INTERACTIONS OF THE SIGNAL TRANSDUCTION PROTEIN PII

大肠杆菌glnB基因编码氮的中心成分 被称为PII的法规。PII与三种不同的蛋白质相互作用。 GlnD的产物是一种双功能尿苷酰转移酶(UT)和 尿醛酸基去除酶(UR)催化PII的尿苷酰化 氮是稀有的，在以下情况下催化PII-UMP的脱尿嘧啶 氮是充足的。PII的尿苷化和未修饰形式 也与腺基转移酶(ATase)相互作用，共价 修饰谷氨酰胺合成酶以响应氮素供应；PII 通过以下方式刺激谷氨酰胺合成酶的腺基化(失活) ATase和PII-UMP刺激细胞去腺化(激活) 谷氨酰胺合成酶由AT酶催化。最后，未经修改的PII形式 与双功能蛋白NRII相互作用，产物 GlnL(NtrB)，引发磷酸酶活性，导致 转录激活剂NRI-磷酸的去磷酸化 NRII/PLL磷酸酶。这一事件进而导致西格玛转录。 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 和它的受体蛋白使用遗传和生物化学方法。我们 描述一种分离和快速测序多种glnB的方案 特定破坏与NRII或NRII相互作用的突变 与UT/UR的互动。此外，我们还描述了遗传和 旨在探索PII-NRII相互作用的生化方法。这个 我们的研究结果应该有助于阐明 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.