光から独立するプロトクロロフィリド還元酵素のX線結晶構造
Norifumi Muraki1, Jiro Nomata, Kozue Ebata
1Department of Life Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan.
Nature
|April 20, 2010
まとめ
暗闇で作用するプチリド酸化還元酵素 (DPOR) の結晶構造は,クロロフィルの合成のためのメカニズムを明らかにします. この窒素酵素のような酵素は,触媒活性のためにユニークなアスパルテート結合を使用します.
科学分野:
- バイオケミストリー バイオケミストリー
- 構造生物学 構造生物学とは
- 光合成研究 研究 光合成研究
背景:
- 光合成生物は,クロロフィルを光依存性および光依存性Pchlide oxidoreductase (DPOR) の2つの経路で合成する.
- DPORはLタンパク質とNBタンパク質からなる複雑な酵素で,構造的には窒素酵素成分に類似しています.
研究 の 目的:
- Rhodobacter capsulatusからDPORのNBタンパク質の結晶構造を決定する.
- DPORによって触媒化されたプロトクロロフィリド還元のメカニズムを解明する.
主な方法:
- 2.3Åの解像度のX線結晶学.
- 窒素酵素 MoFe タンパク質との構造比較.
主要な成果:
- NB-タンパク質の構造は,窒素酵素MoFeタンパク質に類似しており,BchN-BchBの各ユニットにはプロトクロロフィリドと鉄硫黄群 (NB-群) が含まれています.
- NB-クラスターへのユニークなアスパルテート結合は,クラスター組立だけでなく,触媒活動に不可欠です.
- 特定のプロトクロロフィリドの結合には,アルファヘリクスの解き放たれがあり,トランス固有の還元機構を容易にします.
結論:
- DPORは,安定したマルチボンドを減らすために,窒素酵素と共通のアーキテクチャを共有しています.
- C17=C18の二重結合還元のために,アスパート酸とプロトクロロフィリドC17-プロピオネートを陽子ドナーとして含む新しいメカニズムが提案されています.
- この構造的な洞察は,クロロフィール生物合成と酵素触媒の理解を前進させる.
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