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首页> 外文期刊>Journal of bacteriology >Posttranslational regulation of nitrogenase activity in Azospirillum brasilense ntrBC mutants: ammonium and anaerobic switch-off occurs through independent signal transduction pathways.
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Posttranslational regulation of nitrogenase activity in Azospirillum brasilense ntrBC mutants: ammonium and anaerobic switch-off occurs through independent signal transduction pathways.

机译：翻译过程中调节巴西固氮螺旋菌ntrBC突变体中的固氮酶活性：铵和厌氧性关闭通过独立的信号转导途径发生。

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摘要

Nitrogenase activity is regulated by reversible ADP-ribosylation in response to NH4+ and anaerobic conditions in Azospirillum brasilense. The effect of mutations in ntrBC on this regulation was examined. While NH4+ addition to ntrBC mutants caused a partial loss of nitrogenase activity, the effect was substantially smaller than that seen in ntr+ strains. In contrast, nitrogenase activity in these mutants was normally regulated in response to anaerobic conditions. The analysis of mutants lacking both the ntrBC gene products and dinitrogenase reductase activating glycohydrolase (DRAG) suggested that the primary effect of the ntrBC mutations was to alter the regulation of DRAG activity. Although nif expression in the ntr mutants appeared normal, as judged by activity, glutamine synthetase activity was significantly lower in ntrBC mutants than in the wild type. We hypothesize that this lower glutamine synthetase activity may delay the transduction of the NH4+ signal necessary for the inactivation of DRAG, resulting in a reduced response of nitrogenase activity to NH4+. Finally, data presented here suggest that different environmental stimuli use independent signal pathways to affect this reversible ADP-ribosylation system.
机译：响应于NH4 +和巴西厌氧螺旋藻的厌氧条件，可逆性ADP-核糖基化调节了固氮酶的活性。检查了ntrBC中的突变对该调节的影响。尽管向ntrBC突变体中添加NH4 +会导致部分固氮酶活性损失，但其效果远小于ntr +菌株中的效果。相反，这些突变体中的固氮酶活性通常是根据厌氧条件而调节的。对既缺乏ntrBC基因产物又缺乏双氮酶还原酶激活糖水解酶（DRAG）的突变体的分析表明，ntrBC突变的主要作用是改变DRAG活性的调节。尽管通过活性判断，ntr突变体中的nif表达正常，但ntrBC突变体中的谷氨酰胺合成酶活性明显低于野生型。我们假设这种较低的谷氨酰胺合成酶活性可能会延迟DRAG灭活所必需的NH4 +信号的转导，从而导致硝化酶活性对NH4 +的响应降低。最后，此处提供的数据表明，不同的环境刺激使用独立的信号途径来影响此可逆的ADP-核糖基化系统。

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