Pakrasi H B, Nyhus K J, Granok H
Department of Biology, Washington University, St. Louis, MO 63130.
Z Naturforsch C J Biosci. 1990 May;45(5):423-9. doi: 10.1515/znc-1990-0519.
Oligonucleotide-directed mutagenesis techniques were used to delete the psbF gene, encoding the beta subunit of the cytochrome b559 protein of the photosystem II complex in the cyanobacterium, Synechocystis 6803. Cyt b559 is an integral component of PS II complex. However, its precise functional role in PS II remains to be determined. Previously, we created a mutant in which the psbF gene as well as three of its neighbouring genes, psbE, psbL and psbJ were simultaneously deleted from the chromosome of Synechocystis 6803 (Pakrasi, Williams and Arntzen, EMBO J. 7, 325-332, 1988). This mutant had no PS II activity. However, the role of any one of the four individual gene products could not be determined by studying this mutant. The newly generated mutant, T256, had only one gene, psbF, deleted from the genome. This mutant was also impaired in its PS II activities. In addition, it had barely detectable levels of two other protein components, D1 (herbicide binding protein) and D2, of the reaction center of PS II, in its thylakoid membranes. In contrast, two other proteins of PS II, CP47 and CP43 were present in appreciable amounts. Fluorescence spectra (77 K) of the mutant showed the absence of a peak at 695 nm that was previously believed to originate from CP47. In addition, phycobilisomes, the light-harvesting antenna system of PS II, were found to be assembled normally in this mutant. We conclude that the presence of the beta subunit of Cyt b559 in the thylakoid membranes is critically important for the assembly of PS II reaction center.
采用寡核苷酸定向诱变技术删除了集胞藻6803中编码光系统II复合体细胞色素b559蛋白β亚基的psbF基因。细胞色素b559是光系统II复合体的一个组成成分。然而，其在光系统II中的具体功能仍有待确定。此前，我们构建了一个突变体，其中psbF基因及其三个相邻基因psbE、psbL和psbJ同时从集胞藻6803的染色体上被删除（帕克拉西、威廉姆斯和阿恩岑，《欧洲分子生物学组织杂志》7，325 - 332，1988年）。该突变体没有光系统II活性。然而，通过研究这个突变体无法确定这四个单独基因产物中任何一个的作用。新产生的突变体T256基因组中仅删除了一个基因psbF。该突变体的光系统II活性也受到损害。此外，在其类囊体膜中，光系统II反应中心的另外两个蛋白质成分D1（除草剂结合蛋白）和D2的水平几乎检测不到。相比之下，光系统II的另外两个蛋白质CP47和CP43含量可观。该突变体的荧光光谱（77K）显示在695nm处没有峰，此前认为该峰源自CP47。此外，发现光系统II的捕光天线系统藻胆体在这个突变体中正常组装。我们得出结论，类囊体膜中细胞色素b559β亚基的存在对光系统II反应中心的组装至关重要。
