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首页> 外文期刊>Journal of bacteriology >Characterization of the DraT/DraG System for Posttranslational Regulation of Nitrogenase in the Endophytic Betaproteobacterium Azoarcus sp. Strain BH72
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Characterization of the DraT/DraG System for Posttranslational Regulation of Nitrogenase in the Endophytic Betaproteobacterium Azoarcus sp. Strain BH72

机译：DraT / DraG系统用于内吞β变形杆菌Azoarcus sp。中的固氮酶翻译后调控的表征。菌株BH72

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DraT/DraG-mediated posttranslational regulation of the nitrogenase Fe protein by ADP-ribosylation has been described for a few diazotrophic bacteria belonging to the class Alphaproteobacteria. Here we present for the first time the DraT/DraG system of a betaproteobacterium, Azoarcus sp. strain BH72, a diazotrophic grass endophyte. Its genome harbors one draT ortholog and two physically unlinked genes coding for ADP-ribosylhydrolases. Northern blot analysis revealed cotranscription of draT with two genes encoding hypothetical proteins. Furthermore, draT and draG2 were expressed under all studied conditions, whereas draG1 expression was nitrogen regulated. By using Western blot analysis of deletion mutants and nitrogenase assays in vivo, we demonstrated that DraT is required for the nitrogenase Fe protein modification but not for the physiological inactivation of nitrogenase activity. A second mechanism responsible for nitrogenase inactivation must operate in this bacterium, which is independent of DraT. Fe protein demodification was dependent mainly on DraG1, corroborating the assumption from phylogenetic analysis that DraG2 might be mostly involved in processes other than the posttranslational regulation of nitrogenase. Nitrogenase in vivo reactivation was impaired in a draG1 mutant and a mutant lacking both draG alleles after anaerobiosis shifts and subsequent adjustment to microaerobic conditions, suggesting that modified dinitrogenase reductase was inactive. Our results demonstrate that the DraT/DraG system, despite some differences, is functionally conserved in diazotrophic proteobacteria.
机译：DraT / DraG介导的ADP-核糖基化对Nase Fe蛋白的翻译后调节作用已针对少数属于 Alphaproteobacteria 类的重氮营养细菌进行了描述。在这里，我们首次展示了β变形杆菌 Azoarcus sp的DraT / DraG系统。菌株BH72，重氮营养草内生菌。它的基因组包含一个 draT 直系同源物和两个物理上不相关的编码ADP-核糖基水解酶的基因。 Northern印迹分析显示 draT 与两个编码假想蛋白的基因共转录。此外， draT 和 draG2 在所有研究条件下均表达，而 draG1 的表达受氮调节。通过使用体内缺失突变体的蛋白质印迹分析和体内固氮酶测定，我们证明了固氮酶Fe蛋白修饰需要DraT，固氮酶活性的生理失活不是必需的。负责固氮酶失活的第二种机制必须在这种细菌中起作用，这独立于DraT。 Fe蛋白质的降解主要取决于DraG1，从而证实了系统发育分析所得出的假设，即DraG2可能主要参与除翻译酶后的固氮酶调控。在 draG1 突变体中，以及在缺乏厌氧菌转移和随后对微需氧条件的调节后，缺少两个 draG 等位基因的突变体中，氮酶的体内再激活受到损害，这表明修饰的二氮酶还原酶是无效的。我们的结果表明，尽管存在一些差异，DraT / DraG系统在重氮营养性蛋白菌中功能上是保守的。

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