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.
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.
Fink
Doran L
DL
Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St Louis, MO 63110, USA.
Buscher
Amy Z
AZ
Green
Bruce
B
Fernsten
Phillip
P
St  Geme
Joseph W
JW
D000818:Animals; D000911:Antibodies, Monoclonal; D001422:Bacterial Adhesion / Q000502:physiology*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry* / Q000378:metabolism; D002460:Cell Line; D004847:Epithelial Cells / Q000382:microbiology*; D005109:Extracellular Matrix / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial; D006193:Haemophilus influenzae / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D008958:Models, Molecular; D017434:Protein Structure, Tertiary; D012697:Serine Endopeptidases; D037521:Virulence Factors / Q000737:chemistry / Q000378:metabolism
D000911:Antibodies, Monoclonal; D001425:Bacterial Outer Membrane Proteins; D002352:Carrier Proteins; C091552:Hap protein, Hemophilus influenzae; D037521:Virulence Factors; D012697:Serine Endopeptidases