Two-step mechanism of photodamage to photosystem II: Step 1 occurs at the oxygen-evolving complex and step 2 occurs at the photochemical reaction center
Two-step mechanism of photodamage to photosystem II: Step 1 occurs at the oxygen-evolving complex and step 2 occurs at the photochemical reaction center
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DOI：
10.1021/bi047518q
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发表时间：
2005-06-14
期刊：
影响因子：
2.9
通讯作者：
Murata, N
中科院分区：
文献类型：
--
作者：
Ohnishi, N;Allakhverdiev, SI;Murata, N
在强光下，光合生物的光系统11（PSII）失活，这种现象被称为光抑制。在一个被广泛接受的模型中。光抑制是由过量的光能引起的，过量的光能被叶绿素吸收，但不被光合作用利用。使用单色光从冈崎大型摄谱仪和类囊体膜从高温synechococcus elongatus，我们观察到，紫外线和蓝光失活的放氧复合物比光化学反应中心的PSII。这些观察结果表明，光诱导的损伤与PS Ⅱ的放氧复合体中的紫外光和蓝光吸收中心有关。光损伤PSII的初级事件的作用光谱揭示了紫外光和蓝光的强烈影响，并与叶绿素和类囊体膜的吸收光谱有很大不同。与未处理的类囊体膜中的放氧复合物的光诱导失活相反，红光有效地诱导了Tris处理的类囊体膜中的PSII反应中心的失活，并且作用光谱类似于叶绿素的吸收光谱。我们的观察表明，光损伤PSII发生在两个步骤，步骤I是光诱导失活的放氧复合物。第二步，发生在第一步完成之后，是通过叶绿素吸收的光使PSII反应中心失活。我们通过用蓝光和紫外光照射未处理的类囊体膜来证实我们的模型，蓝光和紫外光使放氧复合物失活，然后用红光使光化学反应中心失活。
Under strong light, photosystem 11 (PSII) of oxygenic photosynthetic organisms is inactivated, and this phenomenon is called photoinhibition. In a widely accepted model. photoinhibition is induced by excess light energy, which is absorbed by chlorophyll but not utilized in photosynthesis. Using monochromatic light from the Okazaki Large Spectrograph and thylakoid membranes from Thermo-synechococcus elongatus, we observed that UV and blue light inactivated the oxygen-evolving complex much faster than the photochemical reaction center of PSII. These observations suggested that the light-induced damage was associated with a UV- and blue light-absorbing center in the oxygen-evolving complex of PSII. The action spectrum of the primary event in photodamage to PSII revealed the strong effects of UV and blue light and differed considerably from the absorption spectra of chlorophyll and thylakoid membranes. By contrast to the photoinduced inactivation of the oxygen-evolving complex in untreated thylakoid membranes, red light efficiently induced inactivation of the PSII reaction center in Tris-treated thylakoid membranes, and the action spectrum resembled the absorption spectrum of chlorophyll. Our observations suggest that photodamage to PSII occurs in two steps, Step I is the light-induced inactivation of the oxygen-evolving complex. Step 2, occurring after step I is complete, is the inactivation of the PSII reaction center by light absorbed by chlorophyll. We confirmed our model by illumination of untreated thylakoid membranes with blue and UV light, which inactivated the oxygen-evolving complex, and then with red light, which inactivated the photochemical reaction center.