH結合受容性を明らかにした.
結論:
- タンパク質マトリクスは,酸化還元結合型陽子伝導を通じてFeSODのEmに大きく影響します.
- Q69E-FeSODにおける変異した水素結合と陽子の移転が,Emの上昇を説明する.
- これらの発見は,金属酵素におけるタンパク質媒介による酸化還元調節の仮説を裏付けている.
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