Mihara Shoko, Sugiura Kazunori, Yoshida Keisuke, Hisabori Toru
Laboratory for Chemistry and Life Science, Institute of Innovative Research, Tokyo Institute of Technology, Nagatsuta-cho, Midori-ku, Yokohama, Japan.
School of Life Science and Technology, Tokyo Institute of Technology, Nagatsuta-cho, Midori-ku, Yokohama, Japan.
J Exp Bot. 2020 Mar 25;71(6):2018-2027. doi: 10.1093/jxb/erz561.
In the nitrogen-fixing cyanobacterium Anabaena sp. PCC 7120, glucose 6-phosphate dehydrogenase (G6PDH) plays an important role in producing the power for reducing nitrogenase under light conditions. Our previous study showed that thioredoxin suppresses G6PDH by reducing its activator protein OpcA, implying that G6PDH is inactivated under light conditions because thioredoxins are reduced by the photosynthetic electron transport system in cyanobacteria. To address how Anabaena sp. PCC 7120 maintains G6PDH activity even under light conditions when nitrogen fixation occurs, we investigated the redox regulation system in vegetative cells and specific nitrogen-fixing cells named heterocysts, individually. We found that thioredoxin target proteins were more oxidized in heterocysts than in vegetative cells under light conditions. Alterations in the redox regulation mechanism of heterocysts may affect the redox states of thioredoxin target proteins, including OpcA, so that G6PDH is activated in heterocysts even under light conditions.
在固氮蓝藻鱼腥藻Anabaena sp. PCC 7120中,6-磷酸葡萄糖脱氢酶(G6PDH)在光照条件下为还原固氮酶提供能量的过程中发挥着重要作用。我们之前的研究表明,硫氧还蛋白通过还原其激活蛋白OpcA来抑制G6PDH,这意味着在光照条件下G6PDH会失活,因为蓝藻中的硫氧还蛋白会被光合电子传递系统还原。为了探究鱼腥藻Anabaena sp. PCC 7120即使在发生固氮作用的光照条件下如何维持G6PDH活性,我们分别研究了营养细胞和名为异形胞的特定固氮细胞中的氧化还原调节系统。我们发现,在光照条件下,异形胞中的硫氧还蛋白靶蛋白比营养细胞中的氧化程度更高。异形胞氧化还原调节机制的改变可能会影响包括OpcA在内的硫氧还蛋白靶蛋白的氧化还原状态,从而使G6PDH即使在光照条件下在异形胞中也能被激活。