Glucose- and Glucokinase-Controlled<i>mal</i>Gene Expression in<i>Escherichia coli</i>

Lengsfeld, Christina; Schönert, Stefan; Dippel, Renate; Boos, Winfried

doi:10.1128/jb.00767-08

Cited by 22 publications

(27 citation statements)

References 60 publications

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“…Early work on the MalQ reaction using purified maltose as substrate demonstrated a considerable lag phase that led to the conclusion that maltotriose is the shortest possible donor (12), an observation that was not confirmed by others (6,8). Likewise, such a lag phase was not observed in our enzyme assay.…”

Section: Comparison Of the Crystal Structures Of Malq In Three Differcontrasting

confidence: 58%

“…Both are subsequently converted to glucose-6-P by glucokinase and phosphoglucomutase, respectively, to enter glycolysis. Previous investigations indicated that increased internal glucose levels reduce the activity of MalQ (8). Furthermore, maltodextrin metabolism is linked to that of glycogen via the shared intermediate maltotriose, which is not only a substrate of MalQ but also constitutes the inducer of the maltose system (9,10).…”

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confidence: 99%

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Structural Basis for the Interconversion of Maltodextrins by MalQ, the Amylomaltase of Escherichia coli

Weiß

Skerra

Schiefner

2015

Journal of Biological Chemistry

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Background: Amylomaltase MalQ catalyzes the transglycosylation of maltose and maltodextrins in E. coli. Results: Three different x-ray structures and the product equilibrium concentrations for different substrates were determined. Conclusion: MalQ undergoes major conformational changes during catalysis, and its product spectrum depends on substrate chain length. Significance: Novel insights into the MalQ mechanism and its key role for maltose metabolism in E. coli were obtained.

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Section: Comparison Of the Crystal Structures Of Malq In Three Differcontrasting

confidence: 58%

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confidence: 99%

Structural Basis for the Interconversion of Maltodextrins by MalQ, the Amylomaltase of Escherichia coli

Weiß

Skerra

Schiefner

2015

Journal of Biological Chemistry

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“…Glucose also acts as an acceptor limiting the extent of polymerization and in increasing concentration becomes a feedback inhibitor of MalQ. The removal of glucose from the reaction mixture, for instance, by ATP and glucokinase (to form glucose-6-P that is not part of the equilibrium), allows the formation of maltodextrins of continually increasing chain length (26). This situation mimics the cytosol of a ⌬malP strain grown on maltose, where the maltodextrins formed by the MalQ activity are not reduced in size by the missing MalP enzyme.…”

Section: Vol 193 2011 Maltose Enzymes In Glycogen Synthesis By E Cmentioning

confidence: 99%

Role of Maltose Enzymes in Glycogen Synthesis by Escherichia coli

et al. 2011

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Mutants with deletion mutations in the glg and mal gene clusters of Escherichia coli MC4100 were used to gain insight into glycogen and maltodextrin metabolism. Glycogen content, molecular mass, and branch chain distribution were analyzed in the wild type and in ⌬malP (encoding maltodextrin phosphorylase), ⌬malQ (encoding amylomaltase), ⌬glgA (encoding glycogen synthase), and ⌬glgA ⌬malP derivatives. The wild type showed increasing amounts of glycogen when grown on glucose, maltose, or maltodextrin. When strains were grown on maltose, the glycogen content was 20 times higher in the ⌬malP strain (0.97 mg/mg protein) than in the wild type (0.05 mg/mg protein). When strains were grown on glucose, the ⌬malP strain and the wild type had similar glycogen contents (0.04 mg/mg and 0.03 mg/mg protein, respectively). The ⌬malQ mutant did not grow on maltose but showed wild-type amounts of glycogen when grown on glucose, demonstrating the exclusive function of GlgA for glycogen synthesis in the absence of maltose metabolism. No glycogen was found in the ⌬glgA and ⌬glgA ⌬malP strains grown on glucose, but substantial amounts (0.18 and 1.0 mg/mg protein, respectively) were found when they were grown on maltodextrin. This demonstrates that the action of MalQ on maltose or maltodextrin can lead to the formation of glycogen and that MalP controls (inhibits) this pathway. In vitro, MalQ in the presence of GlgB (a branching enzyme) was able to form glycogen from maltose or linear maltodextrins. We propose a model of maltodextrin utilization for the formation of glycogen in the absence of glycogen synthase.The synthesis of glycogen in bacteria occurs when they are grown with limited nutrients but an abundance of a carbon source (33,34). Escherichia coli accumulates glycogen at levels of more than half of its cell mass under optimal conditions. The glycogen gene cluster in E. coli consists of two operons oriented in tandem, glgBX and glgCAP, encoding enzymes that synthesize and degrade glycogen (12). The encoded enzymes are a branching enzyme (glgB), a debranching enzyme (glgX), an ADP-glucose pyrophosphorylase (glgC), a glycogen synthase (glgA), and a glycogen phosphorylase (glgP). The polymerization of the ␣-1,4-linked glucosyl chain is mediated via the transfer of glucose from ADP-glucose by GlgA, the glycogen synthase, onto the nonreducing ends of linear dextrins that are subsequently branched (formation of ␣-1,6-glycosyl linkage) by GlgB, the branching enzyme. The expression of the glg gene cluster is complicated. It involves the global carbon storage regulator CsrA (2, 53), the cyclic AMP (cAMP)/catabolite gene activator protein (CAP) system (39), and the stringent response (38). In addition, the two-component regulatory system PhoP-PhoQ (29) connects the system to Mg 2ϩ levels, and even the phosphotransferase system appears to affect the glycogen phosphorylase involved in the degradation of glycogen (42,43). glgS, an additional gene involved in glycogen synthesis, is not part of the glg gene cluster. It is not essential for ...

