Mutations that alter the regulation of the chb operon of Escherichia coli allow utilization of cellobiose

Kachroo, Aashiq H.; Kancherla, Aswani K.; Singh, N. S.; Varshney, Umesh; Mahadevan, S.

doi:10.1111/j.1365-2958.2007.05999.x

Cited by 27 publications

(32 citation statements)

References 28 publications

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“…Strains used were MA9655 (chiQ-lacZ), MA9841 (chiQ-lacZ DchiX), and MA9923 (DchiP chiQ-lacZ). (Plumbridge and Pellegrini 2004;Kachroo et al 2007). Conceivably, the two conditional ChbR alleles described above (S135L and N238Y) may mimic the allosteric change at low temperature in the absence of inducers.…”

Section: Chip Is An Inducible Chitoporinmentioning

confidence: 99%

Caught at its own game: regulatory small RNA inactivated by an inducible transcript mimicking its target

Figueroa‐Bossi¹,

Valentini²,

Malleret³

et al. 2009

Genes Dev.

208

254

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A relevant, yet little recognized feature of antisense regulation is the possibility of switching roles between regulatory and regulated RNAs. Here we show that induction of a Salmonella gene relies on the conversion of a small RNA from effector to regulatory target. The chiP gene (formerly ybfM), identified and characterized in the present study, encodes a conserved enterobacterial chitoporin required for uptake of chitin-derived oligosaccharides. In the absence of inducer, chiP is kept silent by the action of a constitutively made small RNA, ChiX (formerly SroB, RybC), which pairs with a sequence at the 59 end of chiP mRNA. Silencing is relieved in the presence of chitooligosaccharides due to the accumulation of an RNA that pairs with ChiX and promotes its degradation. Anti-ChiX RNA originates from an intercistronic region of the chb operon, which comprises genes for chitooligosaccharide metabolism and whose transcription is activated in the presence of these sugars. We present evidence suggesting that the chb RNA destabilizes ChiX sRNA by invading the stem of its transcription terminator hairpin. Overall, our findings blur the distinction between effector and target in sRNA regulation, raising the possibility that some of the currently defined targets could actually be inhibitors of sRNA function.[Keywords: Antisense regulation; chitoporin; chitobiose; Hfq; small RNA] Supplemental material is available at http://www.genesdev.org.

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Section: Chip Is An Inducible Chitoporinmentioning

confidence: 99%

Caught at its own game: regulatory small RNA inactivated by an inducible transcript mimicking its target

Figueroa‐Bossi¹,

Valentini²,

Malleret³

et al. 2009

Genes Dev.

208

254

View full text Add to dashboard Cite

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“…SWNT caused about 1.2 fold increase in cell lysis over MWNT-1 and 2.5 fold increase over MWNT-2. The enzyme activity measured in strain prpoS:lacZ was much higher than in strain pchbB:lacZ, which is almost certainly due to the different strength of the two promoters (the rpoS promoter being stronger than the chbB promoter); [26,27].…”

Section: Discussionmentioning

confidence: 99%

β-Galactosidase Leakage from Escherichia coli Points to Mechanical Damageas Likely Cause of Carbon Nanotube Toxicity

Amarnath¹,

Hussain²,

Nanjundiah³

et al. 2012

SNL

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We show that the cytotoxic effect of carbon nanotubes (CNTs) on bacteria is mediated by mechanical damage to the cell wall and membrane. Two β-galactosidase-producing strains of Escherichia coli harboringgenomically integrated reporter gene constructs, namely pchbB:lacZ and prpoS:lacZ, were used for the purpose. We first verified that CNTs result in an inhibition of cell growth. Enzyme activity was determined using a reporter gene assay in which CNTs were used without the lysis buffer (containing detergent). β-galactosidase activity in the presence of CNTs alone measured several fold more than the controls used (without nanotubes). This suggests that CNTs damage the cell membrane in a manner similar to the detergent in the lysis buffer and render E. coli cell walls porous, causing cell contents including enzymes to leak out into the medium. Our results support the hypothesis that mechanical damage to bacterial cell membranes is the prevailing cause of CNT-cytotoxicity.

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“…The presence of the chbR-N238S allele was verified by mismatch amplification mutation assay PCR (MAMA-PCR) (16). Similarly, strains JM-Rji90, JM-Rji91, JM-Rji92, and JM-Rji94 were constructed by replacing the wild-type chbR locus of JM-Rji84 with the chbR-K184E, chbR-N137K, chbR-F146L, and chbR-S135A alleles, respectively, amplified from Cel ϩ mutants (29). However, upon sequencing the chbR locus from strains selected on M9 minimal cellobiose medium, it was found that JM-Rji91 carries the chbR-K184E mutation in addition to the chbR-N137K and JM-Rji94 carries the chbR-S134P instead of S135A.…”

Section: Methodsmentioning

confidence: 99%

“…The presence of chitobiose abrogates NagC-mediated repression and produces an activating signal for ChbR that along with CRP-cAMP activates transcription from the chb promoter (45). The chb operon has also been shown to be involved in the utilization of cellobiose, a disaccharide of glucose, in E. coli strains carrying mutations that alter the regulation of the operon (29).…”

mentioning

confidence: 99%

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

Verma

Mahadevan

2012

J. Bacteriol.

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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 thatchbGencodes a monodeacetylase that is essential for growth on the acetylated chitooligosaccharides chitobiose and chitotriose but is dispensable for growth on cellobiose and chitosan dimer, the deacetylated form of chitobiose. The predicted active site of the enzyme was validated by demonstrating loss of function upon substitution of its putative metal-binding residues that are conserved across the YdjC family of proteins. We show that activation of thechbpromoter by the regulatory protein ChbR is dependent on ChbG, suggesting that deacetylation of chitobiose-6-P and chitotriose-6-P is necessary for their recognition by ChbR as inducers. Strains carrying mutations inchbRconferring the ability to grow on both cellobiose and chitobiose are independent ofchbGfunction for induction, suggesting that gain of function mutations in ChbR allow it to recognize the acetylated form of the oligosaccharides. ChbR-independent expression of the permease and phospho-β-glucosidase from a heterologous promoter did not support growth on both chitobiose and chitotriose in the absence ofchbG, suggesting an additional role ofchbGin the hydrolysis of chitooligosaccharides. The homologs ofchbGin metazoans have been implicated in development and inflammatory diseases of the intestine, indicating that understanding the function ofE. colichbGhas a broader significance.

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Mutations that alter the regulation of the chb operon of Escherichia coli allow utilization of cellobiose

Cited by 27 publications

References 28 publications

Caught at its own game: regulatory small RNA inactivated by an inducible transcript mimicking its target

Caught at its own game: regulatory small RNA inactivated by an inducible transcript mimicking its target

<i>β</i>-Galactosidase Leakage from <i>Escherichia coli</i> Points to Mechanical Damageas Likely Cause of Carbon Nanotube Toxicity

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

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Mutations that alter the regulation of the chb operon of Escherichia coli allow utilization of cellobiose

Cited by 27 publications

References 28 publications

Caught at its own game: regulatory small RNA inactivated by an inducible transcript mimicking its target

Caught at its own game: regulatory small RNA inactivated by an inducible transcript mimicking its target

&lt;i&gt;β&lt;/i&gt;-Galactosidase Leakage from &lt;i&gt;Escherichia coli&lt;/i&gt; Points to Mechanical Damageas Likely Cause of Carbon Nanotube Toxicity

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

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<i>β</i>-Galactosidase Leakage from <i>Escherichia coli</i> Points to Mechanical Damageas Likely Cause of Carbon Nanotube Toxicity