Physiological role of GlpB of anaerobic glycerol-3-phosphate dehydrogenase of<i>Escherichia coli</i>

Varga, Monica E. R.; Weiner, Joël H.

doi:10.1139/o95-018

Cited by 28 publications

(19 citation statements)

References 26 publications

(24 reference statements)

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“…S1 in the supplemental material). In contrast to the haloarchaea, the latter archaea do not encode homologs of the bacterial GlpB or GlpC proteins, which (in addition to GlpA) are essential for the anaerobic growth of E. coli on G3P (31). Thus, among the archaea, only the haloarchaea appear to encode bacterial protein-like G3PDH complexes in addition to homologs of bacterial glycerol kinase and PTS components, including a putative PEP:PTS-dependent DHA kinase (27).…”

Section: Resultsmentioning

confidence: 98%

Activity and Transcriptional Regulation of Bacterial Protein-Like Glycerol-3-Phosphate Dehydrogenase of the Haloarchaea in Haloferax volcanii

2011

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Glycerol is a primary energy source for heterotrophic haloarchaea and a major component of "salty" biodiesel waste. Glycerol is catabolized solely by glycerol kinase (encoded by glpK) to glycerol-3-phosphate (G3P) in Haloferax volcanii. Here we characterized the next critical step of this metabolic pathway: the conversion of G3P to dihydroxyacetone phosphate by G3P dehydrogenase (G3PDH). H. volcanii harbors two putative G3PDH operons: (i) glpA1B1C1, located on the chromosome within the neighborhood of glpK, and (ii) glpA2B2C2, on megaplasmid pHV4. Analysis of knockout strains revealed that glpA1 (and not glpA2) is required for growth on glycerol. However, both glpA1 and glpA2 could complement a glpA1 knockout strain (when expressed from a strong promoter in trans) and were required for the total G3PDH activity of cell lysates. The glpA1B1C1, glpK, glpF (encoding a putative glycerol facilitator), and ptsH2 (encoding a homolog of the bacterial phosphotransferase system protein Hpr) genes were transcriptionally linked and appeared to be under the control of a strong, G3P-inducible promoter upstream of glpA1. Overall, this study provides fundamental insights into glycerol metabolism in H. volcanii and enhances our understanding of central metabolic pathways of haloarchaea.Glycerol is a highly abundant energy source in hypersaline environments as a result of leakage from and lysis of Dunaliella cells, which are known to accumulate glycerol in molar quantities as an organic, osmotic solute (3,5,7,32). Thus, glycerol is a primary energy source for heterotrophic members of this community.In biological systems, glycerol is metabolized to dihydroxyacetone phosphate (DHAP) by one of two routes: (i) phosphorylation by glycerol kinase and subsequent conversion of sn-glycerol-3-phosphate (G3P) into DHAP through G3P dehydrogenase (G3PDH) or (ii) oxidation by glycerol dehydrogenase to form dihydroxyacetone (DHA), which is subsequently phosphorylated by an ATP-dependent or phosphoenolpyruvate:phosphotransferase system (PEP:PTS)-dependent DHA kinase to form DHAP. Once generated from glycerol, DHAP can be channeled into metabolic intermediates, including pyruvate, G3P, and/or sn-glycerol-1-phosphate (G1P).Recently, we demonstrated through Haloferax volcanii that haloarchaea require glycerol kinase (encoded by glpK) for the catabolism of glycerol (27). These results suggest that (i) G3PDH is needed for glycerol metabolism and (ii) the homologs of bacterial PEP:PTS-dependent DHA kinase are not needed for glycerol catabolism in H. volcanii but may serve in the metabolism of DHA overflow products generated by other members of the hypersaline community, such as Dunaliella salina (4).In this study, we investigated the oxidation of G3P to DHAP by G3PDH, a metabolic step likely to be central to glycerol catabolism and subsequent to the phosphorylation of glycerol by glycerol kinase in haloarchaea. Since archaea use G1PDH (encoded by egsA) to convert DHAP to G1P for the biosynthesis of phospholipids, G3PDH homologs are not common in this d...

