光系统I
莱茵衣藻
铁氧还蛋白
光合作用
细胞色素b6f复合物
电子传输链
光系统
类囊体
化学
生物物理学
电子流
叶绿体
光化学
光系统II
生物
生物化学
突变体
基因
酶
作者
Masakazu Iwai,Kayoko Takizawa,Ryutaro Tokutsu,Akira Okamuro,Yuichiro Takahashi,Jun Minagawa
出处
期刊:Nature
[Springer Nature]
日期:2010-04-01
卷期号:464 (7292): 1210-1213
被引量:386
摘要
Photosynthetic light reactions establish electron flow in the chloroplast's thylakoid membranes, leading to the production of the ATP and NADPH that participate in carbon fixation. Two modes of electron flow exist-linear electron flow (LEF) from water to NADP(+) via photosystem (PS) II and PSI in series and cyclic electron flow (CEF) around PSI (ref. 2). Although CEF is essential for satisfying the varying demand for ATP, the exact molecule(s) and operational site are as yet unclear. In the green alga Chlamydomonas reinhardtii, the electron flow shifts from LEF to CEF on preferential excitation of PSII (ref. 3), which is brought about by an energy balancing mechanism between PSII and PSI (state transitions). Here, we isolated a protein supercomplex composed of PSI with its own light-harvesting complex (LHCI), the PSII light-harvesting complex (LHCII), the cytochrome b(6)f complex (Cyt bf), ferredoxin (Fd)-NADPH oxidoreductase (FNR), and the integral membrane protein PGRL1 (ref. 5) from C. reinhardtii cells under PSII-favouring conditions. Spectroscopic analyses indicated that on illumination, reducing equivalents from downstream of PSI were transferred to Cyt bf, whereas oxidised PSI was re-reduced by reducing equivalents from Cyt bf, indicating that this supercomplex is engaged in CEF (Supplementary Fig. 1). Thus, formation and dissociation of the PSI-LHCI-LHCII-FNR-Cyt bf-PGRL1 supercomplex not only controlled the energy balance of the two photosystems, but also switched the mode of photosynthetic electron flow.
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