Characterization of the Pseudomonas aeruginosa pilus adhesin: confirmation that the pilin structural protein subunit contains a human epithelial cell-binding domain.

Previous studies have suggested that the Pseudomonas aeruginosa PAK pilus adhesin moiety resides in an epithelial cell-binding domain located in the C-terminal region of the PAK pilin structural protein. Synthetic peptides Ac17red (a synthetic peptide with a sequence identical to that of PAK pilin residues 128 to 144, with the Cys-129 and Cys-142 residues being in the reduced state) and Ac17ox (a synthetic peptide with a sequence identical to that of PAK pilin residues 128 to 144, with a formed disulfide bridge between the amino acid residues Cys-129 and Cys-142), which should contain the epithelial cell-binding domain, were synthesized. Ac17red and Ac17ox both bound to buccal epithelial cells (BECs) and to ciliated tracheal epithelial cells (TECs). Ac17ox had a Km of 6.40 microM for binding to BECs, while Ac17red had a Km of 9.87 microM. Ac17red bound to the same receptor sites that purified pili did and competitively inhibited the binding of purified PAK pili to BECs. BEC glycoproteins with molecular masses of 82, 55 to 51, and 40 kilodaltons immobilized on nitrocellulose exhibited periodate-sensitive receptor activity for Ac17red; similar activity has been found for PAK pili. Ac17red, Ac17ox, and PAK pili bound to the cilia and luminal portions of the cytoplasmic membrane of human TECs, the same regions to which P. aeruginosa whole cells bind. PAK pilin has an epithelial cell-binding domain that resides in the C-terminal region of the protein.