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“…It is possible that the filamentation and cell death in dGTP-starved cultures release maltodextrins into the medium. Alternatively, maltotriose can be generated from endogenous sources, such as glycogen (46) or trehalose (47), or by factors associated with the accumulation of unphosphorylated glucose (48). For example, during unbalanced growth, the flow of carbon in and out of the glycogen reservoir may be altered, leading to upregulated maltotriose levels, as could be the upregulation of trehalose import (treB; 3.1-fold) ( Table 4).…”

Section: Figmentioning

confidence: 99%

Transcriptome Analysis of Escherichia coli during dGTP Starvation

Itsko

Schaaper

2016

J Bacteriol

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Our laboratory recently discovered that Escherichia coli cells starved for the DNA precursor dGTP are killed efficiently (dGTP starvation) in a manner similar to that described for thymineless death (TLD). Conditions for specific dGTP starvation can be achieved by depriving an E. coli optA1 gpt strain of the purine nucleotide precursor hypoxanthine (Hx). To gain insight into the mechanisms underlying dGTP starvation, we conducted genome-wide gene expression analyses of actively growing optA1 gpt cells subjected to hypoxanthine deprivation for increasing periods. The data show that upon Hx withdrawal, the optA1 gpt strain displays a diminished ability to derepress the de novo purine biosynthesis genes, likely due to internal guanine accumulation. The impairment in fully inducing the purR regulon may be a contributing factor to the lethality of dGTP starvation. At later time points, and coinciding with cell lethality, strong induction of the SOS response was observed, supporting the concept of replication stress as a final cause of death. No evidence was observed in the starved cells for the participation of other stress responses, including the rpoS-mediated global stress response, reinforcing the lack of feedback of replication stress to the global metabolism of the cell. The genome-wide expression data also provide direct evidence for increased genome complexity during dGTP starvation, as a markedly increased gradient was observed for expression of genes located near the replication origin relative to those located toward the replication terminus. IMPORTANCE Control of the supply of the building blocks (deoxynucleoside triphosphates [dNTPs]) for DNA replication is important for ensuring genome integrity and cell viability. When cells are starved specifically for one of the four dNTPs, dGTP, the process of DNA replication is disturbed in a manner that can lead to eventual death. In the present study, we investigated the transcriptional changes in the bacterium E. coli during dGTP starvation. The results show increasing DNA replication stress with an increased time of starvation, as evidenced by induction of the bacterial SOS system, as well as a notable lack of induction of other stress responses that could have saved the cells from cell death by slowing down cell growth. The direct DNA precursors, deoxyribonucleoside 5=-triphosphates (dNTPs), are important determinants of the progress of DNA replication, as they affect cell cycle continuity and viability. They are also critical determinants of the accuracy of DNA replication, ultimately affecting genomic stability and the longterm fitness of populations (1-5). Many studies on the role of dNTPs have been conducted with the bacterial model Escherichia coli, and these studies have contributed to our understanding of DNA metabolism and other aspects of cellular physiology. Examples are the effects of dNTPs on replication fork progress (6), progress through the cell cycle (7, 8), regulation of the error-prone SOS system (9), and the bacterial mutation rate (...

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Glucose- and Glucokinase-ControlledmalGene Expression inEscherichia coli

Cited by 22 publications

References 60 publications

Structural Basis for the Interconversion of Maltodextrins by MalQ, the Amylomaltase of Escherichia coli

Structural Basis for the Interconversion of Maltodextrins by MalQ, the Amylomaltase of Escherichia coli

Role of Maltose Enzymes in Glycogen Synthesis by Escherichia coli

Transcriptome Analysis of Escherichia coli during dGTP Starvation

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