title: Analysis of Edwardsiella tarda DegP, a serine protease and a protective immunogen.
abstract: Edwardsiella tarda is a severe aquaculture pathogen with a broad host range that includes humans, animal, and fish. A gene (degP(Et)) encoding a DegP homologue was cloned from TX01, a pathogenic E. tarda strain isolated from diseased fish. DegP(Et) shares high sequence identities with the DegP proteins of several bacterial species. Functional analyses showed that degP(Et) could complement the temperature-sensitive phenotype of an Escherichia coli degP null mutant. Expression of degP(Et) in TX01 was modulated by growth phase and temperature, the latter possibly through the action of the sigma(E)-like factor. Overexpression of degP(Et) (i) enhanced the ability of TX01 to disseminate in fish blood at the advanced stage of infection, (ii) heightened the activity of type 2 autoinducer, and (iii) increased the expression of luxS and the genes encoding components of the virulence-associated type III secretion system. Recombinant DegP(Et) purified from E. coli was a serine protease that exhibited maximum activity at 40 degrees C and pH8.0. The proteolytic activity of recombinant DegP(Et) depended on the catalytic triad and the PDZ domains. Immunoprotective analyses showed that purified recombinant DegP(Et) was a protective immunogen that could induce the production of specific serum antibodies and elicit strong protective immunity in fish vaccinated with DegP(Et).
authors.affiliation: Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, PR China; Graduate University of the Chinese Academy of Sciences, Beijing 100049, PR China.
authors.forename: Xu-dong
authors.initials: XD
authors.lastname: Jiao
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Shuang
authors.initials: S
authors.lastname: Cheng
authors.forename: Li
authors.initials: L
authors.lastname: Sun
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001428:Bacterial Vaccines / Q000276:immunology*; D004252:DNA Mutational Analysis; D020609:Edwardsiella tarda / Q000235:genetics* / Q000276:immunology*; D004756:Enterobacteriaceae Infections / Q000276:immunology / Q000517:prevention & control / Q000662:veterinary*; D004926:Escherichia coli / Q000378:metabolism; D005393:Fish Diseases / Q000517:prevention & control*; D005432:Flounder; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000276:immunology*; D033903:Periplasmic Proteins / Q000235:genetics* / Q000276:immunology*; D011994:Recombinant Proteins / Q000276:immunology; D012689:Sequence Homology, Nucleic Acid; D012697:Serine Endopeptidases / Q000235:genetics* / Q000276:immunology*; D013696:Temperature; D013997:Time Factors
chemical_list: D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D006360:Heat-Shock Proteins; D033903:Periplasmic Proteins; D011994:Recombinant Proteins; C061682:DegP protease; D012697:Serine Endopeptidases