Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023241 (Legionella)
 6,990 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Flagellin gene regulation in Legionella pneumophila is modulated by various environmental factors. The expression of the virulent phenotype seems to be linked genetically to flagellum expression. To better understand the mechanisms of flagellin gene expression in L. pneumophila (Lp), we screened a pool of plasmids from a L. pneumophila Corby genomic library for the ability to prevent or reduce luciferase activity in the Escherichia coli strain YK410, which harbours a Lp-pflaA-luxAB fusion. We cloned a DNA fragment encoding the N-terminal part of a protein with significant similarity to members of the LysR family of transcriptional regulators (LTTRs). The entire gene, cloned by inverse PCR, was named flaR. It encodes a protein of 302 amino acids, and computer-assisted analysis of the amino acid sequence revealed a helix-turn-helix motif located near the N-terminus of the protein. The FlaR protein exhibits 21-31% identity to various LTTRs. Furthermore, gel retardation experiments indicate that the FlaR protein is able to bind to its own promoter region and, to a lesser extent, to the flaA promoter of L. pneumophila. The flaR promoter region contains putative LysR binding motifs and two putative Fur boxes. Taken together, these results indicate that FlaR is a DNA-binding protein which belongs to the LTTR family. Southern analysis with a L. pneumophila Corby-specific flaR probe revealed homologous genes in various L. pneumophila strains, but not in the 12 nonpneumophila strains tested so far.
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PMID:Cloning and characterization of a Legionella pneumophila-specific gene encoding a member of the LysR family of transcriptional regulators. 1101 50

To survive in host cells, intracellular pathogens or symbiotic bacteria require protective mechanisms to overcome the oxidative stress generated by phagocytic activities of the host. By genomic library tagging, we cloned a dps (stands for DNA-binding protein from starved cells) gene of the symbiotic "Candidatus Legionella jeonii" organism (called the X bacterium) (dps(X)) that grows in Amoeba proteus. The gene encodes a 17-kDa protein (pI 5.19) with 91% homology to Dps and DNA-binding ferritin-like proteins of other organisms. The cloned gene complemented the dps mutant of Escherichia coli and conferred resistance to hydrogen peroxide. Dps(X) proteins purified from E. coli transformed with the dps(X) gene were in oligomeric form, formed a complex with pBlueskript SKII DNA, and protected the DNA from DNase I digestion and H(2)O(2)-mediated damage. The expression of the dps(X) gene in "Candidatus Legionella jeonii" was enhanced when the host amoeba was treated with 2 mM H(2)O(2) and by phagocytic activities of the host cell. These results suggested that the Dps protein has a function protective of the bacterial DNA and that its gene expression responds to oxidative stress generated by phagocytic activities of the host cell. With regard to the fact that invasion of Legionella sp. into respiratory phagocytic cells causes pneumonia in mammals, further characterization of dps(X) expression in the Legionella sp. that multiplies in a protozoan host in the natural environment may provide valuable information toward understanding the protective mechanisms of intracellular pathogens.
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PMID:The dps gene of symbiotic "Candidatus Legionella jeonii" in Amoeba proteus responds to hydrogen peroxide and phagocytosis. 1695 Sep 18