INTERACTIONS OF THE SIGNAL TRANSDUCTION PROTEIN PII

大肠杆菌glnB基因编码氮的中心组分 这就是所谓的PII。 PII与三种不同的蛋白质相互作用。 glnD的产物，一种双功能尿苷酰转移酶（UT）， 尿苷酰去除酶（UR）催化PII的尿苷酰化， 氮是稀缺的，催化PII-UMP的脱氧尿苷酰化， 氮气充足。 尿苷酰化和未修饰形式的PII 也与腺苷酰转移酶（ATase）相互作用， 响应氮可用性而改变谷氨酰胺合成酶 刺激谷氨酰胺合成酶的腺苷酰化（失活）， ATase和PII-UMP刺激去腺苷酸化（激活） 谷氨酰胺合成酶。 最后，未经修改的PII形式 与双功能激酶/磷酸酶蛋白质NRII相互作用， 的glnL（ntrB），引发磷酸酶活性， 转录激活因子NRI-磷酸的去磷酸化 NRII/PII磷酸酶。 这一事件反过来又导致在sigma转录 54-依赖氮调节的启动子停止。 我们建议研究PII蛋白的蛋白质-蛋白质相互作用 及其受体蛋白的研究。 我们 描述了一个计划，分离和快速测序的许多glnB 特异性破坏与NRII相互作用的突变， 与UT/UR的交互。 此外，我们还描述了遗传和 设计用于探测PII-NRII相互作用的生物化学方法。 的 我们的研究结果应该有助于阐明的性质， PII与其接触的其他三种蛋白质之间的相互作用。

The Escherichia coli glnB gene encodes a central component of nitrogen regulation known as PII. PII interacts with three different proteins. The product of glnD, a bifunctional uridylyltransferase (UT) and uridylyl-removing enzyme (UR) catalyzes the uridylylation of PII when nitrogen is scarce and catalyzes the deuridylylation of PII-UMP when nitrogen is plentiful. Both the uridylylated and unmodified forms of PII also interact with the adenylyltransferase enzyme (ATase) that covalently modifies glutamine synthetase in response to nitrogen availability; PII stimulates the adenylylation (inactivation) of glutamine synthetase by the ATase, and PII-UMP stimulates the de-adenylylation (activation) of glutamine synthetase by the ATase. Finally, the unmodified form of PII interacts with the bifunctional kinase/phosphatase protein NRII, product of glnL (ntrB), eliciting a phosphatase activity that results in the dephosphorylation of the transcriptional activator NRI-Phosphate by the NRII/Pll phosphatase. This event in turn causes transcription at sigma 54-dependant nitrogen regulated promoters to cease. We propose to study the protein-protein interactions of the PII protein and its receptor proteins using genetic and biochemical methods. We describe a plan for the isolation and rapid sequencing of many glnB mutations that specifically destroy either the interaction with NRII or the interaction with the UT/UR. In addition, we describe genetic and biochemical methods designed to probe the PII-NRII interaction. The results of our study should help to elucidate the nature of the interactions between PII and the three other proteins that it contacts.