The<i>chbG</i>Gene of the Chitobiose (<i>chb</i>) Operon of Escherichia coli Encodes a Chitooligosaccharide Deacetylase

Verma, Subhash C.; Mahadevan, S.

doi:10.1128/jb.00533-12

Cited by 32 publications

(41 citation statements)

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“…S1A in the supplemental material). The chb locus was chosen to target fhs because the whole locus, including the promoter and operator, could be deleted without a consequence for our investigation (29). The single-copy integration of fhs (linked to the kan marker) in the genome of E. coli TG1 ⌬folD-fhs-kan (referred to as the ⌬folD-fhs strain) was also confirmed by PCR, resulting in a 3.9-kb amplicon (as opposed to 3.3-kb amplicon for the wild-type locus) using Ch-KI-C-FP and Ch-KI-C-RP primers (see Fig.…”

Section: Resultsmentioning

confidence: 99%

One-Carbon Metabolic Pathway Rewiring in Escherichia coli Reveals an Evolutionary Advantage of 10-Formyltetrahydrofolate Synthetase (Fhs) in Survival under Hypoxia

et al. 2015

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bIn cells, N 10 -formyltetrahydrofolate (N 10 -fTHF) is required for formylation of eubacterial/organellar initiator tRNA and purine nucleotide biosynthesis. Biosynthesis of N 10 -fTHF is catalyzed by 5,10-methylene-tetrahydrofolate dehydrogenase/cyclohydrolase (FolD) and/or 10-formyltetrahydrofolate synthetase (Fhs). All eubacteria possess FolD, but some possess both FolD and Fhs. However, the reasons for possessing Fhs in addition to FolD have remained unclear. We used Escherichia coli, which naturally lacks fhs, as our model. We show that in E. coli, the essential function of folD could be replaced by Clostridium perfringens fhs when it was provided on a medium-copy-number plasmid or integrated as a single-copy gene in the chromosome. The fhs-supported folD deletion (⌬folD) strains grow well in a complex medium. However, these strains require purines and glycine as supplements for growth in M9 minimal medium. The in vivo levels of N 10 -fTHF in the ⌬folD strain (supported by plasmid-borne fhs) were limiting despite the high capacity of the available Fhs to synthesize N 10 -fTHF in vitro. Auxotrophy for purines could be alleviated by supplementing formate to the medium, and that for glycine was alleviated by engineering THF import into the cells. The ⌬folD strain (harboring fhs on the chromosome) showed a high NADP ؉ -to-NADPH ratio and hypersensitivity to trimethoprim. The presence of fhs in E. coli was disadvantageous for its aerobic growth. However, under hypoxia, E. coli strains harboring fhs outcompeted those lacking it. The computational analysis revealed a predominant natural occurrence of fhs in anaerobic and facultative anaerobic bacteria.T he pathway of one-carbon metabolism is central to the synthesis of purine nucleotides, thymidylate, glycine, and methionine (Fig. 1). The enzymes that catalyze interconversions of the pathway intermediates are highly conserved across the three domains of life (1-6). Serine hydroxymethyltransferase (GlyA) catalyzes the reversible reaction of conversion of serine and tetrahydrofolate (THF) to glycine and 5,10-methylene-tetrahydrofolate (5,10-CH 2 -THF) (7). FolD, a bifunctional enzyme, carries out sequential steps of reversible conversions of 5,10-CH 2 -THF to 5,10-methenyltetrahydrofolate (5,10-CH ϩ -THF), followed by the conversion of the latter to N 10 -formyltetrahydrofolate (N 10 -fTHF) by its dehydrogenase and cyclohydrolase activities, respectively (8). Availability of N 10 -fTHF is crucial for the de novo pathway of purine nucleotide biosynthesis and formylation of the initiator tRNA (tRNA fMet ) to initiate protein synthesis in eubacteria and eukaryotic organelles (9). N 10 -fTHF can also be synthesized by formyltetrahydrofolate synthetase, Fhs (also known as formate-tetrahydrofolate ligase), by utilizing THF, formate, and ATP (Fig. 1). The dual scheme of N 10 -fTHF synthesis is conserved in eukaryotes and some archaea (6). Many eukaryotic organisms possess FolD with trifunctional activities of dehydrogenase-cyclohydrolase-synthetase (10, 11). Among eubacter...

