Regulation of autophosphorylation of Escherichia coli nitrogen regulator II by the PII signal transduction protein
Regulation of autophosphorylation of Escherichia coli nitrogen regulator II by the PII signal transduction protein
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DOI：
10.1128/jb.181.6.1906-1911.1999
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发表时间：
1999-03-01
影响因子：
3.2
通讯作者：
Ninfa, AJ
中科院分区：
文献类型：
--
作者：
Jiang, P;Ninfa, AJ
氮调节因子Ⅱ（NRII或NtrB）-NRI（NtrC）双组分信号转导系统调控大肠杆菌中氮调节基因的转录。NRII蛋白具有激酶和磷酸酶活性，并催化NRI的磷酸化和去磷酸化，当磷酸化时NRI激活转录。NRII的磷酸酶活性被PII信号转导蛋白激活。我们发现PII也是NRII激酶活性的抑制剂。这些数据与双组分系统激酶/磷酸酶蛋白的激酶和磷酸酶活性是协调和非协调调节的假设是一致的。PII调节NRII的能力由小分子效应物2-酮戊二酸（2-ketoglutarate）变构控制，该效应物与PII结合。我们研究了2-酮戊二酸对PII调节NRII的激酶和磷酸酶活性的影响，使用偶联酶系统测量NRII切割ATP的速率。数据与以下假设一致：当不与2-酮戊二酸复合时，PII不能与NRII结合，并且对其竞争性NRI激酶和磷酸酶活性没有影响。在这些条件下，NRII的激酶活性占主导地位。在低2-酮戊二酸浓度下，与2-酮戊二酸单分子复合的PII三聚体与NRII相互作用以抑制其激酶活性并激活其磷酸酶活性。然而，在高的2-酮戊二酸浓度下，PII结合额外的配体分子，并使其不能结合NRII，从而释放对NRII激酶活性的抑制，并有效抑制其磷酸酶活性（通过不能刺激它）。
The nitrogen regulator II (NRII or NtrB)-NRI (NtrC) two-component signal transduction system regulates the transcription of nitrogen-regulated genes in Escherichia coli. The NRII protein has both kinase and phosphatase activities and catalyzes the phosphorylation and dephosphorylation of NRI, which activates transcription when phosphorylated. The phosphatase activity of NRII is activated by the PII signal transduction protein. We showed that PII was also an inhibitor of the kinase activity of NRII. The data were consistent with the hypothesis that the kinase and phosphatase activities of two-component system kinase/phosphatase proteins are coordinately and reciprocally regulated. The ability of PII to regulate NRII is allosterically controlled by the small-molecule effector 2-ketoglutarate, which binds to PII. We studied the effect of 2-ketoglutarate on the regulation of the kinase and phosphatase activities of NRII by PII, using a coupled enzyme system to measure the rate of cleavage of ATP by NRII. The data were consistent with the following hypothesis: when not complexed with 2-ketoglutarate, PII cannot bind to NRII and has no effect on its competing NRI kinase and phosphatase activities. Under these conditions, the kinase activity of NRII is dominant. At low 2-ketoglutarate concentrations, PII trimers complexed with a single molecule of 2-ketoglutarate interact with NRII to inhibit its kinase activity and activate its phosphatase activity. However, at high 2-ketoglutarate concentrations, PII binds additional ligand molecules and is rendered incapable of binding to NRII, thereby releasing inhibition of NRII's kinase activity and effectively inhibiting its phosphatase activity (by failing to stimulate it).