title: Evidence for a ninth gene, ptlI, in the locus encoding the pertussis toxin secretion system of Bordetella pertussis and formation of a PtlI-PtlF complex.
abstract: The pertussis toxin secretion system of Bordetella pertussis initially was thought to comprise eight proteins, PtlA-PtlH. We have investigated the existence of another protein, PtlI, encoded by a putative gene located between ptlD and ptlE. A B. pertussis strain expressing a ptlI::phoA translational fusion possessed alkaline phosphatase activity, suggesting that ptlI encodes a protein. In B. pertussis, a protein with an apparent molecular weight of approximately 5,200 (similar to that predicted by the ptlI sequence) was immunoreactive with an antibody raised to a PtlI-maltose-binding protein fusion protein. PtlE expression in a mutant sustaining an in-frame deletion in ptlI indicated that ptlE starts further downstream than initially predicted. PtlF, not detected in the ptlI deletion mutant, was restored partially by expressing ptlI in trans. A 36-kDa species, consistent with a PtlI-PtlF complex, was immunoreactive with antibodies to PtlI and PtlF in nonreduced cell extracts of a Bordetella bronchiseptica strain which overexpresses the Ptl proteins. Upon dithiothreitol treatment, the 36-kDa species was diminished greatly or undetectable. In B. pertussis, PtlI and PtlF co-precipitated with antibody to PtlF. These findings demonstrate the existence of PtlI and a PtlI-PtlF complex, providing the first description of an interaction between Ptl proteins.
authors.affiliation: Division of Bacterial Products, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892, USA.
authors.forename: K M
authors.initials: KM
authors.lastname: Farizo
authors.forename: T G
authors.initials: TG
authors.lastname: Cafarella
authors.forename: D L
authors.initials: DL
authors.lastname: Burns
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D001886:Bordetella pertussis / Q000235:genetics* / Q000378:metabolism; D004229:Dithiothreitol / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D007163:Immunosorbent Techniques; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D037342:Pertussis Toxin; D010566:Virulence Factors, Bordetella / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D008565:Membrane Proteins; C102588:PtlI protein, Bordetella pertussis; D010566:Virulence Factors, Bordetella; C094736:ptlF protein, Bordetella pertussis; D037342:Pertussis Toxin; D004229:Dithiothreitol