Document Detail

GadE (YhiE) activates glutamate decarboxylase-dependent acid resistance in Escherichia coli K-12.
MedLine Citation:
PMID:  12940989     Owner:  NLM     Status:  MEDLINE    
Commensal and pathogenic strains of Escherichia coli possess three inducible acid resistance systems that collaboratively protect cells against acid stress to pH 2 or below. The most effective system requires glutamate in the acid challenge media and relies on two glutamate decarboxylases (GadA and B) combined with a putative glutamate:gamma-aminobutyric acid antiporter (GadC). A complex network of regulators mediates induction of this system in response to various media, pH and growth phase signals. We report that the LuxR-like regulator GadE (formerly YhiE) is required for expression of gadA and gadBC regardless of media or growth conditions. This protein binds directly to the 20 bp GAD box sequence found in the control regions of both loci. Two previously identified AraC-like regulators, GadX and GadW, are only needed for gadA/BC expression under some circumstances. Overexpression of GadX or GadW will not overcome a need for GadE. However, overexpression of GadE can supplant a requirement for GadX and W. Data provided also indicate that GadX and GadE can simultaneously bind the area around the GAD box region and probably form a complex. The gadA, gadBC and gadE genes are all induced by low pH in exponential phase cells grown in minimal glucose media. The acid induction of gadA/BC results primarily from the acid induction of gadE. Constitutive expression of GadE removes most pH control over the glutamate decarboxylase and antiporter genes. The small amount of remaining pH control is governed by GadX and W. The finding that gadE mutations also diminish the effectiveness of the other two acid resistance systems suggests that GadE influences the expression of additional acid resistance components. The number of regulatory proteins (five), sigma factors (two) and regulatory feedback loops focused on gadA/BC expression make this one of the most intensively regulated systems in E. coli.
Zhuo Ma; Shimei Gong; Hope Richard; Don L Tucker; Tyrrell Conway; John W Foster
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Molecular microbiology     Volume:  49     ISSN:  0950-382X     ISO Abbreviation:  Mol. Microbiol.     Publication Date:  2003 Sep 
Date Detail:
Created Date:  2003-08-27     Completed Date:  2003-12-15     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8712028     Medline TA:  Mol Microbiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  1309-20     Citation Subset:  IM    
Department of Microbiology and Immunology, University of South Alabama College of Medicine, Mobile, AL 36688, USA.
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MeSH Terms
Antiporters / genetics,  metabolism
AraC Transcription Factor / genetics,  metabolism
Bacterial Proteins*
Blotting, Northern
Blotting, Western
Electrophoretic Mobility Shift Assay
Escherichia coli / genetics*,  metabolism*
Escherichia coli Proteins / genetics,  metabolism
Gene Deletion
Gene Expression Regulation, Bacterial
Genes, Bacterial
Genes, Regulator
Glutamate Decarboxylase / genetics,  metabolism*
Hydrogen-Ion Concentration
Membrane Proteins / genetics,  metabolism
Promoter Regions, Genetic
Regulatory Sequences, Nucleic Acid
Transcription Factors
Grant Support
Reg. No./Substance:
0/Antiporters; 0/AraC Transcription Factor; 0/Bacterial Proteins; 0/Escherichia coli Proteins; 0/GadC protein, bacteria; 0/GadE protein, E coli; 0/GadW protein, E coli; 0/GadX protein, E coli; 0/Membrane Proteins; 0/Transcription Factors; 0/xasA protein, E coli; EC 4.1.1.-/gadA protein, E coli; EC Decarboxylase

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