Wray L V, Ferson A E, Rohrer K, Fisher S H
Department of Microbiology, Boston University School of Medicine, MA 02118, USA.
Proc Natl Acad Sci U S A. 1996 Aug 20;93(17):8841-5. doi: 10.1073/pnas.93.17.8841.
Expression of the Bacillus subtilis nrgAB operon is derepressed during nitrogen-limited growth. We have identified a gene, tnrA, that is required for the activation of nrgAB expression under these growth conditions. Analysis of the DNA sequence of the tnrA gene revealed that it encodes a protein with sequence similarity to GlnR, the repressor of the B. subtilis glutamine synthetase operon. The tnrA mutant has a pleiotropic phenotype. Compared with wild-type cells, the tnrA mutant is impaired in its ability to utilize allantoin, gamma-aminobutyrate, isoleucine, nitrate, urea, and valine as nitrogen sources. During nitrogen-limited growth, transcription of the nrgAB, nasB, gabP, and ure genes is significantly reduced in the tnrA mutant compared with the levels seen in wild-type cells. In contrast, the level of glnRA expression is 4-fold higher in the, tnrA mutant than in wild-type cells during nitrogen restriction. The phenotype of the tnrA mutant indicates that a global nitrogen regulatory system is present in B. subtilis and that this system is distinct from the Ntr regulatory system found in enteric bacteria.
枯草芽孢杆菌nrgAB操纵子的表达在氮限制生长期间去阻遏。我们鉴定出一个基因tnrA，它是在这些生长条件下激活nrgAB表达所必需的。对tnrA基因的DNA序列分析表明，它编码一种与枯草芽孢杆菌谷氨酰胺合成酶操纵子的阻遏物GlnR具有序列相似性的蛋白质。tnrA突变体具有多效性表型。与野生型细胞相比，tnrA突变体利用尿囊素、γ-氨基丁酸、异亮氨酸、硝酸盐、尿素和缬氨酸作为氮源的能力受损。在氮限制生长期间，与野生型细胞中观察到的水平相比，tnrA突变体中nrgAB、nasB、gabP和ure基因的转录显著降低。相反，在氮限制期间，tnrA突变体中glnRA的表达水平比野生型细胞高4倍。tnrA突变体的表型表明枯草芽孢杆菌中存在一个全局氮调节系统，并且该系统与在肠道细菌中发现的Ntr调节系统不同。
