title: OmpA of a septicemic Escherichia coli O78--secretion and convergent evolution.
abstract: OmpA is an important constituent of the outer membrane of Gram-negative bacteria. OmpA is involved in a variety of host-bacteria interactions, including crossing of the blood-brain barrier by E. coli strains causing newborn meningitis, and elicits a significant response by the immune system of the host. The bactericidal effect of neutrophil elastase (NE) is also attributed to degradation of the bacterial OmpA. Here we examined the OmpA of septicemic E. coli 078 strains and show that two surface-exposed loops are conserved among invasive strains of E. coli and other pathogenic Enterobacteriaceae. In addition, there is evidence for convergent evolution, implying the existence of selective pressure. Our results also indicate that large quantities of OmpA are secreted into the medium during all phases of growth, where it is present both in secreted vesicles and as a soluble secreted protein. We assume that secreted OmpA can play a role in protection of bacteria from NE by competitive inhibition. Support for this assumption was obtained from experiments indicating that addition of exogenous, purified OmpA reduces killing of bacteria by NE.
authors.affiliation: Department of Molecular Microbiology and Biotechnology, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel.
authors.forename: Uri
authors.initials: U
authors.lastname: Gophna
authors.forename: Diana
authors.initials: D
authors.lastname: Ideses
authors.forename: Ran
authors.initials: R
authors.lastname: Rosen
authors.forename: Adam
authors.initials: A
authors.lastname: Grundland
authors.forename: Eliora Z
authors.initials: EZ
authors.lastname: Ron
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D016470:Bacteremia / Q000382:microbiology*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli / Q000145:classification* / Q000235:genetics; D004927:Escherichia coli Infections / Q000382:microbiology; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism*; D019143:Evolution, Molecular; D006801:Humans; D019272:Leukocyte Elastase / Q000378:metabolism; D008969:Molecular Sequence Data; D009504:Neutrophils / Q000201:enzymology; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D012703:Serotyping
chemical_list: D001425:Bacterial Outer Membrane Proteins; D029968:Escherichia coli Proteins; C078167:OMPA outer membrane proteins; D019272:Leukocyte Elastase