Zhao J, Shen G, Bryant D A
College of Life Sciences, Peking University, Beijing, People's Republic of China.
Biochim Biophys Acta. 2001 Jun 1;1505(2-3):248-57. doi: 10.1016/s0005-2728(01)00175-x.
Phycobilisomes (PBS) function as light-harvesting antenna complexes in cyanobacteria, red algae and cyanelles. They are composed of two substructures: the core and peripheral rods. Interposon mutagenesis of the cpcBA genes of Synechococcus sp. PCC 7002 resulted in a strain (PR6008) lacking phycocyanin and thus the ability to form peripheral rods. Difference absorption spectroscopy of whole cells showed that intact PBS cores were assembled in vivo in the cpcBA mutant strain PR6008. Fluorescence induction measurements demonstrated that the PBS cores are able to deliver absorbed light energy to photosystem (PS) II, and fluorescence induction transients in the presence of DCMU showed that PR6008 cells could perform a state 2 to state 1 transition with similar kinetics to that of the wild-type cells. Thus, PBS core assembly, light-harvesting functions and energy transfer to PS I were not dependent upon the assembly of the peripheral rods. The ratio of PS II:PS I in the PR6008 cells was significantly increased, nearly twice that of the wild-type cells, possibly a result of long-term adaptation to compensate for the reduced antenna size of PS II. However, the ratio of PBS cores:chlorophyll remained unchanged. This result indicates that approximately half of the PS II reaction centers in the PR6008 cells had no closely associated PBS cores.
藻胆体（PBS）在蓝细菌、红藻和蓝藻细胞器中作为捕光天线复合体发挥作用。它们由两个亚结构组成：核心和外周杆。对聚球藻属PCC 7002的cpcBA基因进行插入诱变，产生了一个缺乏藻蓝蛋白因而无法形成外周杆的菌株（PR6008）。全细胞的差分吸收光谱表明，完整的PBS核心在cpcBA突变菌株PR6008体内组装。荧光诱导测量表明，PBS核心能够将吸收的光能传递给光系统（PS）II，并且在存在二氯苯基二甲基脲（DCMU）的情况下的荧光诱导瞬变表明，PR6008细胞能够以与野生型细胞相似的动力学进行从状态2到状态1的转变。因此，PBS核心组装、捕光功能以及向PS I的能量转移并不依赖于外周杆的组装。PR6008细胞中PS II与PS I的比例显著增加，几乎是野生型细胞的两倍，这可能是长期适应以补偿PS II天线尺寸减小的结果。然而，PBS核心与叶绿素的比例保持不变。这一结果表明，PR6008细胞中约一半的PS II反应中心没有紧密相关的PBS核心。