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Section: Resultsmentioning

confidence: 99%

One-Carbon Metabolic Pathway Rewiring in Escherichia coli Reveals an Evolutionary Advantage of 10-Formyltetrahydrofolate Synthetase (Fhs) in Survival under Hypoxia

et al. 2015

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“…This operon encodes proteins involved in uptake and degradation of chitobiose, a β -(1,4)-linked dimer of GlcNAc, which is present in the environment as a result of the breakdown of chitin by chitinases [90]. The chb operon is also repressed by the dual function regulator ChbR [91]. In the absence of chitobiose, both NagC and ChbR act as repressors.…”

Section: Bacterial Glcnac Pathwaysmentioning

confidence: 99%

N-Acetylglucosamine Functions in Cell Signaling

2012

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The amino sugar N-acetylglucosamine (GlcNAc) is well known for the important structural roles that it plays at the cell surface. It is a key component of bacterial cell wall peptidoglycan, fungal cell wall chitin, and the extracellular matrix of animal cells. Interestingly, recent studies have also identified new roles for GlcNAc in cell signaling. For example, GlcNAc stimulates the human fungal pathogen Candida albicans to undergo changes in morphogenesis and expression of virulence genes. Pathogenic E. coli responds to GlcNAc by altering the expression of fimbriae and CURLI fibers that promote biofilm formation and GlcNAc stimulates soil bacteria to undergo changes in morphogenesis and production of antibiotics. Studies with animal cells have revealed that GlcNAc influences cell signaling through the posttranslational modification of proteins by glycosylation. O-linked attachment of GlcNAc to Ser and Thr residues regulates a variety of intracellular proteins, including transcription factors such as NFκB, c-myc, and p53. In addition, the specificity of Notch family receptors for different ligands is altered by GlcNAc attachment to fucose residues in the extracellular domain. GlcNAc also impacts signal transduction by altering the degree of branching of N-linked glycans, which influences cell surface signaling proteins. These emerging roles of GlcNAc as an activator and mediator of cellular signaling in fungi, animals, and bacteria will be the focus of this paper.

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“…In Citrobacter rodentium, the hpnK homologue is annotated as a chitobiose-phosphate hydrolase (chbG). A study of chbG in Escherichia coli demonstrates that this gene encodes a monodeacetylase that acts on chitooligosaccharide substrates similar in structure to acetylglucosamine (Verma and Mahadevan, 2012). BLASTp analysis of E. coli ChbG against the B. cenocepacia J2315 protein database identifies HpnK as the polypeptide providing the most significant alignment (E-value 4e −15 ).…”

Section: Hpni and Hpnk Are Required For Bht Glucosamine Productionmentioning

confidence: 99%

Elucidation of the Burkholderia cenocepacia hopanoid biosynthesis pathway uncovers functions for conserved proteins in hopanoid‐producing bacteria

Schmerk

Welander

Hamad

et al. 2014

Environmental Microbiology

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This is the pre-peer reviewed version of the following article: Schmerk, C. L., Welander, P. V., Hamad, M. A., Bain, K. L., Bernards, M. A., Summons, R. E. and Valvano, M. A. (2015), Elucidation of the Burkholderia cenocepacia hopanoid biosynthesis pathway uncovers functions for conserved proteins in hopanoid-producing bacteria. Environmental Microbiology, 17: 735-750, which has been published in final form at http://onlinelibrary.wiley.com/wol1/doi/10.1111/1462-2920.12509/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving. General rightsCopyright for the publications made accessible via the Queen's University Belfast Research Portal is retained by the author(s) and / or other copyright owners and it is a condition of accessing these publications that users recognise and abide by the legal requirements associated with these rights.Take down policy The Research Portal is Queen's institutional repository that provides access to Queen's research output. Every effort has been made to ensure that content in the Research Portal does not infringe any person's rights, or applicable UK laws. If you discover content in the Research Portal that you believe breaches copyright or violates any law, please contact openaccess@qub.ac.uk. grow under any stress condition tested, whereas ΔhpnI, ΔhpnJ, and ΔhpnK displayed wild type 42 growth rates when exposed to detergent, but varying levels of sensitivity to low pH and 43 polymyxin B. This study not only elucidates the biosynthetic pathway of hopanoids in B. 44 cenocepacia, but also uncovers a biosynthetic role for the conserved proteins HpnI, HpnJ, and 45

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ThechbGGene of the Chitobiose (chb) Operon of Escherichia coli Encodes a Chitooligosaccharide Deacetylase

Abstract: ABSTRACTThechboperon ofEscherichia coliis involved in the utilization of the β-glucosides chitobiose and cellobiose. The function ofchbG(ydjC), the sixth open reading frame of the operon that codes for an evolutionarily conserved protein is unknown. We show that Show more

Cited by 32 publications

References 60 publications

One-Carbon Metabolic Pathway Rewiring in Escherichia coli Reveals an Evolutionary Advantage of 10-Formyltetrahydrofolate Synthetase (Fhs) in Survival under Hypoxia

One-Carbon Metabolic Pathway Rewiring in Escherichia coli Reveals an Evolutionary Advantage of 10-Formyltetrahydrofolate Synthetase (Fhs) in Survival under Hypoxia

N-Acetylglucosamine Functions in Cell Signaling

Elucidation of the Burkholderia cenocepacia hopanoid biosynthesis pathway uncovers functions for conserved proteins in hopanoid‐producing bacteria

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