Regulation of electron transport at photosystem II

研究了高等植物光合电子传递中光系统I（PSI）和光系统II（PSII）平衡受光环境变化的两种主要调节机制，1.电子传递在初级醌受体（QA）上的调控离体重组实验发现，叶绿体psbL基因编码的PS Ⅱ复合体组分L蛋白参与QA位点电子传递的调控。分离由CP 47/D1/D2/Cytb-559/I蛋白质组成的质体醌-9（PQ-9）耗尽的PSII反应中心核心复合物，并将其用PQ-9进行重构。只有当用L蛋白进行重构时，PQ-9才重新插入复合物中并在所得复合物中作为QA。重组L蛋白在大肠杆菌中得到高效表达，与PSII颗粒中分离的L蛋白一致。根据这些发现， ...更多信息 2.光在转录水平对psbC和psbD基因表达的调控在叶绿体psbD/C基因簇中有两个光响应启动子，它们编码PSII的几个重要蛋白，其中一个启动子是光响应启动子，另一个启动子是光响应启动子一个启动子（D/C-3启动子）产生D2蛋白的mRNA，另一个启动子（D/C-4启动子）产生CP 43蛋白的mRNA。在光照下，前者是可逆激活，而后者是失活的，分别表明，这两种蛋白质的合成响应于光强度通过调节这些启动子的活动。我们成功地在一个核编码的调节因子，特异性激活D/C-3启动子的patrial纯化。该因子似乎是一种序列特异性DNA结合蛋白，它识别位于D/C-3转录起始位点上游的顺式元件。少

We examined the two major mechanisms by which balance of photosystem I (PSI) and Photosystem II (PSII) in the photosynthetic electron transport in higher plants was regulated in response to the variation of light environment, focusing on the regulation at PSII.1.Regulation of electron transport at primary quinone acceptor (QA) L protein which is a component of PSII complex and encoded by chloroplast psbL gene was found to be involved in the regulation of electron transport at QA site by in vitro reconstitution experiments. Plastoquinone-9 (PQ-9) depleted PSII reaction center core complex, consisting of CP47/D1/D2/Cytb-559/I proteins was isolated and submitted to the reconstitution with PQ-9. Only when the reconstitution was carried out with the L protein, PQ-9 reinserted in the complex and worked as QA in the resulting complex. Recombinant L protein was successfully over expressed in E.coli.and found to stand for the isolated L protein from PSII particles. Based on these findings, the … More molecular mechanism of the regulation of electron transport at QA site is being examined by the in vitro reconstitution with various types of mutant L protein.2.Regulation of the gene expression of psbC and psbD by light at transcription level There are two light-responsive promoters in chloroplast psbD/C gene cluster which encodes several important proteins of PSII.One (D/C-3 promoter) produces mRNA for D2 protein and the other (D/C-4 promoter) does that for CP43 protein. Upon light illumination, the former is reversibly activated while the latter is inactivated, respectively, suggesting that synthesis of these two proteins responses to light intensity through the regulation of activities of these promoters. We succeeded in the patrial purification of a nuclear-encoded regulatory factor which specifically activates the D/C-3 promoter. This factor seems to be a sequence specific DNA binding protein which recognizes the cis-element residing upstream region of the D/C-3 transcription initiation site. Less