Daddy Soumana, Zhan Jiao, Jantaro Saowarath, He Chenliu, He Qingfang, Wang Qiang
Department of Biology, University of Arkansas at Little Rock, Little Rock, AR 72204.
1] Key Laboratory of Algal Biology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China [2] University of Chinese Academy of Sciences, Beijing 100039, China.
Sci Rep. 2015 Mar 30;5:9480. doi: 10.1038/srep09480.
Synechocystis sp. PCC 6803 is a model cyanobacterium extensively used to study photosynthesis. Here we reveal a novel high light-inducible carotenoid-binding protein complex (HLCC) in the thylakoid membranes of Synechocystis PCC 6803 cells exposed to high intensity light. Zeaxanthin and myxoxanthophyll accounted for 29.8% and 54.8%, respectively, of the carotenoids bound to the complex. Using Blue-Native PAGE followed by 2D SDS-PAGE and mass spectrometry, we showed that the HLCC consisted of Slr1128, IsiA, PsaD, and HliA/B. We confirmed these findings by SEAD fluorescence cross-linking and anti-PsaD immuno-coprecipitation analyses. The expression of genes encoding the protein components of the HLCC was enhanced by high light illumination and artificial oxidative stress. Deletion of these proteins resulted in impaired state transition and increased sensitivity to oxidative and/or high light stress, as indicated by increased membrane peroxidation. Therefore, the HLCC protects thylakoid membranes from extensive photooxidative damage, likely via a mechanism involving state transition.
集胞藻PCC 6803是一种广泛用于研究光合作用的模式蓝细菌。在此，我们揭示了在暴露于高强度光照的集胞藻PCC 6803细胞的类囊体膜中存在一种新型的高光诱导类胡萝卜素结合蛋白复合物（HLCC）。玉米黄质和粘球藻黄素分别占与该复合物结合的类胡萝卜素的29.8%和54.8%。通过蓝色非变性聚丙烯酰胺凝胶电泳（Blue-Native PAGE），随后进行二维十二烷基硫酸钠聚丙烯酰胺凝胶电泳（2D SDS-PAGE）和质谱分析，我们表明HLCC由Slr1128、IsiA、PsaD和HliA/B组成。我们通过SEAD荧光交联和抗PsaD免疫共沉淀分析证实了这些发现。编码HLCC蛋白质成分的基因表达在高光照射和人工氧化应激下增强。这些蛋白质的缺失导致状态转换受损，对氧化和/或高光应激的敏感性增加，如膜过氧化增加所示。因此，HLCC可能通过一种涉及状态转换的机制保护类囊体膜免受广泛的光氧化损伤。
