陽子結合電子移転と酸化還元活性チロシンZは,光合成による酸素生成複合体の中で進化しています
James M Keough1, David L Jenson, Ashley N Zuniga
1School of Chemistry and Biochemistry and the Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Journal of the American Chemical Society
|July 1, 2011
まとめ
フォトシステムII (PSII) のプロトン結合電子移転 (PCET) は,リドックス活性チロシンYZとYDを区別する. YZ PCETはpHから独立しており,溶媒同位体効果を示しており,結合された陽子電子移転機構を示唆しています.
科学分野:
- バイオケミストリー バイオケミストリー
- 光合成研究 研究 光合成研究
- 酵素のメカニズム
背景:
- 陽子結合電子移転 (PCET) は酵素反応において極めて重要であり,しばしばリドックス活性型チロシンが関与する.
- 光システムII (PSII) は,異なる触媒的役割を持つ2つの酸化還元活性チロシン,YDとYZを使用しています.
- YZは酸素の進化に不可欠であり,マンガンの触媒部位によって急速に減少します.
研究 の 目的:
- 酸素が進化するPSIIにおけるYZ PCETのメカニズムを調査する.
- YZ (((•) 崩壊運動とそのpHと溶媒同位体効果への依存を特徴づける.
- PSII内のYZとYDのPCETメカニズムを区別する.
主な方法:
- 低温を利用してYZ(•) 反応を分離し,マンガン・カルシウム・クラスタを保存した.
- 高いマイクロ波電力を使って,YDの信号を飽和させました.
- EPR光譜を用いたYZ(•) 崩壊運動を測定し,pHと溶媒同位素依存性を分析した.
主要な成果:
- YZ(•) 崩壊速度は,有意な溶媒同位体効果を示した.
- YZ(•) リコンビネーションの速度と溶媒同位体効果は,pH 5.0と7.5.5の間のpHから独立していた.
- これらの発見は,低pHで観察されたYD (((•) 崩壊運動とは対照的です.
結論:
- 溶媒同位体効果によるpHに依存しないYZ(•) 崩壊は,速度制限結合陽子電子移転 (CPET) 機構をサポートしています.
- YZを取り巻く広範囲の水素結合ネットワークが,このCPETプロセスを媒介する可能性があります.
- PCET反応は,PSIIにおけるYZとYDの機能的役割を明確に区別する.
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