title: Outer membrane peptides of Yersinia pestis mediating siderophore-independent assimilation of iron.
abstract: It is established that wild-type cells of Yersinia pestis absorb exogenous hemin or Congo red and thus grow as pigmented colonies at 26 degrees C on media containing these chromatophores (Pgm+). Pgm+ isolated are known to possess a siderophore-independent mechanism of iron-transport (required for growth in iron-deficient medium) which is absent in avirulent Pgm- mutants. Production of the bacteriocin pesticin and linked invasins (Pst+) is an additional defined virulence factor of yersiniae; mutation of Pgm+,Pst- organisms to pesticin-resistance (Pstr) results in concomitant conversion to Pgm-. In this study, autoradiograms of two-dimensional gels of [35S]methionine-labeled outer membranes from Pgm- mutants were compared to those of the Pgm+,Pst+ or Pgm+,Pst- parent. An apparently single predominant peptide present in these preparations (greater than 10% of total membrane protein) existed as a family of iron-modifiable 17.9-kDa molecules focusing down to isoelectric points of about 4.6 and up to 5.89. Expression of eight detectable Pst(+)-specific peptides was not significantly influenced by exogenous iron. Pgm+ yersiniae constitutively produced pigmentation-specific peptide F and five iron-repressible peptides termed IrpA to IrpE. Typical spontaneous mutation to Pgm- resulted in loss of peptide F and IrpB-E. A rare Pgm+,Pstr mutant, selected on Congo red agar containing pesticin, also lost IrpB-E but retained peptide F. This isolate, like Pgm- mutants, failed to grow in iron-deficient medium. Regardless of phenotype, all yersiniae utilized hemin, hemopexin, myoglobin, hemoglobin, and ferritin, but not transferrin or lactoferrin, as sole sources of iron.
authors.affiliation: Department of Microbiology and Public Health, Michigan State University, East Lansing 48824.
authors.forename: D J
authors.initials: DJ
authors.lastname: Sikkema
authors.forename: R R
authors.initials: RR
authors.lastname: Brubaker
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001430:Bacteriocins / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000378:metabolism; D009154:Mutation; D010858:Pigmentation / Q000235:genetics / Q000502:physiology; D017262:Siderophores; D015010:Yersinia pestis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001430:Bacteriocins; D007502:Iron Chelating Agents; D017262:Siderophores; C011330:Pesticin; D007501:Iron