Insight into Bacterial Phosphotransferase System-Mediated Signaling by Interspecies Transplantation of a Transcriptional Regulator (original) (raw)
Related papers
Naturwissenschaften, 1998
In many bacteria a crucial link between metabolism and regulation of catabolic genes is based on the phosphotransferase sugar uptake system (PTS). We summarize the mechanisms of the signaling pathways originating from PTS and leading to regulation of transcription. A protein domain, called PTS regulation domain (PRD), is linked to many antiterminators and transcriptional activators and regulates their activity depending on its state of phosphorylation. Two sites can be phosphorylated in most PRDs: HPr-dependent modification at one site leads to activation while enzyme II dependent phosphorylation of the other site renders it inactive. In addition, PTS components are used to generate cofactors for regulators of transcription. The paradigm is the enzyme II dependent activity of adenylate cyclase determining the cyclic AMP level in Escherichia coli and thereby the activity of the catabolite activator protein. In many gram-positive bacteria catabolite repression is mediated by the catabolite control protein CcpA, which requires HPr Ser-46 phosphate as a cofactor to regulate transcription of catabolic genes. HPr Ser-46 phosphate is produced by HPr kinase, the activity of which is under metabolic control via the concentrations of glycolytic intermediates. These recent results establish a multifaceted regulatory role for PTS in addition to its wellestablished function in active sugar uptake.
Journal of Bacteriology, 2007
The histidine protein (HPr) is the energy-coupling protein of the phosphoenolpyruvate (PEP)-dependent carbohydrate:phosphotransferase system (PTS), which catalyzes sugar transport in many bacteria. In its functions, HPr interacts with a number of evolutionarily unrelated proteins. Mainly, it delivers phosphoryl groups from enzyme I (EI) to the sugar-specific transporters (EIIs). HPr proteins of different bacteria exhibit almost identical structures, and, where known, they use similar surfaces to interact with their target proteins. Here we studied the in vivo effects of the replacement of HPr and EI of Escherichia coli with the homologous proteins from Bacillus subtilis , a gram-positive bacterium. This replacement resulted in severe growth defects on PTS sugars, suggesting that HPr of B. subtili s cannot efficiently phosphorylate the EIIs of E. coli . In contrast, activation of the E. coli BglG regulatory protein by HPr-catalyzed phosphorylation works well with the B. subtilis HPr ...
EMBO Journal, 2000
The global regulator Mlc controls several genes implicated in sugar utilization systems, notably the phosphotransferase system (PTS) genes, ptsG, manXYZ and ptsHI, as well as the malT activator. No speci®c low molecular weight inducer has been identi®ed that can inactivate Mlc, but its activity appeared to be modulated by transport of glucose via Enzyme IICB Glc (PtsG). Here we demonstrate that inactivation of Mlc is achieved by sequestration of Mlc to membranes containing dephosphorylated Enzyme IICB Glc. We show that Mlc binds speci®cally to membrane fractions which carry PtsG and that excess Mlc can inhibit Enzyme IICB Glc phosphorylation by the general PTS proteins and also Enzyme IICB Glc-mediated phosphorylation of a-methylglucoside. Binding of Mlc to Enzyme IICB Glc in vitro required the IIB domain and the IIC±B junction region. Moreover, we show that these same regions are suf®cient for Mlc regulation in vivo, via cross-dephosphorylation of IIB Glc during transport of other PTS sugars. The control of Mlc activity by sequestration to a transport protein represents a novel form of signal transduction in gene regulation.
Journal of Bacteriology, 2000
Escherichia coli adapted to glucose-limited chemostats contained mutations in ptsG resulting in V12G, V12F, and G13C substitutions in glucose-specific enzyme II (EII Glc ) and resulting in increased transport of glucose and methyl-␣-glucoside. The mutations also resulted in faster growth on mannose and glucosamine in a PtsG-dependent manner. By use of enhanced growth on glucosamine for selection, four further sites were identified where substitutions caused broadened substrate specificity (G176D, A288V, G320S, and P384R). The altered amino acids include residues previously identified as changing the uptake of ribose, fructose, and mannitol. The mutations belonged to two classes. First, at two sites, changes affected transmembrane residues (A288V and G320S), probably altering sugar selectivity directly. More remarkably, the five other specificity mutations affected residues unlikely to be in transmembrane segments and were additionally associated with increased ptsG transcription in the absence of glucose. Increased expression of wild-type EII Glc was not by itself sufficient for growth with other sugars. A model is proposed in which the protein conformation determining sugar accessibility is linked to transcriptional signal transduction in EII Glc . The conformation of EII Glc elicited by either glucose transport in the wild-type protein or permanently altered conformation in the second category of mutants results in altered signal transduction and interaction with a regulator, probably Mlc, controlling the transcription of pts genes.
