Kura-Hotta M, Satoh K, Katoh S
Arch Biochem Biophys. 1986 Aug 15;249(1):1-7. doi: 10.1016/0003-9861(86)90553-9.
Photosystem II oxygen-evolving preparations with attached phycobilisomes were isolated from the thermophilic cyanobacterium Synechococcus sp. with beta-octylglucoside or digitonin. Fluorescence emission spectra of the two preparations determined at 77 K largely lacked a far red band which originates from photosystem I. The spectrum of the digitonin preparation was otherwise similar to that of intact cells, whereas the beta-octylglucoside preparation showed a pronounced band at 687 nm, which is considered to be emitted from phycobilisomes. The relative yield of phycobilin fluorescence was similar between the digitonin preparations and the cells but was considerably larger in the beta-octylglucoside preparations at room temperature. The quantum yield of ferricyanide photoreduction determined with light which is absorbed mainly by phycobiliproteins was 0.85 for the digitonin preparation and 0.57 for the beta-octylglucoside preparation. The results indicate that excitation energy is transferred from phycobilisomes to photosystem II reaction centers in the digitonin preparation as efficiently as in intact cells, while a significant portion of light energy harvested by phycobilisomes is not utilized by the primary photochemistry in the beta-octylglucoside preparation. Digitonin and beta-octylglucoside preparations had 65 and 48 chlorophyll a molecules per photosystem II reaction center, respectively. The beta-octylglucoside preparation contained twice as much phycocyanin and allophycocyanin per photosystem II reaction center as the digitonin preparation, which has a phycobiliprotein-to-photosystem II reaction center ratio very similar to that of cells. It is concluded that whereas the beta-octylglucoside preparation contains a considerable amount of free phycobilisomes, all phycobilisomes present in the digitonin preparation are physically and functionally linked to photosystem II reaction center complexes.
用β-辛基葡糖苷或洋地黄皂苷从嗜热蓝藻集胞藻属中分离出附着有藻胆体的光系统II放氧制剂。在77K下测定的两种制剂的荧光发射光谱在很大程度上缺乏源自光系统I的远红带。洋地黄皂苷制剂的光谱在其他方面与完整细胞的光谱相似，而β-辛基葡糖苷制剂在687nm处显示出明显的带，这被认为是由藻胆体发出的。洋地黄皂苷制剂和细胞之间藻胆蛋白荧光的相对产率相似，但在室温下β-辛基葡糖苷制剂中的相对产率要大得多。用主要被藻胆蛋白吸收的光测定的铁氰化物光还原量子产率，洋地黄皂苷制剂为0.85，β-辛基葡糖苷制剂为0.57。结果表明，在洋地黄皂苷制剂中，激发能从藻胆体转移到光系统II反应中心的效率与在完整细胞中一样高，而在β-辛基葡糖苷制剂中，藻胆体收集的大部分光能未被初级光化学利用。洋地黄皂苷制剂和β-辛基葡糖苷制剂每个光系统II反应中心分别含有65和48个叶绿素a分子。β-辛基葡糖苷制剂每个光系统II反应中心所含的藻蓝蛋白和别藻蓝蛋白是洋地黄皂苷制剂的两倍，洋地黄皂苷制剂的藻胆蛋白与光系统II反应中心的比例与细胞非常相似。得出的结论是，β-辛基葡糖苷制剂含有大量游离藻胆体，而洋地黄皂苷制剂中存在的所有藻胆体在物理和功能上都与光系统II反应中心复合物相连。
