Hu Q, Marquardt J, Iwasaki I, Miyashita H, Kurano N, Mörschel E, Miyachi S
Marine Biotechnology Institute, Kamaishi Laboratories, Kamaishi, Iwate, Japan.
Biochim Biophys Acta. 1999 Aug 4;1412(3):250-61. doi: 10.1016/s0005-2728(99)00067-5.
We investigated the localization, structure and function of the biliproteins of the oxygenic photosynthetic prokaryote Acaryochloris marina, the sole organism known to date that contains chlorophyll d as the predominant photosynthetic pigment. The biliproteins were isolated by means of sucrose gradient centrifugation, ion exchange and gel filtration chromatography. Up to six biliprotein subunits in a molecular mass range of 15.5-18.4 kDa were found that cross-reacted with antibodies raised against phycocyanin or allophycocyanin from a red alga. N-Terminal sequences of the alpha- and beta-subunits of phycocyanin showed high homogeneity to those of cyanobacteria and red algae, but not to those of cryptomonads. As shown by electron microscopy, the native biliprotein aggregates are organized as rod-shaped structures and located on the cytoplasmic side of the thylakoid membranes predominantly in unstacked thylakoid regions. Biochemical and spectroscopic analysis revealed that they consist of four hexameric units, some of which are composed of phycocyanin alone, others of phycocyanin together with allophycocyanin. Spectroscopic analysis of isolated photosynthetic reaction center complexes demonstrated that the biliproteins are physically attached to the photosystem II complexes, transferring light energy to the photosystem II reaction center chlorophyll d with high efficiency.
我们研究了产氧光合原核生物滨海红藻(Acaryochloris marina)中双蛋白的定位、结构和功能。滨海红藻是迄今为止已知的唯一一种以叶绿素d作为主要光合色素的生物。通过蔗糖梯度离心、离子交换和凝胶过滤色谱法分离双蛋白。发现了分子量范围在15.5 - 18.4 kDa的多达六个双蛋白亚基,它们与针对红藻藻蓝蛋白或别藻蓝蛋白产生的抗体发生交叉反应。藻蓝蛋白α亚基和β亚基的N端序列与蓝细菌和红藻的序列高度同源,但与隐藻的序列不同源。如电子显微镜所示,天然双蛋白聚集体呈棒状结构,主要位于类囊体膜的细胞质一侧,且多在未堆叠的类囊体区域。生化和光谱分析表明,它们由四个六聚体单元组成,其中一些仅由藻蓝蛋白组成,另一些则由藻蓝蛋白和别藻蓝蛋白共同组成。对分离的光合反应中心复合物的光谱分析表明,双蛋白与光系统II复合物物理相连,能高效地将光能传递给光系统II反应中心叶绿素d。