8A解像度の植物光システムII反応センターの3次元構造
K H Rhee1, E P Morris, J Barber
1Max-Planck-Institut für Biophysik, Abteilung Strukturbiologie, Frankfurt am Main, Germany.
Nature
|December 2, 1998
まとめ
研究者は電子結晶学を用いて,フォトシステムII亜複合体の構造を決定した. これは,光による反応と,他の光システムとの進化的つながりについての洞察を明らかにします.
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:
- 光システムII (PSII) は,植物光合成における重要な酵素複合体であり,太陽エネルギーを用いて水の分裂を担当しています.
- ネイティブPSIIは,分子量600Kを超える25以上のサブユニットからなる大きく複雑なアセンブリです.
- PSIIの構造を理解することは,光合成のメカニズムと潜在的なバイオエネルギーアプリケーションの解明の鍵です.
研究 の 目的:
- 特定のフォトシステムII亜複合体の3次元構造を決定する.
- このサブコンプレックス内のD1,D2,CP47,およびサイトクロームb-559タンパク質の機能的能力と構造的組織を調査する.
主な方法:
- 電子結晶学を用いて構造を解明した.
- この研究は,D1,D2,CP47,およびサイトクロームb-559タンパク質を含むサブコンプレックスに焦点を当てた.
主要な成果:
- CP47反応センターサブコンプレックス (160K) の3次元構造を決定しました.
- このサブコンプレックスは,光媒介のエネルギーと電子の転送を行いますが,水を酸化することはできません.
- 構造は23のトランスメブランアルファヘリクスを明らかにし,16はD1,D2およびCP47タンパク質に割り当てられています.
- 紫色のバクテリアの反応センターと植物写真系Iとの構造的類似性は,共通の進化的起源を示唆しています.
- レドックスコファクターの位置は,細菌の反応センターに類似しているが",特殊なペア"のクロロフィルの間の距離が大きい.
結論:
- 決定された構造は,機能的なフォトシステムII亜複合体の詳細な視点を提供します.
- 構造的な類似性は,光合成反応センターの保存された進化の経路を強調しています.
- この発見は,光合成における光エネルギー変換の初期段階についての洞察を提供します.
さらに関連する動画
関連する概念動画
Photosystem II
The multi-protein complex photosystem II (PS II) harvests photons and transfers their energy through its bound pigments to its reaction center, and ultimately to photosystem I (PSI) through the electron transport chain. The pigments responsible for caputirng the light energy in photosystems include chlorophyll a, chlorophyll b, and carotenoids.
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Photosystem I
Although structurally similar to photosystem II (PSII), photosystem I (PSI) is has a different electron supplier and electron acceptor.
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
The Photochemical Reaction Center
Reaction centers are pigment-protein complexes that initiate energy conversion from photons to chemical entities. Therefore, photochemical reaction center is a more appropriate term that describes these complexes. The Nobel laureates Robert Emerson and William Arnold provided the first experimental evidence of photochemical reaction centers by demonstrating the participation of nearly 2,500 chlorophyll molecules for the release of just one molecule of oxygen. Despite thousands of photosynthetic...
The Antenna Complex
Plants and other photosynthetic organisms comprise pigments capable of absorption of direct sunlight. These pigments are present in the reaction center - the main site of photochemical reactions as well as in the antenna complex. Under average light conditions, the rate at which reaction center pigments absorb light is far below the electron transport chain's capacity. As a result, the reaction center alone cannot provide enough energy to drive photosynthesis. The photosynthetic efficiency can...
Photosystems
Photosystems are multiprotein complexes that form the functional units of photosynthesis in plants, algae, and cyanobacteria. They are found embedded in the membrane of tiny sac-like structures called thylakoids placed inside the chloroplast.
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The Z-Scheme of Electron Transport in Photosynthesis
The light reactions of photosynthesis assume a linear flow of electrons from water to NADP+. During this process, light energy drives the splitting of water molecules to produce oxygen. However, oxidation of water molecules is a thermodynamically unfavorable reaction and requires a strong oxidizing agent. This is accomplished by the first product of light reactions: oxidized P680 (or P680+), the most powerful oxidizing agent known in biology. The oxidized P680 that acquires an electron from the...


