Effect of Polyphosphate Metabolism on the Escherichia coli Phosphate-Starvation Response (original) (raw)
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Inorganic Polyphosphate in Escherichia coli : the Phosphate Regulon and the Stringent Response
Journal of Bacteriology, 1998
Escherichia coli transiently accumulates large amounts of inorganic polyphosphate (polyP), up to 20 mM in phosphate residues (P i), in media deficient in both P i and amino acids. This transient accumulation is preceded by the appearance of nucleotides ppGpp and pppGpp, generated in response to nutritional stresses. Mutants which lack PhoB, the response regulator of the phosphate regulon, do not accumulate polyP even though they develop wild-type levels of (p)ppGpp when subjected to amino acid starvation. When complemented with a phoB-containing plasmid, phoB mutants regain the ability to accumulate polyP. PolyP accumulation requires high levels of (p)ppGpp independent of whether they are generated by RelA (active during the stringent response) or SpoT (expressed during P i starvation). Hence, accumulation of polyP requires a functional phoB gene and elevated levels of (p)ppGpp. A rapid assay of polyP depends on its adsorption to an anion-exchange disk on which it is hydrolyzed by a yeast exopolyphosphatase.
A dynamic model of the phosphate response system with synthetic promoters in Escherichia coli
Proceedings of the 14th European Conference on Artificial Life ECAL 2017
The bacteria E. coli have developed one of the most efficient regulatory response to phosphate starvation that is known in detail. Achieving a mechanistic understanding of this system, realized by Pho regulon at the genetic level, has implications for applications in artificial life and for others in biotechnology that exploit such mechanisms. To this end, we present a dynamical model of Pho regulon, coupled with a layered description of its regulation in the experimental conditions of phosphate starvation. The model describes the dynamics of two-component regulatory system together with the key regulatory promoter PhoB and experimental data on promoter PhoA. The model is parameterized according to the feasible range given in the literature, and fitted to the dynamic response of our experimental data on alkaline phosphatase production, coded as Gfp. Sensitivity analysis demonstrates that the rate of Pho transcription has a significant influence over the expression of Pho-controlled genes. Variations in the transcription rates alter the sensitivity of the phosphate starvation response to external phosphate concentration, whereas variations in the translation rates affect the gain of the system. Our model provides a dynamic description of the core determinants of Pho regulon and promoter activities and their response to the change of external phosphate level. As the model architecture is intrinsically open to integrate supplementary layers, together with experimental findings, it should provide insights in investigations on engineering new dynamic sensors and regulators for living technologies.
Overlapping and separate controls on the phosphate regulon in Escherichia coli K12
Journal of Molecular Biology, 1983
Tile physiological and genetic controls operating on phosphate-regulated promoters were studied in greater detail. This was done by defining tile control for three phosphate-regulated genes: phoA, psiE, and psiO. Each is highly inducible by phosphate starvation. Individually, these phosphate-starvation-inducible, psi, genes at the same time show common and differing features in their molecular control.
Gene regulation by phosphate in enteric bacteria
Journal of Cellular Biochemistry, 1993
The Escherichia coli phosphate (PHO) regulon includes 31 (or more) genes arranged in eight separate operons. All are coregulated by environmental (extra-cellular) phosphate and are probably involved in phosphorus assimilation. Pi control of these genes requires the sensor PhoR, the response regulator PhoB, the binding proteindependent Pi-specific transporter Pst, and the accessory protein PhoU. During Pi limitation, PhoR turns on genes of the PHO regulon by phosphorylating PhoB that in turn activates transcription by binding to promoters that share an 1 &base consensus PHO Box. When Pi is in excess, PhoR, Pst, and PhoU together turn off the PHO regulon, presumably by dephosphorylating PhoB. In addition, two Pi-independent controls that may be forms of cross regulation turn on the PHO regulon in the absence of PhoR. The sensor CreC, formerly called PhoM, phosphorylates PhoB in response to some (unknown) catabolite, while acetyl phosphate may directly phosphorylate PhoB. Cross regulation of the PHO regulon by CreC and acetyl phosphate may be examples of underlying control mechanisms important for the general (global) control of cell growth and metabolism. o 1993 W I I~Y -L I S S , Inc.
Journal of Bacteriology, 1992
Two controls of the phosphate (PHO) regulon require sensor proteins that are protein kinases that phosphorylate the regulator, PhoB, which in turn activates transcription only when phosphorylated. Pi control requires the Pi sensor PhoR; the other control is Pi independent and requires the sensor CreC (formerly called PhoM). Here we describe an additional control of the PHO regulon which is Pi independent and requires neither PhoR nor CreC. This control is regulated by a two-step pathway in carbon metabolism in which acetyl coenzyme A, Pi, and ADP are converted into acetate, coenzyme A, and ATP via the enzymes phosphotransacetylase (Pta) and acetate kinase (AckA). It responds to the synthesis of acetyl phosphate, an intermediate in the Pta-AckA pathway. Since the synthesis of acetyl phosphate via this pathway leads to the incorporation of Pi into ATP, the primary phosphoryl donor in metabolism, we propose that a regulatory coupling(s) may exist between the PHO regulon, which encodes ...
Expression parameters for target gene cloned in Escherichia coli in response to phosphate supply
Biotechnology letters, 1996
Recombinant strain of E. coli 1727 overexpressed target gene at enhanced level when supplied with excess of inorganic phosphate. Rate of target gene expression, yield coefficient for target gene product and plasmid copy number increased significantly: 50%, 100% and 40% respectively at 125 mM excess phosphate. This was, however, accompanied by 26% decrease in specific growth rate and 30% in cellular growth yield coefficient.