Institute of Plant Biology, Biological Research Centre, Hungarian Academy of Sciences, P.O. Box 521, H-6701 Szeged, Hungary.
Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, 30-387 Kraków, Poland.
Biochim Biophys Acta Bioenerg. 2017 Jul;1858(7):510-518. doi: 10.1016/j.bbabio.2017.05.001. Epub 2017 May 3.
The function of xanthophylls in the organisation and structure of the photosynthetic complexes is not completely clarified yet. Recently, we observed a reduced level of the photosystem oligomers upon xanthophyll deficiency, although xanthophylls are not considered to be part of the photosynthetic complexes of cyanobacteria. The present study aimed at further investigating the relationship between xanthophylls and photosytem I (PSI) complex in the cyanobacterium Synechocystis sp. PCC 6803. Interestingly, we recorded the presence of echinenone and zeaxanthin in the isolated PSI trimers. These two xanthophyll species are among the most abundant xanthophylls in this cyanobacterial species. Various xanthophyll biosynthesis mutants were used to investigate the specific role of these xanthophylls. Our spectroscopic results revealed specific structural changes manifested in altered pigment-pigment or pigment-protein interactions within PSI complex in the absence of zeaxanthin and echinenone. These structural modifications of the complexes seem to destabilize the PSI trimeric complexes and eventually result in an increased propensity for monomerization. Our results clearly demonstrate that xanthophylls are important for the fine-tuning of the PSI trimer structure. These xanthophylls could be part of the complex or be embedded in the membrane in the vicinity of PSI.
叶黄素在光合作用复合物的组织和结构中的功能尚未完全阐明。最近，我们观察到叶黄素缺乏时光合作用寡聚体的水平降低，尽管叶黄素不被认为是蓝藻光合作用复合物的一部分。本研究旨在进一步研究蓝藻集胞藻 PCC 6803 中叶黄素与光系统 I（PSI）复合物之间的关系。有趣的是，我们在分离的 PSI 三聚体中记录到了玉米黄质和玉米黄素的存在。这两种叶黄素是该蓝藻物种中最丰富的叶黄素之一。我们使用各种叶黄素生物合成突变体来研究这些叶黄素的特定作用。我们的光谱结果揭示了在缺乏玉米黄质和玉米黄素的情况下 PSI 复合物内色素-色素或色素-蛋白相互作用的特定结构变化。这些复合物的结构修饰似乎使 PSI 三聚体复合物不稳定，并最终导致单体化倾向增加。我们的结果清楚地表明，叶黄素对于 PSI 三聚体结构的微调很重要。这些叶黄素可能是复合物的一部分，或者位于 PSI 附近的膜中。
