1,720,976 research outputs found
Killing two birds with one stone: an ABC transporter regulates gene expression through sequestration of a transcriptional regulator at the membrane
No full textTranscriptional regulators are controlled through various, mostly well-understood, principles. In the study of Richet et al., published in this issue of Molecular Microbiology, fluorescence microscopy was used to uncover an unorthodox mechanism that relies on the dynamic shuttling of a gene regulator between the membrane and the chromosome. When not occupied with transport, the maltose-specific ABC transporter sequesters and thereby inactivates its cognate transcriptional regulator MalT. Upon maltose transport, MalT is released from the membrane and activates the maltose utilization and transport genes. This mechanism prevents induction of MalT by endogenously produced maltotriose, which is the inducer. Thus, the maltose uptake system is a trigger transporter with a bi-functional role in transport and regulation.DFG [GO1355/6-1, GO1355/7-1
Rewiring two-component signal transduction with small RNAs
No full textBacterial two-component systems (TCSs) and small regulatory RNAs (sRNAs) form densely interconnected networks that integrate and transduce information from the environment into fine-tuned changes of gene expression. Many TCSs control target genes indirectly through regulation of sRNAs, which in turn regulate gene expression by base-pairing with mRNAs or targeting a protein. Conversely, sRNAs may control TCS synthesis, thereby recruiting the TCS regulon to other regulatory networks. Several TCSs control expression of multiple homologous sRNAs providing the regulatory networks with further flexibility. These sRNAs act redundantly, additively or hierarchically on targets. The regulatory speed of sRNAs and their unique features in gene regulation make them ideal players extending the flexibility, dynamic range or timing of TCS signaling.DFG [GO1355/6-1, SPP1258]; Gottingen universit
Regulatory roles of the bacterial nitrogen-related phosphotransferase system
No full textIn addition to the sugar phosphotransferase system (sugar PTS) dedicated to carbohydrate uptake, many Gram-negative bacteria possess a so-called nitrogen PTS (PTSNtr). Although fulfilling very different functions, both systems can communicate with each other by phosphate exchange. PTSNtr regulates diverse processes implicated in metabolism of nitrogen and carbon, and is essential for virulence in some bacteria. Additionally, it plays a role in potassium homeostasis by regulating the expression and activity of a high- and a low-affinity K+ transporter, respectively. In this article, we review recent advances in the understanding of the regulatory roles of PTSNtr in various organisms.Deutsche Forschungsgemeinschaft; PSYSMO-ERANE
Noncoding RNA control of the making and breaking of sugars
No full textNoncoding RNA regulators have been implicated in almost all imaginable cellular processes. Here we review how regulatory small RNAs such as Spot42, SgrS, GlmY, and GlmZ and a cis-encoded ribozyme in glmS mRNA control sugar metabolism. Besides discussing the physiological implications, we show how the study of these molecules contributed to our understanding of the mechanisms and of general principles of RNA-based regulation. These include the post-transcriptional repression or activation of gene expression within polycistronic mRNAs; novel ribonucleoprotein complexes composed of small RNA, Hfq, and/or RNase E; and the hierarchical action of regulatory RNAs.Deutsche Forschungsgemeinschaft; DFG [SPP1258
The phosphotransferase protein EIIANtr modulates the phosphate starvation response through interaction with histidine kinase PhoR in Escherichia coli
No full textMany Proteobacteria possess the paralogous PTSNtr, in addition to the sugar transport phosphotransferase system (PTS). In the PTSNtr phosphoryl-groups are transferred from phosphoenolpyruvate to protein EIIANtr via the phosphotransferases EINtr and NPr. The PTSNtr has been implicated in regulation of diverse physiological processes. In Escherichia coli, the PTSNtr plays a role in potassium homeostasis. In particular, EIIANtr binds to and stimulates activity of a two-component histidine kinase (KdpD) resulting in increased expression of the genes encoding the high-affinity K+ transporter KdpFABC. Here, we show that the phosphate (pho) regulon is likewise modulated by PTSNtr. The pho regulon, which comprises more than 30 genes, is activated by the two-component system PhoR/PhoB under conditions of phosphate starvation. Mutants lacking EIIANtr are unable to fully activate the pho genes and exhibit a growth delay upon adaptation to phosphate limitation. In contrast, pho expression is increased above the wild-type level in mutants deficient for EIIANtr phosphorylation suggesting that non-phosphorylated EIIANtr modulates pho. Protein interaction analyses reveal binding of EIIANtr to histidine kinase PhoR. This interaction increases the amount of phosphorylated response regulator PhoB. Thus, EIIANtr is an accessory protein that modulates the activities of two distinct sensor kinases, KdpD and PhoR, in E. coli
