還元中の窒素酵素MoFeタンパク質Pクラスタの電子構造変異の解剖

Bryant Chica¹, Jesse Ruzicka², Lauren M Pellows²

¹Biosciences Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States.

Journal of the American Chemical Society

|March 22, 2022

まとめ

研究者は,窒素酵素MoFeタンパク質のPクラスタにおける電子移転を,光化学的還元を用いて研究した. P-クラスタの酸化状態の変化における重要な中間物質を特定し,アンモニアの生成に不可欠である.

科学分野:

生物化学
バイオ有機化学
酵素触媒

背景:

窒素酵素 MoFe タンパク質の [8Fe-7S] P クラスターは,アンモニア合成中に Fe タンパク質からの電子移転に不可欠です.
P-クラスターは酸化状態 (P^N,P⁺,P²⁺) を経由して循環し,P^NP⁺移行は窒素酶複合体の活動に不可欠である.

研究の目的:

電子移転中のP⁺酸化状態の形成における中間段階を調査する.
P-クラスタにおけるスピン状態の移行と酸化状態の変化の間の結合を理解する.

主な方法:

中間物質を捕まえるために低温 (231~263K) でMoFeタンパク質を光化学的に還元する.
電子パラマグネティック共振 (EPR) スペクトロスコーピーは,閉じ込められた中間物質を分析します.
ダークアニリング中のEPR信号の変化の運動分析.

主要な成果:

MoFeタンパク質をCdSナノ結晶で照射すると,P-クラスター減少 (P²⁺) が誘発される.
3つの異なるEPR信号 (S=1/2軸,S=1/2ロムビック,S=7/2高スピン) が観察されました.
ダークアニリングは軸と高スピン信号の減少を示し,ロムビック信号の同時増加で,それらの中間的役割を示した.

結論:

P⁺の静止状態の形成において,軸と高スピンの EPR 信号は一時的な中間状態を表します.
スピン状態の変化は,電子移転中のPクラスター内の酸化状態の変動と密接に関連しています.

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