Masuda Shinji, Berleman James, Hasselbring Ben M, Bauer Carl E
Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, 226-8501, Japan.
Photochem Photobiol Sci. 2008 Oct;7(10):1267-72. doi: 10.1039/b802365b. Epub 2008 Sep 16.
Genes coding for putative CrtJ and AerR homologs were identified and characterized in the purple photosynthetic bacterium Rhodospirillum centenum (also known as Rhodocista centenaria), an organism that synthesizes photopigments even under highly aerated conditions. Mutational analysis indicated that in Rsp. centenum, gene crtJ codes for a repressor for photosynthesis gene expression as in Rhodobacter capsulatus, which exhibits a high level of oxygen repression of photosystem synthesis. In contrast to Rba. capsulatus, AerR in Rsp. centenum appears to be an aerobic activator; an aerR mutation resulted in significantly reduced levels of photopigment synthesis. Both aerR and crtJ mutants retained essentially normal levels of photosystem synthesis under anaerobic conditions, indicating that their activities are specific for aerobic photosystem synthesis. The readthrough transcript from crtE promoter, which is regulated by AerR and CrtJ, seems to be significant in maintaining the expression levels of the light harvesting I (puf) genes in Rsp. centenum. We suggest that AerR and CrtJ regulate aerobic photosystem synthesis primarily through controlling activity of the transcriptional readthrough.
在紫色光合细菌百日红螺菌（也称为百日红球菌）中鉴定并表征了编码假定的CrtJ和AerR同源物的基因，该生物体即使在高通气条件下也能合成光合色素。突变分析表明，在百日红螺菌中，crtJ基因与荚膜红细菌一样，编码光合作用基因表达的阻遏物，荚膜红细菌对光系统合成表现出高水平的氧抑制。与荚膜红细菌不同，百日红螺菌中的AerR似乎是一种需氧激活剂；aerR突变导致光合色素合成水平显著降低。aerR和crtJ突变体在厌氧条件下基本保持正常的光系统合成水平，表明它们的活性对需氧光系统合成具有特异性。由AerR和CrtJ调控的crtE启动子的通读转录本，似乎对维持百日红螺菌中光捕获I（puf）基因的表达水平具有重要意义。我们认为，AerR和CrtJ主要通过控制转录通读的活性来调节需氧光系统的合成。
