Ochi K, Kandala J C, Freese E
J Biol Chem. 1981 Jul 10;256(13):6866-75.
We have controlled the rates at which three different amino acids were available to auxotrophs of Bacillus subtilis by avoiding active transport of the respective substrate. The active transport of oxomethylvalerate, a precursor of isoleucine, was prevented by a kauA mutation, the uptake of L-aspartate was competed by 20 mM L-glutamate, and D-methionine was used instead of L-methionine. When in this way conditions of partial amino acid deprivation were achieved, a partial "stringent response" occurred which included the increase of ppGpp and pppGpp, and the decrease of GTP; such conditions initiated sporulation. In the corresponding relaxed (relA) mutants, the changes of guanine nucleotides were greatly reduced and no sporulation was observed at any substrate concentration; but addition of decoyinine produced a further decrease of GTP and caused sporulation.
我们通过避免相应底物的主动转运，控制了三种不同氨基酸提供给枯草芽孢杆菌营养缺陷型的速率。异亮氨酸前体氧甲基缬氨酸的主动转运通过kauA突变得以阻止，20 mM L-谷氨酸可竞争性抑制L-天冬氨酸的摄取，并且使用D-甲硫氨酸替代L-甲硫氨酸。当通过这种方式实现部分氨基酸剥夺条件时，会发生部分“严紧反应”，包括ppGpp和pppGpp增加以及GTP减少；这种条件引发了芽孢形成。在相应的松弛型（relA）突变体中，鸟嘌呤核苷酸的变化大幅减少，并且在任何底物浓度下均未观察到芽孢形成；但添加脱氧野尻霉素会使GTP进一步减少并导致芽孢形成。
