Pakrasi H B, Goldenberg A, Sherman L A
Division of Biological Sciences, University of Missouri, Columbia, Missouri 65211.
Plant Physiol. 1985 Sep;79(1):290-5. doi: 10.1104/pp.79.1.290.
Deprivation of iron from the growth medium results in physiological as well as structural changes in the unicellular cyanobacterium Anacystis nidulans R2. Important among these changes are alterations in the composition and function of the photosynthetic membranes. Room-temperature absorption spectra of iron-starved cyanobacterial cells show a chlorophyll absorption peak at 672 nanometers, 7 nanometers blue-shifted from its normal position at 679 nanometers. Iron-starved cells have decreased amounts of chlorophyll and phycobilins. Their fluorescence spectra (77K) have one prominent chlorophyll emission peak at 684 nanometers as compared to three peaks at 687, 696, and 717 nanometers from normal cells. Chlorophyll-protein analysis of iron-deprived cells indicated the absence of high molecular weight bands. Addition of iron to iron-starved cells induced a restoration process in which new components were initially synthesized and integrated into preexisting membranes; at later times, new membranes were assembled and cell division commenced. Synthesis of chlorophyll and phycocyanins started almost immediately after the addition of iron. The absorption peak slowly returned to its normal wavelength within 24 to 28 hours. The fluorescence emission spectrum at 77K changed over a period of 14 to 24 hours during which the 696- and 717-nanometer peaks grew to their normal levels, and the 684 nanometer peak moved to 687 nanometers and its relative intensity decreased to its normal level. Analysis of chlorophyll-protein complexes on polyacrylamide gels showed that high molecular weight chlorophyll-protein bands were formed during this time, and that low molecular weight bands (related to photosystem II) disappeared. The origin of the fluorescence emission at 687 and 696 nanometers is discussed in relation to the specific chlorophyll-protein complexes formed during iron reconstitution.
从生长培养基中去除铁会导致单细胞蓝藻集胞藻6803（Anacystis nidulans R2）出现生理和结构变化。这些变化中重要的是光合膜的组成和功能改变。缺铁蓝藻细胞的室温吸收光谱显示，叶绿素吸收峰位于672纳米处，比其正常位置679纳米蓝移了7纳米。缺铁细胞的叶绿素和藻胆素含量减少。它们的荧光光谱（77K）在684纳米处有一个突出的叶绿素发射峰，而正常细胞在687、696和717纳米处有三个峰。对缺铁细胞的叶绿素-蛋白质分析表明不存在高分子量条带。向缺铁细胞中添加铁会引发一个恢复过程，在此过程中，新的成分最初被合成并整合到预先存在的膜中；在后期，新的膜被组装起来，细胞分裂开始。添加铁后几乎立即开始合成叶绿素和藻蓝蛋白。吸收峰在24至28小时内缓慢恢复到其正常波长。77K时的荧光发射光谱在14至24小时内发生变化，在此期间，696纳米和717纳米的峰增长到正常水平，684纳米的峰移至687纳米，其相对强度降至正常水平。对聚丙烯酰胺凝胶上的叶绿素-蛋白质复合物分析表明，在此期间形成了高分子量的叶绿素-蛋白质条带，而低分子量条带（与光系统II相关）消失。结合铁重构过程中形成的特定叶绿素-蛋白质复合物，讨论了687纳米和696纳米处荧光发射的起源。
