Control of hydrogen photoproduction by the proton gradient generated by cyclic electron flow阅读笔记.doc
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1、Control of hydrogen photoproduction by the proton gradient generated by cyclic electron flow in Chlamydomonas reinhardtii题目翻译:莱茵衣藻中通过环式电子传递产生的质子梯度控制光致产氢作者:摘要:阅读笔记:真核微藻的光致产氢,通过光合电子传递链和质体氢化酶之间的联系:“Hydrogen photoproduction by eukaryotic microalgae results from a connection between the photosynthetic el
2、ectron transport chain and a plastidial hydrogenase. ”藻类产氢,在自然条件下,通常是一种短暂的现象,通常被认为是一种避免光合电子传递链过度还原的一种保护安全阀:“Algal H2 production is a transitory phenomenon under most natural conditions, often viewed as a safety valve protecting the photosynthetic electron transport chain from overreduction. ”分析莱茵衣藻的
3、突变株,基于暗-光叶绿素荧光分析,分离出一株环绕PSI的环式电子传递CEF受损的突变株,由于其缺乏“质子梯度调节蛋白Proton Gradient Regulation Like1 (PGRL1) protein”:“From the colony screening of an insertion mutant library of the unicellular green alga Chlamydomonas reinhardtii based on the analysis of dark-light chlorophyll fluorescence transients, we is
4、olated a mutant impaired in cyclic electron flow around photosystem I (CEF) due to a defect in the Proton Gradient Regulation Like1 (PGRL1) protein. ”在好氧生活条件下,在突变株pgrl1中,非光化学淬灭(NPQ)显著降低:“Under aerobiosis, nonphotochemical quenching of fluorescence (NPQ) is strongly decreased in pgrl1.”在厌氧生活条件下,在突变株p
5、grl1中的光致产氢显著增加,无论是在短期还是长期测量中(缺硫条件下):“Under anaerobiosis, H2 photoproduction is strongly enhanced in the pgrl1 mutant, both during short-term and long-term measurements (in conditions of sulfur deprivation).”根据NPQ和产生氢气的光依赖性,同时,在加入解耦联剂FCCP(uncoupling agent carbonyl cyanide p-trifluoromethoxyphenylhydr
6、azone (FCCP))时野生型的产氢量也增加,得出结论:CEF产生的质子梯度引起野生型中氢化酶的电子供应抑制,而在突变株pgrl1中是没有这种抑制的:“Based on the light dependence of NPQ and hydrogen production, as well as on the enhanced hydrogen production observed in the wild-type strain in the presence of the uncoupling agent carbonyl cyanide p-trifluoromethoxypheny
7、lhydrazone, we conclude that the proton gradient generated by CEF provokes a strong inhibition of electron supply to the hydrogenase in the wild-type strain, which is released in the pgrl1 mutant.”通过检测pgrl1的表达对跨类囊体膜质子梯度的调节,展示了重新设计微藻细胞的代谢来增加氢气生产量的新视野:“Regulation of thetrans-thylakoidal proton gradien
8、t by monitoring pgrl1 expression opens new perspectives toward reprogramming the cellular metabolism of microalgae for enhanced H2 production.”模式生物 莱茵衣藻 在产氢中的研究应用:“A few microalgae species, including the model species Chlamydomonas reinhardtii , have been reported to produce H2 in the light (Gaffron
9、 and Rubin, 1942; Healey, 1970)”藻类产氢的过程(WX):“During this process, electrons produced by the photosynthetic electron transport chain are diverted at the level of ferredoxin toward Fe-Fe hydrogenase, which catalyzes the reversible reduction of protons into molecular hydrogen in algae (Florin et al., 2
10、001).”藻类产氢优势/前景(WX):“The use of microalgae is considered to be a promising approach for developing sustainable H2 production from sunlight energy and water as the main resources (Melis and Happe, 2001).”藻类产氢开发的障碍,增加产量和控制(WX):“Harnessing and enhancing microalgal H2 production is recognized as a major
11、 step in developing clean and sustainable hydrogen economy (Ghirardi et al., 2000; Melis, 2002; Kruse et al., 2005a).”产氢过程的主要限制:光合产的氧使敏感的产氢的氢化酶失活:“The main limitation to hydrogen production is considered to result from the O2 sensitivity of hydrogenase enzymes: molecular O2 produced at photosystem I
12、I (PSII) during photosynthesis rapidly induces the irreversible inhibition of the algal FeFe-hydrogenase (Happe et al., 2002; Stripp et al., 2009).”实验操作发现,缺硫可以避免这种情况,通过产氧气和产氢气的阶段在时间上分离:“ An experimental protocol based on sulfur deficiency was reported to circumvent this limitation by inducing a time
