Membrane targeting of a bacterial virulence factor harbouring an extended signal peptide.
Filamentous haemagglutinin (FHA) is the major adhesin of Bordetella pertussis, the whooping cough agent. FHA is synthesized as a 367-kDa precursor harbouring a remarkably long signal peptide with an N-terminal extension that is conserved among related virulence proteins. FHA is secreted via the two-partner secretion pathway that involves transport across the outer membrane by a cognate transporter protein. Here we have analyzed the mechanism by which FHA is targeted to, and translocated across, the inner membrane. Studies were performed both in vitro using Escherichia coli inside-out inner membrane vesicles and in vivo by pulse-chase labelling of Bordetella pertussis cells. The data collectively indicate that like classical periplasmic and outer membrane proteins, FHA requires SecA and SecB for its export through the SecYEG translocon in the inner membrane. Although short nascent chains of FHA were found to cross-link to signal recognition particle (SRP), we did not obtain indication for an SRP-dependent, co-translational membrane targeting provoked by the FHA signal sequence. Our results rule out that the extended signal peptide of FHA determines a specific mode of membrane targeting but rather suggest that it might influence the export rate at the inner membrane.
Chevalier
Nina
N
Institut für Biochemie and Molekularbiologie, Universität Freiburg, DE-79104 Freiburg, Germany.
Moser
Michael
M
Koch
Hans-Georg
HG
Schimz
Karl-Ludwig
KL
Willery
Eve
E
Locht
Camille
C
Jacob-Dubuisson
Françoise
F
Müller
Matthias
M
D000251:Adenosine Triphosphatases / Q000378:metabolism; D018829:Adhesins, Bacterial / Q000378:metabolism*; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000378:metabolism; D001692:Biological Transport / Q000502:physiology; D001886:Bordetella pertussis / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000378:metabolism; D006388:Hemagglutinins / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase / Q000378:metabolism; D011485:Protein Binding; D021382:Protein Sorting Signals / Q000502:physiology*; D000069816:SEC Translocation Channels; D000081416:SecA Proteins; D018271:Signal Recognition Particle / Q000378:metabolism*; D010566:Virulence Factors, Bordetella / Q000378:metabolism*
D018829:Adhesins, Bacterial; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; C082931:Ffh protein, E coli; D006388:Hemagglutinins; D026901:Membrane Transport Proteins; D021382:Protein Sorting Signals; D000069816:SEC Translocation Channels; C057842:SecB protein, Bacteria; D018271:Signal Recognition Particle; D010566:Virulence Factors, Bordetella; C065273:filamentous hemagglutinin adhesin, Bordetella pertussis; D000251:Adenosine Triphosphatases; C403324:trigger factor, E coli; D019696:Peptidylprolyl Isomerase; D000081416:SecA Proteins