The Escherichia coli glucose transporter enzyme IICBGlc recruits the global repressor Mlc
The EMBO Journal, 2001
In addition to effecting the catalysis of sugar uptake, the bacterial phosphoenolpyruvate:sugar phosphotransferase system regulates a variety of physiological processes. Exposure of cells to glucose can result in repression or induction of gene expression. While the mechanism for carbon catabolite repression by glucose was well documented, that for glucose induction was not clearly understood in Escherichia coli. Recently, glucose induction of several E.coli genes has been shown to be mediated by the global repressor Mlc. Here, we elucidate a general mechanism for glucose induction of gene expression in E.coli, revealing a novel type of regulatory circuit for gene expression mediated by the phosphorylation state-dependent interaction of a membrane-bound protein with a repressor. The dephospho-form of enzyme IICB Glc , but not its phospho-form, interacts directly with Mlc and induces transcription of Mlc-regulated genes by displacing Mlc from its target sequences. Therefore, the glucose induction of Mlc-regulated genes is caused by dephosphorylation of the membrane-bound transporter enzyme IICB Glc , which directly recruits Mlc to derepress its regulon.
Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics, 2013
Numerous bacteria possess transcription activators and antiterminators composed of regulatory domains phosphorylated by components of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). These domains, called PTS regulation domains (PRDs), usually contain two conserved histidines as potential phosphorylation sites. While antiterminators possess two PRDs with four phosphorylation sites, transcription activators contain two PRDs plus two regulatory domains resembling PTS components (EIIA and EIIB). The activity of these transcription regulators is controlled by up to five phosphorylations catalyzed by PTS proteins. Phosphorylation by the general PTS components EI and HPr is usually essential for the activity of PRD-containing transcription regulators, whereas phosphorylation by the sugar-specific components EIIA or EIIB lowers their activity. For a specific regulator, for example the Bacillus subtilis mtl operon activator MtlR, the functional phosphorylation sites can be different in other bacteria and consequently the detailed mode of regulation varies. Some of these transcription regulators are also controlled by an interaction with a sugar-specific EIIB PTS component. The EIIBs are frequently fused to the membrane-spanning EIIC and EIIB-mediated membrane sequestration is sometimes crucial for the control of a transcription regulator. This is also true for the Escherichia coli repressor Mlc, which does not contain a PRD but nevertheless interacts with the EIIB domain of the glucose-specific PTS. In addition, some PRD-containing transcription activators interact with a distinct EIIB protein located in the cytoplasm. The phosphorylation state of the EIIB components, which changes in response to the presence or absence of the corresponding carbon source, affects their interaction with transcription regulators. This article is part of a Special Issue entitled: Inhibitors of Protein Kinases (2012).
Molecular Microbiology, 1991
Glucose is taken up in Bacillus subtilis via the phosphoenolpyruvate:glucose phosphotransferase system (glucose PTS). Two genes, orfG and ptsX, have been implied in the glucose-specific part of this PTS, encoding an Enzyme 11'^'" and an Enzyme 111°"=, respectively. We now show that the glucose permease consists of a single, membrane-bound, polypeptide with an apparent molecular weight of 80000, encoded by a single gene which will be designated ptsG. The glucose permease contains domains that are 40-50% identical to the 11°"' and 111°"= proteins of Escherichia coli. The B. subtilis 111°"= domain can replace III°"= in E. coli err mutants in supporting growth on glucose and transport of methyl o-glucoside.
Activation of Escherichia coli antiterminator BglG requires its phosphorylation
Proceedings of the National Academy of Sciences, 2012
Transcriptional antiterminator proteins of the BglG family control the expression of enzyme II (EII) carbohydrate transporters of the bacterial phosphotransferase system (PTS). In the PTS, phosphoryl groups are transferred from phosphoenolpyruvate (PEP) via the phosphotransferases enzyme I (EI) and HPr to the EIIs, which phosphorylate their substrates during transport. Activity of the antiterminators is negatively controlled by reversible phosphorylation catalyzed by the cognate EIIs in response to substrate availability and positively controlled by the PTS. For the Escherichia coli BglG antiterminator, two different mechanisms for activation by the PTS were proposed. According to the first model, BglG is activated by HPr-catalyzed phosphorylation at a site distinct from the EII-dependent phosphorylation site. According to the second model, BglG is not activated by phosphorylation, but solely through interaction with EI and HPr, which are localized at the cell pole. Subsequently Bgl...
Proceedings of the National Academy of Sciences, 1990
The beta-glucoside (bgl) operon of Escherichia coli is subject to both positive control by transcriptional termination/antitermination and negative control by the beta-glucoside-specific transport protein, an integral membrane protein known as enzyme IIBgl. Previous results led us to speculate that enzyme IIBgl exerts its negative control by phosphorylating and thereby inactivating the antiterminator protein, BglG. Specifically, our model postulated that the transport protein enzyme IIBgl exhibits protein-phosphotransferase activity in the absence of beta-glucosides. We now present biochemical evidence that the phosphorylation of protein BglG does indeed occur in vivo and that it is accompanied by the loss of antitermination activity. BglG persists in the phosphorylated state in the absence of beta-glucosides but is rapidly dephosphorylated when beta-glucosides become available for transport. Our data also suggested specific interactions between the beta-glucoside transport protein ...