CHARACTERIZATION OF THE REGULON CONTROLLED BY THE LEUCINE-RESPONSIVE REGULATORY PROTEIN IN ESCHERICHIA-COLI
CHARACTERIZATION OF THE REGULON CONTROLLED BY THE LEUCINE-RESPONSIVE REGULATORY PROTEIN IN ESCHERICHIA-COLI
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DOI：
10.1128/jb.174.4.1109-1118.1992
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发表时间：
1992-02-01
影响因子：
3.2
通讯作者：
MATTHEWS, RG
中科院分区：
文献类型：
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作者：
ERNSTING, BR;ATKINSON, MR;MATTHEWS, RG
亮氨酸反应调节蛋白（Lrp）已被证明可以正向或负向调节几种大肠杆菌基因对亮氨酸的转录。我们用二维凝胶电泳分析了在亮氨酸存在或不存在的情况下，等基因lrp+和lrp突变株的多肽表达模式。缺乏功能性Lrp蛋白会改变至少30种多肽的表达。大多数多肽的表达不受10 mM外源亮氨酸存在与否的影响。电泳分析发现，外膜孔蛋白OmpC和OmpF、谷氨酰胺合成酶（GlnA）、谷氨酸合成酶（GltD）小亚基、赖氨酸- trna合成酶形式II （LysU）、支链氨基酸特异性高亲和力周质结合蛋白（LivJ）、W蛋白以及苏氨酸转化为甘氨酸途径中的苏氨酸脱氢酶（Tdh）和2-氨基-3-酮丁酸辅酶a连接酶（Kbl）都是Lrp调控的成员。我们已经证明Lrp是谷氨酸合成酶和谷氨酰胺合成酶的正调节因子，而外源亮氨酸对这些蛋白的表达几乎没有影响。在携带glnL缺失的菌株和携带glnL2302等位基因的菌株中，谷氨酰胺合成酶的表达不再受Lrp的调节，这表明Lrp对谷氨酰胺合成酶水平的影响是间接的，需要一个完整的glnL基因。当精氨酸或鸟氨酸作为培养基中唯一的氮源时，lrp::Tn10菌株生长不良。根据目前的研究和以往的研究，我们提出Lrp参与了大肠杆菌细胞对环境重大变化的适应，例如大肠杆菌离开其动物宿主肠道时发生的环境变化。氨基酸和多肽运输和分解代谢所需的一些基因受到Lrp的负向调控，而在缺氮环境下氨基酸生物合成和氨同化所需的其他基因则受到Lrp的正向调控。
The leucine-responsive regulatory protein (Lrp) has been shown to regulate, either positively or negatively, the transcription of several Escherichia coli genes in response to leucine. We have used two-dimensional gel electrophoresis to analyze the patterns of polypeptide expression in isogenic lrp+ and lrp mutant strains in the presence or absence of leucine. The absence of a functional Lrp protein alters the expression of at of least 30 polypeptides. The expression of the majority of these polypeptides is not affected by the presence or absence of 10 mM exogenous leucine. Outer membrane porins OmpC and OmpF, glutamine synthetase (GlnA), the small subunit of glutamate synthase (GltD), lysyl-tRNA synthetase form II (LysU), a high-affinity periplasmic binding protein specific for branched-chain amino acids (LivJ), W protein, and the enzymes of the pathway converting threonine to glycine, namely, threonine dehydrogenase (Tdh) and 2-amino-3-ketobutyrate coenzyme A ligase (Kbl), were identified as members of the Lrp regulon by electrophoretic analysis. We have shown that Lrp is a positive regulator of glutamate synthase and glutamine synthetase and that exogenous leucine has little or no effect on the expression of these proteins. In strains carrying a glnL deletion and in strains carrying the glnL2302 allele, which directs the synthesis of a GlnL protein that is constitutively active, expression of glutamine synthetase is no longer regulated by Lrp, demonstrating that the effect of Lrp on glutamine synthetase levels is indirect and requires an intact glnL gene. lrp::Tn10 strains grow poorly when arginine or ornithine is present as the sole nitrogen source in the medium. On the bases of present studies and previous research, we propose that Lrp is involved in the adaptation of E. coli cells to major shifts in environment, such as those which occur when E. coli leaves the intestinal tract of its animal host. Several genes required for amino acid and peptide transport and catabolism are negatively regulated by Lrp, and other genes required for amino acid biosynthesis and ammonia assimilation in a nitrogen-poor environment are positively regulated by Lrp.