Friesen J D, Parker J, Watson R J, Fill N P, Pedersen S, Pedersen F S
J Bacteriol. 1976 Aug;127(2):917-22. doi: 10.1128/jb.127.2.917-922.1976.
In Escherichia coli the relA and pyrG loci are 99% cotransducible. On the basis of this knowledge, we have isolated lambdacI857S7dpyrG transducing bacteriophages carrying both the pyrG and relA genes. Single lysogens of this bacteriophage show basal levels of ppGpp that are 10-fold higher than normal. Stringent factor is present among the gene products synthesized by lambdadpyrG relA after infection of ultraviolet-killed cells, as analyzed by polyacrylamide gel electrophoresis. The intracellular content of stringent factor, as determined by enzymatic activity, rises 20-fold after induction of a single lysogen of lambdadpyrG relA. As measured by two-dimensional gel electrophoresis, the amount of stringent factor in an exponentially growing strain carrying a pyrG relA plasmid is at least 10-fold greater than in a normal strain. These data constitute strong evidence that stringent factor is the relA gene product.
在大肠杆菌中，relA和pyrG基因座的共转导率为99%。基于这一认识，我们分离出了携带pyrG和relA基因的λcI857S7d pyrG转导噬菌体。这种噬菌体的单个溶原菌显示出的ppGpp基础水平比正常水平高10倍。通过聚丙烯酰胺凝胶电泳分析，在感染紫外线杀死的细胞后，λd pyrG relA合成的基因产物中存在严谨因子。通过酶活性测定，单个λd pyrG relA溶原菌诱导后，细胞内严谨因子的含量增加了20倍。通过二维凝胶电泳测量，携带pyrG relA质粒的指数生长菌株中严谨因子的量比正常菌株至少高10倍。这些数据构成了强有力的证据，证明严谨因子是relA基因的产物。
