title: Release of pertussis toxin and its interaction with outer-membrane antigens.
abstract: The absence of subunit S3 in cell-associated pertussis toxin (PT) from a mutant of Bordetella pertussis which failed to produce cell-free toxin suggested that this subunit was involved in the release of PT into the culture medium. The addition of methylated beta-cyclodextrin (MCD) to the culture medium caused a small but consistent increase in the release of lipopolysaccharide (LPS) by four wild-type strains of B. pertussis. Since previous studies have shown that MCD also enhances the levels of PT in culture supernates, it seemed probable that the increased shedding of outer-membranes vesicles (OMV) may explain the increased levels of both cell-free PT and LPS. Release of PT was inhibited in media buffered with HEPES but was unaffected in Tris/HC1 buffer. This suggested that in addition to shedding of the outer membrane, increased permeability and greater destabilization of the outer membrane, as caused by Tris/HC1 buffer, may be important in the release of PT. Our data do not support the idea that PT is packaged into OMV because only an insignificant proportion (0.01%) of the total cell-free PT was associated with LPS. The association of PT with small micelles derived from outer-membrane amphiphiles may be more important since the LPS content of PT purified from culture supernates (containing no large OMV) was nearly 18% by weight.
mesh_terms: D000942:Antigens, Bacterial / Q000378:metabolism*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism*; D001886:Bordetella pertussis / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D008070:Lipopolysaccharides / Q000378:metabolism; D037342:Pertussis Toxin; D010566:Virulence Factors, Bordetella / Q000096:biosynthesis*
chemical_list: D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; D008070:Lipopolysaccharides; D010566:Virulence Factors, Bordetella; D037342:Pertussis Toxin