School of Biological and Chemical Sciences, Queen Mary University of London, Mile End Road, London E14NS, UK.
Plant J. 2012 Jan;69(2):289-301. doi: 10.1111/j.1365-313X.2011.04790.x. Epub 2011 Oct 21.
We characterized a set of Arabidopsis mutants deficient in specific light-harvesting proteins, using freeze-fracture electron microscopy to probe the organization of complexes in the membrane and confocal fluorescence recovery after photobleaching to probe the dynamics of thylakoid membranes within intact chloroplasts. The same methods were used to characterize mutants lacking or over-expressing PsbS, a protein related to light-harvesting complexes that appears to play a role in regulation of photosynthetic light harvesting. We found that changes in the complement of light-harvesting complexes and PsbS have striking effects on the photosystem II macrostructure, and that these effects correlate with changes in the mobility of chlorophyll proteins within the thylakoid membrane. The mobility of chlorophyll proteins was found to correlate with the extent of photoprotective non-photochemical quenching, consistent with the idea that non-photochemical quenching involves extensive re-organization of complexes in the membrane. We suggest that a key feature of the physiological function of PsbS is to decrease the formation of ordered semi-crystalline arrays of photosystem II in the low-light state. Thus the presence of PsbS leads to an increase in the fluidity of the membrane, accelerating the re-organization of the photosystem II macrostructure that is necessary for induction of non-photochemical quenching.
我们利用冰冻断裂电子显微镜来探测膜中的复合物的组织，利用荧光淬灭后再荧光恢复来探测完整叶绿体中叶绿体膜的动力学，从而对一组在特定光捕获蛋白中缺乏的拟南芥突变体进行了特征描述。同样的方法被用来描述缺乏或过表达 PsbS 的突变体，PsbS 是一种与光捕获复合物相关的蛋白质，似乎在调节光合作用的光捕获中发挥作用。我们发现，光捕获复合物和 PsbS 的组成变化对光系统 II 宏观结构有显著影响，这些影响与类囊体膜中叶绿素蛋白的流动性变化有关。发现叶绿素蛋白的流动性与光保护非光化学猝灭的程度相关，这与非光化学猝灭涉及膜中复合物的广泛重组的观点一致。我们认为，PsbS 的生理功能的一个关键特征是在低光照条件下减少光系统 II 的有序半晶状排列的形成。因此，PsbS 的存在导致膜的流动性增加，加速光系统 II 宏观结构的重组，这对于诱导非光化学猝灭是必要的。
