Escherichia coli PII signal transduction protein controlling nitrogen assimilation.: Acts as a sensor of adenylate energy charge in Vitro
Escherichia coli PII signal transduction protein controlling nitrogen assimilation.: Acts as a sensor of adenylate energy charge in Vitro
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DOI：
10.1021/bi701062t
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发表时间：
2007-11-13
期刊：
影响因子：
2.9
通讯作者：
Ninfa, Alexander J.
中科院分区：
文献类型：
--
作者：
Jiang, Peng;Ninfa, Alexander J.
PII信号转导蛋白是自然界中分布最广泛的信号转导蛋白之一，控制着从细菌到高等植物等各种生物的氮同化。PII蛋白整合细胞代谢状态的信号，与作为信号转导酶或关键代谢酶的受体相互作用并进行调节。以前对大肠杆菌PII的研究表明，PII的所有信号转导功能都需要与PII结合ATP，并且ATP结合与α-酮戊二酸与PII结合是协同作用的。此外，α-酮戊二酸，一种氮和碳状态的细胞信号，被观察到强烈地调节PII功能。在这里，我们发现在重组的信号转导系统中，ADP对两种大肠杆菌PII受体ATase和NRII(NtrB)的PII调节以及通过信号转导Utase/UR对PII的尿苷基化有显著影响。ADP对α-酮戊二酸有拮抗作用，即低能荷腺苷起抑制氮素限制信号的作用。通过单独研究重组信号转导系统中发生的相互作用，我们观察到基本上所有的PII和PII-UMP相互作用都受到ADP的影响。我们的实验还表明，在一定条件下，PII三聚体的三个核苷酸结合位点可能被ATP和ADP的结合所占据。总体而言，我们的结果表明，PII蛋白除了作为α-酮戊二酸的感受器外，还具有作为腺苷酸能荷的直接感受器的能力。
PII signal transduction proteins are among the most widely distributed signaling proteins in nature, controlling nitrogen assimilation in organisms ranging from bacteria to higher plants. PII proteins integrate signals of cellular metabolic status and interact with and regulate receptors that are signal transduction enzymes or key metabolic enzymes. Prior work with Escherichia coli PII showed that all signal transduction functions of PII required ATP binding to PII and that ATP binding was synergistic with the binding of alpha-ketoglutarate to PII. Furthermore, alpha-ketoglutarate, a cellular signal of nitrogen and carbon status, was observed to strongly regulate PII functions. Here, we show that in reconstituted signal transduction systems, ADP had a dramatic effect on PII regulation of two E. coli PII receptors, ATase, and NRII (NtrB), and on PII uridylylation by the signal transducing UTase/UR. ADP acted antagonistically, to alpha-ketoglutarate, that is, low adenylylate energy charge acted to diminish signaling of nitrogen limitation. By individually studying the interactions that occur in the reconstituted signal transduction systems, we observed that essentially all PII and PII-UMP interactions were influenced by ADP. Our experiments also suggest that under certain conditions, the three nucleotide binding sites of the PII trimer may be occupied by combinations of ATP and ADP. In the aggregate, our results show that PII proteins, in addition to serving as sensors of alpha-ketoglutarate, have the capacity to serve as direct sensors of the adenylylate energy charge.