基于結(jié)構(gòu)的光合作用狀態(tài)轉(zhuǎn)換機(jī)理研究立項(xiàng)報(bào)告

柳振峰 劉秀穎

摘 要：自然界的光照條件隨著季節(jié)和一天中的不同時(shí)段會不斷地發(fā)生變化，光的強(qiáng)度和光線的光譜特征都會發(fā)生劇烈變化。對于像植物和藻類這些放氧光合生物來說，它們進(jìn)化出了一系列的有效機(jī)制，用以應(yīng)對光照環(huán)境的變化，一方面保護(hù)自身不受過強(qiáng)光線照射所造成的光損傷；另一方面又能夠在弱光條件下達(dá)到最為優(yōu)化的光合作用效率。狀態(tài)轉(zhuǎn)換是這一些巧妙調(diào)節(jié)機(jī)制中的一種，通過這一機(jī)制，放氧光合生物得以響應(yīng)光質(zhì)條件的變化而調(diào)節(jié)光能在兩個(gè)光系統(tǒng)之間的平衡分配。狀態(tài)轉(zhuǎn)換過程中涉及一對關(guān)鍵的激酶和磷酸酶，即Stt7/STN7激酶和PPH1/TAP38磷酸酶。它們是狀態(tài)轉(zhuǎn)換所必需的一對蛋白，并且與捕光蛋白LHCII的磷酸化和去磷酸化密切相關(guān)。該課題以植物狀態(tài)轉(zhuǎn)換機(jī)制為主題，開展Stt7/STN7激酶和PPH1/TAP38磷酸酶的結(jié)構(gòu)與功能研究，目標(biāo)是在高分辨率三維結(jié)構(gòu)分析基礎(chǔ)上結(jié)合生物化學(xué)研究方法深入探討光合作用狀態(tài)轉(zhuǎn)換的分子機(jī)理。對于光合作用狀態(tài)轉(zhuǎn)換中所形成的捕光蛋白LHCII與兩個(gè)光系統(tǒng)（PSII或PSI）所形成的超級復(fù)合物樣品進(jìn)行分離純化制備，通過嘗試三維結(jié)晶或應(yīng)用電子顯微鏡分析其三維結(jié)構(gòu)，以獲得較為精確的關(guān)于捕光蛋白LHCII與PSII或pLHCII與PSI相互作用的結(jié)構(gòu)信息。

關(guān)鍵詞：光合作用 狀態(tài)轉(zhuǎn)換 膜蛋白 捕光復(fù)合物

Abstract： The lighting conditions in nature are constantly changing on daily or seasonal bases. The intensity and spectroscopic features of the light are subject to drastic changes. For oxygenic photosynthetic organisms， like plants and algae， they have evolved a series of effective mechanisms in order to adapt to the fluctuation of lighting conditions. On one hand， these mechanisms will protect them from photodamage caused by excess energy intensity， while one the other hand， they can achieve optimal photosynthesis efficiency under dim light conditions. State transition is one of these sophisticated regulatory mechanisms through which the oxygenic photosynthesis organisms are able to respond to the change of light quality and regulate energy distribution balance between the two photosystems. A pair of vital kinase and phosphatase， namely Stt7/STN7 kinases and PPH1/TAP38 phosphatases， are involved in the state transition. They are essential for the operation of state transition， and closely related to the phosphorylation and dephosphorylation of light-harvesting complex II （LHCII）. This project centers on the mechanistic studies of plant state transition process. Structural and functional studies of Stt7/STN7 kinases and PPH1/TAP38 phosphatases are being carried out. The aim is to investigate the molecular mechanism of photosynthetic state transition by combining the analysis of high-resolution structures and biochemical studies. The supercomplexes between LHCII and the two photosystems （PSII or PSI） formed during state transition will be isolated and purified. Three-dimensional crystallization and electron microscopic analysis will be attempted in order to characterize the three-dimensional structures of these supercomplexes and obtain the precise information about the interactions between LHCII and PSII or pLHCII and PSI.

Key Words： Photosynthesis； State transition； Membrane protein； Light-harvesting complexes

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