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The Escherichia coli chromosome contains two distantly located genes, gadA and gadB, which encode biochemically undistinguishable isoforms of glutamic acid decarboxylase (Gad). The Gad reaction contributes to pH homeostasis by consuming intracellular H(+) and producing gamma-aminobutyric acid. This compound is exported via the protein product of the gadC(More)
Gel shift and DNase I footprinting experiments showed that Escherichia coli FIS (factor for inversion stimulation) protein binds to at least seven sites in the promoter region of hns. These sites extend from -282 to +25 with two sites, closely flanking the DNA bend located at -150 from the transcriptional startpoint, partly overlapping the H-NS binding(More)
The virulence gene icsA of Shigella flexneri encodes an invasion protein crucial for host colonization by pathogenic bacteria. Within the intergenic region virA-icsA, we have discovered a new gene that encodes a non-translated antisense RNA (named RnaG), transcribed in cis on the complementary strand of icsA. In vitro transcription assays show that RnaG(More)
Escherichia coli hns, encoding the abundant nucleoid protein H-NS, was subjected to site-directed mutagenesis either to delete Pro115 or to replace it with alanine. Unlike the wild-type protein, hyperproduction of the mutant proteins did not inhibit macromolecular syntheses, was not toxic to cells and caused a less drastic compaction of the nucleoid. Gel(More)
Proteins H-NS and Hha form a nucleoprotein complex that modulates expression of the thermoregulated hly operon of Escherichia coli. We have been able to identify two H-NS binding sites in the hly regulatory region. One of them partially overlaps the promoter region (site II), and the other is located about 2 kbp upstream (site I). In contrast, Hha protein(More)
The Escherichia coli hns gene, which encodes the nucleoid protein H-NS, was deprived of its natural promoter and placed under the control of the inducible lambda PL promoter. An hns mutant yielding a protein (H-NS delta 12) with a deletion of four amino acids (Gly112-Arg-Thr-Pro115) was also obtained. Overproduction of wild-type (wt) H-NS, but not of H-NS(More)
The expression of plasmid-borne virF of Shigella encoding a transcriptional regulator of the AraC family, is required to initiate a cascade of events resulting in activation of several operons encoding invasion functions. H-NS, one of the main nucleoid-associated proteins, controls the temperature-dependent expression of the virulence genes by repressing(More)
In the human enteropathogen Shigella transcription of virF, the primary regulator of the invasion functions, is strictly temperature-dependent and is antagonistically mediated by H-NS and FIS, which bind to specific sites on the virF promoter. Here we report on the relevance of DNA geometry to the thermoregulation of virF and demonstrate that the virF(More)
Expression of a promoterless cat gene fused to a DNA fragment of approximately 400 bp, beginning at -313 of Escherichia coli hns, was significantly repressed in E. coli and Salmonella typhimurium strains with wild-type hns but not in mutants carrying hns alleles. CAT expression from fusions containing a shorter (110 bp) segment of hns was essentially(More)
One of the most efficient systems of acid resistance in Escherichia coli, the gad system, is based on the coordinated action of two isoforms of glutamate decarboxylase (GadA and GadB) and of a specific glutamate/gamma-aminobutyrate antiporter (GadC). The gadA/BC genes, activated in response to acid stress and in stationary phase cells, are subjected to(More)