13、-based separation of O2- and H2-producing phases (Melis et al., 2000). ”解释:在好氧时,光合作用的还原力以淀粉形式贮存,在之后厌氧时通过产生氢气或在线粒体进行呼吸作用维持厌氧环境(WX。):“During this process, the reducing power generated by photosynthesis is temporarily stored as starch during the aerobic phase and consumed during a subsequent anaerobic
14、period to supply reductants either to produce H2 or to maintain anaerobiosis by feeding mitochondrial respiration (Melis et al., 2000; Chochois et al., 2009).”其他一些实验通过基因手段降低氢化酶对氧气的活性:“Other experimental approaches have used genetic engineering aiming at lowering the O2 sensitivity of hydrogenase.”在产
15、氢气时两条电子传递的途径(在缺硫的情况下):一条是“直接的途径”:电子来自光合过程中从PSII传递到PSI的电子,之后经过【还原态铁氧还蛋白】传递到氢化酶;在“间接途径”中:光合作用的还原力首先由于缺硫而贮存为淀粉starch,淀粉分解作用的还原当量进入系统间的电子传递链质体醌库 plastoquinone (PQ) pool,现已发现此过程中的酶(WX。)。“Two main pathways of electron supply have been previously identified under conditions of sulfur limitation, a direct a
16、nd an indirect pathway (Fouchard et al., 2005; Chochois et al., 2009). During the direct pathway, hydrogen is produced using electrons supplied by the photosynthetic electron transport chain from PSII to photosystem I (PSI) and then to the hydrogenase via reduced ferredoxin. During the indirect path
17、way, the reducing power generated by oxygenic photosynthesis, first stored as starch in response to sulfur starvation, is remobilized in a second step. During this process, the reducing equivalents generated during starch catabolism are injected into the intersystem electron transport chain at the l
18、evel of the plastoquinone (PQ) pool. The enzyme involved in this process has recently been identified as a plastidial type II NADH dehydrogenase called Nda2 (Jans et al., 2008; Desplats et al., 2009).” 这两种途径都公用的电子载体有:cytochrome b6/f complex, plastocyanin, and PSI(注意,当然还有PQ库):“ Both pathways of hydro
19、gen production share common electron carriers, such as the cytochrome b6/f complex, plastocyanin, and PSI.”【CEF】产生跨类囊体膜质子梯度,促进建立NPQ:“CEF has been shown to generate a thylakoid trans-membrane proton gradient involved in the establishment of nonphotochemical quenching (NPQ).”在衣藻中,CEF受到状态转换的调控,这包含在激发能在
20、PSI与PSII之间的再分配:“In Chlamydomonas, CEF is regulated by state transition (Finazzi et al., 2002), a phenomenon involved in the redistribution of the excitation energy between PSI and PSII.”状态转换12:发生在PQ库的氧环状态增加时,如:在厌氧条件下:“Transition from state 1 to state 2 occurs in response to an increase in the redox
21、state of the PQ pool, for instance, under anaerobic conditions. ”诱导了STT7 激酶的激发来磷酸化可移动的LHCII从PSII向PSI移动(WX):“This triggers the STT7 kinase to phosphorylate mobile light-harvesting complex II (LHCII), resulting in a move of phosphorylated LHCII from PSII to PSI (Depge et al., 2003). ”CEF的调控蛋白:PGR5 和后来
22、发现的PGRL1,后者可以与PGR5 和铁氧还蛋白相互作用(WX):“PGR5 was first identified in Arabidopsis thaliana as an essential molecular component of CEF from a screen of Arabidopsis mutants affected in NPQ (Munekage et al., 2002). More recently, Proton Gradient Regulation Like1 (PGRL1) has been identified in Arabidopsis as
23、another essential component of CEF, interacting with both PGR5 and ferredoxin (DalCorso et al., 2008).”CEF的调控蛋白:PGR5 和后来发现的PGRL1,后者可以与PGR5 和铁氧还蛋白相互作用(WX):“PGR5 was first identified in Arabidopsis thaliana as an essential molecular component of CEF from a screen of Arabidopsis mutants affected in NPQ
24、 (Munekage et al., 2002). More recently, Proton Gradient Regulation Like1 (PGRL1) has been identified in Arabidopsis as another essential component of CEF, interacting with both PGR5 and ferredoxin (DalCorso et al., 2008).”在莱茵衣藻中,PGRL1 的下行调节使CEF受损,特别是在缺铁的条件下(WX):“In C. reinhardtii,downregulation of
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