Involved in virulence (PubMed:23716608, PubMed:24731253). Mediates adherence to human respiratory epithelial cells (PubMed:24731253). Homotrimer. The C-terminal translocator domain is localized in the outer membrane and the passenger domain is at the cell surface. Expressed in vivo during the course of aerosol infection. Expressed at very low levels under routine laboratory growth conditions. Contains a well-conserved 23 amino acid extended signal peptide region (ESPR) preceding a typical N-terminal signal sequence. ESPR region may be involved in regulating the translocation of the autotransporter across the inner membrane into the periplasm. The signal peptide, cleaved at the inner membrane, guides the autotransporter protein to the periplasmic space. Then, insertion of the C-terminal translocator domain in the outer membrane forms a hydrophilic pore for the translocation of the passenger domain to the bacterial cell surface. Lafontaine et al. show that disruption of the gene reduces adherence to cultures of normal human bronchial epithelium (NHBE) but does not impair binding to HEp-2 laryngeal cells and A549 type II pneumocytes (PubMed:24731253). In contrast, Campos et al. show that disruption of the gene decreases adherence to A549 cells and attenuates the ability of the bacteria to invade A549 cells (PubMed:23716608). Mutant does not show a plaque formation defect (PubMed:23716608). Mutation reduces the ability to disseminate and/or survive within the liver in a mouse model of infection (PubMed:23716608). Mutation does not affect the virulence in a mouse model of aerosol infection (PubMed:24731253). Belongs to the autotransporter-2 (AT-2) (TC 1.B.40) family.