Department of Molecular Reproduction, Development, and Genetics, Indian Institute of Science, Bangalore, 560012, India.
Curr Microbiol. 2022 Apr 9;79(5):153. doi: 10.1007/s00284-022-02837-1.
BglG, an RNA binding regulatory protein encoded by the β-glucoside (bgl) operon of E. coli is known to be involved in the regulation of several metabolic functions in stationary phase. A genome-wide comparative transcriptome analysis performed earlier between a ∆bglG strain and its isogenic WT counterpart revealed that genes involved in lipopolysaccharide (LPS) biosynthesis and transport were significantly down-regulated in the absence of BglG in stationary phase, suggesting a role for BglG in their regulation. We have investigated the involvement of BglG in LPS biosynthesis and transport. Consistent with the down-regulation of LPS synthesis and transport genes, the ∆bglG strain showed a loss of permeability barrier specifically in stationary phase, which could be rescued by introduction of wild type bglG on a plasmid. A search for a putative transcription factor involved in the regulation mediated by BglG led to the identification of GadE, which is one of the primary positive regulators of pH homeostasis and LPS core biosynthesis. Using RNA mobility shift and stability assays, we show that BglG binds specifically to gadE mRNA and enhances its stability. Consistent with this, loss of gadE leads to a partial defect in permeability. Based on our findings, we propose a model for the molecular mechanism involved in the regulation on LPS synthesis and transport by BglG.
BglG 是大肠杆菌 bgl 操纵子编码的一种 RNA 结合调节蛋白，已知其参与了静止期的几种代谢功能的调节。早期在 ∆bglG 菌株与其同源 WT 菌株之间进行的全基因组比较转录组分析显示，在静止期缺乏 BglG 时，参与脂多糖（LPS）生物合成和运输的基因显著下调，表明 BglG 在它们的调节中发挥作用。我们已经研究了 BglG 在 LPS 生物合成和运输中的参与情况。与 LPS 合成和运输基因的下调一致，∆bglG 菌株在静止期表现出特定的通透性屏障丧失，这可以通过在质粒上引入野生型 bglG 来挽救。对参与 BglG 介导的调节的假定转录因子的搜索导致了 GadE 的鉴定，GadE 是 pH 平衡和 LPS 核心生物合成的主要正调节因子之一。通过 RNA 迁移率变化和稳定性测定，我们表明 BglG 特异性地结合 gadE mRNA 并增强其稳定性。与此一致，gadE 的缺失导致通透性的部分缺陷。基于我们的发现，我们提出了一个 BglG 调节 LPS 合成和运输的分子机制模型。
