Suh Hwa-Jin, Kim Chang Sook, Lee Ji-Yeun, Jung Jin
School of Agricultural Biotechnology, Seoul National University, Suwon, Korea.
Photochem Photobiol. 2002 May;75(5):513-8. doi: 10.1562/0031-8655(2002)075<0513:peoieo>2.0.co;2.
An earlier mechanistic phase of iron toxicity in photosynthetic cells was interpreted in terms of enhanced photodynamic action by the cytochrome b6/f complex (Cyt b6/f) via singlet oxygen (1O2) on the photosystem II complex (PS II). Iron excess was induced in hydroponically cultured pea (Pisum sativum L.) plants, and its effect on the function of PS II in vivo as well as in vitro was studied under high-irradiance conditions. Iron excess in plants gave rise to a significant increase in Cyt b6/f content of thylakoids. It appeared that the larger the content of Cyt b6/f, the more susceptible PS II was to photoinhibition, and the higher the rate of 1O2 photoproduction in thylakoids was. The action spectrum for degradation of the D1 protein in thylakoids revealed that photosensitization by nonporphyrin chromophore(s) was apparently associated with near UV to blue light-induced deterioration of PS II. The results are pertinent to the concept that photooxidative damage to PS 11, exacerbated by iron accumulation in thylakoid membranes in the form of Cyt b6/f, is involved in the mechanism of iron toxicity in leaf cells.
光合细胞中铁毒性的早期机制阶段被解释为细胞色素b6/f复合体（Cyt b6/f）通过单线态氧（1O2）对光系统II复合体（PS II）的光动力作用增强。在水培豌豆（Pisum sativum L.）植株中诱导铁过量，并在高辐照条件下研究其对PS II体内和体外功能的影响。植物中铁过量导致类囊体中Cyt b6/f含量显著增加。似乎Cyt b6/f含量越高，PS II对光抑制越敏感，类囊体中1O2的光产生速率越高。类囊体中D1蛋白降解的作用光谱表明，非卟啉发色团的光敏化显然与近紫外到蓝光诱导的PS II降解有关。这些结果与以下概念相关：以Cyt b6/f形式在类囊体膜中积累的铁加剧了对PS II的光氧化损伤，这参与了叶细胞中铁毒性的机制。
