光系統(tǒng)II是光合水氧化站,，它包括，總分子量為350 kDa的20個亞基,。光系統(tǒng)II的結(jié)構(gòu)已報道的分辨率為3.8 ~2.9 Å,。這些分辨率提供了很多蛋白亞基和共組合因子的排列信息,，但這些不足以揭示水分離反應(yīng)中心的詳細(xì)結(jié)構(gòu),。日本大阪市立大學(xué)的Yasufumi Umena 等報道了分辨率1.9 Å的光系統(tǒng)的晶體結(jié)構(gòu),。“從我們的電子密度圖，我們定位了Mn4CaO5蔟的所有金屬原子以及配體,。我們發(fā)現(xiàn),，5個氧原子作為氧絡(luò)橋連接5個金屬原子，4個水分子束縛到Mn4CaO5蔟上,，因此,，它們部分作為分子氧形成的底物。我們在每個光系統(tǒng)II單體中分別鑒別了1300個以上的水分子,。它們的一部分形成廣泛的氫結(jié)合網(wǎng)絡(luò),，服務(wù)為質(zhì)子、水或氧分子通道,，” Yasufumi Umena說,。“光系統(tǒng)II的高分辨率結(jié)構(gòu)的確定將允許我們進(jìn)一步詳細(xì)地分析與理解其功能。”（生物谷Bioon.com）
生物谷推薦原文出處：
Nature doi:10.1038/nature09913
Crystal structure of oxygen-evolving photosystem II at a resolution of 1.9 Å
Yasufumi Umena,1, 3, 4 Keisuke Kawakami,2, 3, 4 Jian-Ren Shen2 & Nobuo Kamiya1, 3
Photosystem II is the site of photosynthetic water oxidation and contains 20 subunits with a total molecular mass of 350 kDa. The structure of photosystem II has been reported at resolutions from 3.8 to 2.9 Å. These resolutions have provided much information on the arrangement of protein subunits and cofactors but are insufficient to reveal the detailed structure of the catalytic centre of water splitting. Here we report the crystal structure of photosystem II at a resolution of 1.9 Å. From our electron density map, we located all of the metal atoms of the Mn4CaO5 cluster, together with all of their ligands. We found that five oxygen atoms served as oxo bridges linking the five metal atoms, and that four water molecules were bound to the Mn4CaO5 cluster; some of them may therefore serve as substrates for dioxygen formation. We identified more than 1,300 water molecules in each photosystem II monomer. Some of them formed extensive hydrogen-bonding networks that may serve as channels for protons, water or oxygen molecules. The determination of the high-resolution structure of photosystem II will allow us to analyse and understand its functions in great detail.