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Section: Resultsmentioning

confidence: 98%

Activity and Transcriptional Regulation of Bacterial Protein-Like Glycerol-3-Phosphate Dehydrogenase of the Haloarchaea in Haloferax volcanii

2011

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“…These compounds can be utilized as carbon sources for growth. In addition, EHEC can also use glycerol-3-phosphate as an electron donor for anaerobic respiration, where it is oxidized to dihydroxyacetone phosphate (DHAP) by glycerol-3-phosphate dehydrogenase and transfers electrons to the terminal reductases (33,34). Therefore, GlpT and UhpT are closely related to biological fitness for EHEC, and repression of their genes indeed imposes a metabolic burden (17,18).…”

Section: Discussionmentioning

confidence: 99%

Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions

Kurabayashi

Tanimoto

Fueki

et al. 2015

Antimicrob Agents Chemother

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Because a shortage of new antimicrobial agents is a critical issue at present, and with the spread of multidrug-resistant (MDR) pathogens, the use of fosfomycin to treat infections is being revisited as a "last-resort option." This drug offers a particular benefit in that it is more effective against bacteria growing under oxygen-limited conditions, unlike other commonly used antimicrobials, such as fluoroquinolones and aminoglycosides. In this study, we showed that Escherichia coli strains, including enterohemorrhagic E. coli (EHEC), were more susceptible to fosfomycin when grown anaerobically than when grown aerobically, and we investigated how the activity of this drug was enhanced during anaerobic growth of E. coli. Our quantitative PCR analysis and a transport assay showed that E. coli cells grown under anaerobic conditions had higher levels of expression of glpT and uhpT, encoding proteins that transport fosfomycin into cells with their native substrates, i.e., glycerol-3-phosphate and glucose-6-phosphate, and led to increased intracellular accumulation of the drug. Elevation of expression of these genes during anaerobic growth requires FNR, a global transcriptional regulator that is activated under anaerobic conditions. Purified FNR bound to DNA fragments from regions upstream of glpT and uhpT, suggesting that it is an activator of expression of glpT and uhpT during anaerobic growth. We concluded that the increased antibacterial activity of fosfomycin toward E. coli under anaerobic conditions can be attributed to elevated expression of GlpT and UhpT following activation of FNR, leading to increased uptake of the drug.

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“…5). In the case of the A. ambivalens SDH, these modules remained unassembled but for instance, in Thiol:fumarate reductase from M. thermoautotrophicum Marburg (43) and anaerobic sn-glycerol-3-phosphate dehydrogenase and Glicolate oxidase from E. coli (40,41,44,45), two of the modules fused and a single peptide holds the cysteine-motif as well as the iron sulfur clusters. In the case of the Hdr from M. thermoautotrophicum Marburg (46), the flavinic peptide bears additional iron-sulfur clusters while maintaining separated the remaining modules.…”

Section: Alternative Anchormentioning

confidence: 99%

Acidianus ambivalens Complex II Typifies a Novel Family of Succinate Dehydrogenases

Lemos

Gomes

Teixeira

2001

Biochemical and Biophysical Research Communications

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Physiological role of GlpB of anaerobic glycerol-3-phosphate dehydrogenase ofEscherichia coli

Cited by 28 publications

References 26 publications

Activity and Transcriptional Regulation of Bacterial Protein-Like Glycerol-3-Phosphate Dehydrogenase of the Haloarchaea in Haloferax volcanii

Activity and Transcriptional Regulation of Bacterial Protein-Like Glycerol-3-Phosphate Dehydrogenase of the Haloarchaea in Haloferax volcanii

Elevated Expression of GlpT and UhpT via FNR Activation Contributes to Increased Fosfomycin Susceptibility in Escherichia coli under Anaerobic Conditions

Acidianus ambivalens Complex II Typifies a Novel Family of Succinate Dehydrogenases

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