title: The dps gene of symbiotic "Candidatus Legionella jeonii" in Amoeba proteus responds to hydrogen peroxide and phagocytosis.
abstract: 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.
authors.affiliation: Department of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea.
authors.forename: Miey
authors.initials: M
authors.lastname: Park
authors.forename: Seong Tae
authors.initials: ST
authors.lastname: Yun
authors.forename: Sue-Yun
authors.initials: SY
authors.lastname: Hwang
authors.forename: Choong-Ill
authors.initials: CI
authors.lastname: Chun
authors.forename: Tae In
authors.initials: TI
authors.lastname: Ahn
mesh_terms: D000595:Amino Acid Sequence; D000656:Amoeba / Q000382:microbiology*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003001:Cloning, Molecular; D015169:Colony Count, Microbial; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D015870:Gene Expression; D005816:Genetic Complementation Test; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007875:Legionella / Q000187:drug effects / Q000235:genetics* / Q000502:physiology*; D008969:Molecular Sequence Data; D016877:Oxidants / Q000494:pharmacology*; D010587:Phagocytosis; D010802:Phylogeny; D011485:Protein Binding; D012329:RNA, Bacterial / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C083911:DPS protein, Bacteria; D016877:Oxidants; D012329:RNA, Bacterial; D012333:RNA, Messenger; D006861:Hydrogen Peroxide