Is there any role for cAMP–CRP in carbon catabolite repression of the Escherichia coli lac operon? Reply from Görke and Stülke
No full textDual control by perfectly overlapping sigma 54-and sigma 70-promoters adjusts small RNA GlmY expression to different environmental signals
No full textP>In Escherichia coli synthesis of glucosamine-6-phosphate synthase GlmS is feedback-controlled by a regulatory cascade composed of small RNAs GlmY and GlmZ. When GlcN6P becomes limiting, GlmY accumulates and inhibits processing of GlmZ. Full-length GlmZ base-pairs with the glmS transcript and activates synthesis of GlmS, which re-synthesizes GlcN6P. Here we show that glmY expression is controlled by two overlapping promoters with the same transcription start site. A sigma 70-dependent promoter contributes to glmY transcription during exponential growth. Alternatively, glmY can be transcribed from a sigma 54-dependent promoter, which requires the YfhK/YfhA two-component system for activity. YfhK is a sensor kinase and YfhA is a response regulator that contains a sigma 54 interaction domain. YfhA binds to a DNA region located more than 100 bp upstream of glmY. Three copies of the conserved sequence TGTCN(10)GACA contribute to binding, and the two sites next to glmY are essential for activation of the sigma 54-dependent promoter by YfhA. YfhK and YfhA upregulate GlmY when cells enter the stationary growth phase, whereas regulation by glucosamine-6-phosphate occurs post GlmY transcription. Target genes regulated by YfhK and YfhA were unknown so far. We propose to rename these proteins to GlrK and GlrR, for glmY regulating kinase and response regulator respectively
Carbon catabolite repression in bacteria: many ways to make the most out of nutrients
No full textMost bacteria can selectively use substrates from a mixture of different carbon sources. The presence of preferred carbon sources prevents the expression, and often also the activity, of catabolic systems that enable the use of secondary substrates. This regulation, called carbon catabolite repression (CCR), can be achieved by different regulatory mechanisms, including transcription activation and repression and control of translation by an RNA-binding protein, in different bacteria. Moreover, CCR regulates the expression of virulence factors in many pathogenic bacteria. In this Review, we discuss the most recent findings on the different mechanisms that have evolved to allow bacteria to use carbon sources in a hierarchical manner
Control of the phosphorylation state of the HPr protein of the phosphotransferase system in Bacillus subtilis: Implication of the protein phosphatase PrpC
No full textIn the Gram-positive bacterium Bacillus subtilis as well as in other firmicutes, the HPr protein of the phosphotransferase system (PTS) has two distinct phosphorylation sites, His-15 and Ser-46. These sites are phosphorylated by the Enzyme I of the PTS and by the ATP-dependent HPr kinase/phosphorylase, respectively. As a result, the phosphorylation state of HPr reflects the nutrient supply of the cell and is in turn involved in several responses at the levels of transport activity and expression of catabolic genes. Most important, HPr( SerP) serves as a cofactor for the pleiotropic transcription regulator CcpA. In addition to the proteins that phosphorylate HPr, those that are involved in the dephosphorylation are important in controlling the overall HPr phosphorylation state and the resulting regulatory and physiological outputs. In this study, we found that in addition to the phosphorylase activity of the HPr kinase/phosphorylase, the serine/threonine protein phosphatase PrpC uses HPr(Ser-P) as a target. Copyright (c) 2007 S. Karger AG, Basel
Requirements for the phosphorylation of the Escherichia coli EIIA(Ntr) protein in vivo
No full textThe nitrogen-related phosphotransferase system (Ntr-PTS) is a paralogous system working in parallel to the well-known carbohydrate: PTS. In a chain of phospho-transfer reactions, EI(Ntr) and NPr (PtsO) deliver phosphoryl groups to the EIIA(Ntr) (PtsN) protein. EIIA(Ntr) is implicated in important regulatory processes such as the sigma(E)-dependent cell envelope stress response and regulation of K(+) uptake. Phosphorylation is believed to trigger the output of EIIA(Ntr) these regulations. EIIA(Ntr) is encoded within the gene cluster ptsN-yhbJ-ptsO, which is highly conserved in Proteobacteria. In this study, we investigated the phosphorylation of the Escherichia coli EIIA(Ntr) protein in vivo by (32)p-labeling. We show that EIIA(Ntr) is readily phosphorylated in wild-type cells. This phosphorylation occurs at a single site, the histidine 73 in EIIA(Ntr). YhbJ and NPr are dispensable for this phosphorylation. A detailed analysis revealed that both the energy coupling phosphotransferases of the Ntr-PTS as well as the 'sugar'-PTS contribute to the phosphorylation of EIIA(Ntr), suggesting cross talk between both systems.Deutsche Forschungsgemeinschaft [GO 1355/2-2
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