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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Bacillus subtilis glutamine synthetase regulates its own synthesis by acting as a chaperone to stabilize GlnR-DNA complexes
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Bacillus subtilis glutamine synthetase regulates its own synthesis by acting as a chaperone to stabilize GlnR-DNA complexes

机译：枯草芽孢杆菌谷氨酰胺合成酶通过充当伴侣来稳定GlnR-DNA复合物来调节自身的合成

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The Bacillus subtilis GlnR repressor controls gene expression in response to nitrogen availability. Because all GlnR-regulated genes are expressed constitutively in mutants lacking glutamine synthetase (G5), GS is required for repression by GlnR. Feedback-inhibited GS (FBI-GS) was shown to activate GlnR DNA binding with an in vitro electophoretic mobility shift assay (EMSA). The activation of GlnR DNA binding by GS in these experiments depended on the feedback inhibitor glutamine and did not occur with mutant GS proteins defective in regulating GlnR activity in vivo. Although stable GS-GlnR-DNA ternary complexes were not observed in the EMSA experiments, cross-linking experiments showed that a protein-protein interaction occurs between GlnR and FBI-GS. This interaction was reduced in the absence of the feedback inhibitor glutamine and with mutant GS proteins. Because FBI-GS significantly reduced the dissociation rate of the GlnR-DNA complexes, the stability of these complexes is enhanced by FBI-GS. These results argue that FBI-GS acts as a chaperone that activates GlnR DNA binding through a transient protein-protein interaction that stabilizes GlnR-DNA complexes. GS was shown to control the activity of the B. subtilis nitrogen transcription factor TnrA by forming a stable complex between FBI-GS and TnrA that inhibits TnrA DNA binding. Thus, B. subtilis GS is an enzyme with dual catalytic and regulatory functions that uses distinct mechanisms to control the activity of two different transcription factors.
机译：枯草芽孢杆菌GlnR阻遏物响应氮的有效利用来控制基因表达。由于所有GlnR调控的基因均在缺乏谷氨酰胺合成酶（G5）的突变体中组成性表达，因此需要GS来抑制GlnR。反馈抑制的GS（FBI-GS）已被证明可以通过体外电泳迁移率测定（EMSA）激活GlnR DNA结合。在这些实验中，GS对GlnR DNA结合的激活取决于反馈抑制剂谷氨酰胺，而在体内调节GlnR活性方面存在缺陷的突变GS蛋白则不会发生。尽管在EMSA实验中未观察到稳定的GS-GlnR-DNA三元复合物，但交联实验表明GlnR与FBI-GS之间发生蛋白质-蛋白质相互作用。在缺少反馈抑制剂谷氨酰胺和突变GS蛋白的情况下，这种相互作用被减少。由于FBI-GS大大降低了GlnR-DNA复合物的解离速率，因此FBI-GS增强了这些复合物的稳定性。这些结果表明，FBI-GS可以作为分子伴侣，通过稳定GlnR-DNA复合物的短暂蛋白质-蛋白质相互作用来激活GlnR DNA结合。 GS通过在FBI-GS和TnrA之间形成抑制TnrA DNA结合的稳定复合物来控制枯草芽孢杆菌氮转录因子TnrA的活性。因此，枯草芽孢杆菌GS是具有双重催化和调节功能的酶，其使用独特的机制来控制两个不同转录因子的活性。

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