title: Aeromonas salmonicida possesses two genes encoding homologs of the major outer membrane protein, OmpA.
abstract: Two homologs of the outer membrane protein OmpA were identified in Aeromonas salmonicida by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, immunoblotting, and amino-terminal sequence analyses. An A. salmonicida genomic DNA library was constructed by using lambda GEM-11 and recombinant phage carrying both genes ompAI and ompAII) selected by immunoscreening. A 5.0-kb BamHI fragment containing the two genes in tandem was subcloned in pBluescript and used for further subcloning and sequencing of the genes. The encoded proteins (Mr = 33,564 and 32,536 for mature OmpAI and OmpAII, respectively) had only 64% identity with each other and otherwise had the highest level of homology to OmpA proteins from the members of the family Enterobacteriaceae. Based on the Escherichia coli OmpA model, an eight-stranded amphipathic beta-barrel model for the membrane assembly of the N-terminal half of OmpAI and OmpAII was predicted. Most variation between the two proteins was localized to the predicted surface loops and periplasmic turns, while the transmembrane strands and C-terminals domains were highly conserved. Expression of ompAI and ompAII separately in E. coli indicated that both genes could be independently transcribed from their own promoters and that both gene products were assembled into the E. coli outer membrane. A survey of different Aeromonas spp. by PCR revealed that possession of two tandem ompA genes was widespread among this genus. This is the first report of any bacterial species possessing two genes for homologs of this major outer membrane protein.
authors.affiliation: School of Animal and Microbial Sciences, University of Reading, UK.
authors.forename: G M
authors.initials: GM
authors.lastname: Costello
authors.forename: R
authors.initials: R
authors.lastname: Vipond
authors.forename: S
authors.initials: S
authors.lastname: MacIntyre
mesh_terms: D000333:Aeromonas / Q000235:genetics*; D000595:Amino Acid Sequence; D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D005810:Multigene Family; D018272:Porins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000096:biosynthesis; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D018272:Porins; D011994:Recombinant Proteins