フォトシステムIIにおける陽子結合電子移転:リドックス活性型チロシンの陽子在庫
David L Jenson1, Bridgette A Barry
1School of Chemistry and Biochemistry and the Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
Journal of the American Chemical Society
|July 10, 2009
まとめ
フォトシステムII
科学分野:
- バイオケミストリー バイオケミストリー
- 光合成の研究研究である.
- タンパク質の生体物理学
背景:
- 光システムII (PSII) は,水の酸化とプラストキノン還元を含む光合成に不可欠です.
- D1とD2ポリペプチドはPSIIの核を形成し,酸素進化複合体 (OEC) は水の酸化を担当する.
- タイロシンY (D) はOECの安定化に関与し,ヒスティジン189と陽子結合電子移転 (PCET) を示しています.
研究 の 目的:
- フォトシステムIIで高pH下でのY(D) 陽子結合電子移転 (PCET) のメカニズムを調査する.
- Y (((D)) リドックス反応に関与する陽子伝達経路を解明する.
主な方法:
- 陽子在庫技術を使用して,高pHでY(D) PCETを分析しました.
- 以前の研究で,同位体ラベリングとサイト・ダイレクト・ミュータゲネシスを適用し,Y (D) を割り当て,その相互作用を研究した.
主要な成果:
- 陽子在庫データは,Y(D) ((*)) への複数の陽子献血経路を示し,超曲線を示した.
- 少なくとも1つの経路は,1つ以上の陽子の移転を伴う.
- 高pHでのPCETメカニズムは,これまで理解していたよりも複雑です.
結論:
- この発見は,Photosystem IIのY(D) PCET.の複雑なプロトン伝送ダイナミクスを明らかにしています.
- マルチプロトン移転を含む複数の陽子経路は,高pH下でのY (((D)) 機能に不可欠です.
- この研究は,光合成による水の酸化の基礎となる分子機構の理解を前進させています.
関連する概念動画
01:22Photosystem 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...
01:27Photosystem 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...
01:29The 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...
01:34The 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...
01:32Photosystems
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...
01:43Electron Transport Chain: Complex III and IV
During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...