Institut für Biologie II , Universität Freiburg, Schänzlestr. 1, 79104 Freiburg, Germany.
Physiol Plant. 2010 Apr;138(4):463-73. doi: 10.1111/j.1399-3054.2009.01312.x. Epub 2009 Oct 23.
The function of cytochrome b559 (cyt b559) in photosystem II (PSII) was studied in a tobacco mutant in which the conserved phenylalanine at position 26 in the beta-subunit was changed to serine. Young leaves of the mutant showed no significant difference in chloroplast ultra structure or in the amount and activity of PSII, while in mature leaves the size of the grana stacks and the amount of PSII were significantly reduced. Mature leaves of the mutant showed a higher susceptibility to photoinhibition and a higher production of singlet oxygen, as shown by spin trapping electron paramagnetic resonance (EPR) spectroscopy. Oxygen consumption and superoxide production were studied in thylakoid membranes in which the Mn cluster was removed to ensure that all the cyt b559 was present in its low potential form. In thylakoid membranes, from wild-type plants, the larger fraction of superoxide production was 3-(3,4-dichlorophenyl)-1,1-dimethylurea-sensitive. This type of superoxide formation was absent in thylakoid membranes from the mutant. The physiological importance of the plastoquinol oxidation by cyt b559 for photosynthesis is discussed.
细胞色素 b559（cyt b559）在光系统 II（PSII）中的功能在一个烟草突变体中进行了研究，该突变体中β亚基位置 26 的保守苯丙氨酸被突变为丝氨酸。突变体的幼叶在叶绿体超微结构或 PSII 的数量和活性方面没有明显差异，而在成熟叶片中，堆垛的大小和 PSII 的数量显著减少。成熟叶片的突变体表现出更高的光抑制敏感性和更高的单线态氧产生，如自旋捕获电子顺磁共振（EPR）光谱所示。在类囊体膜中研究了氧气消耗和超氧化物的产生，在类囊体膜中去除了 Mn 簇以确保所有 cyt b559 都以其低电势形式存在。在来自野生型植物的类囊体膜中，较大比例的超氧化物产生是 3-（3,4-二氯苯基）-1,1-二甲基脲敏感的。这种类型的超氧化物形成在突变体的类囊体膜中不存在。讨论了 cyt b559 对质体醌氧化还原对光合作用的生理重要性。
