リボヌクレオチド還元酵素中介物質Xのプロトン化酸素リガンドの識別
Muralidharan Shanmugam1, Peter E Doan, Nicholas S Lees
1Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, USA.
Journal of the American Chemical Society
|February 18, 2009
まとめ
この研究では,リボヌクレオチド還元酵素の前駆体である中間Xは,端末aquaリガンドとmu-oxoブリッジを含んでいるが,mu-hydroxoブリッジは含まれていないことを確認した. これらの発見は,酵素の野生型と変異型の両方に適用されます.
科学分野:
- バイオケミストリー バイオケミストリー
- バイオ・オーガニック化学 バイオ・オーガニック化学
- スペクトロスコーピーは,スペクトロスコーピーを用います.
背景:
- インターミディエイトXは,Escherichia coliのリボヌクレオチド還元酵素 (RNR) のディフェルリック・タイロシル・ラジカルコファクターの直接前駆体である.
- 電子核二重共鳴 (ENDOR) を用いた以前の研究では,ミュー-ヒドロキソブリッジが欠けていた中間のXの [H (x) O (Fe (III) O (Fe (IV)) ] 断片を提案した.
- 中間Xの無機核構造に関して,矛盾するモデルが提案されている.
研究 の 目的:
- 中間XのFe (III) /Fe (IV) クラスタの酸素リガンドのプロトネーション状態を再検討する.
- (2) Hパルス型ENDORスペクトロスコーピーを用いて交換可能な陽子を直接探査する.
- 中間物質Xの無機核に関する構造的不一致を明らかにする.
主な方法:
- 最先端の35GHzパルス式ENDORスペクトロスコーピーを利用しました.
- (2) Hパルス型ENDORを用いて,酸素リガンドの交換可能な陽子を研究した.
- ヒスティジルリガンドに関する (14) N ENDOR測定を行った.
主要な成果:
- 中間X.でFe (III) に結合した終端水リンガンド (H (x) O) の存在が確認されました.
- 橋渡しヒドロキシル陽子の兆候を示すスペクトル特徴は観察されなかった.
- これらの発見は,野生型およびY122F-β2 RNR変異体の両方において一貫していることが実証されました.
- 2つの変種間の末端酸素陽子の特性またはヒスティジルリガンド結合の違いは検出されなかった.
結論:
- インターミディアットXには,ターミナルアクアリガンドと1つまたは2つのムオキソブリッジが含まれ,ムオキソヒドロキソブリッジは完全に除外されます.
- 構造的結論は堅実で,野生型とY122F-β2RNRの両方に適用できます.
- この研究は,中間物質Xの無機核に関する構造的曖昧さを解消している.
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