N-terminal characterization of the Bordetella pertussis filamentous haemagglutinin.
The major adhesin of Bordetella pertussis, filamentous haemagglutinin (FHA), is produced and secreted at high levels by the bacterium. Mature FHA derives from a large precursor, FhaB, that undergoes several post-translational maturations. In this work, we demonstrate by site-directed mutagenesis that the N-terminal signal peptide of FHA is composed of 71 amino acids, including a 22-residue-long 'N-terminal extension' sequence. This sequence, although highly conserved in various other secretory proteins, does not appear to play an essential part in FHA secretion, as shown by deletion mutagenesis. The entire N-terminal signal region of FhaB is removed in the course of secretion by proteolytic cleavage at a site that corresponds to a Lep signal peptidase recognition sequence. After this maturation, the N-terminal glutamine residue is modified to a pyroglutamate residue. This modification is not crucial for heparin binding, haemagglutination or secretion. Interestingly, however, the modification is absent from Escherichia coli secreted FHA derivatives. In addition, it is dependent in B. pertussis on the presence of all three cysteines contained in the signal peptide of FhaB. These observations suggest that it does not occur spontaneously but perhaps requires a specific enzymatic machinery.
INSERM U447, IBL, Institut Pasteur de Lille, France.
C
C
Lambert-Buisine
E
E
Willery
C
C
Locht
F
F
Jacob-Dubuisson
D018829:Adhesins, Bacterial / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D019677:Artificial Gene Fusion; D001886:Bordetella pertussis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D018387:Codon, Initiator; D006388:Hemagglutinins / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D021382:Protein Sorting Signals / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion; D010566:Virulence Factors, Bordetella
D018829:Adhesins, Bacterial; D018387:Codon, Initiator; D006388:Hemagglutinins; D021382:Protein Sorting Signals; D010566:Virulence Factors, Bordetella; C065273:filamentous hemagglutinin adhesin, Bordetella pertussis