The Haemophilus influenzae Hap autotransporter mediates microcolony formation and adherence to epithelial cells and extracellular matrix via binding regions in the C-terminal end of the passenger domain

Cell Microbiol. 2003 Mar;5(3):175-86. doi: 10.1046/j.1462-5822.2003.00266.x.


The pathogenesis of non-typable Haemophilus influenzae disease begins with colonization of the nasopharynx and is facilitated by bacterial adherence to respiratory mucosa. The H. influenzae Hap autotransporter is a non-pilus adhesin that promotes adherence to epithelial cells and selected extracellular matrix proteins and mediates bacterial aggregation and microcolony formation. In addition, Hap has serine protease activity. Hap contains a 110 kDa internal passenger domain called HapS and a 45 kDa C-terminal translocator domain called Hapbeta. In the present study, we sought to define the structural basis for Hap adhesive activities. Based on experiments using a panel of monoclonal antibodies against HapS, a deletion derivative lacking most of HapS and a purified fragment of HapS, we established that adherence to epithelial cells is mediated by sequences within the C-terminal 311 residues of HapS. In additional experiments, we discovered that bacterial aggregation is also mediated by sequences within the C-terminal 311 residues of HapS and occurs via HapS-HapS interaction between molecules on neighbouring organisms. Finally, we found that adherence to fibronectin, laminin and collagen IV is mediated in part by sequences within the C-terminal 311 residues of HapS and in full by sequences within the C-terminal 511 residues of HapS. Taken together, these results demonstrate that all Hap adhesive activities reside in the C-terminal portion of HapS. Coupled with earlier observations, the current results establish that HapS adhesive activities and HapS protease activity are contained in separate modules of the protein.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies, Monoclonal
  • Bacterial Adhesion / physiology*
  • Bacterial Outer Membrane Proteins / chemistry*
  • Bacterial Outer Membrane Proteins / metabolism
  • Bacterial Outer Membrane Proteins / pharmacology
  • Binding Sites
  • Carrier Proteins / chemistry*
  • Carrier Proteins / metabolism
  • Cell Line
  • Epithelial Cells / microbiology*
  • Extracellular Matrix / microbiology
  • Gene Expression Regulation, Bacterial
  • Haemophilus influenzae / genetics
  • Haemophilus influenzae / growth & development
  • Haemophilus influenzae / pathogenicity*
  • Models, Molecular
  • Protein Structure, Tertiary
  • Serine Endopeptidases*
  • Virulence Factors / chemistry
  • Virulence Factors / metabolism


  • Antibodies, Monoclonal
  • Bacterial Outer Membrane Proteins
  • Carrier Proteins
  • Hap protein, Hemophilus influenzae
  • Virulence Factors
  • Serine Endopeptidases