Bueno R, Pahel G, Magasanik B
J Bacteriol. 1985 Nov;164(2):816-22. doi: 10.1128/jb.164.2.816-822.1985.
We have isolated insertion and deletion mutants in glnB, the structural gene of PII, a member of the adenylylation system for glutamine synthetase of Escherichia coli, to study the role of PII in the regulation of the synthesis of glutamine synthetase and of histidase in response to nitrogen deprivation or excess. We have studied the effects of this mutation alone and combined with null mutations resulting from the insertion of transposons or from a deletion in the other genes affecting this regulation, glnD, glnF (ntrA), glnG (ntrC), and glnL (ntrB). Our results confirm that only the products of glnF and glnG are essential for this regulation. In cells of the wild type, the response is mediated by the products of glnD and glnB via the product of glnL. In the condition of nitrogen excess, PII, the product of glnB, appears to convert the product of glnL to a form that prevents the activation of transcription of the structural genes for glutamine synthetase and for histidase by the products of glnF and glnG. During nitrogen deprivation, uridylyltransferase, the product of glnD, is activated by the intracellular excess of 2-ketoglutarate over glutamine and converts PII to PII-UMP and changes the form of the glnL product to one that stimulates the activation of transcription of glutamine synthetase and histidase by the products of glnF and glnG.
我们已经分离出大肠杆菌谷氨酰胺合成酶腺苷酰化系统成员PII的结构基因glnB中的插入和缺失突变体，以研究PII在响应氮缺乏或过量时对谷氨酰胺合成酶和组氨酸酶合成调控中的作用。我们研究了这种突变单独的影响，以及与转座子插入或其他影响该调控的基因（glnD、glnF(ntrA)、glnG(ntrC)和glnL(ntrB)）中的缺失所导致的无效突变相结合时的影响。我们的结果证实，只有glnF和glnG的产物对于这种调控是必不可少的。在野生型细胞中，这种响应是由glnD和glnB的产物通过glnL的产物介导的。在氮过量的情况下，glnB的产物PII似乎将glnL的产物转化为一种形式，这种形式可阻止谷氨酰胺合成酶和组氨酸酶的结构基因被glnF和glnG的产物激活转录。在氮缺乏期间，glnD的产物尿苷酰转移酶被细胞内过量的2-酮戊二酸相对于谷氨酰胺激活，并将PII转化为PII-UMP，同时将glnL产物的形式改变为一种可刺激谷氨酰胺合成酶和组氨酸酶被glnF和glnG的产物激活转录的形式。
