title: A C1q-binding 40 kDa porin from Aeromonas salmonicida: cloning, sequencing, role in serum susceptibility and fish immunoprotection.
abstract: A 40 kDa C1q-binding outer membrane protein from Aeromonas salmonicida was identified by direct-binding assay with biotinylated C1q, a subcomponent of the complement classical pathway component C1. The 40 kDa porin structural gene from the A450 A. salmonicida typical strain (A+:O+) was cloned in Escherichia coli and sequenced. The amino acid sequence of the 40 kDa A. salmonicida porin, its ability to bind C1q in an antibody independent process, and its immunological cross-reaction with the A. hydrophila AH-3 porin II, allow us to determine the role of this protein in serum susceptibility. Furthermore, we obtained defined A. salmonicida 40 kDa porin insertion mutants in serum sensitive or resistant strains, and we complemented these mutants with a plasmid harboring only the 40 kDa porin gene from A. salmonicida A450 in order to define its role as an important surface molecule involved in serum susceptibility and C1q binding. Similar complementation was obtained using the A. hydrophila AH-3 porin II gene. The 40 kDa porin gene and/or protein was present in all the A. salmonicida typical or atypical strains tested. Furthermore, the A. hydrophila AH-3 porin II seems to be an important molecule for fish immunoprotection against either A. salmonicida or A. hydrophila strains.
authors.affiliation: Departamento Microbiología, Facultad Biología, Universidad Barcelona, Diagonal 645, 08071 Barcelona, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Merino
authors.forename: Silvia
authors.initials: S
authors.lastname: Vilches
authors.forename: Rocío
authors.initials: R
authors.lastname: Canals
authors.forename: Silvia
authors.initials: S
authors.lastname: Ramirez
authors.forename: Juan M
authors.initials: JM
authors.lastname: Tomás
mesh_terms: D016980:Aeromonas hydrophila / Q000235:genetics / Q000276:immunology; D048409:Aeromonas salmonicida / Q000235:genetics / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000032:analysis / Q000737:chemistry / Q000235:genetics / Q000276:immunology; D001483:Base Sequence; D001770:Blood Bactericidal Activity; D003001:Cloning, Molecular; D015922:Complement C1q / Q000378:metabolism*; D003429:Cross Reactions; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016254:Mutagenesis, Insertional; D009154:Mutation; D017686:Oncorhynchus mykiss / Q000276:immunology*; D018272:Porins / Q000032:analysis / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D018272:Porins; D015922:Complement C1q