Mapping the surface regions of Pseudomonas aeruginosa PAK pilin: the importance of the C‐terminal region for adherence to human buccal epithelial cells

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Abstract
The adherence of non‐mucoid Pseudomonas aeruginosa strains is believed to be mediated by the pilus, which consists of a single protein subunit of 15000 Oaltons called pilin. Ten antipeptide antisera were raised to map the surface regions of pilin from P. aeruginosa strain K (PAK). Only one of the antipeptide antisera to the eight predicted surface regions failed to react with PAK pili in direct ELISA. Five out of eight synthetic peptides representing the eight predicted surface regions reacted with anti‐PAK pilus anti‐serum, indicating their surface exposure. Combining the antipeptide and antipilus antisera results, all eight predicted surface regions were demonstrated to be surface‐exposed. The PAK 128‐144‐OH peptide produced the best binding antiserum to PAK pili. Only antipeptide Fab fragments directed against the disulphide bridged C‐terminal region of PAK piiin blocked the adherence of pili to human buccal epithelial cells, which suggests that this region contains the receptor‐binding domain of the PAK pilus.