サイトクロームb ((6) f複合体の非典型のヘム

David Stroebel¹, Yves Choquet, Jean-Luc Popot

¹Laboratoire de Physico-Chimie Moléculaire des Membranes Biologiques, CNRS/Université Paris 7, UMR 7099, France.

Nature

|December 4, 2003

まとめ

研究者らは,光合成に不可欠なサイトクロームb6f複合体の構造を明らかにした. この構造は,酸素光合成の理解に鍵となるかもしれないユニークなヘム群を強調しています.

科学分野:

バイオケミストリーバイオケミストリー
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:

光システムIとII (PSIとII) は,酸素光合成において光エネルギーを捕捉するために不可欠である.
サイトクロームb) (6) f複合体は,PSIIとPSIの間で電子を転送し,陽子をポンプする中間体として作用する.
サイトクロームb ((6) fは,未知のメカニズムでPSIの周りのサイクル電子移転に関与する能力によって同類のものと異なる.

研究の目的:

光合成におけるシトクロームb ((6) f複合体の機能の構造的基礎を解明する.
サイトクロームb ((6) fのユニークな特徴,特にPSIとの相互作用と周期性電子伝送能力を調査する.
酸素 fotosynthesis に関する新しいヘム群などの潜在的な重要な成分を特定する.

主な方法:

サイトクロームb ((6) f複合体の構造を決定するために,X線結晶学を用いた.
この研究は,藻類クラミドモナスの再硬化菌から分離されたシトクロームb6f複合体に焦点を当てた.
構造分析は3.1 Åの解像度で行われました.

主要な成果:

サイトクロームbc(6) fの決定されたX線構造は,サイトクロームbc(1) との類似性を明らかにしますが,ユニークな特徴も示しています.
構造は,クロロフィール,ベータカロチン,およびキノンのサイトを共有する異常なヘム群の結合を示しています.
この非典型のヘムは,単一のチオエーテル結合を介して共振的に結合し,軸性アミノ酸リガンドが欠けています.

結論:

サイトクロームb ((6) fのユニークな構造的特徴,特に非典型のヘムが,その機能に関する新しい洞察を提供します.
この非典型的ヘム群は,酸素 fotosynthesisの複雑なメカニズムを理解する上で潜在的な"欠けているリンク"として提案されています.
構造データは,光合成生物におけるQサイクルと周期性電子移転に関するさらなる研究のための基盤を提供します.

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