P-73 グアノシン5'-二リン酸3'-二リン酸の葉緑体RNAポリメラーゼ結合部位に関する研究(ポスター発表の部)

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Chloroplasts, which are thought to have originated from cyanobacteria, have their own genetic system which is similar to that of the bacteria from which they were derived. Recently, bacterial alarmone guanosine 5'-diphosphate 3'-diphosphate (ppGpp), a key regulatory molecule controlling the stringent response, was identified in chloroplasts of plant cells. Similar to its function in bacteria, ppGpp inhibits chloroplast RNA polymerase, suggesting that ppGpp mediates gene expression through the stringent response in chloroplasts. However, a detailed mechanism of ppGpp action in chloroplasts remains elusive. We synthesized 6-thioguanosine 5'-diphosphate 3'-diphosphate (6-thioppGpp) as a photoaffinity probe of ppGpp, thus enabling the investigation of ppGpp binding to chloroplast RNA polymerase. We found that 6-thioppGpp, as well as ppGpp, inhibits chloroplast RNA synthesis in vitro in a dose-dependent manner. Crosslinking experiments with 6-thioppGpp and chloroplast RNA polymerase demonstrated that ppGpp binds the β' subunit (corresponding to the Escherichia coli β' subunit) of plastid-encoded plastid RNA polymerase composed of α, β, β', β", and σ subunits. Furthermore, ppGpp did not inhibit transcription in plastid nuclei prepared from tobacco BY-2 cells, suggesting that ppGpp does not inhibit nuclear-encoded plastid RNA polymerase. These results demonstrate that ppGpp functions as a stringent factor, governing gene expression in chloroplasts.
天然有機化合物討論会の論文
2008-09-01

P-73 グアノシン5'-二リン酸3'-二リン酸の葉緑体RNAポリメラーゼ結合部位に関する研究(ポスター発表の部)

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